/// 连拍页（UI-03 页面 13 深色摄影界面；P3 计划 Task 9 / R17 连拍入队）。
///
/// 进入时选定目标相册与分类（相册详情 FAB 传入）；快门每张立即经准备器
/// 入队（preparing→queued，不逐张确认）。全屏取景（恒深色 #10161E，不随
/// 系统主题）：顶部常驻层 = 返回 + 相册名 + 待传/失败徽章 + 分类 chips
/// （可切换，**仅影响之后拍摄**——引擎只读任务行归属）；底部 = 最近一张
/// 缩略图（兼相册多选入口，iOS 相机惯例）+ 快门（≥72dp 白环）+ 前后摄
/// 切换 + 闪光灯（源支持才出现）。预览按传感器比例居中（所见即所得，
/// 不裁切不变形）；源支持变焦（maxZoom > 1）时捏合缩放 + 双击复位 1×。
/// 入队成功以触觉 + 200ms 浮层轻反馈，
/// 不逐张弹确认；退出时若有待传任务弹确认（任务在后台继续——Android
/// 原生 WorkManager 承担，见 native_transport.dart）。
///
/// 相机/相册经注入点（[captureSourceFactoryProvider]/[multiImagePickerProvider]）
/// 隔离平台通道，widget 测试注入替身驱动。
library;

import 'dart:async';
import 'dart:io';

import 'package:camera/camera.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart' show HapticFeedback;
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../features/albums/models.dart';
import '../features/uploads/enqueue.dart';
import '../features/uploads/queue_controller.dart';
import '../l10n/app_localizations.dart';
import '../ui/tokens.dart';

// ── 相机源抽象（生产=camera 插件；测试替身） ─────────────────────────────

/// 拍摄源：初始化/拍摄/预览/释放。
abstract class CaptureSource {
  /// 初始化（权限缺失/失败抛异常；权限拒绝抛 [CameraException]）。
  Future<void> initialize();

  /// 拍摄一张（返回源文件）。
  Future<XFile> capture();

  /// 取景预览（按传感器比例居中——所见即所得，不裁切不变形）。
  Widget buildPreview();

  /// 释放底层资源。
  Future<void> dispose();

  /// 闪光灯能力（默认不支持——子类按硬件能力覆写；不支持则 UI 不显示
  /// 闪光开关，不提供假开关）。
  bool get supportsFlash => false;

  /// 设置闪光灯（仅 [supportsFlash] 为真时有意义；失败抛异常由调用方回滚）。
  Future<void> setFlashEnabled(bool enabled) async {}

  /// 变焦能力下限（默认 1=不支持变焦；子类按硬件覆写）。
  double get minZoom => 1;

  /// 变焦能力上限（默认 1=不支持变焦；不支持则 UI 不启用手势）。
  double get maxZoom => 1;

  /// 设置变焦倍数（默认 no-op——能力为 1 时 UI 不启用手势）。
  Future<void> setZoom(double level) async {}
}

/// 生产拍摄源：camera 插件（后摄优先，最高分辨率，静音连拍）。
class CameraPluginSource extends CaptureSource {
  CameraPluginSource._(this._controller);

  /// 创建并初始化（[preferFront] 为真选前摄，否则后摄优先）。
  static Future<CameraPluginSource> create({bool preferFront = false}) async {
    final cameras = await availableCameras();
    if (cameras.isEmpty) {
      throw CameraException('noCamera', 'no camera available');
    }
    CameraDescription pick() => cameras.firstWhere(
      (c) =>
          c.lensDirection ==
          (preferFront ? CameraLensDirection.front : CameraLensDirection.back),
      orElse: () => cameras.first,
    );
    final controller = CameraController(
      pick(),
      ResolutionPreset.max,
      enableAudio: false,
    );
    await controller.initialize();
    final source = CameraPluginSource._(controller);
    try {
      source._minZoom = await controller.getMinZoomLevel();
      source._maxZoom = await controller.getMaxZoomLevel();
    } on Object {
      // 能力探测失败（部分设备/模拟器）：保持 1/1，捏合不启用。
    }
    return source;
  }

  final CameraController _controller;

  double _zoomLevel = 1.0;
  double _minZoom = 1;
  double _maxZoom = 1;

  @override
  Future<void> initialize() async {}

  @override
  Future<XFile> capture() => _controller.takePicture();

