const MEDIAPIPE_TASKS_VERSION = "0.10.35";
const MEDIAPIPE_TASKS_URLS = [
  `https://cdn.jsdelivr.net/npm/@mediapipe/tasks-vision@${MEDIAPIPE_TASKS_VERSION}/vision_bundle.mjs`,
  `https://cdn.jsdelivr.net/npm/@mediapipe/tasks-vision@${MEDIAPIPE_TASKS_VERSION}`,
  `https://unpkg.com/@mediapipe/tasks-vision@${MEDIAPIPE_TASKS_VERSION}/vision_bundle.mjs`,
];
const MEDIAPIPE_WASM_URL = `https://cdn.jsdelivr.net/npm/@mediapipe/tasks-vision@${MEDIAPIPE_TASKS_VERSION}/wasm`;
const POSE_MODEL_URL =
  "https://storage.googleapis.com/mediapipe-models/pose_landmarker/pose_landmarker_lite/float16/latest/pose_landmarker_lite.task";
const FRAME_INTERVAL_MS = 66;
const GESTURE_COOLDOWN_MS = 420;
const VIDEO_METADATA_TIMEOUT_MS = 900;
const LEFT_WRIST_LAYER_DELTA_Y = 0.05;
const HEAD_TILT_DELTA_Y = 0.035;
const ARM_PATTERN_TERMINAL_TOLERANCE_DEG = 32;
const ARM_PATTERN_UPPER_TOLERANCE_DEG = 34;
const ARM_PATTERN_MIN_SEGMENT = 0.045;
const ARM_PATTERN_MIN_SIDE_REACH = 0.06;
const ARM_PATTERN_MIN_VERTICAL_REACH = 0.055;
const MIN_GESTURE_INTENSITY = 0.45;
const ARM_PATTERN_INTENSITY_SCALE = 5;
const WRIST_LAYER_INTENSITY_SCALE = 9;
const HEAD_TILT_INTENSITY_SCALE = 12;
const ZOOM_CLOSE_WRIST_SPREAD_FACTOR = 1.28;
const ZOOM_SUPPRESS_WRIST_SPREAD_FACTOR = 1.18;
// Trend-based zoom detection. Pose matching is brittle because MediaPipe
// keypoints jitter and the absolute "T-pose" pattern only matches in a
// narrow window. Track frame-to-frame motion instead: if both wrists are
// moving anti-symmetrically along the x axis (one moving outward, the other
// moving outward in the opposite direction), the user's intent is a zoom,
// regardless of where exactly the wrists end up.
const ZOOM_TREND_MIN_WRIST_DELTA = 0.010;
const ZOOM_TREND_HEIGHT_TOLERANCE = 0.18;
const ZOOM_TREND_INTENSITY_SCALE = 14;
const ZOOM_TREND_MIN_INTENSITY = 0.6;
// Left wrist must hang at least this far below the shoulder line for the
// arm to count as "at rest" -- distinguishes a deliberate single right-arm
// rotate from any two-arm or chest-height gesture in flight.
const LEFT_ARM_REST_HANGING_BELOW_SHOULDER = 0.13;
// Sustained pose-hold thresholds for continuous zoom emission while the
// user keeps their arms in a spread / closed pose. Mirror-safe (all checks
// are span-based, not direction-based) so they work regardless of whether
// the camera feed is mirrored.
const ZOOM_HOLD_HEIGHT_TOLERANCE = 0.18;
const ZOOM_HOLD_WRIST_BELOW_SHOULDER_LIMIT = 0.10;
const ZOOM_HOLD_SPREAD_FACTOR = 1.30;
const ZOOM_HOLD_CLOSE_FACTOR = 0.85;
const ZOOM_HOLD_ELBOW_OUT_FACTOR = 0.25;
const CAMERA_CONSTRAINTS = {
  video: {
    facingMode: "user",
    width: { ideal: 1280 },
    height: { ideal: 720 },
  },
  audio: false,
};
const POSE_JOINTS = [
  [0, "nose"],
  [7, "left_ear"],
  [8, "right_ear"],
  [11, "left_shoulder"],
  [12, "right_shoulder"],
  [13, "left_elbow"],
  [14, "right_elbow"],
  [15, "left_wrist"],
  [16, "right_wrist"],
];
const POSE_BONES = [
  ["left_shoulder", "left_elbow"],
  ["left_elbow", "left_wrist"],
  ["right_shoulder", "right_elbow"],
  ["right_elbow", "right_wrist"],
  ["left_shoulder", "right_shoulder"],
];

