/// 相册创建/编辑表单页（UI-01 §4.5 分组重构，P3 计划 Task 4 基础）。
///
/// 三分组（SectionHeader）：活动信息（开始/结束时间 + 时区）/ 多语言
/// 内容（zh-CN · en 双语 tab：标题/描述/场地/地址按语言各一份——契约
/// translations 的场地/地址是逐语言字段，不合并为共享输入）/ 访问设置
/// （默认语言 + 开关组：创建仅 download/original，编辑四开关独立）。
/// 保存按钮固定在 bottomNavigationBar——键盘打开时常驻可达（§4.5）。
/// 编辑提交经 [AlbumFormDraft.toUpdatePatch] 最小化 PATCH（仅变更字段）；
/// 无变更时保存禁用。成功 pop(true) 供调用方刷新列表/详情。
library;

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../core/api_client.dart';
import '../core/app_exception.dart';
import '../core/error_l10n.dart';
import '../features/albums/album_format.dart';
import '../features/albums/album_form.dart';
import '../features/albums/models.dart';
import '../l10n/app_localizations.dart';
import '../ui/components/section_header.dart';
import '../ui/tokens.dart';

/// 创建（[existing] 为 null）/ 编辑相册表单。
class AlbumFormPage extends ConsumerStatefulWidget {
  const AlbumFormPage({this.existing, this.initialDraft, super.key});

  /// 编辑目标；null = 创建模式。
  final Album? existing;

  /// 初始草稿（测试注入/预填）；缺省从 [existing] 构建或全新（创建）。
  final AlbumFormDraft? initialDraft;

  @override
  ConsumerState<AlbumFormPage> createState() => _AlbumFormPageState();
}

class _AlbumFormPageState extends ConsumerState<AlbumFormPage> {
  static const String _zh = 'zh-CN';
  static const String _en = 'en';

  late final List<TextEditingController> _controllers;

  late final TextEditingController _zhTitle;
  late final TextEditingController _zhDescription;
  late final TextEditingController _zhVenue;
  late final TextEditingController _zhAddress;
  late final TextEditingController _enTitle;
  late final TextEditingController _enDescription;
  late final TextEditingController _enVenue;
  late final TextEditingController _enAddress;
  late final TextEditingController _timezone;

  late String _defaultLocale;
  DateTime? _startAt;
  DateTime? _endAt;
  late bool _uploadEnabled;
  late bool _publicEnabled;
  late bool _downloadEnabled;
  late bool _originalDownloadEnabled;

  int _tabIndex = 0;
  List<AlbumFormError> _errors = const <AlbumFormError>[];
  bool _submitting = false;

  bool get _isCreate => widget.existing == null;

  @override
  void initState() {
    super.initState();
    final initial = widget.existing == null
        ? (widget.initialDraft ??
              AlbumFormDraft(
                zh: const AlbumTranslationDraft(locale: _zh),
                en: const AlbumTranslationDraft(locale: _en),
                defaultLocale: _zh,
                timezone: 'Asia/Shanghai',
              ))
        : (widget.initialDraft ?? AlbumFormDraft.fromAlbum(widget.existing!));
    _zhTitle = TextEditingController(text: initial.zh.title);
    _zhDescription = TextEditingController(text: initial.zh.description);
    _zhVenue = TextEditingController(text: initial.zh.venue);
    _zhAddress = TextEditingController(text: initial.zh.address);
    _enTitle = TextEditingController(text: initial.en.title);
    _enDescription = TextEditingController(text: initial.en.description);
    _enVenue = TextEditingController(text: initial.en.venue);
    _enAddress = TextEditingController(text: initial.en.address);
    _timezone = TextEditingController(text: initial.timezone);
    _controllers = [
      _zhTitle,
      _zhDescription,
      _zhVenue,
      _zhAddress,
      _enTitle,
      _enDescription,
      _enVenue,
      _enAddress,
      _timezone,
    ];
    _defaultLocale = initial.defaultLocale;
    _startAt = initial.startAt;
    _endAt = initial.endAt;
    _uploadEnabled = initial.uploadEnabled;
    _publicEnabled = initial.publicEnabled;
    _downloadEnabled = initial.downloadEnabled;
    _originalDownloadEnabled = initial.originalDownloadEnabled;
  }

