X-Git-Url: https://git.madduck.net/etc/neomutt.git/blobdiff_plain/a6fa49f581a117f8344b700ba5ca522206b278b5..34926144a6ff1605e0449d90eaccf80c4dfddfe7:/.config/neomutt/buildmimetree.py?ds=sidebyside

diff --git a/.config/neomutt/buildmimetree.py b/.config/neomutt/buildmimetree.py
index d0493b3..a27f64c 100755
--- a/.config/neomutt/buildmimetree.py
+++ b/.config/neomutt/buildmimetree.py
@@ -6,9 +6,12 @@
 #
 # Configuration:
 #   neomuttrc (needs to be a single line):
+#     set my_mdwn_extensions="extra,admonition,codehilite,sane_lists,smarty"
 #     macro compose B "\
-#       <enter-command> source '$my_confdir/buildmimetree.py setup|'<enter>\
-#       <enter-command> sourc e \$my_mdwn_postprocess_cmd_file<enter>\
+#       <enter-command> source '$my_confdir/buildmimetree.py \
+#       --tempdir $tempdir --extensions $my_mdwn_extensions \
+#       --css-file $my_confdir/htmlmail.css |'<enter>\
+#       <enter-command> source \$my_mdwn_postprocess_cmd_file<enter>\
 #     " "Convert message into a modern MIME tree with inline images"
 #
 #     (Yes, we need to call source twice, as mutt only starts to process output
@@ -19,24 +22,46 @@
 # Requirements:
 #   - python3
 #   - python3-markdown
+#   - python3-beautifulsoup4
 # Optional:
 #   - pytest
-#   - Pynliner
-#   - Pygments, if installed, then syntax highlighting is enabled
+#   - Pynliner, provides --css-file and thus inline styling of HTML output
+#   - Pygments, then syntax highlighting for fenced code is enabled
+#
+# Running tests:
+#   pytest -x buildmimetree.py
 #
 # Latest version:
 #   https://git.madduck.net/etc/neomutt.git/blob_plain/HEAD:/.config/neomutt/buildmimetree.py
 #
-# Copyright © 2023 martin f. krafft <madduck@madduck.net>
-# Released under the GPL-2+ licence, just like Mutt itself.
+# Copyright © 2023–24 martin f. krafft <madduck@madduck.net>
+# Released under the GPL-2+ licence, just like NeoMutt itself.
 #
 
 import sys
+import os.path
 import pathlib
 import markdown
 import tempfile
 import argparse
-from collections import namedtuple
+import re
+import mimetypes
+import bs4
+import xml.etree.ElementTree as etree
+import io
+import enum
+import warnings
+from contextlib import contextmanager
+from collections import namedtuple, OrderedDict
+from markdown.extensions import Extension
+from markdown.blockprocessors import BlockProcessor
+from markdown.inlinepatterns import (
+    SimpleTextInlineProcessor,
+    ImageInlineProcessor,
+    IMAGE_LINK_RE,
+)
+from email.utils import make_msgid
+from urllib import request
 
 
 def parse_cli_args(*args, **kwargs):
@@ -47,67 +72,500 @@ def parse_cli_args(*args, **kwargs):
         )
     )
     parser.epilog = (
-        "Copyright © 2022 martin f. krafft <madduck@madduck.net>.\n"
+        "Copyright © 2023-24 martin f. krafft <madduck@madduck.net>.\n"
         "Released under the MIT licence"
     )
 
-    subp = parser.add_subparsers(help="Sub-command parsers", dest="mode")
-    parser_setup = subp.add_parser("setup", help="Setup phase")
-    parser_massage = subp.add_parser("massage", help="Massaging phase")
+    parser.add_argument(
+        "--extensions",
+        metavar="EXT[,EXT[,EXT]]",
+        type=str,
+        default="",
+        help="Markdown extension to use (comma-separated list)",
+    )
 
-    parser_setup.add_argument(
-        "--debug-commands",
+    if _PYNLINER:
+        parser.add_argument(
+            "--css-file",
+            metavar="FILE",
+            type=pathlib.Path,
+            default=os.devnull,
+            help="CSS file to merge with the final HTML",
+        )
+    else:
+        parser.set_defaults(css_file=None)
+
+    parser.add_argument(
+        "--related-to-html-only",
         action="store_true",
-        help="Turn on debug logging of commands generated to stderr",
+        help="Make related content be sibling to HTML parts only",
     )
 
-    parser_setup.add_argument(
-        "--extension",
-        "-x",
-        metavar="EXTENSION",
-        dest="extensions",
-        nargs="?",
-        default=[],
-        action="append",
-        help="Markdown extension to add to the list of extensions use",
+    def positive_integer(value):
+        try:
+            if int(value) > 0:
+                return int(value)
+
+        except ValueError:
+            pass
+
+        raise ValueError("Must be a positive integer")
+
+    parser.add_argument(
+        "--max-number-other-attachments",
+        metavar="INTEGER",
+        type=positive_integer,
+        default=20,
+        help="Maximum number of other attachments to expect",
+    )
+
+    parser.add_argument(
+        "--only-build",
+        "--just-build",
+        action="store_true",
+        help="Only build, don't send the message",
     )
 
-    parser_massage.add_argument(
+    parser.add_argument(
+        "--domain",
+        help="Domain to use in content IDs",
+    )
+
+    parser.add_argument(
+        "--tempdir",
+        metavar="DIR",
+        type=pathlib.Path,
+        help="Specify temporary directory to use for attachments",
+    )
+
+    parser.add_argument(
         "--debug-commands",
         action="store_true",
         help="Turn on debug logging of commands generated to stderr",
     )
 
-    parser_massage.add_argument(
+    parser.add_argument(
         "--debug-walk",
         action="store_true",
         help="Turn on debugging to stderr of the MIME tree walk",
     )
 
-    parser_massage.add_argument(
-        "--extensions",
-        metavar="EXTENSIONS",
-        type=str,
-        default="",
-        help="Markdown extension to use (comma-separated list)",
+    parser.add_argument(
+        "--dump-html",
+        metavar="FILE",
+        type=pathlib.Path,
+        help="Write the generated HTML to the file",
+    )
+
+    subp = parser.add_subparsers(help="Sub-command parsers", dest="mode")
+    massage_p = subp.add_parser(
+        "massage", help="Massaging phase (internal use)"
     )
 
-    parser_massage.add_argument(
+    massage_p.add_argument(
         "--write-commands-to",
-        metavar="PATH",
+        "-o",
+        metavar="FILE",
         dest="cmdpath",
+        type=pathlib.Path,
+        required=True,
         help="Temporary file path to write commands to",
     )
 
-    parser_massage.add_argument(
+    massage_p.add_argument(
         "MAILDRAFT",
         nargs="?",
+        type=pathlib.Path,
         help="If provided, the script is invoked as editor on the mail draft",
     )
 
     return parser.parse_args(*args, **kwargs)
 