  @override
  Widget buildPreview() {
    // 所见即所得（§4 页面 13 修订，决策 ④）：按传感器纵向比例居中显示，
    // 上下露出深色背景——不再 FittedBox cover 全屏（那会横向裁 ~38% 画面，
    // 且预览所见 ≠ takePicture 全幅照片）。
    final size = _controller.value.previewSize;
    Widget preview = CameraPreview(_controller);
    if (size != null && size.width > 0 && size.height > 0) {
      preview = Center(
        child: AspectRatio(
          // 交换：竖屏用 height 作宽、width 作高（传感器横向 → 纵向）。
          aspectRatio: size.height / size.width,
          child: preview,
        ),
      );
    }
    return preview;
  }

  @override
  double get minZoom => _minZoom;

  @override
  double get maxZoom => _maxZoom;

  @override
  Future<void> setZoom(double level) async {
    final clamped = level.clamp(minZoom, maxZoom).toDouble();
    if (clamped == _zoomLevel) return;
    await _controller.setZoomLevel(clamped);
    _zoomLevel = clamped;
  }

  @override
  bool get supportsFlash => true;

  @override
  Future<void> setFlashEnabled(bool enabled) =>
      _controller.setFlashMode(enabled ? FlashMode.always : FlashMode.off);

  @override
  Future<void> dispose() => _controller.dispose();
}

/// 拍摄源工厂 Provider（测试 override 为替身）。
final captureSourceFactoryProvider =
    Provider<Future<CaptureSource> Function({bool preferFront})>(
      (ref) => CameraPluginSource.create,
    );

// ── 连拍页 ────────────────────────────────────────────────────────────────

/// 连拍页参数：目标相册（相册详情 FAB 进入时固定）与分类候选。
class CaptureTarget {
  const CaptureTarget({
    required this.accountId,
    required this.albumId,
    required this.albumTitle,
    this.categories = const <Category>[],
  });

  /// 入队账号（TaskStore 隔离键）。
  final String accountId;

  /// 目标相册 ID。
  final String albumId;

  /// 目标相册展示名（信息层常驻显示）。
  final String albumTitle;

  /// 相册分类（空 = 无可切换项，仅默认分类）。
  final List<Category> categories;
}

/// 连拍页。
class CapturePage extends ConsumerStatefulWidget {
  const CapturePage({required this.target, super.key});

  final CaptureTarget target;

  @override
  ConsumerState<CapturePage> createState() => _CapturePageState();
}

enum _CameraPhase { loading, ready, denied, failed }

class _CapturePageState extends ConsumerState<CapturePage>
    with WidgetsBindingObserver {
  CaptureSource? _source;
  _CameraPhase _phase = _CameraPhase.loading;

  /// 当前镜头方向（快门旁切换按钮翻转；重试沿用）。
  bool _preferFront = false;

  /// 闪光灯开关（源不支持则无 UI；重开相机后复位）。
  bool _flashOn = false;

  /// 最近一张拍摄文件（底部缩略图；拍摄前显示相册入口占位）。
  String? _lastShotPath;

  /// 当前分类（null = 相册默认分类；切换仅影响之后拍摄）。
  String? _categoryId;

  /// 连拍串行链：快门连点逐张落地（相机硬件本就串行）。
  Future<void> _shotTail = Future<void>.value();

  /// 入队成功短暂反馈（150-220ms 轻量动效档，§3.1）。
  bool _showEnqueuedFeedback = false;
  Timer? _feedbackTimer;

  // ── 捏合变焦（Task 7：源 maxZoom > 1 时启用手势） ──────────────────────

  /// 捏合起始倍数基线（手势中目标 = 基线 × scale；手势结束置 null）。
  double? _pinchBaseZoom;

  /// 最近一次已下发到源的变焦值（节流阈值基准；源重开时复位 1）。
  double _lastSentZoom = 1;

  /// setZoom 在途标记（在途时缓存最新目标，完成后补发——防平台通道乱序
  /// 导致徽标与硬件漂移）。
  bool _zoomInFlight = false;
  double? _zoomQueued;

  /// 倍数徽标：显示当前目标倍数（1.0× 格式），停止更新 1s 后隐藏。
  double _zoomDisplay = 1;
  bool _zoomBadgeVisible = false;
  Timer? _zoomBadgeTimer;