  @override
  void dispose() {
    for (final c in _controllers) {
      c.dispose();
    }
    super.dispose();
  }

  AlbumFormDraft _currentDraft() => AlbumFormDraft(
    zh: AlbumTranslationDraft(
      locale: _zh,
      title: _zhTitle.text,
      description: _zhDescription.text,
      venue: _zhVenue.text,
      address: _zhAddress.text,
    ),
    en: AlbumTranslationDraft(
      locale: _en,
      title: _enTitle.text,
      description: _enDescription.text,
      venue: _enVenue.text,
      address: _enAddress.text,
    ),
    defaultLocale: _defaultLocale,
    timezone: _timezone.text,
    startAt: _startAt,
    endAt: _endAt,
    uploadEnabled: _uploadEnabled,
    publicEnabled: _publicEnabled,
    downloadEnabled: _downloadEnabled,
    originalDownloadEnabled: _originalDownloadEnabled,
  );

  /// 编辑模式：与原值无任何差异时禁用保存（PATCH minProperties 1）。
  bool get _canSubmit {
    if (_submitting) return false;
    if (_isCreate) return true;
    return _currentDraft().toUpdatePatch(widget.existing!) != null;
  }

  Future<void> _submit() async {
    final draft = _currentDraft();
    final errors = draft.validate();
    if (errors.isNotEmpty) {
      setState(() => _errors = errors);
      return;
    }
    setState(() {
      _submitting = true;
      _errors = const <AlbumFormError>[];
    });
    final l10n = AppLocalizations.of(context);
    final messenger = ScaffoldMessenger.of(context);
    final navigator = Navigator.of(context);
    try {
      if (_isCreate) {
        await ref.read(apiClientProvider).createAlbum(draft.toCreateRequest());
      } else {
        final patch = draft.toUpdatePatch(widget.existing!);
        if (patch == null) {
          navigator.pop(false);
          return;
        }
        await ref
            .read(apiClientProvider)
            .updateAlbum(widget.existing!.id, patch);
      }
      navigator.pop(true);
    } on AppException catch (error) {
      messenger.showSnackBar(
        SnackBar(content: Text(l10n.messageForError(error))),
      );
    } on Object {
      messenger.showSnackBar(SnackBar(content: Text(l10n.errorGeneric)));
    } finally {
      if (mounted) setState(() => _submitting = false);
    }
  }