function nowMs() {
  return Math.round(performance?.now?.() || Date.now());
}

function wallClockMs() {
  return Date.now();
}

function waitForVideoMetadata(video) {
  if (video.videoWidth > 0 && video.videoHeight > 0) {
    return Promise.resolve();
  }
  return new Promise((resolve) => {
    const done = () => resolve();
    video.addEventListener?.("loadedmetadata", done, { once: true });
    video.addEventListener?.("canplay", done, { once: true });
    setTimeout(done, VIDEO_METADATA_TIMEOUT_MS);
  });
}

function getUserMediaErrorMessage(error) {
  if (error?.name === "NotAllowedError" || error?.name === "PermissionDeniedError") {
    return "浏览器摄像头权限被拒绝";
  }
  if (error?.name === "NotFoundError" || error?.name === "DevicesNotFoundError") {
    return "没有找到可用摄像头";
  }
  if (error?.name === "NotReadableError") {
    return "摄像头正被其他程序占用";
  }
  return `浏览器摄像头启动失败: ${error?.message || String(error)}`;
}

function canUseBrowserCamera(mediaDevices) {
  return Boolean(
    mediaDevices &&
      typeof mediaDevices.getUserMedia === "function",
  );
}

function isSecureCameraContext() {
  if (typeof window === "undefined") return false;
  const hostname = window.location?.hostname || "";
  return Boolean(window.isSecureContext || hostname === "localhost" || hostname === "127.0.0.1");
}

function normalizePoseLandmarks(landmarks = []) {
  return POSE_JOINTS.map(([index, id]) => {
    const point = landmarks[index];
    if (!point) return null;
    const x = Number(point.x);
    const y = Number(point.y);
    if (!Number.isFinite(x) || !Number.isFinite(y)) return null;
    return {
      id,
      x: Math.max(0, Math.min(1, x)),
      y: Math.max(0, Math.min(1, y)),
      confidence: Math.max(0, Math.min(1, Number(point.visibility ?? point.presence ?? 1))),
    };
  }).filter(Boolean);
}

function getJoint(joints, id) {
  return joints.find((joint) => joint.id === id) || null;
}

function vectorBetween(start, end) {
  if (!start || !end) return null;
  const dx = end.x - start.x;
  const dy = end.y - start.y;
  return {
    dx,
    dy,
    length: Math.hypot(dx, dy),
  };
}

function vectorAngleDeg(vector) {
  return Math.atan2(vector.dy, vector.dx) * 180 / Math.PI;
}

function normalizeAngleDelta(angle, target) {
  let delta = angle - target;
  while (delta > 180) delta -= 360;
  while (delta < -180) delta += 360;
  return Math.abs(delta);
}

function isAngleNear(angle, target, toleranceDeg) {
  return normalizeAngleDelta(angle, target) <= toleranceDeg;
}

function isHorizontalArm(upperVector) {
  if (!upperVector || upperVector.length < ARM_PATTERN_MIN_SEGMENT) return false;
  const angle = vectorAngleDeg(upperVector);
  return (
    isAngleNear(angle, 0, ARM_PATTERN_UPPER_TOLERANCE_DEG) ||
    isAngleNear(angle, 180, ARM_PATTERN_UPPER_TOLERANCE_DEG)
  );
}

function isTerminalToward(vector, targetAngle) {
  if (!vector || vector.length < ARM_PATTERN_MIN_SEGMENT) return false;
  return isAngleNear(vectorAngleDeg(vector), targetAngle, ARM_PATTERN_TERMINAL_TOLERANCE_DEG);
}