  @override
  void initState() {
    super.initState();
    // P0-3：监听 App 生命周期——后台释放相机（省电 + 隐私），回前台重开。
    WidgetsBinding.instance.addObserver(this);
    _initCamera();
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    _feedbackTimer?.cancel();
    _zoomBadgeTimer?.cancel();
    _source?.dispose().ignore();
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    super.didChangeAppLifecycleState(state);
    // P0-3：后台 → 释放相机硬件（不释放则摄像头指示灯常亮 + 耗电）；
    // 回前台 → 重新初始化（沿用当前前后摄/闪光灯偏好）。
    if (state == AppLifecycleState.paused && _source != null) {
      _source?.dispose().ignore();
      _source = null;
      setState(() => _phase = _CameraPhase.loading);
    } else if (state == AppLifecycleState.resumed && _source == null) {
      _initCamera();
    }
  }

  Future<void> _initCamera({bool? preferFront}) async {
    final front = preferFront ?? _preferFront;
    setState(() => _phase = _CameraPhase.loading);
    try {
      final source = await ref.read(captureSourceFactoryProvider)(
        preferFront: front,
      );
      await source.initialize();
      if (!mounted) {
        await source.dispose();
        return;
      }
      _source = source;
      _zoomBadgeTimer?.cancel();
      setState(() {
        _preferFront = front;
        _flashOn = false; // 新相机实例回默认关。
        // 新源变焦天然回 1（新控制器默认倍数）；徽标状态同步清理。
        _zoomDisplay = 1;
        _zoomBadgeVisible = false;
        _phase = _CameraPhase.ready;
      });
      _pinchBaseZoom = null;
      _lastSentZoom = 1;
      _zoomQueued = null;
    } on Object catch (error) {
      if (!mounted) return;
      setState(
        () => _phase = _isPermissionDenied(error)
            ? _CameraPhase.denied
            : _CameraPhase.failed,
      );
    }
  }

  /// camera 插件的权限拒绝错误码族（CameraAccessDenied /
  /// CameraAccessDeniedWithoutRestriction 等）。
  static bool _isPermissionDenied(Object error) =>
      error is CameraException &&
      (error.code.toLowerCase().contains('denied') ||
          error.code.toLowerCase().contains('permission'));

  /// 前后摄切换：释放当前源 → 反向重建（能力缺失自然落 failed 态重试）。
  Future<void> _flipCamera() async {
    if (_phase != _CameraPhase.ready) return;
    final old = _source;
    _source = null;
    await old?.dispose();
    await _initCamera(preferFront: !_preferFront);
  }

  /// 闪光灯开关：硬件设置失败则回滚（不留假状态）。
  Future<void> _toggleFlash() async {
    final source = _source;
    if (source == null || !source.supportsFlash) return;
    final next = !_flashOn;
    try {
      await source.setFlashEnabled(next);
      if (mounted) setState(() => _flashOn = next);
    } on Object {
      // 设置失败：保持原状态（下次点击重试）。
    }
  }

  /// 快门：立即入队（R17 不逐张确认）；连点串行不丢张。
  void _shoot() {
    final source = _source;
    if (source == null || _phase != _CameraPhase.ready) return;
    final categoryId = _categoryId;
    _shotTail = _shotTail
        .then((_) async {
          final photo = await source.capture();
          if (!mounted) return;
          // 最近一张缩略图（拍摄原文件；缺失走占位）。
          setState(() => _lastShotPath = photo.path);
          final enqueued = await enqueueForUpload(
            ref,
            accountId: widget.target.accountId,
            albumId: widget.target.albumId,
            categoryId: categoryId,
            sourcePaths: [photo.path],
          );
          // 入队成功：短暂反馈（轻触 + 200ms 浮层），不逐张弹确认（§4.5）。
          if (enqueued.enqueued > 0 && mounted) _flashEnqueued();
        })
        .catchError((Object _) {
          // 单张失败吞掉（连拍不中断；失败任务/错误在徽章与队列页可见）。
        });
  }

  /// 入队成功反馈：触觉轻点 + 顶部短暂浮层（200ms 后自动消退）。
  void _flashEnqueued() {
    HapticFeedback.selectionClick();
    _feedbackTimer?.cancel();
    setState(() => _showEnqueuedFeedback = true);
    _feedbackTimer = Timer(const Duration(milliseconds: 200), () {
      if (mounted) setState(() => _showEnqueuedFeedback = false);
    });
  }