  /// 日期 + 时间选择器 → 相册时区墙钟 → UTC 瞬间。
  Future<void> _pickDateTime({required bool isStart}) async {
    final tzName = _timezone.text.trim();
    final initial = (isStart ? _startAt : _endAt) ?? _startAt ?? DateTime.now();
    final wall = tryToAlbumZone(initial, tzName) ?? initial.toUtc();
    final pickedDate = await showDatePicker(
      context: context,
      initialDate: wall,
      firstDate: DateTime(2000),
      lastDate: DateTime(2100),
    );
    if (pickedDate == null || !mounted) return;
    final pickedTime = await showTimePicker(
      context: context,
      initialTime: TimeOfDay(hour: wall.hour, minute: wall.minute),
    );
    if (pickedTime == null || !mounted) return;
    final naive = DateTime(
      pickedDate.year,
      pickedDate.month,
      pickedDate.day,
      pickedTime.hour,
      pickedTime.minute,
    );
    final utc = albumWallClockToUtc(naive, tzName);
    setState(() {
      if (isStart) {
        _startAt = utc;
      } else {
        _endAt = utc;
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    // DefaultTabController 仅为 TabBar 提供 controller（内容区非
    // TabBarView，而是按 _tabIndex 手动切换，避免两 tab 表单失焦重建）。
    return DefaultTabController(
      length: 2,
      child: Scaffold(
        appBar: AppBar(
          title: Text(_isCreate ? l10n.albumCreate : l10n.albumEdit),
        ),
        // 保存按钮固定底部：键盘打开时常驻可达（§4.5）。
        bottomNavigationBar: SafeArea(
          minimum: const EdgeInsets.fromLTRB(16, 8, 16, 12),
          child: FilledButton(
            onPressed: _canSubmit ? _submit : null,
            child: _submitting
                ? const SizedBox(
                    height: 20,
                    width: 20,
                    child: CircularProgressIndicator(strokeWidth: 2),
                  )
                : Text(_isCreate ? l10n.create : l10n.save),
          ),
        ),
        body: Form(
          child: SingleChildScrollView(
            child: Padding(
              padding: const EdgeInsets.all(16),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  // ── 分组 1：活动信息 ────────────────────────────────
                  SectionHeader(title: l10n.albumSectionEventInfo),
                  const SizedBox(height: kSpace12),
                  _dateTimeRow(isStart: true),
                  _dateTimeRow(isStart: false),
                  const SizedBox(height: 8),
                  TextFormField(
                    controller: _timezone,
                    onChanged: (_) => setState(() {}),
                    decoration: InputDecoration(labelText: l10n.albumTimezone),
                  ),
                  const SizedBox(height: kSpace24),

                  // ── 分组 2：多语言内容（tab 切换，另一语言按需填写）──
                  SectionHeader(title: l10n.albumSectionContent),
                  const SizedBox(height: kSpace8),
                  TabBar(
                    onTap: (index) => setState(() => _tabIndex = index),
                    tabs: [
                      Tab(text: l10n.localeChinese),
                      Tab(text: l10n.localeEnglish),
                    ],
                  ),
                  const SizedBox(height: kSpace12),
                  if (_tabIndex == 0)
                    _translationFields(
                      title: _zhTitle,
                      description: _zhDescription,
                      venue: _zhVenue,
                      address: _zhAddress,
                      isDefault: _defaultLocale == _zh,
                    )
                  else
                    _translationFields(
                      title: _enTitle,
                      description: _enDescription,
                      venue: _enVenue,
                      address: _enAddress,
                      isDefault: _defaultLocale == _en,
                    ),
                  const SizedBox(height: kSpace24),

                  // ── 分组 3：访问设置 ────────────────────────────────
                  SectionHeader(title: l10n.albumSectionAccess),
                  const SizedBox(height: kSpace12),
                  Text(l10n.albumDefaultLocale),
                  const SizedBox(height: kSpace8),
                  SegmentedButton<String>(
                    segments: [
                      ButtonSegment(value: _zh, label: Text(l10n.localeChinese)),
                      ButtonSegment(value: _en, label: Text(l10n.localeEnglish)),
                    ],
                    selected: {_defaultLocale},
                    onSelectionChanged: (selection) =>
                        setState(() => _defaultLocale = selection.first),
                  ),
                  const SizedBox(height: kSpace16),
                  if (!_isCreate) ...[
                    SwitchListTile(
                      contentPadding: EdgeInsets.zero,
                      title: Text(l10n.switchUpload),
                      value: _uploadEnabled,
                      onChanged: (v) => setState(() => _uploadEnabled = v),
                    ),
                    SwitchListTile(
                      contentPadding: EdgeInsets.zero,
                      title: Text(l10n.switchPublic),
                      value: _publicEnabled,
                      onChanged: (v) => setState(() => _publicEnabled = v),
                    ),
                  ],
                  SwitchListTile(
                    contentPadding: EdgeInsets.zero,
                    title: Text(l10n.switchDownload),
                    value: _downloadEnabled,
                    onChanged: (v) => setState(() => _downloadEnabled = v),
                  ),
                  SwitchListTile(
                    contentPadding: EdgeInsets.zero,
                    title: Text(l10n.switchOriginalDownload),
                    value: _originalDownloadEnabled,
                    onChanged: (v) =>
                        setState(() => _originalDownloadEnabled = v),
                  ),
                  if (_errors.isNotEmpty) ...[
                    const SizedBox(height: kSpace8),
                    ..._errors.map(
                      (e) => Padding(
                        padding: const EdgeInsets.only(bottom: 4),
                        child: Text(
                          _errorText(l10n, e),
                          style: TextStyle(
                            color: Theme.of(context).colorScheme.error,
                          ),
                        ),
                      ),
                    ),
                  ],
                  const SizedBox(height: kSpace24),
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }

