// 手账编辑器页面 — 三层 Stack 架构
//
// Layer 1 (底层): HandwritingCanvas — 手写画布
// Layer 2 (中层): DraggableElements — 贴纸/照片/文字元素
// Layer 3 (顶层): EditorToolbar — 底部工具栏 + 顶栏操作
//
// 交互逻辑：
// - 画笔模式 → Layer 1 接收手势，Layer 2 透传
// - 选择模式 → Layer 2 接收手势，Layer 1 透传
// - 工具栏 → 始终在最顶层

import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:go_router/go_router.dart';

import '../../../core/constants/design_tokens.dart';
import '../../../data/models/journal_element.dart';
import '../../../data/models/journal_entry.dart';
import '../../../data/repositories/journal_repository.dart';
import '../bloc/editor_bloc.dart';
import '../widgets/handwriting_canvas.dart';
import '../widgets/stroke_model.dart';
import '../widgets/draggable_element.dart';
import '../widgets/editor_toolbar.dart';

/// 手账编辑器页面
class EditorPage extends StatelessWidget {
  final String? journalId;

  const EditorPage({super.key, this.journalId});

  @override
  Widget build(BuildContext context) {
    // 从 Provider 树获取 JournalRepository（IsarJournalRepository）
    final repo = context.read<JournalRepository>();

    // 可变闭包变量：跟踪已保存的日记 ID
    // 新建日记首次保存后赋值，后续自动更新使用此 ID
    String? savedJournalId = journalId;

    return BlocProvider(
      create: (_) => EditorBloc(
        onSave: (state) async {
          try {
            await _persistState(repo, state, (id) => savedJournalId = id, savedJournalId);
          } catch (e) {
            debugPrint('自动保存失败: $e');
          }
        },
      ),
      child: _EditorView(
        journalId: journalId,
        onSaveComplete: () {
          if (context.canPop()) {
            context.pop();
          } else {
            context.go('/home');
          }
        },
      ),
    );
  }

  /// 持久化编辑器状态到 Isar
  ///
  /// 策略：
  /// - 首次保存（savedJournalId == null）→ createJournal + addElement
  /// - 后续保存 → updateJournal + upsert 元素
  /// - 笔画序列化为 handwriting_ref 元素
  Future<void> _persistState(
    JournalRepository repo,
    EditorState state,
    void Function(String) setId,
    String? savedJournalId,
  ) async {
    final now = DateTime.now();

    if (savedJournalId == null) {
      // --- 新建日记 ---
      final entry = JournalEntry.create(
        authorId: 'local', // TODO: 从 AuthBloc 获取真实用户 ID
        title: '${now.month}月${now.day}日的日记',
        date: now,
      );
      await repo.createJournal(entry);
      setId(entry.id);

      // 保存笔画
      if (state.strokes.isNotEmpty) {
        await _saveStrokesAsElement(repo, entry.id, state.strokes);
      }

      // 保存其他元素
      for (final element in state.elements) {
        await repo.addElement(element.copyWith(journalId: entry.id));
      }
    } else {
      // --- 更新已有日记 ---
      final existing = await repo.getJournal(savedJournalId);
      if (existing != null) {
        await repo.updateJournal(existing);
      }

      // 更新笔画
      if (state.strokes.isNotEmpty) {
        await _saveStrokesAsElement(repo, savedJournalId, state.strokes);
      }

      // upsert 元素（先尝试更新，失败则新建）
      for (final element in state.elements) {
        try {
          await repo.updateElement(element);
        } catch (_) {
          await repo.addElement(element);
        }
      }
    }
  }

  /// 将笔画列表序列化为 handwriting_ref 元素并保存
  ///
  /// 每次保存都替换整个笔画集（Phase 1 简化策略）。
  Future<void> _saveStrokesAsElement(
    JournalRepository repo,
    String journalId,
    List<Stroke> strokes,
  ) async {
    final now = DateTime.now();
    final strokesJson = strokes.map((s) => s.toJson()).toList();

    final element = JournalElement(
      id: '${journalId}_strokes', // 固定 ID，保证每次覆盖
      journalId: journalId,
      elementType: ElementType.handwritingRef,
      content: {
        'strokes': strokesJson,
        'strokeCount': strokes.length,
      },
      version: 1,
      createdAt: now,
      updatedAt: now,
    );

    try {
      await repo.updateElement(element);
    } catch (_) {
      await repo.addElement(element);
    }
  }
}

class _EditorView extends StatelessWidget {
  final String? journalId;
  final VoidCallback onSaveComplete;

  const _EditorView({this.journalId, required this.onSaveComplete});

  @override
  Widget build(BuildContext context) {
    final colorScheme = Theme.of(context).colorScheme;

    return Scaffold(
      backgroundColor: colorScheme.surface,
      body: SafeArea(
        child: Column(
          children: [
            // 顶栏
            _buildTopBar(context),