 
+# [ FILE I/O HANDLING ] #######################################################
+
+
+class File:
+    class Op(enum.Enum):
+        R = enum.auto()
+        W = enum.auto()
+
+    def __init__(self, path=None, mode="r", content=None, **kwargs):
+        if path:
+            if content:
+                raise RuntimeError("Cannot specify path and content for File")
+
+            self._path = (
+                path if isinstance(path, pathlib.Path) else pathlib.Path(path)
+            )
+        else:
+            self._path = None
+
+        if content and not re.search(r"[r+]", mode):
+            raise RuntimeError("Cannot specify content without read mode")
+
+        self._cache = {File.Op.R: [content] if content else [], File.Op.W: []}
+        self._lastop = None
+        self._mode = mode
+        self._kwargs = kwargs
+        self._file = None
+
+    def open(self):
+        if self._path:
+            self._file = open(self._path, self._mode, **self._kwargs)
+        elif "b" in self._mode:
+            self._file = io.BytesIO()
+        else:
+            self._file = io.StringIO()
+
+    def __enter__(self):
+        self.open()
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.close()
+
+    def close(self):
+        self._file.close()
+        self._file = None
+        self._cache[File.Op.R] = self._cache[File.Op.W]
+        self._lastop = None
+
+    def _get_cache(self, op):
+        return (b"" if "b" in self._mode else "").join(self._cache[op])
+
+    def _add_to_cache(self, op, s):
+        self._cache[op].append(s)
+
+    def read(self, *, cache=True):
+        if cache and self._cache[File.Op.R]:
+            return self._get_cache(File.Op.R)
+
+        if self._lastop == File.Op.W:
+            try:
+                self._file.seek(0)
+            except io.UnsupportedOperation:
+                pass
+
+        self._lastop = File.Op.R
+
+        if cache:
+            self._add_to_cache(File.Op.R, self._file.read())
+            return self._get_cache(File.Op.R)
+        else:
+            return self._file.read()
+
+    def write(self, s, *, cache=True):
+        if self._lastop == File.Op.R:
+            try:
+                self._file.seek(0)
+            except io.UnsupportedOperation:
+                pass
+
+        if cache:
+            self._add_to_cache(File.Op.W, s)
+
+        self._cache[File.Op.R] = self._cache[File.Op.W]
+
+        written = self._file.write(s)
+        self._file.flush()
+        self._lastop = File.Op.W
+        return written
+
+    path = property(lambda s: s._path)
+
+    def __repr__(self):
+        return (
+            f'<File path={self._path or "(buffered)"} open={bool(self._file)} '
+            f"rcache={sum(len(c) for c in self._rcache) if self._rcache is not None else False} "
+            f"wcache={sum(len(c) for c in self._wcache) if self._wcache is not None else False}>"
+        )
+
+
+class FileFactory:
+    def __init__(self):
+        self._files = []
+
+    def __call__(self, path=None, mode="r", content=None, **kwargs):
+        f = File(path, mode, content, **kwargs)
+        self._files.append(f)
+        return f
+
+    def __len__(self):
+        return self._files.__len__()
+
+    def pop(self, idx=-1):
+        return self._files.pop(idx)
+
+    def __getitem__(self, idx):
+        return self._files.__getitem__(idx)
+
+    def __contains__(self, f):
+        return self._files.__contains__(f)
+
+
+class FakeFileFactory(FileFactory):
+    def __init__(self):
+        super().__init__()
+        self._paths2files = OrderedDict()
+
+    def __call__(self, path=None, mode="r", content=None, **kwargs):
+        if path in self._paths2files:
+            return self._paths2files[path]
+
+        f = super().__call__(None, mode, content, **kwargs)
+        self._paths2files[path] = f
+
+        mypath = path
+
+        class FakeFile(File):
+            path = mypath
+
+        # this is quality Python! We do this so that the fake file, which has
+        # no path, fake-pretends to have a path for testing purposes.
+
+        f.__class__ = FakeFile
+        return f
+
+    def __getitem__(self, path):
+        return self._paths2files.__getitem__(path)
+
+    def get(self, path, default):
+        return self._paths2files.get(path, default)
+
+    def pop(self, last=True):
+        return self._paths2files.popitem(last)
+
+    def __repr__(self):
+        return (
+            f"<FakeFileFactory nfiles={len(self._files)} "
+            f"paths={len(self._paths2files)}>"
+        )
+
+
+# [ IMAGE HANDLING ] ##########################################################
+
+
+InlineImageInfo = namedtuple(
+    "InlineImageInfo", ["cid", "desc"], defaults=[None]
+)
+
+
+class ImageRegistry:
+    def __init__(self):
+        self._images = OrderedDict()
+
+    def register(self, path, description=None, *, domain=None):
+        # path = str(pathlib.Path(path).expanduser())
+        path = os.path.expanduser(path)
+        if path.startswith("/"):
+            path = f"file://{path}"
+        cid = make_msgid(domain=domain)[1:-1]
+        self._images[path] = InlineImageInfo(cid, description)
+        return cid
+
+    def __iter__(self):
+        return self._images.__iter__()
+
+    def __getitem__(self, idx):
+        return self._images.__getitem__(idx)
+
+    def __len__(self):
+        return self._images.__len__()
+
+    def items(self):
+        return self._images.items()
+
+    def __repr__(self):
+        return f"<ImageRegistry(items={len(self._images)})>"
+
+    def __str__(self):
+        return self._images.__str__()
+
+
+class InlineImageExtension(Extension):
+    class RelatedImageInlineProcessor(ImageInlineProcessor):
+        def __init__(self, re, md, registry):
+            super().__init__(re, md)
+            self._registry = registry
+
+        def handleMatch(self, m, data):
+            el, start, end = super().handleMatch(m, data)
+            if "src" in el.attrib:
+                src = el.attrib["src"]
+                if "://" not in src or src.startswith("file://"):
+                    # We only inline local content
+                    cid = self._registry.register(
+                        el.attrib["src"],
+                        el.attrib.get("title", el.attrib.get("alt")),
+                    )
+                    el.attrib["src"] = f"cid:{cid}"
+            return el, start, end
+
+    def __init__(self, registry):
+        super().__init__()
+        self._image_registry = registry
+
+    INLINE_PATTERN_NAME = "image_link"
+
+    def extendMarkdown(self, md):
+        md.registerExtension(self)
+        inline_image_proc = self.RelatedImageInlineProcessor(
+            IMAGE_LINK_RE, md, self._image_registry
+        )
+        md.inlinePatterns.register(
+            inline_image_proc, InlineImageExtension.INLINE_PATTERN_NAME, 150
+        )
+
+
+def markdown_with_inline_image_support(
+    text,
+    *,
+    mdwn=None,
+    image_registry=None,
+    extensions=None,
+    extension_configs=None,
+):
+    registry = (
+        image_registry if image_registry is not None else ImageRegistry()
+    )
+    inline_image_handler = InlineImageExtension(registry=registry)
+    extensions = extensions or []
+    extensions.append(inline_image_handler)
+    mdwn = markdown.Markdown(
+        extensions=extensions, extension_configs=extension_configs
+    )
+
+    htmltext = mdwn.convert(text)
+
+    def replace_image_with_cid(matchobj):
+        for m in (matchobj.group(1), f"file://{matchobj.group(1)}"):
+            if m in registry:
+                return f"(cid:{registry[m].cid}"
+        return matchobj.group(0)
+
+    text = re.sub(r"\(([^)\s]+)", replace_image_with_cid, text)
+    return text, htmltext, registry, mdwn
+
+
+# [ CSS STYLING ] #############################################################
+
+
+try:
+    with warnings.catch_warnings():
+        # https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1081037
+        warnings.filterwarnings("ignore", category=SyntaxWarning)
+        import pynliner
+
+    _PYNLINER = True
+
+except ImportError:
+    _PYNLINER = False
+
+try:
+    from pygments.formatters import get_formatter_by_name
+
+    _CODEHILITE_CLASS = "codehilite"
+
+    _PYGMENTS_CSS = get_formatter_by_name(
+        "html", style="default"
+    ).get_style_defs(f".{_CODEHILITE_CLASS}")
+
+except ImportError:
+    _PYGMENTS_CSS = None
+
+
+def apply_styling(html, css):
+    return (
+        pynliner.Pynliner()
+        .from_string(html)
+        .with_cssString("\n".join(s for s in [_PYGMENTS_CSS, css] if s))
+        .run()
+    )
+
+
+# [ FORMAT=FLOWED HANDLING ] ##################################################
+
+
+class FormatFlowedNewlineExtension(Extension):
+    FFNL_RE = r"(?!\S)(\s)\n"
+
+    def extendMarkdown(self, md):
+        ffnl = SimpleTextInlineProcessor(self.FFNL_RE)
+        md.inlinePatterns.register(ffnl, "ffnl", 125)
+
+
+# [ QUOTE HANDLING ] ##########################################################
+
+
+class QuoteToAdmonitionExtension(Extension):
+    class BlockProcessor(BlockProcessor):
+        RE = re.compile(r"(?:^|\n)>\s*(.*)")
+
+        def __init__(self, parser):
+            super().__init__(parser)
+            self._title = None
+            self._disable = False
+
+        def test(self, parent, blocks):
+            if self._disable:
+                return False
+
+            if markdown.util.nearing_recursion_limit():
+                return False
+
+            lines = blocks.splitlines()
+            if len(lines) < 2:
+                if not self._title:
+                    return False
+
+                elif not self.RE.search(lines[0]):
+                    return False
+
+                return len(lines) > 0
+
+            elif not self.RE.search(lines[0]) and self.RE.search(lines[1]):
+                return True
+
+            elif self._title and self.RE.search(lines[1]):
+                return True
+
+            return False
+
+        def run(self, parent, blocks):
+            quotelines = blocks.pop(0).splitlines()
+
+            cont = bool(self._title)
+            if not self.RE.search(quotelines[0]):
+                self._title = quotelines.pop(0)
+
+            admonition = etree.SubElement(parent, "div")
+            admonition.set(
+                "class", f"admonition quote{' continued' if cont else ''}"
+            )
+            self.parser.parseChunk(admonition, self._title)
+
+            admonition[0].set("class", "admonition-title")
+            with self.disable():
+                self.parser.parseChunk(admonition, "\n".join(quotelines))
+
+        @contextmanager
+        def disable(self):
+            self._disable = True
+            yield True
+            self._disable = False
+
+        @classmethod
+        def clean(klass, line):
+            m = klass.RE.match(line)
+            return m.group(1) if m else line
+
+    def extendMarkdown(self, md):
+        md.registerExtension(self)
+        email_quote_proc = self.BlockProcessor(md.parser)
+        md.parser.blockprocessors.register(email_quote_proc, "emailquote", 25)
+
+
 # [ PARTS GENERATION ] ########################################################
 
 
@@ -133,101 +591,301 @@ class Multipart(
     def __str__(self):
         return f"<multipart/{self.subtype}> children={len(self.children)}"
 
+    def __hash__(self):
+        return hash(str(self.subtype) + "".join(str(self.children)))
 
-def convert_markdown_to_html(maildraft, *, extensions=None):
-    draftpath = pathlib.Path(maildraft)
-    textpart = Part(
-        "text", "plain", draftpath, "Plain-text version", orig=True
+
+def collect_inline_images(
+    image_registry, *, tempdir=None, filefactory=FileFactory()
+):
+    relparts = []
+    for path, info in image_registry.items():
+        if path.startswith("cid:"):
+            continue
+
+        data = request.urlopen(path)
+
+        mimetype = data.headers["Content-Type"]
+        ext = mimetypes.guess_extension(mimetype)
+        tempfilename = tempfile.mkstemp(prefix="img", suffix=ext, dir=tempdir)
+        path = pathlib.Path(tempfilename[1])
+
+        with filefactory(path, "w+b") as out_f:
+            out_f.write(data.read())
+
+        # filewriter_fn(path, data.read(), "w+b")
+
+        desc = (
+            f'Inline image: "{info.desc}"'
+            if info.desc
+            else f"Inline image {str(len(relparts)+1)}"
+        )
+        relparts.append(
+            Part(*mimetype.split("/"), path, cid=info.cid, desc=desc)
+        )
+
+    return relparts
+
+
+EMAIL_SIG_SEP = "\n-- \n"
+HTML_SIG_MARKER = "=htmlsig "
+
+
+def make_html_doc(body, sig=None):
+    ret = (
+        "<!DOCTYPE html>\n"
+        "<html>\n"
+        "<head>\n"
+        '<meta http-equiv="content-type" content="text/html; charset=UTF-8">\n'  # noqa: E501
+        '<meta name="viewport" content="width=device-width, initial-scale=1.0">\n'  # noqa: E501
+        "</head>\n"
+        "<body>\n"
+        f"{body}\n"
     )
 
-    with open(draftpath, "r", encoding="utf-8") as textmarkdown:
-        text = textmarkdown.read()
+    if sig:
+        nl = "\n"
+        ret = (
+            f'{ret}<div id="signature"><span class="sig_separator">{EMAIL_SIG_SEP.strip(nl)}</span>\n'  # noqa: E501
+            f"{sig}\n"
+            "</div>"
+        )
+
+    return f"{ret}\n  </body>\n</html>"
 
