from __future__ import annotations

import enum
import itertools
import json
import logging
import re
import subprocess
import sys
from collections import defaultdict
from dataclasses import dataclass
from functools import lru_cache
from pathlib import Path

BASE_URL = 'https://github.com'
LOCATION_PATH = Path(__file__).parent

logger = logging.getLogger(__name__)


class CommitGroup(enum.Enum):
    UPSTREAM = None
    PRIORITY = 'Important'
    CORE = 'Core'
    EXTRACTOR = 'Extractor'
    DOWNLOADER = 'Downloader'
    POSTPROCESSOR = 'Postprocessor'
    MISC = 'Misc.'

    @classmethod
    @lru_cache
    def commit_lookup(cls):
        return {
            name: group
            for group, names in {
                cls.PRIORITY: {''},
                cls.UPSTREAM: {'upstream'},
                cls.CORE: {
                    'aes',
                    'cache',
                    'compat_utils',
                    'compat',
                    'cookies',
                    'core',
                    'dependencies',
                    'jsinterp',
                    'outtmpl',
                    'plugins',
                    'update',
                    'utils',
                },
                cls.MISC: {
                    'build',
                    'cleanup',
                    'devscripts',
                    'docs',
                    'misc',
                    'test',
                },
                cls.EXTRACTOR: {'extractor', 'extractors'},
                cls.DOWNLOADER: {'downloader'},
                cls.POSTPROCESSOR: {'postprocessor'},
            }.items()
            for name in names
        }

    @classmethod
    def get(cls, value):
        result = cls.commit_lookup().get(value)
        if result:
            logger.debug(f'Mapped {value!r} => {result.name}')
        return result


@dataclass
class Commit:
    hash: str | None
    short: str
    authors: list[str]

    def __str__(self):
        result = f'{self.short!r}'

        if self.hash:
            result += f' ({self.hash[:7]})'

        if self.authors:
            authors = ', '.join(self.authors)
            result += f' by {authors}'

        return result


@dataclass
class CommitInfo:
    details: str | None
    sub_details: tuple[str, ...]
    message: str
    issues: list[str]
    commit: Commit
    fixes: list[Commit]

    def key(self):
        return ((self.details or '').lower(), self.sub_details, self.message)


class Changelog:
    MISC_RE = re.compile(r'(?:^|\b)(?:lint(?:ing)?|misc|format(?:ting)?|fixes)(?:\b|$)', re.IGNORECASE)

    def __init__(self, groups, repo):
        self._groups = groups
        self._repo = repo

    def __str__(self):
        return '\n'.join(self._format_groups(self._groups)).replace('\t', '    ')

    def _format_groups(self, groups):
        for item in CommitGroup:
            group = groups[item]
            if group:
                yield self.format_module(item.value, group)

    def format_module(self, name, group):
        result = f'\n#### {name} changes\n' if name else '\n'
        return result + '\n'.join(self._format_group(group))

    def _format_group(self, group):
        sorted_group = sorted(group, key=CommitInfo.key)
        detail_groups = itertools.groupby(sorted_group, lambda item: (item.details or '').lower())
        for details, items in detail_groups:
            if not details:
                indent = ''
            else:
                yield f'- {details}'
                indent = '\t'

            if details == 'cleanup':
                items, cleanup_misc_items = self._filter_cleanup_misc_items(items)

            sub_detail_groups = itertools.groupby(items, lambda item: item.sub_details)
            for sub_details, entries in sub_detail_groups:
                if not sub_details:
                    for entry in entries:
                        yield f'{indent}- {self.format_single_change(entry)}'
                    continue

                prefix = f'{indent}- {", ".join(sub_details)}'
                entries = list(entries)
                if len(entries) == 1:
                    yield f'{prefix}: {self.format_single_change(entries[0])}'
                    continue

                yield prefix
                for entry in entries:
                    yield f'{indent}\t- {self.format_single_change(entry)}'

            if details == 'cleanup' and cleanup_misc_items:
                yield from self._format_cleanup_misc_sub_group(cleanup_misc_items)

