#!/usr/bin/python3
#
# NeoMutt helper script to create multipart/* emails with Markdown → HTML
# alternative conversion, and handling of inline images, using NeoMutt's
# ability to manually craft MIME trees, but automating this process.
#
# 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 \
#       --tempdir $tempdir --extensions $my_mdwn_extensions \
#       --css-file $my_confdir/htmlmail.css |'<enter>\
#       <enter-command> sourc e \$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
#     from a source command when the command exits, and since we need to react
#     to the output, we need to be invoked again, using a $my_ variable to pass
#     information)
#
# Requirements:
#   - python3
#   - python3-markdown
#   - python3-beautifulsoup4
# Optional:
#   - pytest
#   - Pynliner, provides --css-file and thus inline styling of HTML output
#   - Pygments, then syntax highlighting for fenced code is enabled
#
# 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.
#

import sys
import os.path
import pathlib
import markdown
import tempfile
import argparse
import re
import mimetypes
import bs4
import xml.etree.ElementTree as etree
import io
from collections import namedtuple, OrderedDict
from markdown.extensions import Extension
from markdown.blockprocessors import BlockProcessor
from markdown.inlinepatterns import ImageInlineProcessor, IMAGE_LINK_RE
from email.utils import make_msgid
from urllib import request


def parse_cli_args(*args, **kwargs):
    parser = argparse.ArgumentParser(
        description=(
            "NeoMutt helper to turn text/markdown email parts "
            "into full-fledged MIME trees"
        )
    )
    parser.epilog = (
        "Copyright © 2023 martin f. krafft <madduck@madduck.net>.\n"
        "Released under the MIT licence"
    )

    parser.add_argument(
        "--extensions",
        metavar="EXT[,EXT[,EXT]]",
        type=str,
        default="",
        help="Markdown extension to use (comma-separated list)",
    )

    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="Make related content be sibling to HTML parts only",
    )

    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.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.add_argument(
        "--debug-walk",
        action="store_true",
        help="Turn on debugging to stderr of the MIME tree walk",
    )

    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)"
    )

    massage_p.add_argument(
        "--write-commands-to",
        "-o",
        metavar="FILE",
        dest="cmdpath",
        type=pathlib.Path,
        required=True,
        help="Temporary file path to write commands to",
    )

    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:
    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._rcache = [content] if content else []
        self._wcache = []
        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._rcache = self._wcache

    def _get_rcache(self):
        return (b"" if "b" in self._mode else "").join(self._rcache)

    def _get_wcache(self):
        return (b"" if "b" in self._mode else "").join(self._wcache)

    def _add_to_rcache(self, s):
        self._rcache.append(s)

    def _add_to_wcache(self, s):
        self._wcache.append(s)

    def read(self, *, cache=True):
        if cache and self._rcache:
            return self._get_rcache()

        if not self._file:
            with self as f:
                return f.read(cache=cache)

        self._file.seek(0)
        if cache:
            self._add_to_rcache(self._file.read())
            return self._get_rcache()
        else:
            return self._file.read()

    def write(self, s, *, cache=True):
        if not self._file:
            with self as f:
                return f.write(s, cache=cache)

        self._file.seek(0)
        self._rcache = self._wcache

        if cache:
            self._add_to_wcache(s)

        written = self._file.write(s)
        self._file.flush()
        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):
        # path = str(pathlib.Path(path).expanduser())
        path = os.path.expanduser(path)
        if path.startswith("/"):
            path = f"file://{path}"
        cid = make_msgid()[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:
    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()
    )


# [ QUOTE HANDLING ] ##########################################################


class QuoteToAdmonitionExtension(Extension):
    class EmailQuoteBlockProcessor(BlockProcessor):
        RE = re.compile(r"(?:^|\n)>\s*(.*)")

        def __init__(self, parser):
            super().__init__(parser)
            self._title = None

        def test(self, parent, blocks):
            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")
            self.parser.parseChunk(
                admonition, "\n".join(self.clean(line) for line in quotelines)
            )

        @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.EmailQuoteBlockProcessor(md.parser)
        md.parser.blockprocessors.register(email_quote_proc, "emailquote", 25)