-    mdwn = markdown.Markdown(extensions=extensions)
-    html = mdwn.convert(text)
 
-    htmlpath = draftpath.with_suffix(".html")
-    htmlpart = Part("text", "html", htmlpath, "HTML version")
+def make_text_mail(text, sig=None):
+    return EMAIL_SIG_SEP.join((text, sig)) if sig else text
 
-    with open(
-        htmlpath, "w", encoding="utf-8", errors="xmlcharrefreplace"
-    ) as texthtml:
-        texthtml.write(html)
-
-    logopart = Part(
-        "image",
-        "png",
-        "/usr/share/doc/neomutt/logo/neomutt-256.png",
-        "Logo",
-        "neomutt-256.png",
+
+def extract_signature(text, *, filefactory=FileFactory()):
+    parts = text.split(EMAIL_SIG_SEP, 1)
+    if len(parts) == 1:
+        return text, None, None
+
+    lines = parts[1].splitlines()
+    if lines[0].startswith(HTML_SIG_MARKER):
+        path = pathlib.Path(re.split(r" +", lines.pop(0), maxsplit=1)[1])
+        textsig = "\n".join(lines)
+
+        with filefactory(path.expanduser()) as sig_f:
+            sig_input = sig_f.read()
+
+        soup = bs4.BeautifulSoup(sig_input, "html.parser")
+
+        style = str(soup.style.extract()) if soup.style else ""
+        for sig_selector in (
+            "#signature",
+            "#signatur",
+            "#emailsig",
+            ".signature",
+            ".signatur",
+            ".emailsig",
+            "body",
+            "div",
+        ):
+            sig = soup.select_one(sig_selector)
+            if sig:
+                break
+
+        if not sig:
+            return parts[0], textsig, style + sig_input
+
+        if sig.attrs.get("id") == "signature":
+            sig = "".join(str(c) for c in sig.children)
+
+        return parts[0], textsig, style + str(sig)
+
+    return parts[0], parts[1], None
+
+
+def convert_markdown_to_html(
+    draft_f,
+    *,
+    related_to_html_only=False,
+    css_f=None,
+    htmldump_f=None,
+    filefactory=FileFactory(),
+    tempdir=None,
+    extensions=None,
+    extension_configs=None,
+    domain=None,
+):
+    # TODO extension_configs need to be handled differently
+    extension_configs = extension_configs or {}
+    extension_configs.setdefault("pymdownx.highlight", {})[
+        "css_class"
+    ] = _CODEHILITE_CLASS
+
+    extensions = extensions or []
+    extensions.append(FormatFlowedNewlineExtension())
+    extensions.append(QuoteToAdmonitionExtension())
+
+    draft = draft_f.read()
+    origtext, textsig, htmlsig = extract_signature(
+        draft, filefactory=filefactory
     )
 
-    return Multipart(
-        "relative",
-        [
-            Multipart(
-                "alternative",
-                [textpart, htmlpart],
-                "Group of alternative content",
-            ),
-            logopart,
-        ],
-        "Group of related content",
+    (
+        origtext,
+        htmltext,
+        image_registry,
+        mdwn,
+    ) = markdown_with_inline_image_support(
+        origtext, extensions=extensions, extension_configs=extension_configs
     )
 
+    if htmlsig:
+        if not textsig:
+            # TODO: decide what to do if there is no plain-text version
+            raise NotImplementedError("HTML signature but no text alternative")
+
+        soup = bs4.BeautifulSoup(htmlsig, "html.parser")
+        for img in soup.find_all("img"):
+            uri = img.attrs["src"]
+            desc = img.attrs.get("title", img.attrs.get("alt"))
+            cid = image_registry.register(uri, desc, domain=domain)
+            img.attrs["src"] = f"cid:{cid}"
+
+        htmlsig = str(soup)
+
+    elif textsig:
+        (
+            textsig,
+            htmlsig,
+            image_registry,
+            mdwn,
+        ) = markdown_with_inline_image_support(
+            textsig,
+            extensions=extensions,
+            extension_configs=extension_configs,
+            image_registry=image_registry,
+            mdwn=mdwn,
+        )
+
+    origtext = make_text_mail(origtext, textsig)
+    draft_f.write(origtext)
+    textpart = Part(
+        "text", "plain", draft_f.path, "Plain-text version", orig=True
+    )
+
+    htmltext = make_html_doc(htmltext, htmlsig)
+    htmltext = apply_styling(htmltext, css_f.read() if css_f else None)
+
+    if draft_f.path:
+        htmlpath = draft_f.path.with_suffix(".html")
+    else:
+        htmlpath = pathlib.Path(
+            tempfile.mkstemp(suffix=".html", dir=tempdir)[1]
+        )
+    with filefactory(
+        htmlpath, "w", encoding="utf-8", errors="xmlcharrefreplace"
+    ) as out_f:
+        out_f.write(htmltext)
+    htmlpart = Part("text", "html", htmlpath, "HTML version")
+
+    if htmldump_f:
+        htmldump_f.write(htmltext)
+
+    imgparts = collect_inline_images(
+        image_registry, tempdir=tempdir, filefactory=filefactory
+    )
+
+    if related_to_html_only:
+        # If there are inline image part, they will be contained within a
+        # multipart/related part along with the HTML part only
+        if imgparts:
+            # replace htmlpart with a multipart/related container of the HTML
+            # parts and the images
+            htmlpart = Multipart(
+                "relative", [htmlpart] + imgparts, "Group of related content"
+            )
+
+        return Multipart(
+            "alternative", [textpart, htmlpart], "Group of alternative content"
+        )
+
+    else:
+        # If there are inline image part, they will be siblings to the
+        # multipart/alternative tree within a multipart/related part
+        altpart = Multipart(
+            "alternative", [textpart, htmlpart], "Group of alternative content"
+        )
+        if imgparts:
+            return Multipart(
+                "relative", [altpart] + imgparts, "Group of related content"
+            )
+        else:
+            return altpart
+
 
 class MIMETreeDFWalker:
     def __init__(self, *, visitor_fn=None, debug=False):
-        self._visitor_fn = visitor_fn
+        self._visitor_fn = visitor_fn or self._echovisit
         self._debug = debug
 
+    def _echovisit(self, node, ancestry, debugprint):
+        debugprint(f"node={node} ancestry={ancestry}")
+
     def walk(self, root, *, visitor_fn=None):
         """
         Recursive function to implement a depth-dirst walk of the MIME-tree
         rooted at `root`.
         """
-
         if isinstance(root, list):
-            root = Multipart("mixed", children=root)
+            if len(root) > 1:
+                root = Multipart("mixed", children=root)
+            else:
+                root = root[0]
 
         self._walk(
             root,
-            stack=[],
+            ancestry=[],
+            descendents=[],
             visitor_fn=visitor_fn or self._visitor_fn,
         )
 
-    def _walk(self, node, *, stack, visitor_fn):
+    def _walk(self, node, *, ancestry, descendents, visitor_fn):
         # Let's start by enumerating the parts at the current level. At the
-        # root level, stack will be the empty list, and we expect a multipart/*
-        # container at this level. Later, e.g. within a mutlipart/alternative
-        # container, the subtree will just be the alternative parts, while the
-        # top of the stack will be the multipart/alternative container, which
-        # we will process after the following loop.
-
-        lead = f"{'| '*len(stack)}|-"
+        # root level, ancestry will be the empty list, and we expect a
+        # multipart/* container at this level. Later, e.g. within a
+        # mutlipart/alternative container, the subtree will just be the
+        # alternative parts, while the top of the ancestry will be the
+        # multipart/alternative container, which we will process after the
+        # following loop.
+
+        lead = f"{'│ '*len(ancestry)}"
         if isinstance(node, Multipart):
             self.debugprint(
-                f"{lead}{node} parents={[s.subtype for s in stack]}"
+                f"{lead}├{node} ancestry={[s.subtype for s in ancestry]}"
             )
 
-            # Depth-first, so push the current container onto the stack,
-            # then descend …
-            stack.append(node)
-            self.debugprint("| " * (len(stack) + 1))
+            # Depth-first, so push the current container onto the ancestry
+            # stack, then descend …
+            ancestry.append(node)
+            self.debugprint(lead + "│ " * 2)
             for child in node.children:
                 self._walk(
                     child,
-                    stack=stack,
+                    ancestry=ancestry,
+                    descendents=descendents,
                     visitor_fn=visitor_fn,
                 )
-            self.debugprint("| " * len(stack))
-            assert stack.pop() == node
+            assert ancestry.pop() == node
+            sibling_descendents = descendents
+            descendents.extend(node.children)
 
         else:
-            self.debugprint(f"{lead}{node}")
+            self.debugprint(f"{lead}├{node}")
+            sibling_descendents = descendents
+
+        if False and ancestry:
+            self.debugprint(lead[:-1] + " │")
 
         if visitor_fn:
-            visitor_fn(node, stack, debugprint=self.debugprint)
+            visitor_fn(
+                node, ancestry, sibling_descendents, debugprint=self.debugprint
+            )
 
     def debugprint(self, s, **kwargs):
         if self._debug:
@@ -265,7 +923,7 @@ class MuttCommands:
             self._cmd1.append(s)
 
     def push(self, s):
-        s = s.replace('"', '"')
+        s = s.replace('"', r"\"")
         s = f'push "{s}"'
         self.debugprint(s)
         self._push.insert(0, s)
@@ -282,17 +940,18 @@ class MuttCommands:
 
 
 def do_setup(
-    extensions=None, *, out_f=sys.stdout, temppath=None, debug_commands=False
+    *,
+    out_f=sys.stdout,
+    temppath=None,
+    tempdir=None,
+    debug_commands=False,
 ):
-    extensions = extensions or []
     temppath = temppath or pathlib.Path(
-        tempfile.mkstemp(prefix="muttmdwn-")[1]
+        tempfile.mkstemp(prefix="muttmdwn-", dir=tempdir)[1]
     )
     cmds = MuttCommands(out_f, debug=debug_commands)
 
-    editor = f"{sys.argv[0]} massage --write-commands-to {temppath}"
-    if extensions:
-        editor = f'{editor} --extensions {",".join(extensions)}'
+    editor = f"{' '.join(sys.argv)} massage --write-commands-to {temppath}"
 
     cmds.cmd('set my_editor="$editor"')
     cmds.cmd('set my_edit_headers="$edit_headers"')
@@ -304,11 +963,18 @@ def do_setup(
 
 
 def do_massage(
-    maildraft,
-    cmdpath,
+    draft_f,
+    cmd_f,
     *,
     extensions=None,
+    css_f=None,
+    htmldump_f=None,
     converter=convert_markdown_to_html,
+    related_to_html_only=True,
+    only_build=False,
+    max_other_attachments=20,
+    tempdir=None,
+    domain=None,
     debug_commands=False,
     debug_walk=False,
 ):
@@ -316,95 +982,163 @@ def do_massage(
     # draft, and whatever commands we write to the file given as cmdpath will
     # be run by the second source command in the macro definition.
 
