#!/usr/bin/env python3

"""
Fix changelog markdown by wrapping "special links" in brackets,
and by ensuring that lists of special links at the end of a paragraph
are parenthesized and comma-separated.

Ensures that each of these parenthesized links is preceded with
appropriate punctuation, but not followed by a period.

A special link is an MR link (like "!1234"), an issue link (like "#1234"),
or a commit link (like "1234ABCD").
"""

# TODO: When you find yourself inclined to modify this, add more tests!

import re
import sys
from collections.abc import Generator

# Regular expression: Matches a single "special link",
# possibly wrapped in brackets.
#
# There are 3 forms of special link:
#   MR (!1234), issue (#1245), and commit (1234ABCDE)
#
# (Note that in practice, insisting on 7 characters for a commit link
# is enough to ensure that we don't get false positives.)
LINK_RE = re.compile(
    r"""
     # Negative lookbehind assertion: Not preceded by a nonspace.
     (?<!\S)
     (\[?)
         ( \! \d+ | \# \d+ | [\da-fA-F]{7,40} )
     (\]?)
    """,
    re.VERBOSE | re.DOTALL,
)


# Regular expression: matches zero or more "special links" at the end of a
# string, possibly wrapped in parentheses.
TRAILING_LINKS_RE = re.compile(
    r"""
    # Pre-parenthesis punctuation, followed by spaces.
    # (We accept any sentence-ending punctuation, followed optionally
    # by a `)` or `"`, since sentence-ending punctuation can go inside
    # a parenthetical or quotation.)
    ([\.\?\!][\)\"]?)?
    (\s*)

    # Optional opening parenthesis.
    \(?

    ((?:
       \[
           [^\]]+
       \]
       ,? \s*
    )+)

    # Optionally: trailing parenthesis, maybe followed by a bogus period.
    (?: \)  [\ ]* \.? )?
    # Trailing space - typically newlines.
    (\s*)
    $
    """,
    re.VERBOSE | re.DOTALL,
)

# Regular expression: Used to split a list of "special links"
DIVIDER_RE = re.compile(
    r"""
    \[ [^\]]* \]
    """,
    re.VERBOSE | re.DOTALL,
)

# Regular expression: used to match spaces only.
ANY_SPACES = re.compile(
    r"""
    \s+
    """,
    re.VERBOSE | re.DOTALL,
)

# Things that look like links, but are not.
NONLINKS = set(item.lower() for item in ["ed25519"])


def bracket_links(s: str) -> str:
    """
    Wrap all of our the special link expressions expressions found in `s`
    with [brackets].

    >>> bracket_links("Hello world. !123 #456 abcdef12345")
    'Hello world. [!123] [#456] [abcdef12345]'

    >>> bracket_links("https://gitlab.torproject.org/abcdef12345")
    'https://gitlab.torproject.org/abcdef12345'
    """

    def add_brackets(m: re.Match):
        in_brackets = m.group(1) and m.group(3)
        text = m.group(2)
        if not in_brackets and text.lower() in NONLINKS:
            return text
        else:
            return "[{}]".format(text)

    return LINK_RE.sub(add_brackets, s)


def really_changed(s1: str, s2: str) -> bool:
    """
    Return true if s1 and s2 have changes other than in nonempty
    sequences of spaces.
    """
    s1 = ANY_SPACES.subn(" ", s1)[0]
    s2 = ANY_SPACES.subn(" ", s2)[0]
    return s1 != s2


def parenthesize_links(s: str) -> str:
    """
    Ensure that the trailing bracketed special links in `s` are
    wrapped with (parens) and (separated, with, commas).

    Also removes any period-after-parentheses,
    and ensures that there is punctuation before the parentheses.

    >>> parenthesize_links("Hello [!234] world. [!123] [#456] [abcdef12345]")
    'Hello [!234] world. ([!123], [#456], [abcdef12345])'

    >>> parenthesize_links("Hello [!234] world. ([!123] [#456] [abcdef12345])")
    'Hello [!234] world. ([!123], [#456], [abcdef12345])'
    """

    def add_parens_and_commas(m: re.Match):
        punc = m.group(1)
        sp1 = m.group(2)
        links = m.group(3)
        sp2 = m.group(4)

        links = [link.group(0) for link in DIVIDER_RE.finditer(links)]
        if links:
            if not punc:
                punc = "."

            links = "({})".format(", ".join(links))

            return f"{punc}{sp1}{links}{sp2}"
        else:
            return m.group(0)

    outcome = TRAILING_LINKS_RE.subn(add_parens_and_commas, s, 1)[0]
    if really_changed(s, outcome):
        return outcome
    else:
        return s


def paragraphs(s: str) -> Generator[str]:
    r"""
    Divide `s` into "paragraphs".  A paragraph can be indicated by
    a markdown bullet item starting with `- `, or with a blank line
    separating it from other paragraphs.

    >>> s = "a\nb\nc\n\nd\ne\nf"
    >>> list(paragraphs(s))
    ['a\nb\nc\n\n', 'd\ne\nf\n']

    >>> s = "a\n- b.\n- c\nd\n"
    >>> list(paragraphs(s))
    ['a\n', '- b.\n', '- c\n', 'd\n\n']

    """

    cur = []
    graf_type = "none"
    for line in s.split("\n"):
        if line.strip() == "":
            cur.append(line + "\n")
            yield "".join(cur)
            cur = []
            graf_type = "none"

        elif line.startswith("- "):
            if cur:
                yield "".join(cur)
            cur = [line + "\n"]
            graf_type = "list_item"

        elif line.startswith(" "):
            cur.append(line + "\n")

        else:
            if graf_type == "list_item":
                if cur:
                    yield "".join(cur)
                    cur = []
                graf_type = "other"
            cur.append(line + "\n")

    if cur:
        yield "".join(cur)


def process(s: str) -> str:
    """
    Perform all of this script's operations (q.v. toplevel docstring)
    on a given string, and return the result.
    """
    output = []
    # for item in paragraphs(s):
    #    print(parenthesize_links(bracket_links(item)))

    for item in paragraphs(s):
        output.append(parenthesize_links(bracket_links(item)))

    while output[-1] == "\n":
        output = output[:-1]

    return "".join(output)


def run():
    import argparse

    parser = argparse.ArgumentParser(
        prog="format_md_links", description="format markdown links in our changelog"
    )
    parser.add_argument("filename")
    parser.add_argument(
        "--check",
        action="store_true",
        help="check that everything is up-to-date; make no changes",
    )
    args = parser.parse_args()

    text = open(args.filename).read()
    output = process(text)
    if args.check:
        if text == output:
            print("No changes")
        else:
            print("Output would change; re-run without --check to make the changes")
            sys.exit(1)
    else:
        with open(args.filename, "w") as out:
            out.write(output)


if __name__ == "__main__":
    run()