#!/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
import os.path
import pathlib
import markdown
import tempfile
import argparse
import re
import mimetypes
import bs4
from collections import namedtuple, OrderedDict
from markdown.extensions import Extension
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",
    )

    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)


# [ IMAGE HANDLING ] ##########################################################


InlineImageInfo = namedtuple(
    "InlineImageInfo", ["cid", "desc"], defaults=[None]
)


class ImageRegistry:
    def __init__(self):
        self._images = OrderedDict()

    def register(self, path, description=None):
        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()
    )


# [ 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 filereader_fn(path, mode="r", **kwargs):
    with open(path, mode, **kwargs) as in_f:
        return in_f.read()


def filewriter_fn(path, content, mode="w", **kwargs):
    with open(path, mode, **kwargs) as out_f:
        out_f.write(content)


def collect_inline_images(
    image_registry, *, tempdir=None, filewriter_fn=filewriter_fn
):
    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])

        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, *, filereader_fn=filereader_fn):
    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 = filereader_fn(path.expanduser())
        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(
    origtext,
    draftpath,
    *,
    related_to_html_only=False,
    css=None,
    filewriter_fn=filewriter_fn,
    filereader_fn=filereader_fn,
    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", {})
    extension_configs["pymdownx.highlight"]["css_class"] = _CODEHILITE_CLASS

    origtext, textsig, htmlsig = extract_signature(
        origtext, filereader_fn=filereader_fn
    )

    (
        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)

    filewriter_fn(draftpath, origtext, encoding="utf-8")
    textpart = Part(
        "text", "plain", draftpath, "Plain-text version", orig=True
    )

    htmltext = make_html_doc(htmltext, htmlsig)
    htmltext = apply_styling(htmltext, css)

    htmlpath = draftpath.with_suffix(".html")
    filewriter_fn(
        htmlpath, htmltext, encoding="utf-8", errors="xmlcharrefreplace"
    )
    htmlpart = Part("text", "html", htmlpath, "HTML version")

    imgparts = collect_inline_images(
        image_registry, tempdir=tempdir, filewriter_fn=filewriter_fn
    )

    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,
    draftpath,
    cmd_f,
    *,
    extensions=None,
    css_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.read(),
        draftpath,
        css=css_f.read() if css_f else None,
        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 open(args.MAILDRAFT, "r") as draft_f, open(
            args.cmdpath, "w"
        ) as cmd_f, open(args.css_file, "r") as css_f:
            do_massage(
                draft_f,
                args.MAILDRAFT,
                cmd_f,
                extensions=args.extensions,
                css_f=css_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
    from io import StringIO

    class Tests:
        @pytest.fixture
        def const1(self):
            return "CONSTANT STRING 1"

        @pytest.fixture
        def const2(self):
            return "CONSTANT STRING 2"

        # 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.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, const1, string_io, capsys):
            def converter(
                drafttext,
                draftpath,
                css,
                related_to_html_only,
                extensions,
                tempdir,
            ):
                return Part("text", "plain", draftpath, orig=True)

            do_massage(
                draft_f=string_io,
                draftpath=const1,
                cmd_f=sys.stdout,
                converter=converter,
            )

            captured = capsys.readouterr()
            lines = captured.out.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, string_io, const1, mime_tree_related_to_alternative, capsys
        ):
            def converter(
                drafttext,
                draftpath,
                css,
                related_to_html_only,
                extensions,
                tempdir,
            ):
                return mime_tree_related_to_alternative

            max_attachments = 5
            do_massage(
                draft_f=string_io,
                draftpath=const1,
                cmd_f=sys.stdout,
                max_other_attachments=max_attachments,
                converter=converter,
            )

            captured = capsys.readouterr()
            lines = captured.out.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.fixture
        def fake_filewriter(self):
            class FileWriter:
                def __init__(self):
                    self._writes = []

                def __call__(self, path, content, mode="w", **kwargs):
                    self._writes.append((path, content))

                def pop(self, index=-1):
                    return self._writes.pop(index)

            return FileWriter()

        @pytest.fixture
        def markdown_non_converter(self, const1, const2):
            return lambda s, text: f"{const1}{text}{const2}"