function getRightArmPattern(rightShoulder, rightElbow, rightWrist) {
  const upper = vectorBetween(rightShoulder, rightElbow);
  const terminal = vectorBetween(rightElbow, rightWrist);
  if (!upper || !terminal) return null;
  const intensity = Math.min(1, Math.max(MIN_GESTURE_INTENSITY, terminal.length * ARM_PATTERN_INTENSITY_SCALE));

  if (isTerminalToward(terminal, 180) && rightWrist.x < rightShoulder.x - ARM_PATTERN_MIN_SIDE_REACH) {
    return { gesture: "rotate_right", confidence: 0.82, intensity };
  }
  if (isTerminalToward(terminal, 0) && rightWrist.x > rightShoulder.x + ARM_PATTERN_MIN_SIDE_REACH) {
    return { gesture: "rotate_left", confidence: 0.82, intensity };
  }
  if (isHorizontalArm(upper) && isTerminalToward(terminal, -90) && rightWrist.y < rightElbow.y - ARM_PATTERN_MIN_VERTICAL_REACH) {
    return { gesture: "rotate_up", confidence: 0.8, intensity };
  }
  if (isHorizontalArm(upper) && isTerminalToward(terminal, 90) && rightWrist.y > rightElbow.y + ARM_PATTERN_MIN_VERTICAL_REACH) {
    return { gesture: "rotate_down", confidence: 0.8, intensity };
  }
  return null;
}

function isZoomCandidatePose(leftShoulder, leftElbow, leftWrist, rightShoulder, rightElbow, rightWrist, shoulderWidth) {
  const wristsApart = Math.abs(rightWrist.x - leftWrist.x);
  const bothHandsOutside =
    leftWrist.x < leftElbow.x - ARM_PATTERN_MIN_SIDE_REACH * 0.25 &&
    leftWrist.x < leftShoulder.x - ARM_PATTERN_MIN_SIDE_REACH * 0.55 &&
    rightWrist.x > rightElbow.x + ARM_PATTERN_MIN_SIDE_REACH * 0.25 &&
    rightWrist.x > rightShoulder.x + ARM_PATTERN_MIN_SIDE_REACH * 0.55;
  const bothElbowsParticipating =
    leftElbow.x <= leftShoulder.x + ARM_PATTERN_MIN_SIDE_REACH &&
    rightElbow.x >= rightShoulder.x - ARM_PATTERN_MIN_SIDE_REACH;
  const handsNearCenter =
    leftElbow.x < leftShoulder.x - ARM_PATTERN_MIN_SIDE_REACH * 0.5 &&
    rightElbow.x > rightShoulder.x + ARM_PATTERN_MIN_SIDE_REACH * 0.5 &&
    leftWrist.x > leftElbow.x &&
    rightWrist.x < rightElbow.x &&
    wristsApart < shoulderWidth * ZOOM_CLOSE_WRIST_SPREAD_FACTOR;
  return (
    (bothHandsOutside && bothElbowsParticipating && wristsApart > shoulderWidth * ZOOM_SUPPRESS_WRIST_SPREAD_FACTOR) ||
    handsNearCenter
  );
}

// The single-arm rotate detector only looks at the right arm and cannot tell
// whether the user is mid-way through a two-arm gesture. Because the right
// wrist crosses its rotate trigger one or two frames before the left wrist
// catches up to the zoom threshold, rotate routinely fires as the user starts
// to spread their arms. Flip the predicate: a deliberate single right-arm
// wave keeps the left wrist clearly hanging at the side, so refuse to emit
// any right-arm rotate unless we can verify the left arm is at rest (wrist
// hanging well below the shoulder AND elbow + wrist sitting near the body).
// Any ambiguous left-arm state -- raised, extending outward, or held at
// chest level -- yields no gesture, letting getZoomHoldPose handle the next
// frame instead.
function isLeftArmAtRest(leftShoulder, leftElbow, leftWrist) {
  const hangingBelowShoulder = leftWrist.y >= leftShoulder.y + LEFT_ARM_REST_HANGING_BELOW_SHOULDER;
  const wristNearBody = leftWrist.x >= leftShoulder.x - ARM_PATTERN_MIN_SIDE_REACH;
  const elbowNearBody = leftElbow.x >= leftShoulder.x - ARM_PATTERN_MIN_SIDE_REACH;
  return hangingBelowShoulder && wristNearBody && elbowNearBody;
}

