from __future__ import annotations

from dataclasses import dataclass

ReplyToMode = str
REPLY_OFF: ReplyToMode = "off"
REPLY_FIRST: ReplyToMode = "first"
REPLY_ALL: ReplyToMode = "all"
REPLY_BATCHED: ReplyToMode = "batched"
REPLY_MODES = frozenset({REPLY_OFF, REPLY_FIRST, REPLY_ALL, REPLY_BATCHED})


@dataclass
class ReplyConfig:
    mode: ReplyToMode = REPLY_OFF
    thread_only: bool = False

    @classmethod
    def from_config(cls, config: dict) -> ReplyConfig:
        mode = config.get("reply_to_mode", REPLY_OFF)
        if mode not in REPLY_MODES:
            mode = REPLY_OFF
        thread_only = bool(config.get("reply_thread_only", False))
        return cls(mode=mode, thread_only=thread_only)


class ReplyManager:
    def __init__(self, config: dict | None = None):
        self._config = ReplyConfig.from_config(config or {})

    @property
    def mode(self) -> ReplyToMode:
        return self._config.mode

    @property
    def thread_only(self) -> bool:
        return self._config.thread_only

    def reload_config(self, key: str, value) -> None:
        from dataclasses import replace

        if key == "reply_to_mode" and value in REPLY_MODES:
            self._config = replace(self._config, mode=value)

    def should_reply(self, chat_type: str, has_thread: bool = False) -> bool:
        if chat_type == "direct":
            return False

        mode = self._config.mode

        if mode == REPLY_OFF:
            return False
        if mode == REPLY_FIRST and chat_type == "direct":
            return True
        if mode == REPLY_ALL:
            return True
        if mode == REPLY_BATCHED:
            return True

        return False

    def resolve_reply_target(self, chat_id: str, root_id: str | None) -> str | None:
        """返回应该回复到的消息 ID（用作 root_id），None 表示不绑定线程。"""
        if self._config.mode == REPLY_OFF:
            return None

        if self._config.thread_only and root_id:
            return root_id

        if self._config.mode in (REPLY_ALL, REPLY_BATCHED) and root_id:
            return root_id

        return None