-    with open(cmdpath, "w") as cmd_f:
-        # Let's start by cleaning up what the setup did (see above), i.e. we
-        # restore the $editor and $edit_headers variables, and also unset the
-        # variable used to identify the command file we're currently writing
-        # to.
-        cmds = MuttCommands(cmd_f, debug=debug_commands)
-        cmds.cmd('set editor="$my_editor"')
-        cmds.cmd('set edit_headers="$my_edit_headers"')
-        cmds.cmd("unset my_editor")
-        cmds.cmd("unset my_edit_headers")
-
-        # let's flush those commands, as there'll be a lot of pushes from now
-        # on, which need to be run in reverse order
-        cmds.flush()
-
-        extensions = extensions.split(",") if extensions else []
-        tree = converter(maildraft, extensions=extensions)
-
-        mimetree = MIMETreeDFWalker(debug=args.debug_walk)
-
-        def visitor_fn(item, stack, *, debugprint=None):
-            """
-            Visitor function called for every node (part) of the MIME tree,
-            depth-first, and responsible for telling NeoMutt how to assemble
-            the tree.
-            """
-            if isinstance(item, Part):
-                # We've hit a leaf-node, i.e. an alternative or a related part
-                # with actual content.
-
-                # If the part is not an original part, i.e. doesn't already
-                # exist, we must first add it.
-                if not item.orig:
-                    cmds.push(f"<attach-file>{item.path}<enter>")
-                    cmds.push("<toggle-unlink><toggle-disposition>")
-                    if item.cid:
-                        cmds.push(
-                            f"<edit-content-id>\\Ca\\Ck{item.cid}<enter>"
-                        )
-
-                # If the item (including the original) comes with a
-                # description, then we might just as well update the NeoMutt
-                # tree now:
-                if item.desc:
-                    cmds.push(f"<edit-description>\\Ca\\Ck{item.desc}<enter>")
-
-                # Finally, tag the entry that we just processed, so that when
-                # we're done at this level, as we walk up the stack, the items
-                # to be grouped will already be tagged and ready.
-                cmds.push("<tag-entry>")
-
-            elif isinstance(item, Multipart):
-                # This node has children, but we already visited them (see
-                # above), and so they have been tagged in NeoMutt's compose
-                # window. Now it's just a matter of telling NeoMutt to do the
-                # appropriate grouping:
-                if item.subtype == "alternative":
-                    cmds.push("<group-alternatives>")
-                elif item.subtype == "relative":
-                    cmds.push("<group-related>")
-                elif item.subtype == "multilingual":
-                    cmds.push("<group-multilingual>")
-
-                # Again, if there is a description, we might just as well:
-                if item.desc:
-                    cmds.push(f"<edit-description>\\Ca\\Ck{item.desc}<enter>")
-
-                # Finally, if we're at non-root level, tag the new container,
-                # as it might itself be part of a container, to be processed
-                # one level up:
-                if stack:
-                    cmds.push("<tag-entry>")
+    # Let's start by cleaning up what the setup did (see above), i.e. we
+    # restore the $editor and $edit_headers variables, and also unset the
+    # variable used to identify the command file we're currently writing
+    # to.
+    cmds = MuttCommands(cmd_f, debug=debug_commands)
+
+    extensions = extensions.split(",") if extensions else []
+    tree = converter(
+        draft_f,
+        css_f=css_f,
+        htmldump_f=htmldump_f,
+        related_to_html_only=related_to_html_only,
+        tempdir=tempdir,
+        extensions=extensions,
+        domain=domain,
+    )
+
+    mimetree = MIMETreeDFWalker(debug=debug_walk)
+
+    state = dict(pos=1, tags={}, parts=1)
 
+    def visitor_fn(item, ancestry, descendents, *, debugprint=None):
+        """
+        Visitor function called for every node (part) of the MIME tree,
+        depth-first, and responsible for telling NeoMutt how to assemble
+        the tree.
+        """
+        KILL_LINE = r"\Ca\Ck"
+
+        if isinstance(item, Part):
+            # We've hit a leaf-node, i.e. an alternative or a related part
+            # with actual content.
+
+            # Let's add the part
+            if item.orig:
+                # The original source already exists in the NeoMutt tree, but
+                # the underlying file may have been modified, so we need to
+                # update the encoding, but that's it:
+                cmds.push("<first-entry>")
+                cmds.push("<update-encoding>")
+
+                # We really just need to be able to assume that at this point,
+                # NeoMutt is at position 1, and that we've processed only this
+                # part so far. Nevermind about actual attachments, we can
+                # safely ignore those as they stay at the end.
+                assert state["pos"] == 1
+                assert state["parts"] == 1
+            else:
+                # … whereas all other parts need to be added, and they're all
+                # considered to be temporary and inline:
+                cmds.push(f"<attach-file>{item.path}<enter>")
+                cmds.push("<toggle-unlink><toggle-disposition>")
+
+                # This added a part at the end of the list of parts, and that's
+                # just how many parts we've seen so far, so it's position in
+                # the NeoMutt compose list is the count of parts
+                state["parts"] += 1
+                state["pos"] = state["parts"]
+
+            # If the item (including the original) comes with additional
+            # information, then we might just as well update the NeoMutt
+            # tree now:
+            if item.cid:
+                cmds.push(f"<edit-content-id>{KILL_LINE}{item.cid}<enter>")
+
+            # Now for the biggest hack in this script, which is to handle
+            # attachments, such as PDFs, that aren't related or alternatives.
+            # The problem is that when we add an inline image, it always gets
+            # appended to the list, i.e. inserted *after* other attachments.
+            # Since we don't know the number of attachments, we also cannot
+            # infer the postition of the new attachment. Therefore, we bubble
+            # it all the way to the top, only to then move it down again:
+            if state["pos"] > 1:  # skip for the first part
+                for i in range(max_other_attachments):
+                    # could use any number here, but has to be larger than the
+                    # number of possible attachments. The performance
+                    # difference of using a high number is negligible.
+                    # Bubble up the new part
+                    cmds.push("<move-up>")
+
+                # As we push the part to the right position in the list (i.e.
+                # the last of the subset of attachments this script added), we
+                # must handle the situation that subtrees are skipped by
+                # NeoMutt. Hence, the actual number of positions to move down
+                # is decremented by the number of descendents so far
+                # encountered.
+                for i in range(1, state["pos"] - len(descendents)):
+                    cmds.push("<move-down>")
+
+        elif isinstance(item, Multipart):
+            # This node has children, but we already visited them (see
+            # above). The tags dictionary of State should contain a list of
+            # their positions in the NeoMutt compose window, so iterate those
+            # and tag the parts there:
+            n_tags = len(state["tags"][item])
+            for tag in state["tags"][item]:
+                cmds.push(f"<jump>{tag}<enter><tag-entry>")
+
+            if item.subtype == "alternative":
+                cmds.push("<group-alternatives>")
+            elif item.subtype in ("relative", "related"):
+                cmds.push("<group-related>")
+            elif item.subtype == "multilingual":
+                cmds.push("<group-multilingual>")
             else:
-                # We should never get here
-                assert not "is valid part"
+                raise NotImplementedError(
+                    f"Handling of multipart/{item.subtype} is not implemented"
+                )
 
-        # -----------------
-        # End of visitor_fn
+            state["pos"] -= n_tags - 1
+            state["parts"] += 1
 
-        # Let's walk the tree and visit every node with our fancy visitor
-        # function
-        mimetree.walk(tree, visitor_fn=visitor_fn)
+        else:
+            # We should never get here
+            raise RuntimeError(f"Type {type(item)} is unexpected: {item}")
+
+        # If the item has a description, we might just as well add it
+        if item.desc:
+            cmds.push(f"<edit-description>{KILL_LINE}{item.desc}<enter>")
+
+        if ancestry:
+            # If there's an ancestry, record the current (assumed) position in
+            # the NeoMutt compose window as needed-to-tag by our direct parent
+            # (i.e. the last item of the ancestry)
+            state["tags"].setdefault(ancestry[-1], []).append(state["pos"])
+
+            lead = "│ " * (len(ancestry) + 1) + "* "
+            debugprint(
+                f"{lead}ancestry={[a.subtype for a in ancestry]}\n"
+                f"{lead}descendents={[d.subtype for d in descendents]}\n"
+                f"{lead}children_positions={state['tags'][ancestry[-1]]}\n"
+                f"{lead}pos={state['pos']}, parts={state['parts']}"
+            )
 
-        # Finally, cleanup. Since we're responsible for removing the temporary
-        # file, how's this for a little hack?
-        cmds.cmd(f"source 'rm -f {args.cmdpath}|'")
-        cmds.cmd("unset my_mdwn_postprocess_cmd_file")
-        cmds.flush()
+    # -----------------
+    # End of visitor_fn
+
+    # Let's walk the tree and visit every node with our fancy visitor
+    # function
+    mimetree.walk(tree, visitor_fn=visitor_fn)
+
+    if not only_build:
+        cmds.push("<send-message>")
+
+    # Finally, cleanup. Since we're responsible for removing the temporary
+    # file, how's this for a little hack?
+    try:
+        filename = cmd_f.name
+    except AttributeError:
+        filename = "pytest_internal_file"
+    cmds.cmd(f"source 'rm -f {filename}|'")
+    cmds.cmd('set editor="$my_editor"')
+    cmds.cmd('set edit_headers="$my_edit_headers"')
+    cmds.cmd("unset my_editor")
+    cmds.cmd("unset my_edit_headers")
+    cmds.cmd("unset my_mdwn_postprocess_cmd_file")
+    cmds.flush()
 
