"Misc. utility functions/classes for admin documentation generator."

import re
from email.errors import HeaderParseError
from email.parser import HeaderParser
from inspect import cleandoc

from django.urls import reverse
from django.utils.regex_helper import _lazy_re_compile
from django.utils.safestring import mark_safe

try:
    import docutils.core
    import docutils.nodes
    import docutils.parsers.rst.roles
except ImportError:
    docutils_is_available = False
else:
    docutils_is_available = True


def get_view_name(view_func):
    if hasattr(view_func, "view_class"):
        klass = view_func.view_class
        return f"{klass.__module__}.{klass.__qualname__}"
    mod_name = view_func.__module__
    view_name = getattr(view_func, "__qualname__", view_func.__class__.__name__)
    return mod_name + "." + view_name


def parse_docstring(docstring):
    """
    Parse out the parts of a docstring.  Return (title, body, metadata).
    """
    if not docstring:
        return "", "", {}
    docstring = cleandoc(docstring)
    parts = re.split(r"\n{2,}", docstring)
    title = parts[0]
    if len(parts) == 1:
        body = ""
        metadata = {}
    else:
        parser = HeaderParser()
        try:
            metadata = parser.parsestr(parts[-1])
        except HeaderParseError:
            metadata = {}
            body = "\n\n".join(parts[1:])
        else:
            metadata = dict(metadata.items())
            if metadata:
                body = "\n\n".join(parts[1:-1])
            else:
                body = "\n\n".join(parts[1:])
    return title, body, metadata


def parse_rst(text, default_reference_context, thing_being_parsed=None):
    """
    Convert the string from reST to an XHTML fragment.
    """
    overrides = {
        "doctitle_xform": True,
        "initial_header_level": 3,
        "default_reference_context": default_reference_context,
        "link_base": reverse("django-admindocs-docroot").rstrip("/"),
        "raw_enabled": False,
        "file_insertion_enabled": False,
    }
    thing_being_parsed = thing_being_parsed and "<%s>" % thing_being_parsed
    # Wrap ``text`` in some reST that sets the default role to ``cmsreference``,
    # then restores it.
    source = """
.. default-role:: cmsreference

%s

.. default-role::
"""
    parts = docutils.core.publish_parts(
        source % text,
        source_path=thing_being_parsed,
        destination_path=None,
        writer_name="html",
        settings_overrides=overrides,
    )
    return mark_safe(parts["fragment"])


#
# reST roles
#
ROLES = {
    "model": "%s/models/%s/",
    "view": "%s/views/%s/",
    "template": "%s/templates/%s/",
    "filter": "%s/filters/#%s",
    "tag": "%s/tags/#%s",
}


def create_reference_role(rolename, urlbase):
    def _role(name, rawtext, text, lineno, inliner, options=None, content=None):
        if options is None:
            options = {}
        node = docutils.nodes.reference(
            rawtext,
            text,
            refuri=(
                urlbase
                % (
                    inliner.document.settings.link_base,
                    text.lower(),
                )
            ),
            **options,
        )
        return [node], []

    docutils.parsers.rst.roles.register_canonical_role(rolename, _role)


def default_reference_role(
    name, rawtext, text, lineno, inliner, options=None, content=None
):
    if options is None:
        options = {}
    context = inliner.document.settings.default_reference_context
    node = docutils.nodes.reference(
        rawtext,
        text,
        refuri=(
            ROLES[context]
            % (
                inliner.document.settings.link_base,
                text.lower(),
            )
        ),
        **options,
    )
    return [node], []


if docutils_is_available:
    docutils.parsers.rst.roles.register_canonical_role(
        "cmsreference", default_reference_role
    )

    for name, urlbase in ROLES.items():
        create_reference_role(name, urlbase)