            // 编辑区域（三层 Stack）
            Expanded(
              child: BlocBuilder<EditorBloc, EditorState>(
                builder: (context, state) {
                  return _EditorStack(state: state);
                },
              ),
            ),

            // 底部工具栏
            BlocBuilder<EditorBloc, EditorState>(
              builder: (context, state) {
                return EditorToolbar(
                  state: state,
                  onEvent: (event) => context.read<EditorBloc>().add(event),
                );
              },
            ),
          ],
        ),
      ),
    );
  }

  /// 顶部操作栏 — 返回/日记标题/完成
  Widget _buildTopBar(BuildContext context) {
    final colorScheme = Theme.of(context).colorScheme;

    return Container(
      height: 52,
      padding: const EdgeInsets.symmetric(horizontal: DesignTokens.spacing8),
      decoration: BoxDecoration(
        color: colorScheme.surface,
        border: Border(
          bottom: BorderSide(color: colorScheme.outline.withValues(alpha: 0.1)),
        ),
      ),
      child: Row(
        children: [
          // 返回按钮
          IconButton(
            onPressed: () {
              if (context.canPop()) {
                context.pop();
              } else {
                context.go('/home');
              }
            },
            icon: const Icon(Icons.arrow_back_rounded),
            tooltip: '返回',
          ),

          const SizedBox(width: DesignTokens.spacing8),

          // 日记标题
          Expanded(
            child: Text(
              journalId != null ? '编辑日记' : '新建日记',
              style: Theme.of(context).textTheme.titleMedium?.copyWith(
                    fontWeight: FontWeight.w600,
                  ),
            ),
          ),

          // 完成按钮
          FilledButton.tonal(
            onPressed: onSaveComplete,
            style: FilledButton.styleFrom(
              padding: const EdgeInsets.symmetric(horizontal: DesignTokens.spacing16),
              minimumSize: const Size(0, 36),
              shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(12)),
            ),
            child: const Text('完成'),
          ),
        ],
      ),
    );
  }
}

// ============================================================
// 编辑器三层 Stack
// ============================================================

/// 编辑器 Stack — 三层叠加结构
///
/// Layer 1 (底层): HandwritingCanvas
/// Layer 2 (中层): 可拖拽元素（贴纸/照片/文字）
/// Layer 3 (顶层): 由 _EditorView 中的工具栏处理
class _EditorStack extends StatelessWidget {
  final EditorState state;

  const _EditorStack({required this.state});

  @override
  Widget build(BuildContext context) {
    return Stack(
      fit: StackFit.expand,
      children: [
        // Layer 1: 手写画布（底层）
        // 始终渲染，通过 IgnorePointer 控制交互（避免模式切换时销毁重建）
        IgnorePointer(
          ignoring: !state.isDrawingMode,
          child: HandwritingCanvas(
            brushType: state.brushType,
            brushColor: state.brushColor,
            brushWidth: state.brushWidth,
            strokes: state.strokes,
            onStrokeCompleted: (stroke) {
              context.read<EditorBloc>().add(StrokeCompleted(stroke));
            },
          ),
        ),

        // Layer 2: 可拖拽元素（中层）
        if (state.elements.isNotEmpty)
          _buildElementLayer(context),

        // 空状态提示
        if (state.strokes.isEmpty && state.elements.isEmpty)
          _buildEmptyHint(context),
      ],
    );
  }

  /// 元素层 — 所有日记元素叠加显示
  Widget _buildElementLayer(BuildContext context) {
    // 按 zIndex 排序
    final sorted = List<JournalElement>.from(state.elements)
      ..sort((a, b) => a.zIndex.compareTo(b.zIndex));

    return Stack(
      children: sorted.map((element) {
        return DraggableElement(
          key: ValueKey(element.id),
          element: element,
          isSelected: state.selectedElementId == element.id,
          onTap: (id) {
            context.read<EditorBloc>().add(ElementSelected(id));
          },
          onMoved: (id, x, y) {
            context.read<EditorBloc>().add(ElementMoved(
              elementId: id,
              positionX: x,
              positionY: y,
            ));
          },
          onDeleted: (id) {
            context.read<EditorBloc>().add(ElementRemoved(id));
          },
        );
      }).toList(),
    );
  }

  /// 空状态提示
  Widget _buildEmptyHint(BuildContext context) {
    return Center(
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          Icon(
            Icons.draw_rounded,
            size: 48,
            color: Theme.of(context).colorScheme.onSurface.withValues(alpha: 0.15),
          ),
          const SizedBox(height: DesignTokens.spacing12),
          Text(
            '在这里开始书写吧 ✏️',
            style: Theme.of(context).textTheme.bodyLarge?.copyWith(
                  color: Theme.of(context).colorScheme.onSurface.withValues(alpha: 0.3),
                ),
          ),
        ],
      ),
    );
  }
}