// Detect a two-arm zoom intent purely from frame-to-frame motion.
// Mirror-safe: measures the change in span between the wrists, not the
// per-wrist x direction. Spreading widens the span and triggers zoom_in
// regardless of whether the camera feed is mirrored; closing shrinks the
// span and triggers zoom_out. Both wrists must be actively moving (each
// crosses the noise floor) to rule out single-arm drift.
function getZoomTrend(leftWrist, rightWrist, previousLeftWrist, previousRightWrist) {
  if (!previousLeftWrist || !previousRightWrist) return null;
  const heightDelta = Math.abs(rightWrist.y - leftWrist.y);
  if (heightDelta > ZOOM_TREND_HEIGHT_TOLERANCE) return null;

  const leftMoved = Math.abs(leftWrist.x - previousLeftWrist.x);
  const rightMoved = Math.abs(rightWrist.x - previousRightWrist.x);
  if (leftMoved < ZOOM_TREND_MIN_WRIST_DELTA || rightMoved < ZOOM_TREND_MIN_WRIST_DELTA) return null;

  const currentSpread = Math.abs(rightWrist.x - leftWrist.x);
  const previousSpread = Math.abs(previousRightWrist.x - previousLeftWrist.x);
  const spreadDelta = currentSpread - previousSpread;
  const minSpreadDelta = ZOOM_TREND_MIN_WRIST_DELTA * 2;
  const combinedSpeed = leftMoved + rightMoved;
  const intensity = Math.min(1, Math.max(ZOOM_TREND_MIN_INTENSITY, combinedSpeed * ZOOM_TREND_INTENSITY_SCALE));

  if (spreadDelta > minSpreadDelta) {
    return { gesture: "zoom_in", confidence: 0.88, intensity };
  }
  if (spreadDelta < -minSpreadDelta) {
    return { gesture: "zoom_out", confidence: 0.86, intensity };
  }
  return null;
}

// Mirror-safe sustained-pose detector. Decides whether the user is currently
// holding a "spread" or "closed" pose so zoom_in / zoom_out can keep firing
// while no motion is happening (trend would otherwise stop emitting).
//   - heightDelta gate rules out one-arm-up-one-arm-down gestures.
//   - wristsRaised gate ensures the wrists are at chest level or above
//     (excludes "hands hanging at the hips" which would coincidentally have
//     a small span).
//   - span > shoulderWidth * 1.30 -> zoom_in (mirror-safe via Math.abs).
//   - closed pose additionally requires both elbows clearly outside the
//     shoulder line (forming a "hug"), distinguishing it from arms relaxed
//     at the body's centerline.
function getZoomHoldPose(
  leftShoulder,
  leftElbow,
  leftWrist,
  rightShoulder,
  rightElbow,
  rightWrist,
  shoulderWidth,
) {
  const heightDelta = Math.abs(rightWrist.y - leftWrist.y);
  if (heightDelta > ZOOM_HOLD_HEIGHT_TOLERANCE) return null;

  const avgShoulderY = (leftShoulder.y + rightShoulder.y) / 2;
  const wristsRaised =
    leftWrist.y <= avgShoulderY + ZOOM_HOLD_WRIST_BELOW_SHOULDER_LIMIT &&
    rightWrist.y <= avgShoulderY + ZOOM_HOLD_WRIST_BELOW_SHOULDER_LIMIT;
  if (!wristsRaised) return null;

  const span = Math.abs(rightWrist.x - leftWrist.x);

  if (span > shoulderWidth * ZOOM_HOLD_SPREAD_FACTOR) {
    return { gesture: "zoom_in", confidence: 0.82, intensity: 0.8 };
  }

  const leftElbowSpread = Math.abs(leftElbow.x - leftShoulder.x);
  const rightElbowSpread = Math.abs(rightElbow.x - rightShoulder.x);
  const elbowsOutward =
    leftElbowSpread > shoulderWidth * ZOOM_HOLD_ELBOW_OUT_FACTOR &&
    rightElbowSpread > shoulderWidth * ZOOM_HOLD_ELBOW_OUT_FACTOR;
  if (elbowsOutward && span < shoulderWidth * ZOOM_HOLD_CLOSE_FACTOR) {
    return { gesture: "zoom_out", confidence: 0.80, intensity: 0.7 };
  }
  return null;
}

