import 'package:flutter/material.dart';
import 'package:flutter/semantics.dart';
import 'package:patbond_flutter/core/network/api_exception.dart';
import 'package:patbond_flutter/core/theme/app_theme.dart';
import 'package:patbond_flutter/core/widgets/app_text_field.dart';
import 'package:patbond_flutter/core/widgets/inline_error_banner.dart';
import 'package:patbond_flutter/core/widgets/primary_button.dart';
import 'package:patbond_flutter/core/widgets/record_type_dot.dart';
import 'package:patbond_flutter/features/pets/health_record_analytics.dart';
import 'package:patbond_flutter/features/pets/health_record_display.dart';
import 'package:patbond_flutter/features/pets/money.dart';
import 'package:patbond_flutter/features/pets/pet_exceptions.dart';
import 'package:patbond_flutter/features/pets/pet_models.dart';
import 'package:patbond_flutter/features/pets/pets_repository.dart';

/// 健康事件编辑页（T2-14）：顶层短路径 `PATCH /health-events/{id}`。
///
/// - 契约：仅 title / notes / amountCents 可编辑；eventType / occurredAt
///   为条目身份，静态展示不可改；不支持清空回 null（清空输入视为不变更）。
/// - 差量提交：只发送改动字段 + version；无变更不发 PATCH 直接返回。
/// - 40902 版本冲突照 T2-12 模式：明确提示 + 自动取最新版本更新乐观锁
///   基线（保留用户输入），用户核对后重新保存。契约无按 id 读取端点，
///   最新版本经时间线分页检索取回。
/// - 埋点：health_record_edit_succeeded(fieldCount) / edit_failed
///   （failureReason 含 conflict，recordType=health_event）。
class HealthEventEditPage extends StatefulWidget {
  const HealthEventEditPage({
    required this.repository,
    required this.event,
    super.key,
    this.analytics,
  });

  final PetsRepository repository;

  /// 编辑基线（含 version 乐观锁与差量比较基准）。
  final HealthEvent event;

  final HealthRecordAnalytics? analytics;

  @override
  State<HealthEventEditPage> createState() => _HealthEventEditPageState();
}

class _HealthEventEditPageState extends State<HealthEventEditPage> {
  late final TextEditingController _titleCtrl;
  late final TextEditingController _amountCtrl;
  late final TextEditingController _notesCtrl;

  /// 编辑基线：40902 冲突刷新后更新（version 与差量计算的比较基准）。
  late HealthEvent _base;

  String? _titleError;
  String? _amountError;
  String? _formError;
  bool _submitting = false;

  @override
  void initState() {
    super.initState();
    _base = widget.event;
    _titleCtrl = TextEditingController(text: _base.title);
    _amountCtrl = TextEditingController(
      text: _base.amountCents == null
          ? ''
          : formatCentsAsYuan(_base.amountCents!),
    );
    _notesCtrl = TextEditingController(text: _base.notes ?? '');
  }

  @override
  void dispose() {
    _titleCtrl.dispose();
    _amountCtrl.dispose();
    _notesCtrl.dispose();
    super.dispose();
  }

  void _trackFailed(HealthRecordFailureReason reason, [int? errorCode]) {
    widget.analytics?.editFailed(
      recordType: HealthRecordType.healthEvent,
      reason: reason,
      errorCode: errorCode,
    );
  }

  void _showFormError(String message) {
    setState(() => _formError = message);
    SemanticsService.sendAnnouncement(
      View.of(context),
      message,
      TextDirection.ltr,
    );
  }

  /// 差量请求：只含改动字段（契约不支持清空回 null——清空输入视为不变更）。
  /// 无实际变更返回 null。
  UpdateHealthEventRequest? _buildDiff() {
    final title = _titleCtrl.text.trim();
    final notes = _notesCtrl.text.trim();
    final amountText = _amountCtrl.text.trim();
    final amountCents = amountText.isEmpty
        ? null
        : parseYuanToCents(amountText);
    final request = UpdateHealthEventRequest(
      version: _base.version,
      title: title != _base.title ? title : null,
      notes: notes.isNotEmpty && notes != (_base.notes ?? '') ? notes : null,
      amountCents: amountCents != null && amountCents != _base.amountCents
          ? amountCents
          : null,
    );
    // 只剩 version 一个键 → 无实际变更。
    return request.toJson().length == 1 ? null : request;
  }

  Future<void> _submit() async {
    if (_submitting) return;
    final titleError = _titleCtrl.text.trim().isEmpty ? '标题不能为空' : null;
    final amountText = _amountCtrl.text.trim();
    final amountError =
        amountText.isNotEmpty && parseYuanToCents(amountText) == null
        ? '金额格式不正确，最多两位小数'
        : null;
    if (titleError != null || amountError != null) {
      setState(() {
        _titleError = titleError;
        _amountError = amountError;
      });
      _trackFailed(HealthRecordFailureReason.validationError);
      return;
    }
    final request = _buildDiff();
    if (request == null) {
      Navigator.of(context).pop();
      return;
    }