  // ── 捏合变焦手势 ─────────────────────────────────────────────────────────

  void _onPinchStart(ScaleStartDetails details) {
    final source = _source;
    if (source == null || source.maxZoom <= 1) return;
    // 基线取当前已下发倍数（受源能力夹取）——连续捏合从当前倍数续接。
    _pinchBaseZoom = _lastSentZoom
        .clamp(source.minZoom, source.maxZoom)
        .toDouble();
    // 单指轻点同样触发 onScaleStart——倍数徽标仅在真捏合（≥2 指）时显示，
    // 避免轻点预览也弹 1.0×；基线重定保持无条件（单指转捏合、抬起再捏合
    // 均从当前倍数续接）。
    if (details.pointerCount >= 2) _showZoomBadge(_pinchBaseZoom!);
  }

  void _onPinchUpdate(ScaleUpdateDetails details) {
    final source = _source;
    final base = _pinchBaseZoom;
    if (source == null || base == null) return;
    final target =
        (base * details.scale).clamp(source.minZoom, source.maxZoom).toDouble();
    _showZoomBadge(target);
    _dispatchZoom(target);
  }

  void _onPinchEnd(ScaleEndDetails details) {
    // 手势结束（含单指抬起触发的重定基）——置空基线，下次手势从当前
    // 倍数重新起步（onScaleStart 重新取 _lastSentZoom）。
    _pinchBaseZoom = null;
  }

  /// 双击复位 1.0×。
  void _resetZoom() {
    final source = _source;
    if (source == null || source.maxZoom <= 1) return;
    _showZoomBadge(1);
    _dispatchZoom(1);
  }

  /// 变焦下发：节流 + 串行化。onScaleUpdate 每帧触发（60-120/s），不能
  /// 每次都打平台通道——与最近已发值差 ≥0.05 才发；在途时缓存最新目标，
  /// 完成后补发（防乱序导致徽标与硬件漂移）。
  void _dispatchZoom(double target) {
    if (_zoomInFlight) {
      _zoomQueued = target;
      return;
    }
    if ((target - _lastSentZoom).abs() < 0.05) return;
    _sendZoom(target);
  }

  void _sendZoom(double target) {
    final source = _source;
    if (source == null) return;
    _zoomInFlight = true;
    _lastSentZoom = target;
    source
        .setZoom(target)
        .catchError((Object _) {}) // 硬件设置失败：保持当前值（下次手势重试）。
        .whenComplete(() {
          _zoomInFlight = false;
          final queued = _zoomQueued;
          _zoomQueued = null;
          // 源已更换（翻转/重开相机）：丢弃补发。
          if (_source != source || queued == null) return;
          if ((queued - _lastSentZoom).abs() >= 0.05) _sendZoom(queued);
        });
  }

  /// 倍数徽标：显示当前倍数（四舍五入 1 位小数），停止更新 1s 后隐藏。
  void _showZoomBadge([double? level]) {
    _zoomBadgeTimer?.cancel();
    setState(() {
      if (level != null) _zoomDisplay = level;
      _zoomBadgeVisible = true;
    });
    _zoomBadgeTimer = Timer(const Duration(milliseconds: 1000), () {
      if (mounted) setState(() => _zoomBadgeVisible = false);
    });
  }

  /// 相册多选入队（目标 = 当前相册与分类；入口=底部缩略图位）。
  Future<void> _pickFromGallery() async {
    final paths = await ref.read(multiImagePickerProvider)(context);
    if (paths.isEmpty || !mounted) return;
    final l10n = AppLocalizations.of(context);
    final messenger = ScaffoldMessenger.of(context);

    // P0-1 层 1：入队前查重（同相册已完成的 filename+bytes 匹配）。
    final duplicates = await checkDuplicates(
      ref,
      accountId: widget.target.accountId,
      albumId: widget.target.albumId,
      sourcePaths: paths,
    );

    Set<String> skipPaths;
    Set<String> forcePaths;
    if (duplicates != null && duplicates.isNotEmpty && mounted) {
      // 批量确认弹窗（单次，非逐张）。
      final choice = await _showDuplicateDialog(l10n, duplicates, paths);
      if (choice == null) return; // 取消——不上传。
      skipPaths = choice.skipPaths;
      forcePaths = choice.forcePaths;
    } else {
      skipPaths = <String>{};
      forcePaths = <String>{};
    }

    final result = await enqueueForUpload(
      ref,
      accountId: widget.target.accountId,
      albumId: widget.target.albumId,
      categoryId: _categoryId,
      sourcePaths: paths,
      skipPaths: skipPaths.toList(),
      forcePaths: forcePaths.toList(),
    );
    if (!mounted) return;
    final uploaded = result.enqueued;
    final skipped = result.skipped;
    messenger.showSnackBar(
      SnackBar(
        content: Text(
          skipped > 0
              ? '$uploaded 张已入队，$skipped 张重复已跳过'
              : l10n.uploadEnqueuedCount(uploaded),
        ),
      ),
    );
  }