function applyPoseLatch(observation, state) {
  if (!state || !observation) return observation;
  if (state.activePatternGesture === observation.gesture) return null;
  state.activePatternGesture = observation.gesture;
  return observation;
}

function recognizeGesture(joints, previousJoints, options = {}) {
  const state = options.state || null;
  const leftEar = getJoint(joints, "left_ear");
  const rightEar = getJoint(joints, "right_ear");
  const leftWrist = getJoint(joints, "left_wrist");
  const rightWrist = getJoint(joints, "right_wrist");
  const leftElbow = getJoint(joints, "left_elbow");
  const rightElbow = getJoint(joints, "right_elbow");
  const leftShoulder = getJoint(joints, "left_shoulder");
  const rightShoulder = getJoint(joints, "right_shoulder");
  const previousLeftWrist = getJoint(previousJoints, "left_wrist");
  const previousRightWrist = getJoint(previousJoints, "right_wrist");
  if (!leftWrist || !rightWrist || !leftElbow || !rightElbow || !leftShoulder || !rightShoulder) return null;

  // Trend-based zoom runs first: anti-symmetric wrist motion expresses
  // the user's intent directly and is far more reliable than waiting for
  // an absolute pose to match. It also bypasses the layer / focus / rotate
  // detectors, which would otherwise intercept mid-spread frames.
  const trend = getZoomTrend(leftWrist, rightWrist, previousLeftWrist, previousRightWrist);
  if (trend) {
    if (state) state.activePatternGesture = trend.gesture;
    return trend;
  }

  const shoulderWidth = Math.max(0.08, Math.abs(rightShoulder.x - leftShoulder.x));
  const leftRaised = leftWrist.y < leftShoulder.y - 0.05;
  const rightRaised = rightWrist.y < rightShoulder.y - 0.05;
  const leftDeltaX = previousLeftWrist ? leftWrist.x - previousLeftWrist.x : 0;
  const leftDeltaY = previousLeftWrist ? leftWrist.y - previousLeftWrist.y : 0;
  const headTiltY = leftEar && rightEar ? rightEar.y - leftEar.y : 0;

  if (!rightRaised && leftRaised && leftDeltaY < -LEFT_WRIST_LAYER_DELTA_Y) {
    return { gesture: "layer_prev", confidence: 0.78, intensity: Math.min(1, Math.abs(leftDeltaY) * WRIST_LAYER_INTENSITY_SCALE) };
  }
  if (!rightRaised && leftRaised && leftDeltaY > LEFT_WRIST_LAYER_DELTA_Y) {
    return { gesture: "layer_next", confidence: 0.78, intensity: Math.min(1, Math.abs(leftDeltaY) * WRIST_LAYER_INTENSITY_SCALE) };
  }

  if (headTiltY < -HEAD_TILT_DELTA_Y) {
    return { gesture: "focus_prev", confidence: 0.78, intensity: Math.min(1, Math.abs(headTiltY) * HEAD_TILT_INTENSITY_SCALE) };
  }
  if (headTiltY > HEAD_TILT_DELTA_Y) {
    return { gesture: "focus_next", confidence: 0.78, intensity: Math.min(1, Math.abs(headTiltY) * HEAD_TILT_INTENSITY_SCALE) };
  }

  // Pose-based zoom hold: while the user sustains a spread (zoom_in) or
  // closed (zoom_out) pose without further motion, keep emitting the same
  // zoom direction every frame. Bypasses the pattern latch so the gesture
  // can fire repeatedly; downstream cooldownMs (120ms) rate-limits to
  // ~8 emissions/sec, which produces smooth continuous zooming on the globe
  // until the user changes their pose. Uses the mirror-safe span detector
  // so it works on non-mirrored camera feeds where the absolute left/right
  // pose checks would otherwise fail.
  const zoomPattern = getZoomHoldPose(
    leftShoulder,
    leftElbow,
    leftWrist,
    rightShoulder,
    rightElbow,
    rightWrist,
    shoulderWidth,
  );
  if (zoomPattern) {
    if (state) state.activePatternGesture = zoomPattern.gesture;
    return zoomPattern;
  }

