from dataclasses import dataclass
from datetime import datetime
from operator import attrgetter
from os import path
from pathlib import Path
import re
from typing import Iterator, Optional


def guess_language(filename):
    parent = str(Path(filename).parent)
    if parent == '.':
        return 'fr'
    return parent


def relative_path(*, to, ref):
    # pathlib.Path(x).relative_to(y) cannot handle y not being under x,
    # os.path.dirname('x') yields '' rather than '.'.
    # 😮‍💨
    return path.relpath(to, Path(ref).parent)


_LICENSE_URLS = {
    'CC0': 'https://creativecommons.org/publicdomain/zero',
    'CC BY': 'https://creativecommons.org/licenses/by',
    'CC BY-SA': 'https://creativecommons.org/licenses/by-sa',
}

_LICENSE_RE = re.compile(
    '('+'|'.join(_LICENSE_URLS.keys())+')' + ' ([0-9.]+)'
)

@dataclass
class LicenseInfo:
    tag: str
    version: str

    @classmethod
    def deserialize(cls, info):
        if info is None:
            return None
        return cls(*_LICENSE_RE.fullmatch(info).groups())

    def format(self):
        url = f'{_LICENSE_URLS[self.tag]}/{self.version}/'

        return f'<a href="{url}" target="_blank">{self.tag}</a>'


@dataclass
class Illustration:
    file: str
    alt_text: str
    source_name: str
    source_link: Optional[str]
    license_info: Optional[LicenseInfo]

    @classmethod
    def deserialize(cls, d):
        return cls(d['pic_file'],
                   d['pic_alt'],
                   d['pic_src'],
                   d['pic_link'],
                   LicenseInfo.deserialize(d['pic_license']))


@dataclass
class Concert:
    time: datetime
    place: str
    address: str
    pieces: Iterator[str]
    instructions: str
    illustration: Illustration
    warning: Optional[str]

    @classmethod
    def deserialize(cls, d):
        return cls(
            time=datetime.strptime(d['time'], '%d/%m/%Y %Hh%M'),
            place=d['place'],
            address=d['address'],
            pieces=d['pieces'],
            instructions=d['instructions'],
            illustration=Illustration.deserialize(d),
            warning=d['warning']
        )


def _optional(line):
    return f'(?:{line})?'

_CONCERT_LINES = (
    r'QUAND : (?P<time>[^\n]+)\n',
    r'O[UÙ] : (?P<place>[^\n]+)\n',
    'ADRESSE :\n',
    '(?P<address>.+?)\n',
    'PROGRAMME :\n',
    '(?P<pieces>.+?)\n',
    'INSTRUCTIONS :\n',
    '(?P<instructions>.+?)\n',
    'ILLUSTRATION :\n',
    r'fichier : (?P<pic_file>[^\n]+)\n',
    r'légende : (?P<pic_alt>[^\n]+)\n',
    r'source : (?P<pic_src>[^\n]+)\n',
    _optional(r'lien : (?P<pic_link>[^\n]+)\n'),
    _optional(r'licence : (?P<pic_license>[^\n]+)\n'),
    _optional(r'AVERTISSEMENT : (?P<warning>[^\n]+)\n'),
)

_CONCERT_RE = re.compile(''.join(_CONCERT_LINES), flags=re.DOTALL)


def read_concerts(filename):
    with open(filename) as f:
        concerts = (
            Concert.deserialize(match)
            for match in re.finditer(_CONCERT_RE, f.read())
        )
        return tuple(sorted(concerts, key=attrgetter('time')))