    def _filter_cleanup_misc_items(self, items):
        cleanup_misc_items = defaultdict(list)
        non_misc_items = []
        for item in items:
            if self.MISC_RE.search(item.message):
                cleanup_misc_items[tuple(item.commit.authors)].append(item)
            else:
                non_misc_items.append(item)

        return non_misc_items, cleanup_misc_items

    def _format_cleanup_misc_sub_group(self, group):
        prefix = '\t- Miscellaneous'
        if len(group) == 1:
            yield f'{prefix}: {next(self._format_cleanup_misc_items(group))}'
            return

        yield prefix
        for message in self._format_cleanup_misc_items(group):
            yield f'\t\t- {message}'

    def _format_cleanup_misc_items(self, group):
        for authors, infos in group.items():
            message = ', '.join(
                self._format_message_link(None, info.commit.hash)
                for info in sorted(infos, key=lambda item: item.commit.hash or ''))
            yield f'{message} by {self._format_authors(authors)}'

    def format_single_change(self, info):
        message = self._format_message_link(info.message, info.commit.hash)
        if info.issues:
            message = f'{message} ({self._format_issues(info.issues)})'

        if info.commit.authors:
            message = f'{message} by {self._format_authors(info.commit.authors)}'

        if info.fixes:
            fix_message = ', '.join(f'{self._format_message_link(None, fix.hash)}' for fix in info.fixes)

            authors = sorted({author for fix in info.fixes for author in fix.authors}, key=str.casefold)
            if authors != info.commit.authors:
                fix_message = f'{fix_message} by {self._format_authors(authors)}'

            message = f'{message} (With fixes in {fix_message})'

        return message

    def _format_message_link(self, message, hash):
        assert message or hash, 'Improperly defined commit message or override'
        message = message if message else hash[:7]
        return f'[{message}]({self.repo_url}/commit/{hash})' if hash else message

    def _format_issues(self, issues):
        return ', '.join(f'[#{issue}]({self.repo_url}/issues/{issue})' for issue in issues)

    @staticmethod
    def _format_authors(authors):
        return ', '.join(f'[{author}]({BASE_URL}/{author})' for author in authors)

    @property
    def repo_url(self):
        return f'{BASE_URL}/{self._repo}'


class CommitRange:
    COMMAND = 'git'
    COMMIT_SEPARATOR = '-----'

    AUTHOR_INDICATOR_RE = re.compile(r'Authored by:? ', re.IGNORECASE)
    MESSAGE_RE = re.compile(r'''
        (?:\[
            (?P<prefix>[^\]\/:,]+)
            (?:/(?P<details>[^\]:,]+))?
            (?:[:,](?P<sub_details>[^\]]+))?
        \]\ )?
        (?:`?(?P<sub_details_alt>[^:`]+)`?: )?
        (?P<message>.+?)
        (?:\ \((?P<issues>\#\d+(?:,\ \#\d+)*)\))?
        ''', re.VERBOSE | re.DOTALL)
    EXTRACTOR_INDICATOR_RE = re.compile(r'(?:Fix|Add)\s+Extractors?', re.IGNORECASE)
    FIXES_RE = re.compile(r'(?i:Fix(?:es)?(?:\s+for)?|Revert)\s+([\da-f]{40})')
    UPSTREAM_MERGE_RE = re.compile(r'Update to ytdl-commit-([\da-f]+)')

    def __init__(self, start, end, default_author=None) -> None:
        self._start = start
        self._end = end
        self._commits, self._fixes = self._get_commits_and_fixes(default_author)
        self._commits_added = []

    @classmethod
    def from_single(cls, commitish='HEAD', default_author=None):
        start_commitish = cls.get_prev_tag(commitish)
        end_commitish = cls.get_next_tag(commitish)
        if start_commitish == end_commitish:
            start_commitish = cls.get_prev_tag(f'{commitish}~')
        logger.info(f'Determined range from {commitish!r}: {start_commitish}..{end_commitish}')
        return cls(start_commitish, end_commitish, default_author)

    @classmethod
    def get_prev_tag(cls, commitish):
        command = [cls.COMMAND, 'describe', '--tags', '--abbrev=0', '--exclude=*[^0-9.]*', commitish]
        return subprocess.check_output(command, text=True).strip()