  // Two safeguards must both hold before a single right-arm rotate fires:
  // (1) zoom is not currently a likely interpretation of the pose,
  // (2) the left arm is verifiably at rest. This kills the right-leads-left
  // race that previously emitted a stray rotate at the start of a spread.
  const rotateAllowed =
    !isZoomCandidatePose(
      leftShoulder,
      leftElbow,
      leftWrist,
      rightShoulder,
      rightElbow,
      rightWrist,
      shoulderWidth,
    ) && isLeftArmAtRest(leftShoulder, leftElbow, leftWrist);
  const rotatePattern = rotateAllowed
    ? getRightArmPattern(rightShoulder, rightElbow, rightWrist)
    : null;
  // Rotate stays latched: one deliberate wave = one rotation step. Without
  // the latch, holding the arm out would spin the globe continuously, which
  // is the opposite of what the user wants for navigation.
  if (rotatePattern) return applyPoseLatch(rotatePattern, state);
  if (state) state.activePatternGesture = null;
  return null;
}

async function createDefaultRecognizer() {
  const { FilesetResolver, PoseLandmarker } = await importMediaPipeTasksVision();
  const vision = await FilesetResolver.forVisionTasks(MEDIAPIPE_WASM_URL);
  const pose = await PoseLandmarker.createFromOptions(vision, {
    baseOptions: {
      modelAssetPath: POSE_MODEL_URL,
      delegate: "GPU",
    },
    runningMode: "VIDEO",
    numPoses: 1,
  });

  return {
    recognize(video, timestampMs) {
      const result = pose.detectForVideo(video, timestampMs);
      const landmarks = result?.landmarks?.[0] || [];
      return normalizePoseLandmarks(landmarks);
    },
    close() {
      pose.close?.();
    },
  };
}

async function importMediaPipeTasksVision() {
  const failures = [];
  for (const moduleUrl of MEDIAPIPE_TASKS_URLS) {
    try {
      const module = await import(moduleUrl);
      if (module?.FilesetResolver && module?.PoseLandmarker) {
        return module;
      }
      failures.push(`${moduleUrl}: missing MediaPipe exports`);
    } catch (error) {
      failures.push(`${moduleUrl}: ${error?.message || String(error)}`);
    }
  }
  const error = new Error("无法加载 MediaPipe Tasks Vision 模块，请检查网络或切换 Motion Agent");
  error.details = failures;
  throw error;
}

export function createBrowserCameraProvider(options = {}) {
  const {
    mediaDevices = typeof navigator !== "undefined" ? navigator.mediaDevices : null,
    recognizerFactory = createDefaultRecognizer,
    requestAnimationFrameFn =
      typeof requestAnimationFrame !== "undefined"
        ? requestAnimationFrame.bind(globalThis)
        : (callback) => setTimeout(() => callback(nowMs()), 16),
    cancelAnimationFrameFn =
      typeof cancelAnimationFrame !== "undefined"
        ? cancelAnimationFrame.bind(globalThis)
        : clearTimeout,
    onMessage = () => {},
    onState = () => {},
    onStatus = () => {},
    onVideoSource = () => {},
  } = options;

  let disposed = false;
  let connected = false;
  let stream = null;
  let video = null;
  let recognizer = null;
  let rafId = null;
  let lastFrameAt = 0;
  let lastGestureAt = 0;
  let seq = 0;
  let previousJoints = [];
  const gestureState = {};

  function emitState(detail = {}) {
    onState({
      provider: "browser_camera",
      connected,
      ...detail,
    });
  }

  function emitStatus(message, type = "info", extra = {}) {
    onStatus(message, type);
    emitState({ message, ...extra });
  }

  function stopStream() {
    onVideoSource({
      provider: "browser_camera",
      source: null,
      active: false,
    });
    if (stream) {
      stream.getTracks?.().forEach((track) => track.stop?.());
      stream = null;
    }
    if (video) {
      video.pause?.();
      video.srcObject = null;
      video.remove?.();
      video = null;
    }
  }