    setState(() {
      _submitting = true;
      _formError = null;
    });
    try {
      final updated = await widget.repository.updateHealthEvent(
        _base.id,
        request,
      );
      widget.analytics?.editSucceeded(
        recordType: HealthRecordType.healthEvent,
        fieldCount: request.toJson().length - 1,
      );
      if (mounted) Navigator.of(context).pop(updated);
    } on PetVersionConflictException {
      _trackFailed(HealthRecordFailureReason.conflict, 40902);
      await _handleVersionConflict();
    } on PetRecordNotFoundException {
      if (!mounted) return;
      final navigator = Navigator.of(context);
      ScaffoldMessenger.of(
        context,
      ).showSnackBar(const SnackBar(content: Text('记录不存在或已被删除')));
      _trackFailed(HealthRecordFailureReason.notFound, 40402);
      navigator.pop();
    } on PetAccessDeniedException {
      if (!mounted) return;
      _showFormError('你没有权限修改该记录');
      _trackFailed(HealthRecordFailureReason.permissionDenied, 40300);
    } on ApiRateLimitException {
      if (!mounted) return;
      _showFormError('操作过于频繁，请稍后再试');
      _trackFailed(HealthRecordFailureReason.rateLimited);
    } on ApiBusinessException catch (error) {
      if (!mounted) return;
      final isParam = error.code == ApiCodes.paramError;
      _showFormError(isParam ? '请检查填写内容后重试' : '保存失败，请稍后重试');
      _trackFailed(
        isParam
            ? HealthRecordFailureReason.validationError
            : HealthRecordFailureReason.serverError,
        error.code,
      );
    } on ApiNetworkException {
      if (!mounted) return;
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(
          content: const Text('网络异常，请检查网络后重试'),
          action: SnackBarAction(label: '重试', onPressed: _submit),
        ),
      );
      _trackFailed(HealthRecordFailureReason.networkError);
    } on SessionExpiredException {
      // 会话失效：认证状态机自动回登录页。
    } finally {
      if (mounted) setState(() => _submitting = false);
    }
  }

  /// 40902：提示 + 刷新路径——契约无按 id 读取端点，经时间线分页检索
  /// 取回最新版本更新乐观锁基线（保留用户输入），用户核对后重新保存。
  Future<void> _handleVersionConflict() async {
    try {
      final fresh = await _fetchLatest();
      if (!mounted) return;
      if (fresh == null) {
        final navigator = Navigator.of(context);
        ScaffoldMessenger.of(
          context,
        ).showSnackBar(const SnackBar(content: Text('记录不存在或已被删除')));
        navigator.pop();
        return;
      }
      setState(() => _base = fresh);
      _showFormError('记录已在其他设备被修改，已获取最新版本，请核对后重新保存');
    } on ApiException {
      if (!mounted) return;
      _showFormError('记录已在其他设备被修改，请返回后刷新重试');
    }
  }

  /// 按 occurred_at DESC 分页检索本记录（上限 10 页防御性截断）。
  Future<HealthEvent?> _fetchLatest() async {
    String? cursor;
    for (var page = 0; page < 10; page++) {
      final result = await widget.repository.listHealthEvents(
        _base.petId,
        limit: 50,
        cursor: cursor,
      );
      for (final item in result.items) {
        if (item.id == _base.id) return item;
      }
      if (!result.hasMore) return null;
      cursor = result.nextCursor;
    }
    return null;
  }

  @override
  Widget build(BuildContext context) {
    final style = recordTypeStyles[recordTypeForHealthEvent(_base.eventType)]!;
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.transparent,
        elevation: 0,
        foregroundColor: AppColors.ink,
        title: const Text('编辑健康事件'),
        centerTitle: true,
        titleTextStyle: const TextStyle(
          color: AppColors.ink,
          fontSize: 16,
          fontWeight: FontWeight.w800,
        ),
      ),
      body: SafeArea(
        child: ListView(
          padding: const EdgeInsets.fromLTRB(20, 8, 20, 30),
          children: [
            // 事件身份静态区：类型与发生时间不可编辑（契约不在请求体）。
            Row(
              children: [
                RecordTypeDot(
                  type: recordTypeForHealthEvent(_base.eventType),
                  size: RecordTypeDotSize.md,
                ),
                const SizedBox(width: 12),
                Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    Text(
                      healthEventTypeLabel(_base.eventType),
                      style: TextStyle(
                        color: style.inkColor,
                        fontSize: 14,
                        fontWeight: FontWeight.w700,
                      ),
                    ),
                    const SizedBox(height: 2),
                    Text(
                      formatOccurredAt(_base.occurredAt),
                      style: const TextStyle(
                        color: AppColors.inkSoft,
                        fontSize: 12,
                      ),
                    ),
                  ],
                ),
              ],
            ),
            const SizedBox(height: 18),
            AppTextField(
              label: '标题',
              controller: _titleCtrl,
              prefixIcon: Icons.title_outlined,
              errorText: _titleError,
              enabled: !_submitting,
              textInputAction: TextInputAction.next,
              onChanged: (_) {
                if (_titleError != null || _formError != null) {
                  setState(() {
                    _titleError = null;
                    _formError = null;
                  });
                }
              },
            ),
            const SizedBox(height: 14),
            AppTextField(
              label: '金额（元）',
              controller: _amountCtrl,
              prefixIcon: Icons.payments_outlined,
              errorText: _amountError,
              helperText: '以元填写，最多两位小数；清空视为不变更',
              enabled: !_submitting,
              keyboardType: const TextInputType.numberWithOptions(
                decimal: true,
              ),
              textInputAction: TextInputAction.next,
              onChanged: (_) {
                if (_amountError != null || _formError != null) {
                  setState(() {
                    _amountError = null;
                    _formError = null;
                  });
                }
              },
            ),
            const SizedBox(height: 14),
            AppTextField(
              label: '备注',
              controller: _notesCtrl,
              prefixIcon: Icons.sticky_note_2_outlined,
              enabled: !_submitting,
              textInputAction: TextInputAction.done,
              onSubmitted: (_) => _submit(),
            ),
            if (_formError != null) ...[
              const SizedBox(height: 16),
              InlineErrorBanner(message: _formError!),
            ],
            const SizedBox(height: 24),
            PrimaryButton(
              label: '保存修改',
              isLoading: _submitting,
              onPressed: _submit,
            ),
          ],
        ),
      ),
    );
  }
}