 
 # [ CLI ENTRY ] ###############################################################
@@ -412,18 +1146,34 @@ def do_massage(
 if __name__ == "__main__":
     args = parse_cli_args()
 
-    if args.mode == "setup":
-        do_setup(args.extensions, debug_commands=args.debug_commands)
-
-    elif args.mode == "massage":
-        do_massage(
-            args.MAILDRAFT,
-            args.cmdpath,
-            extensions=args.extensions,
+    if args.mode is None:
+        do_setup(
+            tempdir=args.tempdir,
             debug_commands=args.debug_commands,
-            debug_walk=args.debug_walk,
         )
 
+    elif args.mode == "massage":
+        with (
+            File(args.MAILDRAFT, "r+") as draft_f,
+            File(args.cmdpath, "w") as cmd_f,
+            File(args.css_file, "r") as css_f,
+            File(args.dump_html, "w") as htmldump_f,
+        ):
+            do_massage(
+                draft_f,
+                cmd_f,
+                extensions=args.extensions,
+                css_f=css_f,
+                htmldump_f=htmldump_f,
+                related_to_html_only=args.related_to_html_only,
+                max_other_attachments=args.max_number_other_attachments,
+                only_build=args.only_build,
+                tempdir=args.tempdir,
+                domain=args.domain,
+                debug_commands=args.debug_commands,
+                debug_walk=args.debug_walk,
+            )
+
 
 # [ TESTS ] ###################################################################
 
@@ -433,15 +1183,24 @@ try:
     class Tests:
         @pytest.fixture
         def const1(self):
-            return "CONSTANT STRING 1"
+            return "Curvature Vest Usher Dividing+T#iceps Senior"
 
         @pytest.fixture
         def const2(self):
-            return "CONSTANT STRING 2"
+            return "Habitant Celestial 2litzy Resurf/ce Headpiece Harmonics"
+
+        @pytest.fixture
+        def fakepath(self):
+            return pathlib.Path("/does/not/exist")
+
+        @pytest.fixture
+        def fakepath2(self):
+            return pathlib.Path("/does/not/exist/either")
 
         # NOTE: tests using the capsys fixture must specify sys.stdout to the
         # functions they call, else old stdout is used and not captured
 
+        @pytest.mark.muttctrl
         def test_MuttCommands_cmd(self, const1, const2, capsys):
             "Assert order of commands"
             cmds = MuttCommands(out_f=sys.stdout)
@@ -451,6 +1210,7 @@ try:
             captured = capsys.readouterr()
             assert captured.out == "\n".join((const1, const2, ""))
 
+        @pytest.mark.muttctrl
         def test_MuttCommands_push(self, const1, const2, capsys):
             "Assert reverse order of pushes"
             cmds = MuttCommands(out_f=sys.stdout)
@@ -463,6 +1223,15 @@ try:
                 == ('"\npush "'.join(("", const2, const1, "")))[2:-6]
             )
 
+        @pytest.mark.muttctrl
+        def test_MuttCommands_push_escape(self, const1, const2, capsys):
+            cmds = MuttCommands(out_f=sys.stdout)
+            cmds.push(f'"{const1}"')
+            cmds.flush()
+            captured = capsys.readouterr()
+            assert f'"\\"{const1}\\""' in captured.out
+
+        @pytest.mark.muttctrl
         def test_MuttCommands_cmd_push_mixed(self, const1, const2, capsys):
             "Assert reverse order of pushes"
             cmds = MuttCommands(out_f=sys.stdout)
@@ -486,14 +1255,20 @@ try:
             assert lines[5] in lines_out[7]
 
         @pytest.fixture
-        def basic_mime_tree(self):
+        def mime_tree_related_to_alternative(self):
             return Multipart(
-                "related",
+                "relative",
                 children=[
                     Multipart(
                         "alternative",
                         children=[
-                            Part("text", "plain", "part.txt", desc="Plain"),
+                            Part(
+                                "text",
+                                "plain",
+                                "part.txt",
+                                desc="Plain",
+                                orig=True,
+                            ),
                             Part("text", "html", "part.html", desc="HTML"),
                         ],
                         desc="Alternative",
@@ -505,70 +1280,1008 @@ try:
                 desc="Related",
             )
 
-        def test_MIMETreeDFWalker_depth_first_walk(self, basic_mime_tree):
+        @pytest.fixture
+        def mime_tree_related_to_html(self):
+            return Multipart(
+                "alternative",
+                children=[
+                    Part(
+                        "text",
+                        "plain",
+                        "part.txt",
+                        desc="Plain",
+                        orig=True,
+                    ),
+                    Multipart(
+                        "relative",
+                        children=[
+                            Part("text", "html", "part.html", desc="HTML"),
+                            Part(
+                                "text",
+                                "png",
+                                "logo.png",
+                                cid="logo.png",
+                                desc="Logo",
+                            ),
+                        ],
+                        desc="Related",
+                    ),
+                ],
+                desc="Alternative",
+            )
+
+        @pytest.fixture
+        def mime_tree_nested(self):
+            return Multipart(
+                "relative",
+                children=[
+                    Multipart(
+                        "alternative",
+                        children=[
+                            Part(
+                                "text",
+                                "plain",
+                                "part.txt",
+                                desc="Plain",
+                                orig=True,
+                            ),
+                            Multipart(
+                                "alternative",
+                                children=[
+                                    Part(
+                                        "text",
+                                        "plain",
+                                        "part.txt",
+                                        desc="Nested plain",
+                                    ),
+                                    Part(
+                                        "text",
+                                        "html",
+                                        "part.html",
+                                        desc="Nested HTML",
+                                    ),
+                                ],
+                                desc="Nested alternative",
+                            ),
+                        ],
+                        desc="Alternative",
+                    ),
+                    Part(
+                        "text",
+                        "png",
+                        "logo.png",
+                        cid="logo.png",
+                        desc="Logo",
+                    ),
+                ],
+                desc="Related",
+            )
+
+        @pytest.mark.treewalk
+        def test_MIMETreeDFWalker_depth_first_walk(
+            self, mime_tree_related_to_alternative
+        ):
             mimetree = MIMETreeDFWalker()
 
             items = []
 
-            def visitor_fn(item, stack, debugprint):
-                items.append((item, len(stack)))
+            def visitor_fn(item, ancestry, descendents, debugprint):
+                items.append((item, len(ancestry), len(descendents)))
 
-            mimetree.walk(basic_mime_tree, visitor_fn=visitor_fn)
+            mimetree.walk(
+                mime_tree_related_to_alternative, visitor_fn=visitor_fn
+            )
             assert len(items) == 5
             assert items[0][0].subtype == "plain"
             assert items[0][1] == 2
+            assert items[0][2] == 0
             assert items[1][0].subtype == "html"
             assert items[1][1] == 2
+            assert items[1][2] == 0
             assert items[2][0].subtype == "alternative"
             assert items[2][1] == 1
+            assert items[2][2] == 2
             assert items[3][0].subtype == "png"
             assert items[3][1] == 1
-            assert items[4][0].subtype == "related"
+            assert items[3][2] == 2
+            assert items[4][0].subtype == "relative"
             assert items[4][1] == 0
+            assert items[4][2] == 4
 
-        def test_MIMETreeDFWalker_list_to_mixed(self, basic_mime_tree):
+        @pytest.mark.treewalk
+        def test_MIMETreeDFWalker_list_to_mixed(self, const1):
             mimetree = MIMETreeDFWalker()
-
             items = []
 
-            def visitor_fn(item, stack, debugprint):
+            def visitor_fn(item, ancestry, descendents, debugprint):
                 items.append(item)
 
-            mimetree.walk([basic_mime_tree], visitor_fn=visitor_fn)
+            p = Part("text", "plain", const1)
+            mimetree.walk([p], visitor_fn=visitor_fn)
+            assert items[-1].subtype == "plain"
+            mimetree.walk([p, p], visitor_fn=visitor_fn)
             assert items[-1].subtype == "mixed"
 
+        @pytest.mark.treewalk
         def test_MIMETreeDFWalker_visitor_in_constructor(
-            self, basic_mime_tree
+            self, mime_tree_related_to_alternative
         ):
             items = []
 
-            def visitor_fn(item, stack, debugprint):
+            def visitor_fn(item, ancestry, descendents, debugprint):
                 items.append(item)
 
             mimetree = MIMETreeDFWalker(visitor_fn=visitor_fn)
-            mimetree.walk(basic_mime_tree)
+            mimetree.walk(mime_tree_related_to_alternative)
             assert len(items) == 5
 