    @classmethod
    def get_next_tag(cls, commitish):
        result = subprocess.run(
            [cls.COMMAND, 'describe', '--contains', '--abbrev=0', commitish],
            stdout=subprocess.PIPE, stderr=subprocess.DEVNULL, text=True)
        if result.returncode:
            return 'HEAD'

        return result.stdout.partition('~')[0].strip()

    def __iter__(self):
        return iter(itertools.chain(self._commits.values(), self._commits_added))

    def __len__(self):
        return len(self._commits) + len(self._commits_added)

    def __contains__(self, commit):
        if isinstance(commit, Commit):
            if not commit.hash:
                return False
            commit = commit.hash

        return commit in self._commits

    def _is_ancestor(self, commitish):
        return bool(subprocess.call(
            [self.COMMAND, 'merge-base', '--is-ancestor', commitish, self._start]))

    def _get_commits_and_fixes(self, default_author):
        result = subprocess.check_output([
            self.COMMAND, 'log', f'--format=%H%n%s%n%b%n{self.COMMIT_SEPARATOR}',
            f'{self._start}..{self._end}'], text=True)

        commits = {}
        fixes = defaultdict(list)
        lines = iter(result.splitlines(False))
        for line in lines:
            commit_hash = line
            short = next(lines)
            skip = short.startswith('Release ') or short == '[version] update'

            authors = [default_author] if default_author else []
            for line in iter(lambda: next(lines), self.COMMIT_SEPARATOR):
                match = self.AUTHOR_INDICATOR_RE.match(line)
                if match:
                    authors = sorted(map(str.strip, line[match.end():].split(',')), key=str.casefold)

            commit = Commit(commit_hash, short, authors)
            if skip:
                logger.debug(f'Skipped commit: {commit}')
                continue

            fix_match = self.FIXES_RE.search(commit.short)
            if fix_match:
                commitish = fix_match.group(1)
                fixes[commitish].append(commit)

            commits[commit.hash] = commit

        for commitish, fix_commits in fixes.items():
            if commitish in commits:
                hashes = ', '.join(commit.hash[:7] for commit in fix_commits)
                logger.info(f'Found fix(es) for {commitish[:7]}: {hashes}')
                for fix_commit in fix_commits:
                    del commits[fix_commit.hash]
            else:
                logger.debug(f'Commit with fixes not in changes: {commitish[:7]}')

        return commits, fixes

    def apply_overrides(self, overrides):
        for override in overrides:
            when = override.get('when')
            if when and when not in self and when != self._start:
                logger.debug(f'Ignored {when!r}, not in commits {self._start!r}')
                continue

            override_hash = override.get('hash')
            if override['action'] == 'add':
                commit = Commit(override.get('hash'), override['short'], override.get('authors') or [])
                logger.info(f'ADD    {commit}')
                self._commits_added.append(commit)

            elif override['action'] == 'remove':
                if override_hash in self._commits:
                    logger.info(f'REMOVE {self._commits[override_hash]}')
                    del self._commits[override_hash]

            elif override['action'] == 'change':
                if override_hash not in self._commits:
                    continue
                commit = Commit(override_hash, override['short'], override['authors'])
                logger.info(f'CHANGE {self._commits[commit.hash]} -> {commit}')
                self._commits[commit.hash] = commit

        self._commits = {key: value for key, value in reversed(self._commits.items())}

    def groups(self):
        groups = defaultdict(list)
        for commit in self:
            upstream_re = self.UPSTREAM_MERGE_RE.match(commit.short)
            if upstream_re:
                commit.short = f'[upstream] Merge up to youtube-dl {upstream_re.group(1)}'

            match = self.MESSAGE_RE.fullmatch(commit.short)
            if not match:
                logger.error(f'Error parsing short commit message: {commit.short!r}')
                continue

            prefix, details, sub_details, sub_details_alt, message, issues = match.groups()
            group = None
            if prefix:
                if prefix == 'priority':
                    prefix, _, details = (details or '').partition('/')
                    logger.debug(f'Priority: {message!r}')
                    group = CommitGroup.PRIORITY

