# -*- coding: utf-8 -*-
"""
装备模型生命周期状态机
─────────────────────────────────────────────────────────────────
LifecycleState  枚举：CREATED / READY / RUNNING / PAUSED /
                      STOPPED / ERROR
LifecycleFSM    有限状态机：管理合法状态转移，非法转移抛出异常
─────────────────────────────────────────────────────────────────
"""

from __future__ import annotations

from enum import Enum
from typing import Dict, Set, Callable, Optional


# ─────────────────────────────────────────────────────────────────
# 生命周期状态枚举
# ─────────────────────────────────────────────────────────────────

class LifecycleState(Enum):
    CREATED = "CREATED"   # 刚创建，参数未就绪
    READY   = "READY"     # 参数就绪，可启动
    RUNNING = "RUNNING"   # 仿真运行中
    PAUSED  = "PAUSED"    # 暂停（可恢复）
    STOPPED = "STOPPED"   # 已停止（不可恢复，需 reset）
    ERROR   = "ERROR"     # 发生错误


# ─────────────────────────────────────────────────────────────────
# 合法状态转移表
# ─────────────────────────────────────────────────────────────────

# { 当前状态 → 可转移到的目标状态集合 }
_TRANSITIONS: Dict[LifecycleState, Set[LifecycleState]] = {
    LifecycleState.CREATED: {
        LifecycleState.READY,
        LifecycleState.ERROR,
    },
    LifecycleState.READY: {
        LifecycleState.RUNNING,
        LifecycleState.ERROR,
    },
    LifecycleState.RUNNING: {
        LifecycleState.PAUSED,
        LifecycleState.STOPPED,
        LifecycleState.ERROR,
        LifecycleState.READY,    # reset 时
    },
    LifecycleState.PAUSED: {
        LifecycleState.RUNNING,
        LifecycleState.STOPPED,
        LifecycleState.ERROR,
        LifecycleState.READY,    # reset 时
    },
    LifecycleState.STOPPED: {
        LifecycleState.READY,    # reset 后可重新启动
        LifecycleState.ERROR,
    },
    LifecycleState.ERROR: {
        LifecycleState.READY,    # 错误恢复后 reset
    },
}


# ─────────────────────────────────────────────────────────────────
# 生命周期有限状态机
# ─────────────────────────────────────────────────────────────────

class LifecycleFSM:
    """
    装备模型生命周期有限状态机

    职责：
      - 维护当前状态
      - 校验状态转移合法性
      - 触发转移回调（on_enter / on_exit）
      - 记录状态历史
    """

    def __init__(
        self,
        initial:     LifecycleState                           = LifecycleState.CREATED,
        on_changed:  Optional[Callable[[str, str], None]]     = None,
    ):
        self._state:   LifecycleState       = initial
        self._history: list                 = [(initial, 0.0)]
        self._on_changed                    = on_changed   # (old, new) 回调

    # ── 属性 ──────────────────────────────────────────────────────

    @property
    def state(self) -> LifecycleState:
        return self._state

    @property
    def history(self) -> list:
        return list(self._history)

    # ── 状态查询 ──────────────────────────────────────────────────

    @property
    def is_running(self) -> bool:
        return self._state == LifecycleState.RUNNING

    @property
    def is_paused(self) -> bool:
        return self._state == LifecycleState.PAUSED

    @property
    def is_stopped(self) -> bool:
        return self._state == LifecycleState.STOPPED

    @property
    def is_ready(self) -> bool:
        return self._state == LifecycleState.READY

    @property
    def is_error(self) -> bool:
        return self._state == LifecycleState.ERROR

    @property
    def can_step(self) -> bool:
        """是否可以执行 step()"""
        return self._state == LifecycleState.RUNNING

    # ── 状态转移 ──────────────────────────────────────────────────

    def transition(
        self,
        target:    LifecycleState,
        timestamp: float = 0.0,
        force:     bool  = False,
    ) -> bool:
        """
        执行状态转移
        :param target:    目标状态
        :param timestamp: 当前仿真时刻（用于历史记录）
        :param force:     True=强制转移（跳过合法性检查，仅内部使用）
        :return:          True=转移成功，False=已在目标状态
        :raises ValueError: 非法状态转移
        """
        if self._state == target:
            return False

        if not force:
            allowed = _TRANSITIONS.get(self._state, set())
            if target not in allowed:
                raise ValueError(
                    f"非法状态转移: {self._state.value} → {target.value}  "
                    f"（允许: {[s.value for s in allowed]}）"
                )

        old_state  = self._state
        self._state = target
        self._history.append((target, timestamp))

        if self._on_changed:
            self._on_changed(old_state.value, target.value)

        return True

    # ── 快捷转移方法 ──────────────────────────────────────────────

    def to_ready(self,   t: float = 0.0) -> bool:
        return self.transition(LifecycleState.READY,   t)

    def to_running(self, t: float = 0.0) -> bool:
        return self.transition(LifecycleState.RUNNING, t)

    def to_paused(self,  t: float = 0.0) -> bool:
        return self.transition(LifecycleState.PAUSED,  t)

    def to_stopped(self, t: float = 0.0) -> bool:
        return self.transition(LifecycleState.STOPPED, t)

    def to_error(self,   t: float = 0.0) -> bool:
        return self.transition(LifecycleState.ERROR,   t, force=True)

    # ── 工具 ──────────────────────────────────────────────────────

    def reset(self, t: float = 0.0) -> bool:
        """强制重置到 READY（任意状态均可）"""
        return self.transition(LifecycleState.READY, t, force=True)

    def __repr__(self) -> str:
        return f"LifecycleFSM(state={self._state.value})"