-        def test_do_setup_no_extensions(self, const1, capsys):
-            "Assert basics about the setup command output"
-            do_setup(temppath=const1, out_f=sys.stdout)
-            captout = capsys.readouterr()
-            lines = captout.out.splitlines()
-            assert lines[2].endswith(f'{const1}"')
-            assert lines[4].endswith(const1)
-            assert "first-entry" in lines[-1]
-            assert "edit-file" in lines[-1]
-
-        def test_do_setup_extensions(self, const1, const2, capsys):
-            "Assert that extensions are passed to editor"
-            do_setup(
-                temppath=const1, extensions=[const2, const1], out_f=sys.stdout
-            )
-            captout = capsys.readouterr()
-            lines = captout.out.splitlines()
-            # assert comma-separated list of extensions passed
-            assert lines[2].endswith(f'{const2},{const1}"')
-            assert lines[4].endswith(const1)
+        @pytest.fixture
+        def string_io(self, const1, text=None):
+            return StringIO(text or const1)
+
+        @pytest.mark.massage
+        def test_do_massage_basic(self):
+            def converter(draft_f, **kwargs):
+                return Part("text", "plain", draft_f.path, orig=True)
+
+            with File() as draft_f, File() as cmd_f:
+                do_massage(
+                    draft_f=draft_f,
+                    cmd_f=cmd_f,
+                    converter=converter,
+                )
+                lines = cmd_f.read().splitlines()
+
+            assert "send-message" in lines.pop(0)
+            assert "update-encoding" in lines.pop(0)
+            assert "first-entry" in lines.pop(0)
+            assert "source 'rm -f " in lines.pop(0)
+            assert '="$my_editor"' in lines.pop(0)
+            assert '="$my_edit_headers"' in lines.pop(0)
+            assert "unset my_editor" == lines.pop(0)
+            assert "unset my_edit_headers" == lines.pop(0)
+            assert "unset my_mdwn_postprocess_cmd_file" == lines.pop(0)
+
+        @pytest.mark.massage
+        def test_do_massage_fulltree(self, mime_tree_related_to_alternative):
+            def converter(draft_f, **kwargs):
+                return mime_tree_related_to_alternative
+
+            max_attachments = 5
+
+            with File() as draft_f, File() as cmd_f:
+                do_massage(
+                    draft_f=draft_f,
+                    cmd_f=cmd_f,
+                    max_other_attachments=max_attachments,
+                    converter=converter,
+                )
+                lines = cmd_f.read().splitlines()[:-6]
+
+            assert "first-entry" in lines.pop()
+            assert "update-encoding" in lines.pop()
+            assert "Plain" in lines.pop()
+            assert "part.html" in lines.pop()
+            assert "toggle-unlink" in lines.pop()
+            for i in range(max_attachments):
+                assert "move-up" in lines.pop()
+            assert "move-down" in lines.pop()
+            assert "HTML" in lines.pop()
+            assert "jump>1" in lines.pop()
+            assert "jump>2" in lines.pop()
+            assert "group-alternatives" in lines.pop()
+            assert "Alternative" in lines.pop()
+            assert "logo.png" in lines.pop()
+            assert "toggle-unlink" in lines.pop()
+            assert "content-id" in lines.pop()
+            for i in range(max_attachments):
+                assert "move-up" in lines.pop()
+            assert "move-down" in lines.pop()
+            assert "Logo" in lines.pop()
+            assert "jump>1" in lines.pop()
+            assert "jump>4" in lines.pop()
+            assert "group-related" in lines.pop()
+            assert "Related" in lines.pop()
+            assert "send-message" in lines.pop()
+            assert len(lines) == 0
+
+        @pytest.mark.massage
+        def test_mime_tree_relative_within_alternative(
+            self, mime_tree_related_to_html
+        ):
+            def converter(draft_f, **kwargs):
+                return mime_tree_related_to_html
+
+            with File() as draft_f, File() as cmd_f:
+                do_massage(
+                    draft_f=draft_f,
+                    cmd_f=cmd_f,
+                    converter=converter,
+                )
+                lines = cmd_f.read().splitlines()[:-6]
+
+            assert "first-entry" in lines.pop()
+            assert "update-encoding" in lines.pop()
+            assert "Plain" in lines.pop()
+            assert "part.html" in lines.pop()
+            assert "toggle-unlink" in lines.pop()
+            assert "move-up" in lines.pop()
+            while True:
+                top = lines.pop()
+                if "move-up" not in top:
+                    break
+            assert "move-down" in top
+            assert "HTML" in lines.pop()
+            assert "logo.png" in lines.pop()
+            assert "toggle-unlink" in lines.pop()
+            assert "content-id" in lines.pop()
+            assert "move-up" in lines.pop()
+            while True:
+                top = lines.pop()
+                if "move-up" not in top:
+                    break
+            assert "move-down" in top
+            assert "move-down" in lines.pop()
+            assert "Logo" in lines.pop()
+            assert "jump>2" in lines.pop()
+            assert "jump>3" in lines.pop()
+            assert "group-related" in lines.pop()
+            assert "Related" in lines.pop()
+            assert "jump>1" in lines.pop()
+            assert "jump>2" in lines.pop()
+            assert "group-alternative" in lines.pop()
+            assert "Alternative" in lines.pop()
+            assert "send-message" in lines.pop()
+            assert len(lines) == 0
+
+        @pytest.mark.massage
+        def test_mime_tree_nested_trees_does_not_break_positioning(
+            self, mime_tree_nested
+        ):
+            def converter(draft_f, **kwargs):
+                return mime_tree_nested
+
+            with File() as draft_f, File() as cmd_f:
+                do_massage(
+                    draft_f=draft_f,
+                    cmd_f=cmd_f,
+                    converter=converter,
+                )
+                lines = cmd_f.read().splitlines()
+
+            while "logo.png" not in lines.pop():
+                pass
+            lines.pop()
+            assert "content-id" in lines.pop()
+            assert "move-up" in lines.pop()
+            while True:
+                top = lines.pop()
+                if "move-up" not in top:
+                    break
+            assert "move-down" in top
+            # Due to the nested trees, the number of descendents of the sibling
+            # actually needs to be considered, not just the nieces. So to move
+            # from position 1 to position 6, it only needs one <move-down>
+            # because that jumps over the entire sibling tree. Thus what
+            # follows next must not be another <move-down>
+            assert "Logo" in lines.pop()
+
+        @pytest.mark.converter
+        def test_converter_tree_basic(self, fakepath, const1, fakefilefactory):
+            with fakefilefactory(fakepath, content=const1) as draft_f:
+                tree = convert_markdown_to_html(
+                    draft_f, filefactory=fakefilefactory
+                )
+
+            assert tree.subtype == "alternative"
+            assert len(tree.children) == 2
+            assert tree.children[0].subtype == "plain"
+            assert tree.children[0].path == draft_f.path
+            assert tree.children[0].orig
+            assert tree.children[1].subtype == "html"
+            assert tree.children[1].path == fakepath.with_suffix(".html")
+
+        @pytest.mark.converter
+        def test_converter_writes(
+            self, fakepath, fakefilefactory, const1, monkeypatch
+        ):
+            with fakefilefactory(fakepath, content=const1) as draft_f:
+                convert_markdown_to_html(draft_f, filefactory=fakefilefactory)
+
+            html = fakefilefactory.pop()
+            assert fakepath.with_suffix(".html") == html[0]
+            assert const1 in html[1].read()
+            text = fakefilefactory.pop()
+            assert fakepath == text[0]
+            assert const1 == text[1].read()
+
+        @pytest.mark.imgproc
+        def test_markdown_inline_image_processor(self):
+            imgpath1 = "file:/path/to/image.png"
+            imgpath2 = "file:///path/to/image.png?url=params"
+            imgpath3 = "/path/to/image.png"
+            text = f"""![inline local image]({imgpath1})
+                       ![image inlined
+                         with newline]({imgpath2})
+                       ![image local path]({imgpath3})"""
+            text, html, images, mdwn = markdown_with_inline_image_support(text)
+
+            # local paths have been normalised to URLs:
+            imgpath3 = f"file://{imgpath3}"
+
+            assert 'src="cid:' in html
+            assert "](cid:" in text
+            assert len(images) == 3
+            assert imgpath1 in images
+            assert imgpath2 in images
+            assert imgpath3 in images
+            assert images[imgpath1].cid != images[imgpath2].cid
+            assert images[imgpath1].cid != images[imgpath3].cid
+            assert images[imgpath2].cid != images[imgpath3].cid
+
+        @pytest.mark.imgproc
+        def test_markdown_inline_image_processor_title_to_desc(self, const1):
+            imgpath = "file:///path/to/image.png"
+            text = f'![inline local image]({imgpath} "{const1}")'
+            text, html, images, mdwn = markdown_with_inline_image_support(text)
+            assert images[imgpath].desc == const1
+
+        @pytest.mark.imgproc
+        def test_markdown_inline_image_processor_alt_to_desc(self, const1):
+            imgpath = "file:///path/to/image.png"
+            text = f"![{const1}]({imgpath})"
+            text, html, images, mdwn = markdown_with_inline_image_support(text)
+            assert images[imgpath].desc == const1
+
+        @pytest.mark.imgproc
+        def test_markdown_inline_image_processor_title_over_alt_desc(
+            self, const1, const2
+        ):
+            imgpath = "file:///path/to/image.png"
+            text = f'![{const1}]({imgpath} "{const2}")'
+            text, html, images, mdwn = markdown_with_inline_image_support(text)
+            assert images[imgpath].desc == const2
+
+        @pytest.mark.imgproc
+        def test_markdown_inline_image_not_external(self):
+            imgpath = "https://path/to/image.png"
+            text = f"![inline image]({imgpath})"
+            text, html, images, mdwn = markdown_with_inline_image_support(text)
+
+            assert 'src="cid:' not in html
+            assert "](cid:" not in text
+            assert len(images) == 0
+
+        @pytest.mark.imgproc
+        def test_markdown_inline_image_local_file(self):
+            imgpath = "/path/to/image.png"
+            text = f"![inline image]({imgpath})"
+            text, html, images, mdwn = markdown_with_inline_image_support(text)
+
+            for k, v in images.items():
+                assert k == f"file://{imgpath}"
+                break
+
+        @pytest.mark.imgproc
+        def test_markdown_inline_image_expanduser(self):
+            imgpath = pathlib.Path("~/image.png")
+            text = f"![inline image]({imgpath})"