# [ PARTS GENERATION ] ########################################################


class Part(
    namedtuple(
        "Part",
        ["type", "subtype", "path", "desc", "cid", "orig"],
        defaults=[None, None, False],
    )
):
    def __str__(self):
        ret = f"<{self.type}/{self.subtype}>"
        if self.cid:
            ret = f"{ret} cid:{self.cid}"
        if self.orig:
            ret = f"{ret} ORIGINAL"
        return ret


class Multipart(
    namedtuple("Multipart", ["subtype", "children", "desc"], defaults=[None])
):
    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 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"
    )

    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>"


def make_text_mail(text, sig=None):
    return EMAIL_SIG_SEP.join((text, sig)) if sig else text


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)

        sig_input = filefactory(path.expanduser()).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,
):
    # 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(QuoteToAdmonitionExtension())

    draft = draft_f.read()
    origtext, textsig, htmlsig = extract_signature(
        draft, filefactory=filefactory
    )

    (
        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)
            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 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):
            if len(root) > 1:
                root = Multipart("mixed", children=root)
            else:
                root = root[0]

        self._walk(
            root,
            ancestry=[],
            descendents=[],
            visitor_fn=visitor_fn or self._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, 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} ancestry={[s.subtype for s in ancestry]}"
            )

            # 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,
                    ancestry=ancestry,
                    descendents=descendents,
                    visitor_fn=visitor_fn,
                )
            assert ancestry.pop() == node
            sibling_descendents = descendents
            descendents.extend(node.children)

        else:
            self.debugprint(f"{lead}├{node}")
            sibling_descendents = descendents

        if False and ancestry:
            self.debugprint(lead[:-1] + " │")

        if visitor_fn:
            visitor_fn(
                node, ancestry, sibling_descendents, debugprint=self.debugprint
            )

    def debugprint(self, s, **kwargs):
        if self._debug:
            print(s, file=sys.stderr, **kwargs)


# [ RUN MODES ] ###############################################################


class MuttCommands:
    """
    Stupid class to interface writing out Mutt commands. This is quite a hack
    to deal with the fact that Mutt runs "push" commands in reverse order, so
    all of a sudden, things become very complicated when mixing with "real"
    commands.

    Hence we keep two sets of commands, and one set of pushes. Commands are
    added to the first until a push is added, after which commands are added to
    the second set of commands.

    On flush(), the first set is printed, followed by the pushes in reverse,
    and then the second set is printed. All 3 sets are then cleared.
    """

    def __init__(self, out_f=sys.stdout, *, debug=False):
        self._cmd1, self._push, self._cmd2 = [], [], []
        self._out_f = out_f
        self._debug = debug

    def cmd(self, s):
        self.debugprint(s)
        if self._push:
            self._cmd2.append(s)
        else:
            self._cmd1.append(s)

    def push(self, s):
        s = s.replace('"', r"\"")
        s = f'push "{s}"'
        self.debugprint(s)
        self._push.insert(0, s)

    def flush(self):
        print(
            "\n".join(self._cmd1 + self._push + self._cmd2), file=self._out_f
        )
        self._cmd1, self._push, self._cmd2 = [], [], []

    def debugprint(self, s, **kwargs):
        if self._debug:
            print(s, file=sys.stderr, **kwargs)


def do_setup(
    *,
    out_f=sys.stdout,
    temppath=None,
    tempdir=None,
    debug_commands=False,
):
    temppath = temppath or pathlib.Path(
        tempfile.mkstemp(prefix="muttmdwn-", dir=tempdir)[1]
    )
    cmds = MuttCommands(out_f, debug=debug_commands)

    editor = f"{' '.join(sys.argv)} massage --write-commands-to {temppath}"

    cmds.cmd('set my_editor="$editor"')
    cmds.cmd('set my_edit_headers="$edit_headers"')
    cmds.cmd(f'set editor="{editor}"')
    cmds.cmd("unset edit_headers")
    cmds.cmd(f"set my_mdwn_postprocess_cmd_file={temppath}")
    cmds.push("<first-entry><edit-file>")
    cmds.flush()


def do_massage(
    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,
    debug_commands=False,
    debug_walk=False,
):
    # Here's the big picture: we're being invoked as the editor on the email
    # draft, and whatever commands we write to the file given as cmdpath will
    # be run by the second source command in the macro definition.