        @pytest.mark.converter
        def test_converter_tree_basic(self, const1, const2, fake_filewriter):
            path = pathlib.Path(const2)
            tree = convert_markdown_to_html(
                const1, path, filewriter_fn=fake_filewriter
            )

            assert tree.subtype == "alternative"
            assert len(tree.children) == 2
            assert tree.children[0].subtype == "plain"
            assert tree.children[0].path == path
            assert tree.children[0].orig
            assert tree.children[1].subtype == "html"
            assert tree.children[1].path == path.with_suffix(".html")

        def test_converter_writes(
            self,
            const1,
            const2,
            fake_filewriter,
            monkeypatch,
            markdown_non_converter,
        ):
            path = pathlib.Path(const2)

            with monkeypatch.context() as m:
                m.setattr(markdown.Markdown, "convert", markdown_non_converter)
                convert_markdown_to_html(
                    const1, path, filewriter_fn=fake_filewriter
                )

            assert (path, const1) == fake_filewriter.pop(0)
            written = fake_filewriter.pop(0)
            assert path.with_suffix(".html") == written[0]
            assert const1 in written[1]

        @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, const1, fake_filewriter
        ):
            text = f"![inline base64 image]({test_png})"
            path = pathlib.Path(const1)
            tree = convert_markdown_to_html(
                text,
                path,
                filewriter_fn=fake_filewriter,
                related_to_html_only=False,
            )
            assert tree.subtype == "relative"
            assert tree.children[0].subtype == "alternative"
            assert tree.children[1].subtype == "png"
            written = fake_filewriter.pop()
            assert tree.children[1].path == written[0]
            assert written[1] == request.urlopen(test_png).read()

        @pytest.mark.converter
        def test_converter_tree_inline_image_base64_related_to_html(
            self, test_png, const1, fake_filewriter
        ):
            text = f"![inline base64 image]({test_png})"
            path = pathlib.Path(const1)
            tree = convert_markdown_to_html(
                text,
                path,
                filewriter_fn=fake_filewriter,
                related_to_html_only=True,
            )
            assert tree.subtype == "alternative"
            assert tree.children[1].subtype == "relative"
            assert tree.children[1].children[1].subtype == "png"
            written = fake_filewriter.pop()
            assert tree.children[1].children[1].path == written[0]
            assert written[1] == request.urlopen(test_png).read()

        @pytest.mark.converter
        def test_converter_tree_inline_image_cid(
            self, const1, fake_filewriter
        ):
            text = f"![inline base64 image](cid:{const1})"
            path = pathlib.Path(const1)
            tree = convert_markdown_to_html(
                text,
                path,
                filewriter_fn=fake_filewriter,
                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.mark.imgcoll
        def test_inline_image_collection(
            self, test_png, const1, const2, fake_filewriter
        ):
            test_images = {test_png: InlineImageInfo(cid=const1, desc=const2)}
            relparts = collect_inline_images(
                test_images, filewriter_fn=fake_filewriter
            )

            written = fake_filewriter.pop()
            assert b"PNG" in written[1]

            assert relparts[0].subtype == "png"
            assert relparts[0].path == written[0]
            assert relparts[0].cid == const1
            assert relparts[0].desc.endswith(const2)

        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_massage_styling_to_converter(self, string_io, const1):
                css = "p { color:red }"
                css_f = StringIO(css)
                out_f = StringIO()
                css_applied = []

                def converter(
                    drafttext,
                    draftpath,
                    css,
                    related_to_html_only,
                    extensions,
                    tempdir,
                ):
                    css_applied.append(css)
                    return Part("text", "plain", draftpath, orig=True)

                do_massage(
                    draft_f=string_io,
                    draftpath=const1,
                    cmd_f=out_f,
                    css_f=css_f,
                    converter=converter,
                )
                assert css_applied[0] == css

            @pytest.mark.converter
            def test_converter_apply_styles(
                self, const1, fake_filewriter, monkeypatch
            ):
                path = pathlib.Path(const1)
                text = "Hello, world!"
                css = "p { color:red }"
                with monkeypatch.context() as m:
                    m.setattr(
                        markdown.Markdown,
                        "convert",
                        lambda s, t: f"<p>{t}</p>",
                    )
                    convert_markdown_to_html(
                        text, path, css=css, filewriter_fn=fake_filewriter
                    )
                assert "color: red" in fake_filewriter.pop()[1]

