"""Voice and movement guidance with throttling and tracker-aware alerts."""
import time
from config import VOICE_COOLDOWN_SEC, VOICE_SLOPE_DELTA


class GuidanceEngine:
    """Generates movement guidance and throttled voice messages."""

    def __init__(self):
        self._last_voice = ""
        self._last_voice_time = 0.0
        self._last_slope_announced = 0.0

    def compute(self, slope_angle, slope_dir, terrain, obstacles,
                slope_trend="STABLE", new_obstacles=None, closing_obstacles=None):
        """Return guidance dict with movement recommendations and voice string."""
        sa = abs(slope_angle)

        knee_rec = 135 if sa > 20 else 145 if sa > 10 else 155 if sa > 5 else 165

        if sa > 15 or terrain in ("ROCKY", "ROUGH"):
            step, step_len = "SHORT", "30cm"
        elif sa > 5:
            step, step_len = "MEDIUM", "50cm"
        else:
            step, step_len = "NORMAL", "70cm"

        if slope_dir == "UPHILL":
            foot_adj = round(min(25, sa * 0.7), 1)
            lean = "FORWARD"
        elif slope_dir == "DOWNHILL":
            foot_adj = round(-min(20, sa * 0.6), 1)
            lean = "BACKWARD"
        else:
            foot_adj, lean = 0.0, "UPRIGHT"

        near_obs = [o for o in obstacles if o['proximity'] > 0.6]
        risk_score = min(100, int(sa * 1.5 + len(near_obs) * 20 +
                                  (15 if terrain == "ROCKY" else 0)))

        voice = self._build_voice(
            slope_angle, slope_dir, terrain, obstacles, sa, step,
            near_obs, slope_trend, new_obstacles, closing_obstacles)

        return {
            'knee_rec': knee_rec,
            'step': step,
            'step_len': step_len,
            'foot_adj': foot_adj,
            'lean': lean,
            'risk_score': risk_score,
            'voice': voice,
            'obstacle_warning': self._obstacle_warning(near_obs),
            'slope_trend': slope_trend,
        }

    def _build_voice(self, slope_angle, slope_dir, terrain, obstacles, sa, step,
                     near_obs, slope_trend, new_obstacles, closing_obstacles):
        parts = []

        # Priority 1: NEW obstacles entering scene
        if new_obstacles:
            for ob in new_obstacles[:2]:
                parts.append(f"New {ob['label']} on {ob['direction'].lower()}.")

        # Priority 2: CLOSING obstacles (approaching fast)
        if closing_obstacles:
            for ob in closing_obstacles[:2]:
                if ob['direction'] == "CENTER":
                    parts.append(f"{ob['label']} approaching ahead!")
                else:
                    opp = "right" if ob['direction'] == "LEFT" else "left"
                    parts.append(f"{ob['label']} closing from {ob['direction'].lower()}. Move {opp}.")

        # Priority 3: Already-near obstacles
        if not closing_obstacles:
            for ob in near_obs[:2]:
                if ob['direction'] == "CENTER":
                    parts.append(f"{ob['label']} ahead! Stop.")
                else:
                    opp = "right" if ob['direction'] == "LEFT" else "left"
                    parts.append(f"{ob['label']} on {ob['direction'].lower()}. Move {opp}.")

        # Priority 4: Slope trend changes
        if slope_trend == "STEEPENING" and sa > 5:
            parts.append("Slope increasing. Slow down.")
        elif slope_trend == "FLATTENING" and sa > 3:
            parts.append("Slope easing.")

        # Priority 5: Current slope guidance
        if sa > 3:
            parts.append(f"Slope {slope_angle:+.0f} degrees.")
            if slope_dir == "UPHILL":
                parts.append("Lean forward." if sa > 10 else "Slight forward lean.")
            else:
                parts.append("Lean back." if sa > 10 else "Slight backward lean.")

        if sa > 15 or terrain in ("ROCKY", "ROUGH"):
            parts.append("Short steps.")
        elif sa > 5:
            parts.append("Medium steps.")

        if terrain == "ROCKY":
            parts.append("Uneven ground.")
        elif terrain == "ROUGH":
            parts.append("Rough surface.")

        if not parts:
            parts.append("Path clear.")

        return " ".join(parts)

    def _obstacle_warning(self, near_obs):
        if not near_obs:
            return None
        ob = near_obs[0]
        if ob['direction'] == "CENTER":
            return f"{ob['label']} AHEAD — STOP"
        opp = "RIGHT" if ob['direction'] == "LEFT" else "LEFT"
        return f"{ob['label']} on {ob['direction']} — move {opp}"

    def should_speak(self, voice, slope_angle):
        """Throttle: returns True if this message should be spoken aloud."""
        now = time.time()
        # Always speak obstacle warnings immediately
        if any(kw in voice.lower() for kw in ["ahead", "stop", "new ", "closing", "approaching"]):
            self._last_voice = voice
            self._last_voice_time = now
            return True
        # Slope changed significantly
        if abs(slope_angle - self._last_slope_announced) > VOICE_SLOPE_DELTA:
            self._last_slope_announced = slope_angle
            self._last_voice = voice
            self._last_voice_time = now
            return True
        # Cooldown elapsed and message changed
        if now - self._last_voice_time > VOICE_COOLDOWN_SEC and voice != self._last_voice:
            self._last_voice = voice
            self._last_voice_time = now
            return True
        return False