from dataclasses import dataclass, field
from datetime import timedelta
from os import getenv


def _parse_max_age(raw: str) -> timedelta:
    if raw.endswith('s'):
        return timedelta(seconds=int(raw[:-1]))
    if raw.endswith('m'):
        return timedelta(minutes=int(raw[:-1]))
    if raw.endswith('h'):
        return timedelta(hours=int(raw[:-1]))
    if raw.endswith('d'):
        return timedelta(days=int(raw[:-1]))
    return timedelta(seconds=int(raw))


@dataclass(frozen=True)
class Config:
    host: str = '127.0.0.1'
    port: int = 8080
    path_prefix: str = '/'
    memcache_host: str = '127.0.0.1'
    memcache_port: int = 11211
    key_prefix: str | None = None
    digest: str | None = None
    max_age: timedelta = field(default_factory=lambda: timedelta(days=7))

    @staticmethod
    def from_env() -> 'Config':
        def get_int(name: str, default: int) -> int:
            raw = getenv(name)
            return int(raw) if raw is not None else default

        return Config(
            host=getenv('RBCS_HOST', '127.0.0.1'),
            port=get_int('RBCS_PORT', 8080),
            path_prefix=getenv('RBCS_PATH_PREFIX', '/'),
            memcache_host=getenv('RBCS_MEMCACHE_HOST', '127.0.0.1'),
            memcache_port=get_int('RBCS_MEMCACHE_PORT', 11211),
            key_prefix=getenv('RBCS_KEY_PREFIX'),
            digest=getenv('RBCS_DIGEST'),
            max_age=_parse_max_age(getenv('RBCS_MAX_AGE', '7d')),
        )