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buildmimetree.py: handle stylesheets/styling
[etc/neomutt.git] / .config / neomutt / buildmimetree.py
index d0493b362978a4af878e7429c3bd59a318f6d4d1..0dd18828c36f1140b1a5086e1fe6eb53cac11cfe 100755 (executable)
@@ -6,8 +6,10 @@
 #
 # Configuration:
 #   neomuttrc (needs to be a single line):
+#     set my_mdwn_extensions="extra,admonition,codehilite,sane_lists,smarty"
 #     macro compose B "\
-#       <enter-command> source '$my_confdir/buildmimetree.py setup|'<enter>\
+#       <enter-command> source '$my_confdir/buildmimetree.py \
+#       --tempdir $tempdir --extensions $my_mdwn_extensions|'<enter>\
 #       <enter-command> sourc e \$my_mdwn_postprocess_cmd_file<enter>\
 #     " "Convert message into a modern MIME tree with inline images"
 #
@@ -21,8 +23,8 @@
 #   - python3-markdown
 # Optional:
 #   - pytest
-#   - Pynliner
-#   - Pygments, if installed, then syntax highlighting is enabled
+#   - Pynliner, provides --css-file and thus inline styling of HTML output
+#   - Pygments, then syntax highlighting for fenced code is enabled
 #
 # Latest version:
 #   https://git.madduck.net/etc/neomutt.git/blob_plain/HEAD:/.config/neomutt/buildmimetree.py
@@ -36,7 +38,13 @@ import pathlib
 import markdown
 import tempfile
 import argparse
-from collections import namedtuple
+import re
+import mimetypes
+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):
@@ -47,59 +55,64 @@ def parse_cli_args(*args, **kwargs):
         )
     )
     parser.epilog = (
-        "Copyright © 2022 martin f. krafft <madduck@madduck.net>.\n"
+        "Copyright © 2023 martin f. krafft <madduck@madduck.net>.\n"
         "Released under the MIT licence"
     )
 
-    subp = parser.add_subparsers(help="Sub-command parsers", dest="mode")
-    parser_setup = subp.add_parser("setup", help="Setup phase")
-    parser_massage = subp.add_parser("massage", help="Massaging phase")
+    parser.add_argument(
+        "--extensions",
+        type=str,
+        default="",
+        help="Markdown extension to use (comma-separated list)",
+    )
 
-    parser_setup.add_argument(
-        "--debug-commands",
+    if _PYNLINER:
+        parser.add_argument(
+            "--css-file",
+            type=str,
+            default="",
+            help="CSS file to merge with the final HTML",
+        )
+    else:
+        parser.set_defaults(css_file=None)
+
+    parser.add_argument(
+        "--only-build",
         action="store_true",
-        help="Turn on debug logging of commands generated to stderr",
+        help="Only build, don't send the message",
     )
 
-    parser_setup.add_argument(
-        "--extension",
-        "-x",
-        metavar="EXTENSION",
-        dest="extensions",
-        nargs="?",
-        default=[],
-        action="append",
-        help="Markdown extension to add to the list of extensions use",
+    parser.add_argument(
+        "--tempdir",
+        default=None,
+        help="Specify temporary directory to use for attachments",
     )
 
-    parser_massage.add_argument(
+    parser.add_argument(
         "--debug-commands",
         action="store_true",
         help="Turn on debug logging of commands generated to stderr",
     )
 
-    parser_massage.add_argument(
-        "--debug-walk",
-        action="store_true",
-        help="Turn on debugging to stderr of the MIME tree walk",
-    )
-
-    parser_massage.add_argument(
-        "--extensions",
-        metavar="EXTENSIONS",
-        type=str,
-        default="",
-        help="Markdown extension to use (comma-separated list)",
+    subp = parser.add_subparsers(help="Sub-command parsers", dest="mode")
+    massage_p = subp.add_parser(
+        "massage", help="Massaging phase (internal use)"
     )
 
