#!/usr/bin/env python

from argparse import ArgumentParser
from datetime import datetime
from importlib import import_module
from io import StringIO
from json import loads
from os import getcwd, listdir, makedirs
from os.path import basename, isdir, join
from subprocess import PIPE, run
from sys import argv, exit, path
from uuid import uuid4

from yaml import safe_load_all


def create(argv):
    prog = basename(argv.pop(0))
    parser = ArgumentParser(
        prog=f'{prog} create',
        description='TODO: description',
        epilog='TODO: epilog',
        add_help=True,
    )

    parser.add_argument(
        '-t',
        '--type',
        choices=('none', 'patch', 'minor', 'major'),
        required=True,
        help='TODO: type',
    )
    parser.add_argument('md', metavar='change-description-markdown', nargs='+')

    args = parser.parse_args(argv)

    if not isdir('.changelog'):
        makedirs('.changelog')
    with open(join('.changelog', f'{uuid4().hex}.md'), 'w') as fh:
        fh.write('---\ntype: ')
        fh.write(args.type)
        fh.write('\n---\n')
        fh.write(' '.join(args.md))


def check(argv):
    if isdir('.changelog'):
        result = run(
            ['git', 'diff', '--name-only', 'origin/main', '.changelog/'],
            check=False,
            stdout=PIPE,
        )
        if not result.returncode and result.stdout != b'':
            exit(0)

    print(
        'PR is missing required changelog file, run ./script/changelog create'
    )
    exit(1)


def _get_current_version(module_name):
    cwd = getcwd()
    path.append(cwd)
    module = import_module(module_name)
    return tuple(int(v) for v in module.__version__.split('.', 2))


class _ChangeMeta:
    _pr_cache = None

    @classmethod
    def get(cls, filepath):
        if cls._pr_cache is None:
            result = run(
                [
                    'gh',
                    'pr',
                    'list',
                    '--base',
                    'main',
                    '--state',
                    'merged',
                    '--limit=50',
                    '--json',
                    'files,mergedAt,number',
                ],
                check=True,
                stdout=PIPE,
            )
            cls._pr_cache = {}
            for pr in loads(result.stdout):
                for file in pr['files']:
                    path = file['path']
                    if path.startswith('.changelog'):
                        cls._pr_cache[path] = (
                            pr['number'],
                            datetime.fromisoformat(pr['mergedAt']).replace(
                                tzinfo=None
                            ),
                        )

        try:
            return cls._pr_cache[filepath]
        except KeyError:
            return None, datetime(year=1970, month=1, day=1)


def _get_changelogs():
    ret = []
    dirname = '.changelog'
    for filename in listdir(dirname):
        if not filename.endswith('.md'):
            continue
        filepath = join(dirname, filename)
        with open(filepath) as fh:
            data, md = safe_load_all(fh)
        pr, time = _ChangeMeta.get(filepath)
        ret.append(
            {
                'type': data.get('type', None),
                'md': md,
                'pr': pr,
                'time': time,
                'ordering': {
                    'major': 0,
                    'minor': 1,
                    'patch': 2,
                    'none': 3,
                    '': 3,
                }[data.get('type', '').lower()],
            }
        )

    ret.sort(key=lambda c: (c['ordering'], c['time']))
    return ret


def _get_new_version(current_version, changelogs):
    try:
        bump_type = changelogs[0]['type']
    except IndexError:
        return None
    new_version = list(current_version)
    if bump_type == 'major':
        new_version[0] += 1
        new_version[1] = 0
        new_version[2] = 0
    elif bump_type == 'minor':
        new_version[1] += 1
        new_version[2] = 0
    else:
        new_version[2] += 1
    return tuple(new_version)


def _format_version(version):
    return '.'.join(str(v) for v in version)


def bump(argv):
    buf = StringIO()

    cwd = getcwd()
    module_name = basename(cwd).replace('-', '_')

    buf.write('## ')
    current_version = _get_current_version(module_name)
    changelogs = _get_changelogs()
    new_version = _get_new_version(current_version, changelogs)
    new_version = _format_version(new_version)
    buf.write(new_version)
    buf.write(' - ')
    buf.write(datetime.now().strftime('%Y-%m-%d'))
    buf.write(' - ')
    buf.write(' '.join(argv[1:]))
    buf.write('\n')

    current_type = None
    for changelog in changelogs:
        md = changelog['md']
        if not md:
            continue

        _type = changelog['type']
        if _type != current_type:
            buf.write('\n')
            buf.write(_type.capitalize())
            buf.write(':\n')
            current_type = _type
        buf.write('* ')
        buf.write(md)

        pr = changelog['pr']
        if pr:
            pr = str(pr)
            buf.write(' [#')
            buf.write(pr)
            buf.write('](https://github.com/octodns/')
            buf.write(module_name)
            buf.write('/pull/')
            buf.write(pr)
            buf.write(')')

        buf.write('\n')

    buf.write('\n')

    with open('CHANGELOG.md') as fh:
        existing = fh.read()

    with open('CHANGELOG.md', 'w') as fh:
        fh.write(buf.getvalue())
        fh.write(existing)

    with open(f'{module_name}/__init__.py') as fh:
        existing = fh.read()

    current_version = _format_version(current_version)
    with open(f'{module_name}/__init__.py', 'w') as fh:
        fh.write(existing.replace(current_version, new_version))


cmds = {'create': create, 'check': check, 'bump': bump}

try:
    cmd = cmds[argv.pop(1).lower()]
except IndexError:
    cmd = None
    print('TODO: command usage (missing)')
    exit(1)
except KeyError:
    cmd = None
    print('TODO: command usage (unknown)')
    exit(1)


cmd(argv)