  /// 批量重复确认弹窗（Task 8）：null=取消；「跳过重复」→ skipPaths=
  /// 重复项；「全部上传」→ forcePaths=重复项（用户确认强传，服务端
  /// force 查重跳过仅 owner/admin 生效——协作者仍会被 409 拒绝）。
  Future<DuplicateDialogChoice?> _showDuplicateDialog(
    AppLocalizations l10n,
    List<DuplicateMatch> duplicates,
    List<String> allPaths,
  ) async {
    // 找出与 duplicates 匹配的路径（filename 一致即视为重复项）。
    final dupFilenames = duplicates.map((d) => d.filename).toSet();
    final dupPaths = allPaths
        .where((p) => dupFilenames.contains(p.split('/').last))
        .toSet();
    final nonDupCount = allPaths.length - dupPaths.length;

    final choice = await showDialog<String>(
      context: context,
      builder: (ctx) => AlertDialog(
        title: const Text('可能已上传过'),
        content: Text(
          '${duplicates.length} 张照片可能已上传到该相册'
          '${nonDupCount > 0 ? '（另 $nonDupCount 张不重复）' : ''}\n\n'
          '${duplicates.take(3).map((d) => d.filename).join('、')}'
          '${duplicates.length > 3 ? ' …' : ''}',
        ),
        actions: [
          TextButton(
            onPressed: () => Navigator.of(ctx).pop('cancel'),
            child: const Text('取消'),
          ),
          if (nonDupCount > 0)
            TextButton(
              onPressed: () => Navigator.of(ctx).pop('skip'),
              child: Text('跳过重复，上传 $nonDupCount 张'),
            ),
          FilledButton(
            onPressed: () => Navigator.of(ctx).pop('all'),
            child: Text('全部上传 ${allPaths.length} 张'),
          ),
        ],
      ),
    );

    if (choice == 'cancel' || choice == null) return null;
    if (choice == 'skip') {
      return (skipPaths: dupPaths, forcePaths: <String>{});
    }
    // 'all' = 用户确认强传：重复项 force 入队（不跳过任何）。
    return (skipPaths: <String>{}, forcePaths: dupPaths);
  }

  void _switchCategory(String? categoryId) {
    if (categoryId == _categoryId) return;
    setState(() => _categoryId = categoryId);
    // 归属不变提示（A15）：仅影响之后拍摄。
    ScaffoldMessenger.of(context)
      ..hideCurrentSnackBar()
      ..showSnackBar(
        SnackBar(content: Text(AppLocalizations.of(context).captureSwitchHint)),
      );
  }

  Future<void> _confirmExit() async {
    final l10n = AppLocalizations.of(context);
    final leave = await showDialog<bool>(
      context: context,
      builder: (dialogContext) => AlertDialog(
        title: Text(l10n.captureExitTitle),
        content: Text(
          l10n.captureExitBody(pendingCountOf(ref.read(taskCountsProvider))),
        ),
        actions: [
          TextButton(
            onPressed: () => Navigator.of(dialogContext).pop(false),
            child: Text(l10n.captureKeepShooting),
          ),
          FilledButton(
            onPressed: () => Navigator.of(dialogContext).pop(true),
            child: Text(l10n.captureExitConfirm),
          ),
        ],
      ),
    );
    if (leave == true && mounted) {
      Navigator.of(context).pop();
    }
  }

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    final counts = ref.watch(taskCountsProvider);
    final pending = pendingCountOf(counts);
    final failed = failedCountOf(counts);
    final categories = widget.target.categories;