  function emitSkeleton(joints, matchedGesture = null, confidence = 0) {
    onMessage({
      type: "skeleton",
      timestamp_ms: wallClockMs(),
      source: "browser-camera",
      mode: "single",
      camera_id: "browser:getUserMedia",
      matched_gesture: matchedGesture,
      confidence,
      joints,
      bones: POSE_BONES,
    });
  }

  function emitGesture(observation) {
    seq += 1;
    onMessage({
      type: "gesture",
      gesture: observation.gesture,
      phase: "discrete",
      confidence: observation.confidence,
      intensity: observation.intensity,
      timestamp_ms: wallClockMs(),
      seq,
      source: "browser-camera",
      mode: "single",
      payload: {},
    });
  }

  function scheduleFrame() {
    if (disposed) return;
    rafId = requestAnimationFrameFn(processFrame);
  }

  function processFrame(timestamp) {
    if (disposed || !video || !recognizer) return;
    if (timestamp - lastFrameAt < FRAME_INTERVAL_MS) {
      scheduleFrame();
      return;
    }
    lastFrameAt = timestamp;

    try {
      const joints = recognizer.recognize(video, timestamp) || [];
      const currentWallMs = wallClockMs();
      const observation = recognizeGesture(joints, previousJoints, {
        state: gestureState,
        timestampMs: currentWallMs,
      });
      const canEmitGesture = observation && currentWallMs - lastGestureAt >= GESTURE_COOLDOWN_MS;
      if (canEmitGesture) {
        lastGestureAt = currentWallMs;
        emitGesture(observation);
      }
      emitSkeleton(
        joints,
        observation?.gesture || null,
        observation?.confidence || 0,
      );
      previousJoints = joints;
    } catch (error) {
      emitStatus(`浏览器动捕识别失败: ${error?.message || String(error)}`, "error", {
        error: "recognition_failed",
      });
    }
    scheduleFrame();
  }

  async function startCamera() {
    if (!canUseBrowserCamera(mediaDevices)) {
      emitStatus("当前浏览器不支持 getUserMedia 摄像头接口", "error", {
        error: "get_user_media_unavailable",
      });
      return false;
    }
    if (!isSecureCameraContext()) {
      emitStatus("浏览器摄像头需要 HTTPS 或 localhost 环境", "error", {
        error: "insecure_context",
      });
      return false;
    }

    try {
      recognizer = await recognizerFactory();
    } catch (error) {
      connected = false;
      emitStatus(`浏览器动捕模型加载失败: ${error?.message || String(error)}`, "error", {
        error: "model_load_failed",
      });
      return false;
    }

    try {
      stream = await mediaDevices.getUserMedia(CAMERA_CONSTRAINTS);
      video = document.createElement("video");
      video.muted = true;
      video.playsInline = true;
      video.autoplay = true;
      video.style.display = "none";
      video.srcObject = stream;
      document.body.appendChild(video);
      await video.play();
      await waitForVideoMetadata(video);
      onVideoSource({
        provider: "browser_camera",
        source: video,
        active: true,
      });
    } catch (error) {
      connected = false;
      recognizer?.close?.();
      recognizer = null;
      stopStream();
      emitStatus(getUserMediaErrorMessage(error), "error", {
        error: "browser_camera_failed",
      });
      return false;
    }

    connected = true;
    emitStatus("浏览器摄像头动捕已连接", "info");
    scheduleFrame();
    return true;
  }

  return {
    provider: "browser_camera",
    async start() {
      if (disposed) return false;
      return startCamera();
    },
    stop() {
      disposed = true;
      if (rafId) {
        cancelAnimationFrameFn(rafId);
        rafId = null;
      }
      recognizer?.close?.();
      recognizer = null;
      stopStream();
      connected = false;
      emitState({ connected: false });
    },
    isConnected() {
      return connected;
    },
  };
}

export {
  CAMERA_CONSTRAINTS,
  importMediaPipeTasksVision,
  POSE_BONES,
  recognizeGesture,
};