observer/flutter_app/lib/camera/frame_analyzer.dart

import 'dart:async';
import 'dart:typed_data';

import 'package:camera/camera.dart';

import '../detection/detection_result.dart';
import '../detection/detector_worker.dart';
import '../feedback/false_target_capture.dart';
import 'camera_view_model.dart';

/// 抽帧节流 + 后台推理（对应 Kotlin FrameAnalyzer）。
/// 推理在后台 isolate（DetectorWorker）执行，主 isolate 只投递帧与收结果。
class FrameAnalyzer {
  /// 连续检测：100ms 一帧
  int intervalMs = 100;

  DetectorWorker? _worker;

  /// 当前推理 worker（null = 仅预览不分析）；相机启动后可用 [attachWorker]
  /// 原地替换（相机帧流回调闭包捕获的是本 analyzer 对象，无需重启相机）
  DetectorWorker? get worker => _worker;

  final CameraViewModel viewModel;

  int _lastDetectMs = 0;

  /// 诊断计数：推理调用/异常次数
  int detectCalls = 0;
  int detectErrors = 0;
  String? lastError;

  /// 最近一次完整处理（预处理+推理+运动检测）耗时 ms（worker 侧）
  int lastProcessMs = 0;

  /// 图像流回调是否到达（诊断用）
  int framesReceived = 0;

  /// 假目标上报快照：armed 时下一帧（节流前）拷贝单平面像素并交付。
  /// Completer 泛型必须可空：运行时 future 类型决定 .timeout(onTimeout) 的
  /// 回调签名，非空 Completer 会让 `() => null` 触发运行时子类型错误
  Completer<FrameSnapshot?>? _snapCompleter;

  FrameAnalyzer({DetectorWorker? worker, required this.viewModel}) {
    attachWorker(worker);
  }

  /// 取下一帧快照（假目标上报用；在节流判定之前捕获，~33ms 内必有帧）
  Future<FrameSnapshot?> takeSnapshot() {
    final existing = _snapCompleter;
    if (existing != null && !existing.isCompleted) {
      return existing.future;
    }
    final c = Completer<FrameSnapshot?>();
    _snapCompleter = c;
    return c.future;
  }

  /// 帧到达（节流判定前）：armed 则拷贝像素完成快照
  void _captureIfNeeded(
      Uint8List plane, int bytesPerRow, int width, int height, bool bgra) {
    final c = _snapCompleter;
    if (c == null || c.isCompleted) return;
    _snapCompleter = null;
    c.complete(FrameSnapshot(
      plane: Uint8List.fromList(plane),
      bytesPerRow: bytesPerRow,
      width: width,
      height: height,
      bgra: bgra,
    ));
  }

  /// 替换推理 worker（null = 停识别仅预览）。旧 worker 在此释放；若相机已
  /// 启动则新 worker 立即接管后续帧——重启相机会重新 initialize
  /// （iOS ~1s+）且预览闪断，原地替换即时生效（2026-09-03）。
  void attachWorker(DetectorWorker? w) {
    if (identical(_worker, w)) return;
    final old = _worker;
    _worker = w;
    w?.onResult = _onResult;
    w?.onError = _onError;
    old?.dispose();
    _lastDetectMs = 0;
  }

  void recordStreamError(String msg) {
    lastError = msg;
    detectErrors++;
  }

  void _onResult(
      List<DetectionResult> results,
      List<MotionRegion> motion,
      List<MotionRegion> novelty,
      int rotation,
      int width,
      int height,
      int processMs,
      String yuvDiag) {
    detectCalls++;
    lastProcessMs = processMs;
    viewModel.onFramesAnalyzed(
      results,
      rotation,
      width,
      height,
      motion,
      novelty,
      detectCalls: detectCalls,
      detectErrors: detectErrors,
      lastError: lastError,
      framesReceived: framesReceived,
      lastProcessMs: lastProcessMs,
      yuvDiag: yuvDiag,
    );
  }

  void _onError(String msg) {
    detectErrors++;
    lastError = msg;
    viewModel.onFramesAnalyzed(
      const [],
      90,
      0,
      0,
      const [],
      const [],
      detectCalls: detectCalls,
      detectErrors: detectErrors,
      lastError: lastError,
      framesReceived: framesReceived,
      lastProcessMs: lastProcessMs,
    );
  }

  /// 节流与 busy 丢帧判定（两入口共用）；通过后才允许投递
  bool _canSend() {
    framesReceived++;
    final w = worker;
    if (w == null) return false;
    final now = DateTime.now().millisecondsSinceEpoch;
    if (now - _lastDetectMs < intervalMs) return false;
    _lastDetectMs = now;
    if (w.busy) return false; // 上一帧未返回则丢帧，避免在途积压
    return true;
  }

  void analyze(CameraImage image, int rotationDegrees,
      {bool rgbaOrder = false}) {
    final p = image.planes.isNotEmpty ? image.planes.first : null;
    if (p != null) {
      _captureIfNeeded(
          p.bytes, p.bytesPerRow, image.width, image.height, !rgbaOrder);
    }
    if (!_canSend()) return;
    worker!.analyze(image, rotationDegrees, rgbaOrder: rgbaOrder);
  }

  /// 原生相机通道帧（Android）：字节已在 Kotlin 侧旋转成竖屏，rotation=0。
  /// isBgra=true + rgbaOrder 与插件路径同语义：false=BGRA(rOff=2)/true=RGBA(rOff=0)
  void analyzeRaw({
    required List<Uint8List> planes,
    required List<int> strides,
    required int width,
    required int height,
    required bool isBgra,
    required bool rgbaOrder,
    int rotationDegrees = 0,
  }) {
    if (planes.isNotEmpty) {
      _captureIfNeeded(planes.first, strides.first, width, height, isBgra);
    }
    if (!_canSend()) return;
    worker!.analyzeRaw(
      planes: planes,
      strides: strides,
      width: width,
      height: height,
      isBgra: isBgra,
      rgbaOrder: rgbaOrder,
      rotationDegrees: rotationDegrees,
    );
  }

  void reset() => _lastDetectMs = 0;

  void dispose() => _worker?.dispose();
}