"""Per-host circuit breaker.

One 403, 429, 503 or CAPTCHA page opens the breaker for that host for
ELEC_BREAKER_COOLDOWN_HOURS. While it is open the host is not requested at all
and its products are collected from web search results instead. There is no
retry-with-a-different-identity: a block is an answer.
"""
from __future__ import annotations

import threading
import time
from typing import Callable, Dict, Optional, Tuple

from app.infrastructure.settings import ELEC_BREAKER_COOLDOWN_HOURS


class CircuitBreaker:
    def __init__(
        self,
        cooldown_seconds: float = ELEC_BREAKER_COOLDOWN_HOURS * 3600,
        on_trip: Optional[Callable[[str, str, float], None]] = None,
        clock: Callable[[], float] = time.time,
    ) -> None:
        self.cooldown = cooldown_seconds
        self.on_trip = on_trip
        self._clock = clock
        self._open: Dict[str, Tuple[float, str]] = {}
        self._lock = threading.Lock()

    @staticmethod
    def _key(host: str) -> str:
        host = host.lower()
        return host[4:] if host.startswith("www.") else host

    def preload(self, host: str, until_epoch: float, reason: str) -> None:
        """Restore a breaker that was opened in an earlier run (elec.site)."""
        if until_epoch > self._clock():
            with self._lock:
                self._open[self._key(host)] = (until_epoch, reason)

    def trip(self, host: str, reason: str) -> None:
        until = self._clock() + self.cooldown
        with self._lock:
            self._open[self._key(host)] = (until, reason)
        if self.on_trip:
            self.on_trip(self._key(host), reason, until)

    def is_open(self, host: str) -> bool:
        key = self._key(host)
        with self._lock:
            entry = self._open.get(key)
            if not entry:
                return False
            if entry[0] <= self._clock():
                del self._open[key]
                return False
            return True

    def reason(self, host: str) -> Optional[str]:
        entry = self._open.get(self._key(host))
        return entry[1] if entry else None