/// 成员管理页（P3 计划 Task 4）：成员列表（角色标签、owner 徽标、
/// 本人/创建者不可移除）+ 账号前缀搜索邀请（300ms 防抖、≥2 字符、
/// lookupUsers 远程搜索）+ 移除确认。MEMBER_CONFLICT 本地化覆盖。
library;

import 'dart:async';

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_codes.dart';
import '../core/error_l10n.dart';
import '../features/albums/models.dart';
import '../l10n/app_localizations.dart';

/// 成员管理（从详情页携带完整 [album] 进入）。
class AlbumMembersPage extends ConsumerStatefulWidget {
  const AlbumMembersPage({required this.album, super.key});

  final Album album;

  @override
  ConsumerState<AlbumMembersPage> createState() => _AlbumMembersPageState();
}

class _AlbumMembersPageState extends ConsumerState<AlbumMembersPage> {
  static const int _pageSize = 50;

  List<Member> _items = const <Member>[];
  String? _nextCursor;
  bool _hasMore = false;
  bool _loading = true;
  bool _loadingMore = false;
  String? _errorCode;

  /// 当前登录账号（本人移除 UI 拦截用）；读取失败按未知处理。
  String? _selfAccount;

  final TextEditingController _searchController = TextEditingController();
  Timer? _debounce;
  bool _searching = false;
  List<AdminUserLookupItem>? _results;

  @override
  void initState() {
    super.initState();
    _loadSelfAccount();
    _reload();
  }

  @override
  void dispose() {
    _debounce?.cancel();
    _searchController.dispose();
    super.dispose();
  }

  Future<void> _loadSelfAccount() async {
    try {
      final session = await ref.read(sessionStoreProvider).read();
      if (mounted) {
        setState(() => _selfAccount = session?.account);
      }
    } on Object {
      // 存储读取失败不阻断页面（移除按钮保护回退服务端 403/409 裁决）。
    }
  }

  Future<void> _reload() async {
    setState(() {
      _loading = true;
      _errorCode = null;
    });
    try {
      final page = await ref
          .read(apiClientProvider)
          .listMembers(widget.album.id, limit: _pageSize);
      if (mounted) {
        setState(() {
          _items = page.items;
          _nextCursor = page.nextCursor;
          _hasMore = page.hasMore;
          _loading = false;
        });
      }
    } on AppException catch (e) {
      if (mounted) {
        setState(() {
          _errorCode = e.code;
          _loading = false;
        });
      }
    } on Object {
      if (mounted) {
        setState(() {
          _errorCode = ErrorCodes.internalError;
          _loading = false;
        });
      }
    }
  }

  Future<void> _loadMore() async {
    if (_loading || _loadingMore || !_hasMore) return;
    setState(() => _loadingMore = true);
    try {
      final page = await ref.read(apiClientProvider).listMembers(
            widget.album.id,
            cursor: _nextCursor,
            limit: _pageSize,
          );
      if (mounted) {
        setState(() {
          _items = <Member>[..._items, ...page.items];
          _nextCursor = page.nextCursor;
          _hasMore = page.hasMore;
          _loadingMore = false;
        });
      }
    } on AppException catch (e) {
      if (mounted) {
        setState(() => _loadingMore = false);
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(content: Text(AppLocalizations.of(context).messageForError(e))),
        );
      }
    } on Object {
      if (mounted) {
        setState(() => _loadingMore = false);
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(
            content: Text(AppLocalizations.of(context).errorGeneric),
          ),
        );
      }
    }
  }

  // ── 邀请搜索（防抖 300ms、≥2 字符） ──

  void _onSearchChanged(String text) {
    _debounce?.cancel();
    final query = text.trim();
    if (query.length < 2) {
      setState(() {
        _searching = false;
        _results = null;
      });
      return;
    }
    _debounce = Timer(const Duration(milliseconds: 300), () {
      _runSearch(query);
    });
  }

  Future<void> _runSearch(String query) async {
    setState(() => _searching = true);
    try {
      final items = await ref
          .read(apiClientProvider)
          .lookupUsers(query, limit: 10);
      // 迟到响应守卫：仅当输入未再变化时应用结果。
      if (!mounted || query != _searchController.text.trim()) return;
      setState(() {
        _results = items;
        _searching = false;
      });
    } on AppException catch (e) {
      if (!mounted || query != _searchController.text.trim()) return;
      setState(() => _searching = false);
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(
          content: Text(AppLocalizations.of(context).messageForError(e)),
        ),
      );
    } on Object {
      if (!mounted || query != _searchController.text.trim()) return;
      setState(() => _searching = false);
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text(AppLocalizations.of(context).errorGeneric)),
      );
    }
  }

