from __future__ import annotations

import hashlib
import time


class InboundDebouncer:
    """入站消息防抖 — 按 channel + thread key 去重。

    防止 Mattermost WebSocket 重复推送导致的多次触发。
    """

    def __init__(self, ttl_ms: int = 1000, max_entries: int = 2000):
        self._ttl_ms = ttl_ms
        self._max_entries = max_entries
        self._entries: dict[str, float] = {}

    def should_process(self, channel_id: str, thread_id: str, content: str) -> bool:
        key = self._build_key(channel_id, thread_id, content)
        now = time.monotonic()

        if key in self._entries:
            if now - self._entries[key] < self._ttl_ms / 1000:
                return False

        self._entries[key] = now
        self._prune(now)
        return True

    def _build_key(self, channel_id: str, thread_id: str, content: str) -> str:
        raw = f"{channel_id}:{thread_id}:{content[:100]}"
        return hashlib.md5(raw.encode()).hexdigest()

    def _prune(self, now: float) -> None:
        if len(self._entries) > self._max_entries:
            cutoff = now - self._ttl_ms / 1000
            self._entries = {k: v for k, v in self._entries.items() if v > cutoff}
            if len(self._entries) > self._max_entries:
                overflow = len(self._entries) - self._max_entries
                keys = sorted(self._entries, key=lambda k: self._entries[k])[:overflow]
                for k in keys:
                    del self._entries[k]

    def clear(self) -> None:
        self._entries.clear()