from __future__ import annotations

from app.exercises.dead_bug.rules import detect_diagonal_extension, is_ready_position
from app.exercises.dead_bug.types import DeadBugMetrics, DeadBugPhase, DeadBugResult

class DeadBugStateMachine:
    """死虫式动作状态机：管理READY/EXTENDING/NEED_RESET/NO_POSE状态转换"""

    def __init__(self, *, extension_confirm_frames: int = 4, reset_confirm_frames: int = 3) -> None:
        """初始化并设置状态转换确认帧数"""
        self.extension_confirm_frames = extension_confirm_frames
        self.reset_confirm_frames = reset_confirm_frames

        self.rep_count = 0
        self.phase = DeadBugPhase.READY
        self.active_side: str | None = None
        self._candidate_side: str | None = None
        self._candidate_frames = 0
        self._reset_frames = 0

    def update(self, metrics: DeadBugMetrics) -> DeadBugResult:
        """根据传入指标更新状态机并返回本次结果"""
        side = detect_diagonal_extension(metrics)
        ready = is_ready_position(metrics)

        if side is None:
            self._candidate_side = None
            self._candidate_frames = 0
        elif side == self._candidate_side:
            self._candidate_frames += 1
        else:
            self._candidate_side = side
            self._candidate_frames = 1

        if self.phase in (DeadBugPhase.READY, DeadBugPhase.NO_POSE):
            if self._candidate_frames >= self.extension_confirm_frames and side is not None:
                self.phase = DeadBugPhase.EXTENDING
                self.active_side = side
                self._reset_frames = 0
        elif self.phase == DeadBugPhase.EXTENDING:
            if side == self.active_side:
                self.phase = DeadBugPhase.NEED_RESET
        elif self.phase == DeadBugPhase.NEED_RESET:
            if ready:
                self._reset_frames += 1
                if self._reset_frames >= self.reset_confirm_frames:
                    self.rep_count += 1
                    self.phase = DeadBugPhase.READY
                    self.active_side = None
                    self._candidate_side = None
                    self._candidate_frames = 0
                    self._reset_frames = 0
            else:
                self._reset_frames = 0

        feedback = list(metrics.feedback)
        if side is None and not ready:
            feedback.append("Extend opposite arm and leg only")
        if ready:
            feedback.append("Ready position")
        elif side == "left_arm_right_leg":
            feedback.append("Left arm + right leg")
        elif side == "right_arm_left_leg":
            feedback.append("Right arm + left leg")

        is_standard = side is not None and not metrics.feedback
        return DeadBugResult(
            rep_count=self.rep_count,
            phase=self.phase,
            side=side,
            is_standard=is_standard,
            feedback=feedback[:3],
            metrics=metrics,
        )