-    parser_massage.add_argument(
+    massage_p.add_argument(
         "--write-commands-to",
         metavar="PATH",
         dest="cmdpath",
         help="Temporary file path to write commands to",
     )
 
-    parser_massage.add_argument(
+    massage_p.add_argument(
+        "--debug-walk",
+        action="store_true",
+        help="Turn on debugging to stderr of the MIME tree walk",
+    )
+
+    massage_p.add_argument(
         "MAILDRAFT",
         nargs="?",
         help="If provided, the script is invoked as editor on the mail draft",
@@ -108,6 +121,110 @@ def parse_cli_args(*args, **kwargs):
     return parser.parse_args(*args, **kwargs)
 
 
+# [ MARKDOWN WRAPPING ] #######################################################
+
+
+InlineImageInfo = namedtuple(
+    "InlineImageInfo", ["cid", "desc"], defaults=[None]
+)
+
+
+class InlineImageExtension(Extension):
+    class RelatedImageInlineProcessor(ImageInlineProcessor):
+        def __init__(self, re, md, ext):
+            super().__init__(re, md)
+            self._ext = ext
+
+        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._ext.get_cid_for_image(el.attrib)
+                    el.attrib["src"] = f"cid:{cid}"
+            return el, start, end
+
+    def __init__(self):
+        super().__init__()
+        self._images = OrderedDict()
+
+    def extendMarkdown(self, md):
+        md.registerExtension(self)
+        inline_image_proc = self.RelatedImageInlineProcessor(
+            IMAGE_LINK_RE, md, self
+        )
+        md.inlinePatterns.register(inline_image_proc, "image_link", 150)
+
+    def get_cid_for_image(self, attrib):
+        msgid = make_msgid()[1:-1]
+        path = attrib["src"]
+        if path.startswith("/"):
+            path = f"file://{path}"
+        self._images[path] = InlineImageInfo(
+            msgid, attrib.get("title", attrib.get("alt"))
+        )
+        return msgid
+
+    def get_images(self):
+        return self._images
+
+
+def markdown_with_inline_image_support(
+    text, *, extensions=None, extension_configs=None
+):
+    inline_image_handler = InlineImageExtension()
+    extensions = extensions or []
+    extensions.append(inline_image_handler)
+    mdwn = markdown.Markdown(
+        extensions=extensions, extension_configs=extension_configs
+    )
+    htmltext = mdwn.convert(text)
+
+    images = inline_image_handler.get_images()
+
+    def replace_image_with_cid(matchobj):
+        for m in (matchobj.group(1), f"file://{matchobj.group(1)}"):
+            if m in images:
+                return f"(cid:{images[m].cid}"
+        return matchobj.group(0)
+
+    text = re.sub(r"\(([^)\s]+)", replace_image_with_cid, text)
+    return text, htmltext, images
+
+
+# [ 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 ] ########################################################
 
 
@@ -134,46 +251,82 @@ class Multipart(
         return f"<multipart/{self.subtype}> children={len(self.children)}"
 
 
-def convert_markdown_to_html(maildraft, *, extensions=None):
-    draftpath = pathlib.Path(maildraft)
+def filewriter_fn(path, content, mode="w", **kwargs):
+    with open(path, mode, **kwargs) as out_f:
+        out_f.write(content)
+
+
+def collect_inline_images(
+    images, *, tempdir=None, filewriter_fn=filewriter_fn
+):
+    relparts = []
+    for path, info in images.items():
+        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")
+
+        relparts.append(
+            Part(
+                *mimetype.split("/"),
+                path,
+                cid=info.cid,
+                desc=f"Image: {info.desc}",
+            )
+        )
+
+    return relparts
+
+
+def convert_markdown_to_html(
+    origtext,
+    draftpath,
+    *,
+    cssfile=None,
+    filewriter_fn=filewriter_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, htmltext, images = markdown_with_inline_image_support(
+        origtext, extensions=extensions, extension_configs=extension_configs
+    )
+
+    filewriter_fn(draftpath, origtext, encoding="utf-8")
     textpart = Part(
         "text", "plain", draftpath, "Plain-text version", orig=True
     )
 