    return PopScope(
      // 有待传任务 → 拦截退出弹确认（后台继续文案）；无任务直接退出。
      canPop: pending == 0,
      onPopInvokedWithResult: (didPop, _) {
        if (didPop) return;
        _confirmExit();
      },
      child: Scaffold(
        // 深色摄影界面恒深色（§3）：不读主题，固定 #10161E。
        backgroundColor: kColorPhotoBackdrop,
        body: Stack(
          fit: StackFit.expand,
          children: [
            _buildCameraArea(l10n),
            // 顶部常驻层：返回 + 相册 + 待传/失败徽章 + 分类 chips。
            SafeArea(
              child: Column(
                children: [
                  _TopBar(
                    albumTitle: widget.target.albumTitle,
                    queued: pending,
                    failed: failed,
                    onBack: () => Navigator.of(context).maybePop(),
                  ),
                  if (categories.isNotEmpty)
                    _CategoryChips(
                      categories: categories,
                      categoryId: _categoryId,
                      onCategorySelected: _switchCategory,
                    ),
                ],
              ),
            ),
            // 入队成功短暂反馈浮层（200ms 自动消退，不逐张弹确认）。
            Positioned(
              top: 132,
              left: 0,
              right: 0,
              child: IgnorePointer(
                child: AnimatedOpacity(
                  opacity: _showEnqueuedFeedback ? 1 : 0,
                  duration: const Duration(milliseconds: 180),
                  child: Center(
                    child: Container(
                      padding: const EdgeInsets.symmetric(
                        horizontal: 12,
                        vertical: 6,
                      ),
                      decoration: BoxDecoration(
                        color: Colors.black54,
                        borderRadius: BorderRadius.circular(999),
                      ),
                      child: Row(
                        mainAxisSize: MainAxisSize.min,
                        children: [
                          const Icon(
                            Icons.check_circle,
                            size: 16,
                            color: Colors.white,
                          ),
                          const SizedBox(width: 6),
                          Text(
                            l10n.captureEnqueuedFeedback,
                            style: const TextStyle(
                              color: Colors.white,
                              fontSize: 13,
                            ),
                          ),
                        ],
                      ),
                    ),
                  ),
                ),
              ),
            ),
            // 底部操作层：缩略图（=相册入口）+ 快门（+闪光灯）+ 前后切换。
            Positioned(
              left: 0,
              right: 0,
              bottom: 0,
              child: _BottomControls(
                enabled: _phase == _CameraPhase.ready,
                lastShotPath: _lastShotPath,
                flashSupported: _source?.supportsFlash ?? false,
                flashOn: _flashOn,
                onShutter: _shoot,
                onGallery: _pickFromGallery,
                onFlip: _flipCamera,
                onFlash: _toggleFlash,
              ),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildCameraArea(AppLocalizations l10n) {
    final source = _source;
    switch (_phase) {
      case _CameraPhase.ready:
        return _buildReadyArea(source!);
      case _CameraPhase.loading:
        return const Center(
          child: CircularProgressIndicator(color: Colors.white),
        );
      case _CameraPhase.denied:
        return _CameraMessageView(
          icon: Icons.no_photography_outlined,
          message: l10n.cameraPermissionDenied,
          actionLabel: l10n.retry,
          onAction: _initCamera,
        );
      case _CameraPhase.failed:
        return _CameraMessageView(
          icon: Icons.error_outline,
          message: l10n.cameraInitFailed,
          actionLabel: l10n.retry,
          onAction: _initCamera,
        );
    }
  }

  /// 就绪态：预览 + 捏合变焦手势（源 maxZoom > 1 时挂）+ 倍数徽标。
  Widget _buildReadyArea(CaptureSource source) {
    Widget area = source.buildPreview();
    if (source.maxZoom > 1) {
      area = GestureDetector(
        // opaque：预览任意点均可起手势（含按比例居中后的上下留黑区）。
        behavior: HitTestBehavior.opaque,
        onScaleStart: _onPinchStart,
        onScaleUpdate: _onPinchUpdate,
        onScaleEnd: _onPinchEnd,
        onDoubleTap: _resetZoom,
        child: area,
      );
    }
    if (!_zoomBadgeVisible) return area;
    return Stack(
      fit: StackFit.expand,
      children: [area, _buildZoomBadge()],
    );
  }

  /// 变焦倍数徽标（捏合/双击期间显示，不拦截手势）。
  Widget _buildZoomBadge() {
    return IgnorePointer(
      child: Center(
        child: Container(
          padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
          decoration: BoxDecoration(
            color: Colors.black54,
            borderRadius: BorderRadius.circular(999),
          ),
          child: Text(
            '${_zoomDisplay.toStringAsFixed(1)}×',
            style: const TextStyle(color: Colors.white, fontSize: 13),
          ),
        ),
      ),
    );
  }
}

// ── 信息层组件 ────────────────────────────────────────────────────────────

/// 顶部常驻层：返回 + 相册名 + 待传/失败徽章（§4 页面 13）。
class _TopBar extends StatelessWidget {
  const _TopBar({
    required this.albumTitle,
    required this.queued,
    required this.failed,
    required this.onBack,
  });

  final String albumTitle;
  final int queued;
  final int failed;
  final VoidCallback onBack;