  Widget _translationFields({
    required TextEditingController title,
    required TextEditingController description,
    required TextEditingController venue,
    required TextEditingController address,
    required bool isDefault,
  }) {
    final l10n = AppLocalizations.of(context);
    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        TextFormField(
          controller: title,
          onChanged: (_) => setState(() {}),
          decoration: InputDecoration(
            labelText: isDefault ? '${l10n.albumTitle} *' : l10n.albumTitle,
          ),
        ),
        const SizedBox(height: 12),
        TextFormField(
          controller: description,
          onChanged: (_) => setState(() {}),
          maxLines: 2,
          decoration: InputDecoration(labelText: l10n.albumDescription),
        ),
        const SizedBox(height: 12),
        TextFormField(
          controller: venue,
          onChanged: (_) => setState(() {}),
          decoration: InputDecoration(labelText: l10n.albumVenue),
        ),
        const SizedBox(height: 12),
        TextFormField(
          controller: address,
          onChanged: (_) => setState(() {}),
          decoration: InputDecoration(labelText: l10n.albumAddress),
        ),
      ],
    );
  }

  /// 开始（必填）/ 结束（可选、可清除）时间行；展示按当前时区输入换算。
  Widget _dateTimeRow({required bool isStart}) {
    final l10n = AppLocalizations.of(context);
    final theme = Theme.of(context);
    final value = isStart ? _startAt : _endAt;
    final formatted = value == null
        ? null
        : formatAlbumDateTime(value, _timezone.text, l10n.localeName);
    return Padding(
      padding: const EdgeInsets.only(bottom: 12),
      child: InkWell(
        onTap: () => _submitting ? null : _pickDateTime(isStart: isStart),
        borderRadius: BorderRadius.circular(8),
        child: InputDecorator(
          decoration: InputDecoration(
            labelText: isStart ? l10n.albumStartAt : l10n.albumEndAtOptional,
            suffixIcon: value == null
                ? const Icon(Icons.edit_calendar_outlined)
                : Row(
                    mainAxisSize: MainAxisSize.min,
                    children: [
                      const Icon(Icons.edit_calendar_outlined),
                      if (!isStart)
                        IconButton(
                          tooltip: l10n.clearEndAt,
                          icon: const Icon(Icons.clear),
                          onPressed: _submitting
                              ? null
                              : () => setState(() => _endAt = null),
                        ),
                    ],
                  ),
          ),
          child: Text(
            formatted ?? (isStart ? l10n.formStartAtRequired : l10n.notSet),
            style: formatted == null
                ? theme.textTheme.bodyMedium?.copyWith(
                    color: theme.colorScheme.onSurfaceVariant,
                  )
                : theme.textTheme.bodyMedium,
          ),
        ),
      ),
    );
  }

  String _errorText(AppLocalizations l10n, AlbumFormError error) {
    switch (error) {
      case AlbumFormError.defaultLocaleMissing:
        return l10n.formDefaultLocaleMissing;
      case AlbumFormError.titleRequiredWithFields:
        return l10n.formTitleRequiredWithFields;
      case AlbumFormError.startAtRequired:
        return l10n.formStartAtRequired;
      case AlbumFormError.endAtNotAfterStartAt:
        return l10n.formEndAtNotAfterStartAt;
      case AlbumFormError.timezoneInvalid:
        return l10n.albumTimezoneInvalid;
    }
  }
}