    # 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(
        draft_f,
        css_f=css_f,
        htmldump_f=htmldump_f,
        related_to_html_only=related_to_html_only,
        tempdir=tempdir,
        extensions=extensions,
    )

    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:
                raise NotImplementedError(
                    f"Handling of multipart/{item.subtype} is not implemented"
                )

            state["pos"] -= n_tags - 1
            state["parts"] += 1

        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']}"
            )

    # -----------------
    # 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("unset my_mdwn_postprocess_cmd_file")
    cmds.flush()


# [ CLI ENTRY ] ###############################################################

if __name__ == "__main__":
    args = parse_cli_args()

    if args.mode is None:
        do_setup(
            tempdir=args.tempdir,
            debug_commands=args.debug_commands,
        )

    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,
                debug_commands=args.debug_commands,
                debug_walk=args.debug_walk,
            )


# [ TESTS ] ###################################################################

try:
    import pytest

    class Tests:
        @pytest.fixture
        def const1(self):
            return "Curvature Vest Usher Dividing+T#iceps Senior"

        @pytest.fixture
        def const2(self):
            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)
            cmds.cmd(const1)
            cmds.cmd(const2)
            cmds.flush()
            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)
            cmds.push(const1)
            cmds.push(const2)
            cmds.flush()
            captured = capsys.readouterr()
            assert (
                captured.out
                == ('"\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)
            lines = ["000", "001", "010", "011", "100", "101", "110", "111"]
            for i in range(2):
                cmds.cmd(lines[4 * i + 0])
                cmds.cmd(lines[4 * i + 1])
                cmds.push(lines[4 * i + 2])
                cmds.push(lines[4 * i + 3])
            cmds.flush()

            captured = capsys.readouterr()
            lines_out = captured.out.splitlines()
            assert lines[0] in lines_out[0]
            assert lines[1] in lines_out[1]
            assert lines[7] in lines_out[2]
            assert lines[6] in lines_out[3]
            assert lines[3] in lines_out[4]
            assert lines[2] in lines_out[5]
            assert lines[4] in lines_out[6]
            assert lines[5] in lines_out[7]

        @pytest.fixture
        def mime_tree_related_to_alternative(self):
            return Multipart(
                "relative",
                children=[
                    Multipart(
                        "alternative",
                        children=[
                            Part(
                                "text",
                                "plain",
                                "part.txt",
                                desc="Plain",
                                orig=True,
                            ),
                            Part("text", "html", "part.html", desc="HTML"),
                        ],
                        desc="Alternative",
                    ),
                    Part(
                        "text", "png", "logo.png", cid="logo.png", desc="Logo"
                    ),
                ],
                desc="Related",
            )

        @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, ancestry, descendents, debugprint):
                items.append((item, len(ancestry), len(descendents)))

            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[3][2] == 2
            assert items[4][0].subtype == "relative"
            assert items[4][1] == 0
            assert items[4][2] == 4

        @pytest.mark.treewalk
        def test_MIMETreeDFWalker_list_to_mixed(self, const1):
            mimetree = MIMETreeDFWalker()
            items = []

            def visitor_fn(item, ancestry, descendents, debugprint):
                items.append(item)

            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, mime_tree_related_to_alternative
        ):
            items = []

            def visitor_fn(item, ancestry, descendents, debugprint):
                items.append(item)

            mimetree = MIMETreeDFWalker(visitor_fn=visitor_fn)
            mimetree.walk(mime_tree_related_to_alternative)
            assert len(items) == 5

        @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 '="$my_editor"' in lines.pop(0)
            assert '="$my_edit_headers"' in lines.pop(0)
            assert "unset my_editor" == lines.pop(0)
            assert "unset my_edit_headers" == lines.pop(0)
            assert "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 "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()[4:-2]

            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()[4:-2]

            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):
            draft_f = fakefilefactory(fakepath, content=const1)
            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
        ):
            draft_f = fakefilefactory(fakepath, content=const1)
            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_f = File(content=css)
                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)

                do_massage(
                    draft_f=File(),
                    cmd_f=File(),
                    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, const1):
            path = pathlib.Path("/does/not/exist")
            with pytest.raises(FileNotFoundError):
                origtext, textsig, htmlsig = extract_signature(
                    f"{const1}{EMAIL_SIG_SEP}{HTML_SIG_MARKER}{path}\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_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_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.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_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