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    return Padding(
      padding: const EdgeInsets.fromLTRB(4, 4, 12, 0),
      child: Row(
        children: [
          IconButton(
            tooltip: MaterialLocalizations.of(
              context,
            ).backButtonTooltip, // 语义标签；深色界面固定白色前景。
            color: Colors.white,
            icon: const Icon(Icons.arrow_back),
            onPressed: onBack,
          ),
          const SizedBox(width: kSpace4),
          const Icon(
            Icons.photo_album_outlined,
            size: 16,
            color: Colors.white70,
          ),
          const SizedBox(width: 6),
          Expanded(
            child: Text(
              albumTitle,
              maxLines: 1,
              overflow: TextOverflow.ellipsis,
              style: const TextStyle(
                color: Colors.white,
                fontWeight: FontWeight.w600,
              ),
            ),
          ),
          if (failed > 0) ...[
            _Badge(
              label: l10n.captureFailedBadge(failed),
              color: kColorErrorDark,
              foreground: Colors.white,
            ),
            const SizedBox(width: kSpace8),
          ],
          _Badge(
            label: l10n.captureQueued(queued),
            color: Colors.white24,
            foreground: Colors.white,
          ),
        ],
      ),
    );
  }
}

/// 分类 chips（切换仅影响之后拍摄；A15 归属不变）。
class _CategoryChips extends StatelessWidget {
  const _CategoryChips({
    required this.categories,
    required this.categoryId,
    required this.onCategorySelected,
  });

  final List<Category> categories;
  final String? categoryId;
  final void Function(String?) onCategorySelected;

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    return SizedBox(
      height: 44,
      child: ListView(
        scrollDirection: Axis.horizontal,
        padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 6),
        children: [
          ChoiceChip(
            label: Text(l10n.captureCategoryDefault),
            selected: categoryId == null,
            onSelected: (_) => onCategorySelected(null),
            labelStyle: const TextStyle(color: Colors.white),
            selectedColor: Colors.white24,
            backgroundColor: Colors.black38,
          ),
          for (final category in categories) ...[
            const SizedBox(width: 8),
            ChoiceChip(
              label: Text(_categoryLabel(category, l10n)),
              selected: categoryId == category.id,
              onSelected: (_) => onCategorySelected(category.id),
              labelStyle: const TextStyle(color: Colors.white),
              selectedColor: Colors.white24,
              backgroundColor: Colors.black38,
            ),
          ],
        ],
      ),
    );
  }

  static String _categoryLabel(Category category, AppLocalizations l10n) {
    final lang = l10n.localeName.split('-').first.toLowerCase();
    CategoryTranslation? match;
    for (final t in category.translations) {
      if (t.locale.toLowerCase() == l10n.localeName.toLowerCase() ||
          t.locale.toLowerCase().split('-').first == lang) {
        match = t;
        break;
      }
    }
    if (match != null) return match.name;
    return category.translations.isEmpty
        ? category.id
        : category.translations.first.name;
  }
}

/// 徽章（待传/失败计数）。
class _Badge extends StatelessWidget {
  const _Badge({
    required this.label,
    required this.color,
    required this.foreground,
  });

  final String label;
  final Color color;
  final Color foreground;

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 2),
      decoration: BoxDecoration(
        color: color,
        borderRadius: BorderRadius.circular(999),
      ),
      child: Text(label, style: TextStyle(color: foreground, fontSize: 12)),
    );
  }
}

/// 底部操作层：最近一张缩略图（兼相册多选入口）+ 快门（≥72dp 白环，
/// 源支持时上方附闪光灯）+ 前后摄切换。
class _BottomControls extends StatelessWidget {
  const _BottomControls({
    required this.enabled,
    required this.lastShotPath,
    required this.flashSupported,
    required this.flashOn,
    required this.onShutter,
    required this.onGallery,
    required this.onFlip,
    required this.onFlash,
  });

  final bool enabled;
  final String? lastShotPath;
  final bool flashSupported;
  final bool flashOn;
  final VoidCallback onShutter;
  final VoidCallback onGallery;
  final VoidCallback onFlip;
  final VoidCallback onFlash;