-    with open(draftpath, "r", encoding="utf-8") as textmarkdown:
-        text = textmarkdown.read()
-
-    mdwn = markdown.Markdown(extensions=extensions)
-    html = mdwn.convert(text)
+    htmltext = apply_styling(htmltext, cssfile)
 
     htmlpath = draftpath.with_suffix(".html")
+    filewriter_fn(
+        htmlpath, htmltext, encoding="utf-8", errors="xmlcharrefreplace"
+    )
     htmlpart = Part("text", "html", htmlpath, "HTML version")
 
-    with open(
-        htmlpath, "w", encoding="utf-8", errors="xmlcharrefreplace"
-    ) as texthtml:
-        texthtml.write(html)
-
-    logopart = Part(
-        "image",
-        "png",
-        "/usr/share/doc/neomutt/logo/neomutt-256.png",
-        "Logo",
-        "neomutt-256.png",
+    altpart = Multipart(
+        "alternative", [textpart, htmlpart], "Group of alternative content"
     )
 
-    return Multipart(
-        "relative",
-        [
-            Multipart(
-                "alternative",
-                [textpart, htmlpart],
-                "Group of alternative content",
-            ),
-            logopart,
-        ],
-        "Group of related content",
+    imgparts = collect_inline_images(
+        images, tempdir=tempdir, filewriter_fn=filewriter_fn
     )
+    if imgparts:
+        return Multipart(
+            "relative", [altpart] + imgparts, "Group of related content"
+        )
+    else:
+        return altpart
 
 
 class MIMETreeDFWalker:
@@ -282,17 +435,18 @@ class MuttCommands:
 
 
 def do_setup(
-    extensions=None, *, out_f=sys.stdout, temppath=None, debug_commands=False
+    *,
+    out_f=sys.stdout,
+    temppath=None,
+    tempdir=None,
+    debug_commands=False,
 ):
-    extensions = extensions or []
     temppath = temppath or pathlib.Path(
-        tempfile.mkstemp(prefix="muttmdwn-")[1]
+        tempfile.mkstemp(prefix="muttmdwn-", dir=tempdir)[1]
     )
     cmds = MuttCommands(out_f, debug=debug_commands)
 
-    editor = f"{sys.argv[0]} massage --write-commands-to {temppath}"
-    if extensions:
-        editor = f'{editor} --extensions {",".join(extensions)}'
+    editor = f"{' '.join(sys.argv)} massage --write-commands-to {temppath}"
 
     cmds.cmd('set my_editor="$editor"')
     cmds.cmd('set my_edit_headers="$edit_headers"')
@@ -304,11 +458,15 @@ def do_setup(
 
 
 def do_massage(
-    maildraft,
-    cmdpath,
+    draft_f,
+    draftpath,
+    cmd_f,
     *,
     extensions=None,
+    cssfile=None,
     converter=convert_markdown_to_html,
+    only_build=False,
+    tempdir=None,
     debug_commands=False,
     debug_walk=False,
 ):
@@ -316,95 +474,106 @@ def do_massage(
     # draft, and whatever commands we write to the file given as cmdpath will
     # be run by the second source command in the macro definition.
 