# Match the beginning of a named or unnamed group.
named_group_matcher = _lazy_re_compile(r"\(\?P(<\w+>)")
unnamed_group_matcher = _lazy_re_compile(r"\(")


def replace_named_groups(pattern):
    r"""
    Find named groups in `pattern` and replace them with the group name. E.g.,
    1. ^(?P<a>\w+)/b/(\w+)$ ==> ^<a>/b/(\w+)$
    2. ^(?P<a>\w+)/b/(?P<c>\w+)/$ ==> ^<a>/b/<c>/$
    3. ^(?P<a>\w+)/b/(\w+) ==> ^<a>/b/(\w+)
    4. ^(?P<a>\w+)/b/(?P<c>\w+) ==> ^<a>/b/<c>
    """
    named_group_indices = [
        (m.start(0), m.end(0), m[1]) for m in named_group_matcher.finditer(pattern)
    ]
    # Tuples of (named capture group pattern, group name).
    group_pattern_and_name = []
    # Loop over the groups and their start and end indices.
    for start, end, group_name in named_group_indices:
        # Handle nested parentheses, e.g. '^(?P<a>(x|y))/b'.
        unmatched_open_brackets, prev_char = 1, None
        for idx, val in enumerate(pattern[end:]):
            # Check for unescaped `(` and `)`. They mark the start and end of a
            # nested group.
            if val == "(" and prev_char != "\\":
                unmatched_open_brackets += 1
            elif val == ")" and prev_char != "\\":
                unmatched_open_brackets -= 1
            prev_char = val
            # If brackets are balanced, the end of the string for the current
            # named capture group pattern has been reached.
            if unmatched_open_brackets == 0:
                group_pattern_and_name.append(
                    (pattern[start : end + idx + 1], group_name)
                )
                break

    # Replace the string for named capture groups with their group names.
    for group_pattern, group_name in group_pattern_and_name:
        pattern = pattern.replace(group_pattern, group_name)
    return pattern


def replace_unnamed_groups(pattern):
    r"""
    Find unnamed groups in `pattern` and replace them with '<var>'. E.g.,
    1. ^(?P<a>\w+)/b/(\w+)$ ==> ^(?P<a>\w+)/b/<var>$
    2. ^(?P<a>\w+)/b/((x|y)\w+)$ ==> ^(?P<a>\w+)/b/<var>$
    3. ^(?P<a>\w+)/b/(\w+) ==> ^(?P<a>\w+)/b/<var>
    4. ^(?P<a>\w+)/b/((x|y)\w+) ==> ^(?P<a>\w+)/b/<var>
    """
    unnamed_group_indices = [
        m.start(0) for m in unnamed_group_matcher.finditer(pattern)
    ]
    # Indices of the start of unnamed capture groups.
    group_indices = []
    # Loop over the start indices of the groups.
    for start in unnamed_group_indices:
        # Handle nested parentheses, e.g. '^b/((x|y)\w+)$'.
        unmatched_open_brackets, prev_char = 1, None
        for idx, val in enumerate(pattern[start + 1 :]):
            # Check for unescaped `(` and `)`. They mark the start and end of
            # a nested group.
            if val == "(" and prev_char != "\\":
                unmatched_open_brackets += 1
            elif val == ")" and prev_char != "\\":
                unmatched_open_brackets -= 1
            prev_char = val

            if unmatched_open_brackets == 0:
                group_indices.append((start, start + 2 + idx))
                break
    # Remove unnamed group matches inside other unnamed capture groups.
    group_start_end_indices = []
    prev_end = None
    for start, end in group_indices:
        if prev_end and start > prev_end or not prev_end:
            group_start_end_indices.append((start, end))
        prev_end = end

    if group_start_end_indices:
        # Replace unnamed groups with <var>. Handle the fact that replacing the
        # string between indices will change string length and thus indices
        # will point to the wrong substring if not corrected.
        final_pattern, prev_end = [], None
        for start, end in group_start_end_indices:
            if prev_end:
                final_pattern.append(pattern[prev_end:start])
            final_pattern.append(pattern[:start] + "<var>")
            prev_end = end
        final_pattern.append(pattern[prev_end:])
        return "".join(final_pattern)
    else:
        return pattern