+            text, html, images, mdwn = markdown_with_inline_image_support(text)
+
+            for k, v in images.items():
+                assert k == f"file://{imgpath.expanduser()}"
+                break
+
+        @pytest.fixture
+        def test_png(self):
+            return (
+                "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAE"
+                "AAAABCAAAAAA6fptVAAAACklEQVQI12P4DwABAQEAG7buVgAA"
+            )
+
+        @pytest.mark.imgproc
+        def test_markdown_inline_image_processor_base64(self, test_png):
+            text = f"![1px white inlined]({test_png})"
+            text, html, images, mdwn = markdown_with_inline_image_support(text)
+
+            assert 'src="cid:' in html
+            assert "](cid:" in text
+            assert len(images) == 1
+            assert test_png in images
+
+        @pytest.mark.converter
+        def test_converter_tree_inline_image_base64(
+            self, test_png, fakefilefactory
+        ):
+            text = f"![inline base64 image]({test_png})"
+            with fakefilefactory(content=text) as draft_f:
+                tree = convert_markdown_to_html(
+                    draft_f,
+                    filefactory=fakefilefactory,
+                    related_to_html_only=False,
+                )
+            assert tree.subtype == "relative"
+            assert tree.children[0].subtype == "alternative"
+            assert tree.children[1].subtype == "png"
+            written = fakefilefactory.pop()
+            assert tree.children[1].path == written[0]
+            assert b"PNG" in written[1].read()
+
+        @pytest.mark.converter
+        def test_converter_tree_inline_image_base64_related_to_html(
+            self, test_png, fakefilefactory
+        ):
+            text = f"![inline base64 image]({test_png})"
+            with fakefilefactory(content=text) as draft_f:
+                tree = convert_markdown_to_html(
+                    draft_f,
+                    filefactory=fakefilefactory,
+                    related_to_html_only=True,
+                )
+            assert tree.subtype == "alternative"
+            assert tree.children[1].subtype == "relative"
+            assert tree.children[1].children[1].subtype == "png"
+            written = fakefilefactory.pop()
+            assert tree.children[1].children[1].path == written[0]
+            assert b"PNG" in written[1].read()
+
+        @pytest.mark.converter
+        def test_converter_tree_inline_image_cid(
+            self, const1, fakefilefactory
+        ):
+            text = f"![inline base64 image](cid:{const1})"
+            with fakefilefactory(content=text) as draft_f:
+                tree = convert_markdown_to_html(
+                    draft_f,
+                    filefactory=fakefilefactory,
+                    related_to_html_only=False,
+                )
+            assert len(tree.children) == 2
+            assert tree.children[0].cid != const1
+            assert tree.children[0].type != "image"
+            assert tree.children[1].cid != const1
+            assert tree.children[1].type != "image"
+
+        @pytest.fixture
+        def fakefilefactory(self):
+            return FakeFileFactory()
+
+        @pytest.mark.imgcoll
+        def test_inline_image_collection(
+            self, test_png, const1, const2, fakefilefactory
+        ):
+            test_images = {test_png: InlineImageInfo(cid=const1, desc=const2)}
+            relparts = collect_inline_images(
+                test_images, filefactory=fakefilefactory
+            )
+
+            written = fakefilefactory.pop()
+            assert b"PNG" in written[1].read()
+
+            assert relparts[0].subtype == "png"
+            assert relparts[0].path == written[0]
+            assert relparts[0].cid == const1
+            assert const2 in relparts[0].desc
+
+        if _PYNLINER:
+
+            @pytest.mark.styling
+            def test_apply_stylesheet(self):
+                html = "<p>Hello, world!</p>"
+                css = "p { color:red }"
+                out = apply_styling(html, css)
+                assert 'p style="color' in out
+
+            @pytest.mark.styling
+            def test_apply_no_stylesheet(self, const1):
+                out = apply_styling(const1, None)
+
+            @pytest.mark.massage
+            @pytest.mark.styling
+            def test_massage_styling_to_converter(self):
+                css = "p { color:red }"
+                css_applied = []
+
+                def converter(draft_f, css_f, **kwargs):
+                    css = css_f.read()
+                    css_applied.append(css)
+                    return Part("text", "plain", draft_f.path, orig=True)
+
+                with (
+                    File() as draft_f,
+                    File(mode="w") as cmd_f,
+                    File(content=css) as css_f,
+                ):
+                    do_massage(
+                        draft_f=draft_f,
+                        cmd_f=cmd_f,
+                        css_f=css_f,
+                        converter=converter,
+                    )
+                assert css_applied[0] == css
+
+            @pytest.mark.converter
+            @pytest.mark.styling
+            def test_converter_apply_styles(
+                self, const1, monkeypatch, fakepath, fakefilefactory
+            ):
+                css = "p { color:red }"
+                with (
+                    monkeypatch.context() as m,
+                    fakefilefactory(fakepath, content=const1) as draft_f,
+                    fakefilefactory(content=css) as css_f,
+                ):
+                    m.setattr(
+                        markdown.Markdown,
+                        "convert",
+                        lambda s, t: f"<p>{t}</p>",
+                    )
+                    convert_markdown_to_html(
+                        draft_f, css_f=css_f, filefactory=fakefilefactory
+                    )
+                assert re.search(
+                    r"color:.*red",
+                    fakefilefactory[fakepath.with_suffix(".html")].read(),
+                )
+
+        if _PYGMENTS_CSS:
+
+            @pytest.mark.styling
+            def test_apply_stylesheet_pygments(self):
+                html = (
+                    f'<div class="{_CODEHILITE_CLASS}">'
+                    "<pre>def foo():\n    return</pre></div>"
+                )
+                out = apply_styling(html, _PYGMENTS_CSS)
+                assert f'{_CODEHILITE_CLASS}" style="' in out
+
+        @pytest.mark.sig
+        def test_signature_extraction_no_signature(self, const1):
+            assert (const1, None, None) == extract_signature(const1)
+
+        @pytest.mark.sig
+        def test_signature_extraction_just_text(self, const1, const2):
+            origtext, textsig, htmlsig = extract_signature(
+                f"{const1}{EMAIL_SIG_SEP}{const2}"
+            )
+            assert origtext == const1
+            assert textsig == const2
+            assert htmlsig is None
+
+        @pytest.mark.sig
+        def test_signature_extraction_html(
+            self, fakepath, fakefilefactory, const1, const2
+        ):
+            sigconst = "HTML signature from {path} but as a string"
+            sig = f'<div id="signature">{sigconst.format(path=fakepath)}</div>'
+
+            sig_f = fakefilefactory(fakepath, content=sig)
+
+            origtext, textsig, htmlsig = extract_signature(
+                f"{const1}{EMAIL_SIG_SEP}{HTML_SIG_MARKER} {fakepath}\n{const2}",
+                filefactory=fakefilefactory,
+            )
+            assert origtext == const1
+            assert textsig == const2
+            assert htmlsig == sigconst.format(path=fakepath)
+
+        @pytest.mark.sig
+        def test_signature_extraction_file_not_found(self, fakepath, const1):
+            with pytest.raises(FileNotFoundError):
+                origtext, textsig, htmlsig = extract_signature(
+                    f"{const1}{EMAIL_SIG_SEP}{HTML_SIG_MARKER}{fakepath}\n{const1}"
+                )
+
+        @pytest.mark.imgproc
+        def test_image_registry(self, const1):
+            reg = ImageRegistry()
+            cid = reg.register(const1)
+            assert "@" in cid
+            assert not cid.startswith("<")
+            assert not cid.endswith(">")
+            assert const1 in reg
+
+        @pytest.mark.imgproc
+        def test_image_registry_domain(self, const1, const2):
+            reg = ImageRegistry()
+            cid = reg.register(const1, domain=const2)
+            assert f"@{const2}" in cid
+            assert not cid.startswith("<")
+            assert not cid.endswith(">")
+            assert const1 in reg
+
+        @pytest.mark.imgproc
+        def test_image_registry_file_uri(self, const1):
+            reg = ImageRegistry()
+            reg.register("/some/path")
+            for path in reg:
+                assert path.startswith("file://")
+                break
+
+        @pytest.mark.converter
+        @pytest.mark.sig
+        def test_converter_signature_handling(
+            self, fakepath, fakefilefactory, monkeypatch
+        ):
+            mailparts = (
+                "This is the mail body\n",
+                f"{EMAIL_SIG_SEP}",
+                "This is a plain-text signature only",
+            )
+
+            with (
+                fakefilefactory(
+                    fakepath, content="".join(mailparts)
+                ) as draft_f,
+                monkeypatch.context() as m,
+            ):
+                m.setattr(markdown.Markdown, "convert", lambda s, t: t)
+                convert_markdown_to_html(draft_f, filefactory=fakefilefactory)
+
+            soup = bs4.BeautifulSoup(
+                fakefilefactory[fakepath.with_suffix(".html")].read(),
+                "html.parser",
+            )
+            body = soup.body.contents
+
+            assert mailparts[0] in body.pop(0)
+
+            sig = soup.select_one("#signature")
+            assert sig == body.pop(0)
+
+            sep = sig.select_one("span.sig_separator")
+            assert sep == sig.contents[0]
+            assert f"\n{sep.text}\n" == EMAIL_SIG_SEP
+
+            assert mailparts[2] in sig.contents[1]
+
+        @pytest.mark.converter
+        @pytest.mark.sig
+        def test_converter_signature_handling_htmlsig(
+            self, fakepath, fakepath2, fakefilefactory, monkeypatch
+        ):
+            mailparts = (
+                "This is the mail body",
+                f"{EMAIL_SIG_SEP}",
+                f"{HTML_SIG_MARKER}{fakepath2}\n",
+                "This is the plain-text version",
+            )
+            htmlsig = "HTML Signature from {path} but as a string"
+            html = f'<div id="signature"><p>{htmlsig.format(path=fakepath2)}</p></div>'
+
+            sig_f = fakefilefactory(fakepath2, content=html)
+
+            def mdwn_fn(t):
+                return t.upper()
+
+            with (
+                fakefilefactory(
+                    fakepath, content="".join(mailparts)
+                ) as draft_f,
+                monkeypatch.context() as m,
+            ):
+                m.setattr(
+                    markdown.Markdown, "convert", lambda s, t: mdwn_fn(t)
+                )
+                convert_markdown_to_html(draft_f, filefactory=fakefilefactory)
+
+            soup = bs4.BeautifulSoup(
+                fakefilefactory[fakepath.with_suffix(".html")].read(),