-    with open(cmdpath, "w") as cmd_f:
-        # Let's start by cleaning up what the setup did (see above), i.e. we
-        # restore the $editor and $edit_headers variables, and also unset the
-        # variable used to identify the command file we're currently writing
-        # to.
-        cmds = MuttCommands(cmd_f, debug=debug_commands)
-        cmds.cmd('set editor="$my_editor"')
-        cmds.cmd('set edit_headers="$my_edit_headers"')
-        cmds.cmd("unset my_editor")
-        cmds.cmd("unset my_edit_headers")
-
-        # let's flush those commands, as there'll be a lot of pushes from now
-        # on, which need to be run in reverse order
-        cmds.flush()
-
-        extensions = extensions.split(",") if extensions else []
-        tree = converter(maildraft, extensions=extensions)
-
-        mimetree = MIMETreeDFWalker(debug=args.debug_walk)
-
-        def visitor_fn(item, stack, *, debugprint=None):
-            """
-            Visitor function called for every node (part) of the MIME tree,
-            depth-first, and responsible for telling NeoMutt how to assemble
-            the tree.
-            """
-            if isinstance(item, Part):
-                # We've hit a leaf-node, i.e. an alternative or a related part
-                # with actual content.
-
-                # If the part is not an original part, i.e. doesn't already
-                # exist, we must first add it.
-                if not item.orig:
-                    cmds.push(f"<attach-file>{item.path}<enter>")
-                    cmds.push("<toggle-unlink><toggle-disposition>")
-                    if item.cid:
-                        cmds.push(
-                            f"<edit-content-id>\\Ca\\Ck{item.cid}<enter>"
-                        )
-
-                # If the item (including the original) comes with a
-                # description, then we might just as well update the NeoMutt
-                # tree now:
-                if item.desc:
-                    cmds.push(f"<edit-description>\\Ca\\Ck{item.desc}<enter>")
-
-                # Finally, tag the entry that we just processed, so that when
-                # we're done at this level, as we walk up the stack, the items
-                # to be grouped will already be tagged and ready.
-                cmds.push("<tag-entry>")
-
-            elif isinstance(item, Multipart):
-                # This node has children, but we already visited them (see
-                # above), and so they have been tagged in NeoMutt's compose
-                # window. Now it's just a matter of telling NeoMutt to do the
-                # appropriate grouping:
-                if item.subtype == "alternative":
-                    cmds.push("<group-alternatives>")
-                elif item.subtype == "relative":
-                    cmds.push("<group-related>")
-                elif item.subtype == "multilingual":
-                    cmds.push("<group-multilingual>")
-
-                # Again, if there is a description, we might just as well:
-                if item.desc:
-                    cmds.push(f"<edit-description>\\Ca\\Ck{item.desc}<enter>")
-
-                # Finally, if we're at non-root level, tag the new container,
-                # as it might itself be part of a container, to be processed
-                # one level up:
-                if stack:
-                    cmds.push("<tag-entry>")
+    # Let's start by cleaning up what the setup did (see above), i.e. we
+    # restore the $editor and $edit_headers variables, and also unset the
+    # variable used to identify the command file we're currently writing
+    # to.
+    cmds = MuttCommands(cmd_f, debug=debug_commands)
+    cmds.cmd('set editor="$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()
 
-            else:
-                # We should never get here
-                assert not "is valid part"
+    extensions = extensions.split(",") if extensions else []
+    tree = converter(
+        draft_f.read(),
+        draftpath,
+        cssfile=cssfile,
+        tempdir=tempdir,
+        extensions=extensions,
+    )
 
-        # -----------------
-        # End of visitor_fn
+    mimetree = MIMETreeDFWalker(debug=debug_walk)
 
-        # Let's walk the tree and visit every node with our fancy visitor
-        # function
-        mimetree.walk(tree, visitor_fn=visitor_fn)
+    def visitor_fn(item, stack, *, debugprint=None):
+        """
+        Visitor function called for every node (part) of the MIME tree,
+        depth-first, and responsible for telling NeoMutt how to assemble
+        the tree.
+        """
+        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("<update-encoding>")
+            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>")
+
+            # 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>")
+
+        elif isinstance(item, Multipart):
+            # This node has children, but we already visited them (see
+            # above), and so they have been tagged in NeoMutt's compose
+            # window. Now it's just a matter of telling NeoMutt to do the
+            # appropriate grouping:
+            if item.subtype == "alternative":
+                cmds.push("<group-alternatives>")
+            elif item.subtype in ("relative", "related"):
+                cmds.push("<group-related>")
+            elif item.subtype == "multilingual":
+                cmds.push("<group-multilingual>")
 