        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.massage
        def test_mime_tree_relative_within_alternative(
            self, string_io, const1, capsys, mime_tree_related_to_html
        ):
            def converter(
                drafttext,
                draftpath,
                css,
                related_to_html_only,
                extensions,
                tempdir,
            ):
                return mime_tree_related_to_html

            do_massage(
                draft_f=string_io,
                draftpath=const1,
                cmd_f=sys.stdout,
                converter=converter,
            )

            captured = capsys.readouterr()
            lines = captured.out.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, string_io, const1, capsys
        ):
            def converter(
                drafttext,
                draftpath,
                css,
                related_to_html_only,
                extensions,
                tempdir,
            ):
                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",
                )

            do_massage(
                draft_f=string_io,
                draftpath=const1,
                cmd_f=sys.stdout,
                converter=converter,
            )

            captured = capsys.readouterr()
            lines = captured.out.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.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, const1, const2):
            path = pathlib.Path("somepath")
            sigconst = "HTML signature from {path} but as a string"

            def filereader_fn(path):
                return (
                    f'<div id="signature">{sigconst.format(path=path)}</div>'
                )

            origtext, textsig, htmlsig = extract_signature(
                f"{const1}{EMAIL_SIG_SEP}{HTML_SIG_MARKER} {path}\n{const2}",
                filereader_fn=filereader_fn,
            )
            assert origtext == const1
            assert textsig == const2
            assert htmlsig == sigconst.format(path=path)

        @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, const1, fake_filewriter, monkeypatch
        ):
            path = pathlib.Path(const1)

            mailparts = (
                "This is the mail body\n",
                f"{EMAIL_SIG_SEP}",
                "This is a plain-text signature only",
            )

            def filereader_fn(path):
                return ""

            with monkeypatch.context() as m:
                m.setattr(markdown.Markdown, "convert", lambda s, t: t)
                convert_markdown_to_html(
                    "".join(mailparts),
                    path,
                    filewriter_fn=fake_filewriter,
                    filereader_fn=filereader_fn,
                )

            soup = bs4.BeautifulSoup(fake_filewriter.pop()[1], "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, const1, fake_filewriter, monkeypatch
        ):
            path = pathlib.Path(const1)

            mailparts = (
                "This is the mail body",
                f"{EMAIL_SIG_SEP}",
                f"{HTML_SIG_MARKER}{path}\n",
                "This is the plain-text version",
            )

            htmlsig = "HTML Signature from {path}"

            def filereader_fn(path):
                return f'<div id="signature">{htmlsig.format(path=path)}</div>'

            def mdwn_fn(t):
                return t.upper()

            with monkeypatch.context() as m:
                m.setattr(
                    markdown.Markdown, "convert", lambda s, t: mdwn_fn(t)
                )
                convert_markdown_to_html(
                    "".join(mailparts),
                    path,
                    filewriter_fn=fake_filewriter,
                    filereader_fn=filereader_fn,
                )

            soup = bs4.BeautifulSoup(fake_filewriter.pop()[1], "html.parser")
            sig = soup.select_one("#signature")
            sig.span.extract()

            assert HTML_SIG_MARKER not in sig.text
            assert htmlsig.format(path=path) == sig.text.strip()

            plaintext = fake_filewriter.pop()[1]
            assert plaintext.endswith(EMAIL_SIG_SEP + mailparts[-1])

        @pytest.mark.converter
        @pytest.mark.sig
        def test_converter_signature_handling_htmlsig_with_image(
            self, const1, fake_filewriter, monkeypatch, test_png
        ):
            path = pathlib.Path(const1)

            mailparts = (
                "This is the mail body",
                f"{EMAIL_SIG_SEP}",
                f"{HTML_SIG_MARKER}{path}\n",
                "This is the plain-text version",
            )

            htmlsig = (
                "HTML Signature from {path} with image\n"
                f'<img src="{test_png}">\n'
            )

            def filereader_fn(path):
                return f'<div id="signature">{htmlsig.format(path=path)}</div>'

            def mdwn_fn(t):
                return t.upper()

            with monkeypatch.context() as m:
                m.setattr(
                    markdown.Markdown, "convert", lambda s, t: mdwn_fn(t)
                )
                convert_markdown_to_html(
                    "".join(mailparts),
                    path,
                    filewriter_fn=fake_filewriter,
                    filereader_fn=filereader_fn,
                )

            assert fake_filewriter.pop()[0].suffix == ".png"

            soup = bs4.BeautifulSoup(fake_filewriter.pop()[1], "html.parser")
            assert soup.img.attrs["src"].startswith("cid:")

        @pytest.mark.converter
        @pytest.mark.sig
        def test_converter_signature_handling_textsig_with_image(
            self, const1, fake_filewriter, 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})",

            )
            tree = convert_markdown_to_html
                "".join(mailparts),
                pathlib.Path(const1),
                filewriter_fn=fake_filewriter,
            )

            assert tree.subtype == "relative"
            assert tree.children[0].subtype == "alternative"
            assert tree.children[1].subtype == "png"
            written = fake_filewriter.pop()
            assert tree.children[1].path == written[0]
            assert written[1] == request.urlopen(test_png).read()

        def test_converter_attribution_to_admonition(self, fake_filewriter):


except ImportError:
    pass