                if not details and prefix:
                    if prefix not in ('core', 'downloader', 'extractor', 'misc', 'postprocessor', 'upstream'):
                        logger.debug(f'Replaced details with {prefix!r}')
                        details = prefix or None

                if details == 'common':
                    details = None

                if details:
                    details = details.strip()

            else:
                group = CommitGroup.CORE

            sub_details = f'{sub_details or ""},{sub_details_alt or ""}'.lower().replace(':', ',')
            sub_details = tuple(filter(None, map(str.strip, sub_details.split(','))))

            issues = [issue.strip()[1:] for issue in issues.split(',')] if issues else []

            if not group:
                group = CommitGroup.get(prefix.lower())
                if not group:
                    if self.EXTRACTOR_INDICATOR_RE.search(commit.short):
                        group = CommitGroup.EXTRACTOR
                    else:
                        group = CommitGroup.POSTPROCESSOR
                    logger.warning(f'Failed to map {commit.short!r}, selected {group.name}')

            commit_info = CommitInfo(
                details, sub_details, message.strip(),
                issues, commit, self._fixes[commit.hash])
            logger.debug(f'Resolved {commit.short!r} to {commit_info!r}')
            groups[group].append(commit_info)

        return groups


def get_new_contributors(contributors_path, commits):
    contributors = set()
    if contributors_path.exists():
        with contributors_path.open() as file:
            for line in filter(None, map(str.strip, file)):
                author, _, _ = line.partition(' (')
                authors = author.split('/')
                contributors.update(map(str.casefold, authors))

    new_contributors = set()
    for commit in commits:
        for author in commit.authors:
            author_folded = author.casefold()
            if author_folded not in contributors:
                contributors.add(author_folded)
                new_contributors.add(author)

    return sorted(new_contributors, key=str.casefold)


if __name__ == '__main__':
    import argparse

    parser = argparse.ArgumentParser(
        description='Create a changelog markdown from a git commit range')
    parser.add_argument(
        'commitish', default='HEAD', nargs='?',
        help='The commitish to create the range from (default: %(default)s)')
    parser.add_argument(
        '-v', '--verbosity', action='count', default=0,
        help='increase verbosity (can be used twice)')
    parser.add_argument(
        '-c', '--contributors', action='store_true',
        help='update CONTRIBUTORS file (default: %(default)s)')
    parser.add_argument(
        '--contributors-path', type=Path, default=LOCATION_PATH.parent / 'CONTRIBUTORS',
        help='path to the CONTRIBUTORS file')
    parser.add_argument(
        '--no-override', action='store_true',
        help='skip override json in commit generation (default: %(default)s)')
    parser.add_argument(
        '--override-path', type=Path, default=LOCATION_PATH / 'changelog_override.json',
        help='path to the changelog_override.json file')
    parser.add_argument(
        '--default-author', default='pukkandan',
        help='the author to use without a author indicator (default: %(default)s)')
    parser.add_argument(
        '--repo', default='yt-dlp/yt-dlp',
        help='the github repository to use for the operations (default: %(default)s)')
    args = parser.parse_args()

    logging.basicConfig(
        datefmt='%Y-%m-%d %H-%M-%S', format='{asctime} | {levelname:<8} | {message}',
        level=logging.WARNING - 10 * args.verbosity, style='{', stream=sys.stderr)

    commits = CommitRange.from_single(args.commitish, args.default_author)

    if not args.no_override:
        if args.override_path.exists():
            with args.override_path.open() as file:
                overrides = json.load(file)
            commits.apply_overrides(overrides)
        else:
            logger.warning(f'File {args.override_path.as_posix()} does not exist')

    logger.info(f'Loaded {len(commits)} commits')

    new_contributors = get_new_contributors(args.contributors_path, commits)
    if new_contributors:
        if args.contributors:
            with args.contributors_path.open('a') as file:
                file.writelines(f'{contributor}\n' for contributor in new_contributors)
        logger.info(f'New contributors: {", ".join(new_contributors)}')

    print(Changelog(commits.groups(), args.repo))