-        # Finally, cleanup. Since we're responsible for removing the temporary
-        # file, how's this for a little hack?
-        cmds.cmd(f"source 'rm -f {args.cmdpath}|'")
-        cmds.cmd("unset my_mdwn_postprocess_cmd_file")
-        cmds.flush()
+        else:
+            # We should never get here
+            assert not "is valid part"
+
+        # 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>")
+
+        # Finally, if we're at non-root level, tag the new container,
+        # as it might itself be part of a container, to be processed
+        # one level up:
+        if stack:
+            cmds.push("<tag-entry>")
+
+    # -----------------
+    # 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 ] ###############################################################
@@ -412,23 +581,34 @@ def do_massage(
 if __name__ == "__main__":
     args = parse_cli_args()
 
-    if args.mode == "setup":
-        do_setup(args.extensions, debug_commands=args.debug_commands)
-
-    elif args.mode == "massage":
-        do_massage(
-            args.MAILDRAFT,
-            args.cmdpath,
-            extensions=args.extensions,
+    if args.mode is None:
+        do_setup(
+            tempdir=args.tempdir,
             debug_commands=args.debug_commands,
-            debug_walk=args.debug_walk,
         )
 
+    elif args.mode == "massage":
+        with open(args.MAILDRAFT, "r") as draft_f, open(
+            args.cmdpath, "w"
+        ) as cmd_f:
+            do_massage(
+                draft_f,
+                pathlib.Path(args.MAILDRAFT),
+                cmd_f,
+                extensions=args.extensions,
+                cssfile=args.css_file,
+                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
@@ -488,12 +668,18 @@ try:
         @pytest.fixture
         def basic_mime_tree(self):
             return Multipart(
-                "related",
+                "relative",
                 children=[
                     Multipart(
                         "alternative",
                         children=[
-                            Part("text", "plain", "part.txt", desc="Plain"),
+                            Part(
+                                "text",
+                                "plain",
+                                "part.txt",
+                                desc="Plain",
+                                orig=True,
+                            ),
                             Part("text", "html", "part.html", desc="HTML"),
                         ],
                         desc="Alternative",
@@ -523,12 +709,11 @@ try:
             assert items[2][1] == 1
             assert items[3][0].subtype == "png"
             assert items[3][1] == 1
-            assert items[4][0].subtype == "related"
+            assert items[4][0].subtype == "relative"
             assert items[4][1] == 0
 
         def test_MIMETreeDFWalker_list_to_mixed(self, basic_mime_tree):
             mimetree = MIMETreeDFWalker()
-
             items = []
 
             def visitor_fn(item, stack, debugprint):
@@ -549,26 +734,247 @@ try:
             mimetree.walk(basic_mime_tree)
             assert len(items) == 5
 