+                "html.parser",
+            )
+            sig = soup.select_one("#signature")
+            sig.span.extract()
+
+            assert HTML_SIG_MARKER not in sig.text
+            assert htmlsig.format(path=fakepath2) == sig.text.strip()
+
+            plaintext = fakefilefactory[fakepath].read()
+            assert plaintext.endswith(EMAIL_SIG_SEP + mailparts[-1])
+
+        @pytest.mark.converter
+        @pytest.mark.sig
+        def test_converter_signature_handling_htmlsig_with_image(
+            self, fakepath, fakepath2, fakefilefactory, monkeypatch, test_png
+        ):
+            mailparts = (
+                "This is the mail body",
+                f"{EMAIL_SIG_SEP}",
+                f"{HTML_SIG_MARKER}{fakepath2}\n",
+                "This is the plain-text version",
+            )
+            htmlsig = (
+                "HTML Signature from {path} with image\n"
+                f'<img src="{test_png}">\n'
+            )
+            html = (
+                f'<div id="signature">{htmlsig.format(path=fakepath2)}</div>'
+            )
+
+            sig_f = fakefilefactory(fakepath2, content=html)
+
+            def mdwn_fn(t):
+                return t.upper()
+
+            with (
+                fakefilefactory(
+                    fakepath, content="".join(mailparts)
+                ) as draft_f,
+                monkeypatch.context() as m,
+            ):
+                m.setattr(
+                    markdown.Markdown, "convert", lambda s, t: mdwn_fn(t)
+                )
+                convert_markdown_to_html(draft_f, filefactory=fakefilefactory)
+
+            assert fakefilefactory.pop()[0].suffix == ".png"
+
+            soup = bs4.BeautifulSoup(
+                fakefilefactory[fakepath.with_suffix(".html")].read(),
+                "html.parser",
+            )
+            assert soup.img.attrs["src"].startswith("cid:")
+
+        @pytest.mark.converter
+        @pytest.mark.sig
+        def test_converter_signature_handling_textsig_with_image(
+            self, fakepath, fakefilefactory, test_png
+        ):
+            mailparts = (
+                "This is the mail body",
+                f"{EMAIL_SIG_SEP}",
+                "This is the plain-text version with image\n",
+                f"![Inline]({test_png})",
+            )
+            with (
+                fakefilefactory(
+                    fakepath, content="".join(mailparts)
+                ) as draft_f,
+            ):
+                tree = convert_markdown_to_html(
+                    draft_f, filefactory=fakefilefactory
+                )
+
+            assert tree.subtype == "relative"
+            assert tree.children[0].subtype == "alternative"
+            assert tree.children[1].subtype == "png"
+            written = fakefilefactory.pop()
+            assert tree.children[1].path == written[0]
+            assert written[1].read() == request.urlopen(test_png).read()
+
+        @pytest.mark.converter
+        def test_converter_attribution_to_admonition(
+            self, fakepath, fakefilefactory
+        ):
+            mailparts = (
+                "Regarding whatever",
+                "> blockquote line1",
+                "> blockquote line2",
+                "> ",
+                "> new para with **bold** text",
+            )
+            with fakefilefactory(
+                fakepath, content="\n".join(mailparts)
+            ) as draft_f:
+                convert_markdown_to_html(draft_f, filefactory=fakefilefactory)
+
+            soup = bs4.BeautifulSoup(
+                fakefilefactory[fakepath.with_suffix(".html")].read(),
+                "html.parser",
+            )
+            quote = soup.select_one("div.admonition.quote")
+            assert quote
+            assert (
+                soup.select_one("p.admonition-title").extract().text.strip()
+                == mailparts[0]
+            )
+
+            p = quote.p.extract()
+            assert p.text.strip() == "\n".join(p[2:] for p in mailparts[1:3])
+
+            p = quote.p.extract()
+            assert p.contents[1].name == "strong"
+
+        @pytest.mark.converter
+        def test_converter_attribution_to_admonition_with_blockquote(
+            self, fakepath, fakefilefactory
+        ):
+            mailparts = (
+                "Regarding whatever",
+                "> blockquote line1",
+                "> blockquote line2",
+                "> ",
+                "> new para with **bold** text",
+            )
+            with fakefilefactory(
+                fakepath, content="\n".join(mailparts)
+            ) as draft_f:
+                convert_markdown_to_html(draft_f, filefactory=fakefilefactory)
+
+            soup = bs4.BeautifulSoup(
+                fakefilefactory[fakepath.with_suffix(".html")].read(),
+                "html.parser",
+            )
+            quote = soup.select_one("div.admonition.quote")
+            assert quote.blockquote
+
+        @pytest.mark.converter
+        def test_converter_attribution_to_admonition_multiple(
+            self, fakepath, fakefilefactory
+        ):
+            mailparts = (
+                "Regarding whatever",
+                "> blockquote line1",
+                "> blockquote line2",
+                "",
+                "Normal text",
+                "",
+                "> continued emailquote",
+                "",
+                "Another email-quote",
+                "> something",
+            )
+            with fakefilefactory(
+                fakepath, content="\n".join(mailparts)
+            ) as draft_f:
+                convert_markdown_to_html(draft_f, filefactory=fakefilefactory)
+
+            soup = bs4.BeautifulSoup(
+                fakefilefactory[fakepath.with_suffix(".html")].read(),
+                "html.parser",
+            )
+            quote = soup.select_one("div.admonition.quote.continued").extract()
+            assert quote
+            assert (
+                quote.select_one("p.admonition-title").extract().text.strip()
+                == mailparts[0]
+            )
+
+            p = quote.p.extract()
+            assert p
+
+            quote = soup.select_one("div.admonition.quote.continued").extract()
+            assert quote
+            assert (
+                quote.select_one("p.admonition-title").extract().text.strip()
+                == mailparts[-2]
+            )
+
+        @pytest.mark.converter
+        def test_converter_format_flowed_with_nl2br(
+            self, fakepath, fakefilefactory
+        ):
+            mailparts = (
+                "This is format=flowed text ",
+                "with spaces at the end ",
+                "and there ought be no newlines.",
+                "",
+                "[link](https://example.org) ",
+                "and text.",
+                "",
+                "[link text ",
+                "broken up](https://example.org).",
+                "",
+                "This is on a new line with a hard break  ",
+                "due to the double space",
+            )
+            with fakefilefactory(
+                fakepath, content="\n".join(mailparts)
+            ) as draft_f:
+                convert_markdown_to_html(
+                    draft_f, extensions=["nl2br"], filefactory=fakefilefactory
+                )
+
+            soup = bs4.BeautifulSoup(
+                fakefilefactory[fakepath.with_suffix(".html")].read(),
+                "html.parser",
+            )
+            import ipdb
+
+            p = soup.p.extract().text
+            assert "".join(mailparts[0:3]) == p
+            p = ''.join(map(str, soup.p.extract().contents))
+            assert p == '<a href="https://example.org">link</a> and text.'
+            p = ''.join(map(str, soup.p.extract().contents))
+            assert (
+                p == '<a href="https://example.org">link text broken up</a>.'
+            )
+
+        @pytest.mark.fileio
+        def test_file_class_contextmanager(self, const1, monkeypatch):
+            state = dict(o=False, c=False)
+
+            def fn(t):
+                state[t] = True
+
+            with monkeypatch.context() as m:
+                m.setattr(File, "open", lambda s: fn("o"))
+                m.setattr(File, "close", lambda s: fn("c"))
+                with File() as f:
+                    assert state["o"]
+                    assert not state["c"]
+            assert state["c"]
+
+        @pytest.mark.fileio
+        def test_file_class_no_path(self, const1):
+            with File(mode="w+") as f:
+                f.write(const1, cache=False)
+                assert f.read(cache=False) == const1
+
+        @pytest.mark.fileio
+        def test_file_class_path(self, const1, tmp_path):
+            with File(tmp_path / "file", mode="w+") as f:
+                f.write(const1, cache=False)
+                assert f.read(cache=False) == const1
+
+        @pytest.mark.fileio
+        def test_file_class_path_no_exists(self, fakepath):
+            with pytest.raises(FileNotFoundError):
+                File(fakepath, mode="r").open()
+
+        @pytest.mark.fileio
+        def test_file_class_cache(self, tmp_path, const1, const2):
+            path = tmp_path / "file"
+            file = File(path, mode="w+")
+            with file as f:
+                f.write(const1, cache=True)
+            with open(path, mode="w") as f:
+                f.write(const2)
+            with file as f:
+                assert f.read(cache=True) == const1
+
+        @pytest.mark.fileio
+        def test_file_class_cache_init(self, const1):
+            file = File(path=None, mode="r", content=const1)
+            with file as f:
+                assert f.read() == const1
+
+        @pytest.mark.fileio
+        def test_file_class_content_or_path(self, fakepath, const1):
+            with pytest.raises(RuntimeError):
+                file = File(path=fakepath, content=const1)
+
+        @pytest.mark.fileio
+        def test_file_class_content_needs_read(self, const1):
+            with pytest.raises(RuntimeError):
+                file = File(mode="w", content=const1)
+
+        @pytest.mark.fileio
+        def test_file_class_write_persists_close(self, const1):
+            f = File(mode="w+")
+            with f:
+                f.write(const1)
+            with f:
+                assert f.read() == const1
+
+        @pytest.mark.fileio
+        def test_file_class_write_resets_read_cache(self, const1, const2):
+            with File(mode="w+", content=const1) as f:
+                assert f.read() == const1
+                f.write(const2)
+                assert f.read() == const2
+
+        @pytest.mark.fileio
+        def test_file_factory(self):
+            fact = FileFactory()
+            f = fact()
+            assert isinstance(f, File)
+            assert len(fact) == 1
+            assert f in fact
+            assert f == fact[0]
+
+        @pytest.mark.fileio
+        def test_fake_file_factory(self, fakepath, fakefilefactory):
+            fact = FakeFileFactory()
+            f = fakefilefactory(fakepath)
+            assert f.path == fakepath
+            assert f == fakefilefactory[fakepath]
+
+        @pytest.mark.fileio
+        def test_fake_file_factory_path_persistence(
+            self, fakepath, fakefilefactory
+        ):
+            f1 = fakefilefactory(fakepath)
+            assert f1 == fakefilefactory(fakepath)
 
 except ImportError:
     pass