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    return IgnorePointer(
      // 相机未就绪（加载/权限/失败）时收起操作层——那里是错误态的重试区。
      ignoring: !enabled,
      child: SafeArea(
        minimum: const EdgeInsets.fromLTRB(24, 0, 24, 16),
        child: Row(
          crossAxisAlignment: CrossAxisAlignment.end,
          children: [
            Align(
              alignment: AlignmentDirectional.bottomStart,
              child: _LastShotButton(
                lastShotPath: lastShotPath,
                onPressed: onGallery,
              ),
            ),
            const Spacer(),
            Column(
              mainAxisSize: MainAxisSize.min,
              children: [
                if (flashSupported)
                  IconButton(
                    tooltip: l10n.captureFlash,
                    color: Colors.white,
                    icon: Icon(flashOn ? Icons.flash_on : Icons.flash_off),
                    onPressed: onFlash,
                  ),
                _ShutterButton(onPressed: onShutter, enabled: enabled),
              ],
            ),
            const Spacer(),
            Align(
              alignment: AlignmentDirectional.bottomStart,
              child: IconButton(
                tooltip: l10n.captureFlipCamera,
                color: Colors.white,
                icon: const Icon(Icons.flip_camera_ios_outlined),
                onPressed: onFlip,
              ),
            ),
          ],
        ),
      ),
    );
  }
}

/// 最近一张缩略图：拍摄前为相册入口占位（photo_library 图标），拍摄后
/// 显示最近一张（缺失走占位）；点击均打开相册多选（iOS 相机惯例）。
class _LastShotButton extends StatelessWidget {
  const _LastShotButton({required this.lastShotPath, required this.onPressed});

  final String? lastShotPath;
  final VoidCallback onPressed;

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    Widget content;
    if (lastShotPath == null) {
      content = const Icon(
        Icons.photo_library_outlined,
        size: 24,
        color: Colors.white,
      );
    } else {
      content = Image.file(
        File(lastShotPath!),
        fit: BoxFit.cover,
        errorBuilder: (_, _, _) =>
            const Icon(Icons.image_outlined, size: 24, color: Colors.white),
      );
    }
    return IconButton(
      tooltip: l10n.capturePickFromGallery,
      onPressed: onPressed,
      style: IconButton.styleFrom(
        padding: EdgeInsets.zero,
        fixedSize: const Size(56, 56),
      ),
      icon: ClipRRect(
        borderRadius: BorderRadius.circular(kRadiusBadge),
        child: SizedBox(width: 48, height: 48, child: content),
      ),
    );
  }
}

/// 快门按钮（§4 页面 13：≥72dp 白环；连拍不进入模态确认，逐张自动入队）。
class _ShutterButton extends StatelessWidget {
  const _ShutterButton({required this.onPressed, required this.enabled});

  final VoidCallback onPressed;
  final bool enabled;

  @override
  Widget build(BuildContext context) {
    return Semantics(
      button: true,
      label: AppLocalizations.of(context).captureShutter,
      child: IconButton(
        key: const ValueKey('capture-shutter'),
        onPressed: enabled ? onPressed : null,
        style: IconButton.styleFrom(
          padding: EdgeInsets.zero,
          minimumSize: const Size(76, 76),
          tapTargetSize: MaterialTapTargetSize.shrinkWrap,
        ),
        icon: Container(
          width: 76,
          height: 76,
          decoration: BoxDecoration(
            shape: BoxShape.circle,
            border: Border.all(color: Colors.white, width: 5),
          ),
          alignment: Alignment.center,
          child: Container(
            width: 58,
            height: 58,
            decoration: BoxDecoration(
              shape: BoxShape.circle,
              // 就绪=白心（图标反色）；未就绪=仅白环。
              color: enabled ? Colors.white : Colors.transparent,
            ),
            alignment: Alignment.center,
            child: Icon(
              Icons.camera,
              size: 28,
              color: enabled ? kColorPhotoBackdrop : Colors.white70,
            ),
          ),
        ),
      ),
    );
  }
}

/// 相机不可用视图（权限拒绝/初始化失败）：深色说明 + 重试（§4 页面 13）。
class _CameraMessageView extends StatelessWidget {
  const _CameraMessageView({
    required this.icon,
    required this.message,
    required this.actionLabel,
    required this.onAction,
  });

  final IconData icon;
  final String message;
  final String actionLabel;
  final VoidCallback onAction;

  @override
  Widget build(BuildContext context) {
    return Container(
      color: kColorPhotoBackdrop,
      child: Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Icon(icon, size: 48, color: Colors.white70),
            const SizedBox(height: 12),
            Padding(
              padding: const EdgeInsets.symmetric(horizontal: 32),
              child: Text(
                message,
                textAlign: TextAlign.center,
                style: const TextStyle(color: Colors.white),
              ),
            ),
            const SizedBox(height: 16),
            FilledButton.icon(
              onPressed: onAction,
              icon: const Icon(Icons.refresh),
              label: Text(actionLabel),
            ),
          ],
        ),
      ),
    );
  }
}