-        def test_do_setup_no_extensions(self, const1, capsys):
-            "Assert basics about the setup command output"
-            do_setup(temppath=const1, out_f=sys.stdout)
-            captout = capsys.readouterr()
-            lines = captout.out.splitlines()
-            assert lines[2].endswith(f'{const1}"')
-            assert lines[4].endswith(const1)
-            assert "first-entry" in lines[-1]
-            assert "edit-file" in lines[-1]
-
-        def test_do_setup_extensions(self, const1, const2, capsys):
-            "Assert that extensions are passed to editor"
-            do_setup(
-                temppath=const1, extensions=[const2, const1], out_f=sys.stdout
+        @pytest.fixture
+        def string_io(self, const1, text=None):
+            return StringIO(text or const1)
+
+        def test_do_massage_basic(self, const1, string_io, capsys):
+            def converter(drafttext, draftpath, cssfile, extensions, tempdir):
+                return Part("text", "plain", draftpath, orig=True)
+
+            do_massage(
+                draft_f=string_io,
+                draftpath=const1,
+                cmd_f=sys.stdout,
+                converter=converter,
             )
-            captout = capsys.readouterr()
-            lines = captout.out.splitlines()
-            # assert comma-separated list of extensions passed
-            assert lines[2].endswith(f'{const2},{const1}"')
-            assert lines[4].endswith(const1)
+
+            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 "source 'rm -f " in lines.pop(0)
+            assert "unset my_mdwn_postprocess_cmd_file" == lines.pop(0)
+
+        def test_do_massage_fulltree(
+            self, string_io, const1, basic_mime_tree, capsys
+        ):
+            def converter(drafttext, draftpath, cssfile, extensions, tempdir):
+                return basic_mime_tree
+
+            do_massage(
+                draft_f=string_io,
+                draftpath=const1,
+                cmd_f=sys.stdout,
+                converter=converter,
+            )
+
+            captured = capsys.readouterr()
+            lines = captured.out.splitlines()[4:]
+            assert "send-message" in lines.pop(0)
+            assert "Related" in lines.pop(0)
+            assert "group-related" in lines.pop(0)
+            assert "tag-entry" in lines.pop(0)
+            assert "Logo" in lines.pop(0)
+            assert "content-id" in lines.pop(0)
+            assert "toggle-unlink" in lines.pop(0)
+            assert "logo.png" in lines.pop(0)
+            assert "tag-entry" in lines.pop(0)
+            assert "Alternative" in lines.pop(0)
+            assert "group-alternatives" in lines.pop(0)
+            assert "tag-entry" in lines.pop(0)
+            assert "HTML" in lines.pop(0)
+            assert "toggle-unlink" in lines.pop(0)
+            assert "part.html" in lines.pop(0)
+            assert "tag-entry" in lines.pop(0)
+            assert "Plain" in lines.pop(0)
+            assert "update-encoding" in lines.pop(0)
+            assert len(lines) == 2
+
+        @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}"
+
+        def test_converter_tree_basic(
+            self, const1, const2, fake_filewriter, markdown_non_converter
+        ):
+            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)
+            assert (
+                path.with_suffix(".html"),
+                markdown_non_converter(None, const1),
+            ) == fake_filewriter.pop(0)
+
+        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 = 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
+
+        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 = markdown_with_inline_image_support(text)
+            assert images[imgpath].desc == const1
+
+        def test_markdown_inline_image_processor_alt_to_desc(self, const1):
+            imgpath = "file:///path/to/image.png"
+            text = f"![{const1}]({imgpath})"
+            text, html, images = markdown_with_inline_image_support(text)
+            assert images[imgpath].desc == const1
+
+        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 = markdown_with_inline_image_support(text)
+            assert images[imgpath].desc == const2
+
+        def test_markdown_inline_image_not_external(self):
+            imgpath = "https://path/to/image.png"
+            text = f"![inline image]({imgpath})"
+            text, html, images = markdown_with_inline_image_support(text)
+
+            assert 'src="cid:' not in html
+            assert "](cid:" not in text
+            assert len(images) == 0
+
+        def test_markdown_inline_image_local_file(self):
+            imgpath = "/path/to/image.png"
+            text = f"![inline image]({imgpath})"
+            text, html, images = markdown_with_inline_image_support(text)
+
+            for k, v in images.items():
+                assert k == f"file://{imgpath}"
+                break
+
+        @pytest.fixture
+        def test_png(self):
+            return (
+                "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAE"
+                "AAAABCAAAAAA6fptVAAAACklEQVQI12P4DwABAQEAG7buVgAA"
+            )
+
+        def test_markdown_inline_image_processor_base64(self, test_png):
+            text = f"![1px white inlined]({test_png})"
+            text, html, images = markdown_with_inline_image_support(text)
+
+            assert 'src="cid:' in html
+            assert "](cid:" in text
+            assert len(images) == 1
+            assert test_png in images
+
+        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
+            )
+
+            assert tree.subtype == "relative"
+            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_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)
+
+        def test_apply_stylesheet(self):
+            if _PYNLINER:
+                html = "<p>Hello, world!</p>"
+                css = "p { color:red }"
+                out = apply_styling(html, css)
+                assert 'p style="color' in out
+
+        def test_apply_stylesheet_pygments(self):
+            if _PYGMENTS_CSS:
+                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
+
 
 except ImportError:
     pass