  Future<void> _invite(AdminUserLookupItem user) async {
    final l10n = AppLocalizations.of(context);
    final messenger = ScaffoldMessenger.of(context);
    try {
      await ref.read(apiClientProvider).addMember(
            widget.album.id,
            user.id,
          );
      if (!mounted) return;
      messenger.showSnackBar(
        SnackBar(content: Text(l10n.memberInvited)),
      );
      _searchController.clear();
      setState(() => _results = null);
      await _reload();
    } on AppException catch (e) {
      messenger.showSnackBar(
        SnackBar(
          content: Text(
            e.code == ErrorCodes.memberConflict
                ? l10n.errorMemberConflict
                : l10n.messageForError(e),
          ),
        ),
      );
    } on Object {
      messenger.showSnackBar(
        SnackBar(content: Text(l10n.errorGeneric)),
      );
    }
  }

  Future<void> _remove(Member member) async {
    final l10n = AppLocalizations.of(context);
    final confirmed = await showDialog<bool>(
      context: context,
      builder: (_) => AlertDialog(
        title: Text(l10n.removeMember),
        content: Text(l10n.removeMemberConfirm),
        actions: [
          TextButton(
            onPressed: () => Navigator.of(context).pop(false),
            child: Text(l10n.cancel),
          ),
          FilledButton(
            onPressed: () => Navigator.of(context).pop(true),
            child: Text(l10n.delete),
          ),
        ],
      ),
    );
    if (confirmed != true || !mounted) return;
    final messenger = ScaffoldMessenger.of(context);
    try {
      await ref
          .read(apiClientProvider)
          .removeMember(widget.album.id, member.userId);
      await _reload();
    } on AppException catch (e) {
      messenger.showSnackBar(
        SnackBar(content: Text(l10n.messageForError(e))),
      );
    } on Object {
      messenger.showSnackBar(
        SnackBar(content: Text(l10n.errorGeneric)),
      );
    }
  }

  bool _canRemove(Member member) =>
      member.role != MemberRole.owner && member.account != _selfAccount;

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    return Scaffold(
      appBar: AppBar(title: Text(l10n.albumMembers)),
      body: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          Padding(
            padding: const EdgeInsets.fromLTRB(16, 12, 16, 4),
            child: TextField(
              controller: _searchController,
              onChanged: _onSearchChanged,
              decoration: InputDecoration(
                prefixIcon: const Icon(Icons.person_search_outlined),
                hintText: l10n.inviteSearchHint,
                border: const OutlineInputBorder(),
                suffixIcon: _searching
                    ? const Padding(
                        padding: EdgeInsets.all(12),
                        child: SizedBox(
                          height: 18,
                          width: 18,
                          child: CircularProgressIndicator(strokeWidth: 2),
                        ),
                      )
                    : (_searchController.text.isEmpty
                          ? null
                          : IconButton(
                              icon: const Icon(Icons.clear),
                              onPressed: () {
                                _searchController.clear();
                                _onSearchChanged('');
                              },
                            )),
              ),
            ),
          ),
          if (_results != null) _searchResults(l10n),
          const Divider(height: 1, indent: 16, endIndent: 16),
          Expanded(child: _memberList(l10n)),
        ],
      ),
    );
  }

  /// 搜索结果面板（有限高度内滚动；无结果显示占位文案）。
  Widget _searchResults(AppLocalizations l10n) {
    final results = _results!;
    if (results.isEmpty) {
      return Padding(
        padding: const EdgeInsets.symmetric(vertical: 12),
        child: Text(
          l10n.inviteNoResults,
          textAlign: TextAlign.center,
          style: Theme.of(context).textTheme.bodySmall,
        ),
      );
    }
    return ConstrainedBox(
      constraints: const BoxConstraints(maxHeight: 220),
      child: ListView(
        shrinkWrap: true,
        children: [
          for (final user in results)
            ListTile(
              dense: true,
              leading: CircleAvatar(child: Text(user.account.substring(0, 1).toUpperCase())),
              title: Text(user.account),
              subtitle: Text(user.displayName),
              trailing: FilledButton.tonal(
                onPressed: () => _invite(user),
                child: Text(l10n.invite),
              ),
            ),
        ],
      ),
    );
  }

  Widget _memberList(AppLocalizations l10n) {
    if (_loading) {
      return const Center(child: CircularProgressIndicator());
    }
    if (_items.isEmpty) {
      if (_errorCode != null) {
        return Center(
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              const Icon(Icons.cloud_off, size: 48),
              const SizedBox(height: 12),
              Text(l10n.messageForErrorCode(_errorCode!)),
              const SizedBox(height: 12),
              FilledButton.icon(
                onPressed: _reload,
                icon: const Icon(Icons.refresh),
                label: Text(l10n.retry),
              ),
            ],
          ),
        );
      }
      return Center(child: Text(l10n.albumMembersEmpty));
    }
    return ListView.builder(
      itemCount: _items.length + (_hasMore || _loadingMore ? 1 : 0),
      itemBuilder: (context, index) {
        if (index >= _items.length) {
          return const Padding(
            padding: EdgeInsets.symmetric(vertical: 16),
            child: Center(
              child: SizedBox(
                height: 24,
                width: 24,
                child: CircularProgressIndicator(strokeWidth: 2),
              ),
            ),
          );
        }
        if (index >= _items.length - 3 && _hasMore && !_loadingMore) {
          WidgetsBinding.instance.addPostFrameCallback((_) => _loadMore());
        }
        final member = _items[index];
        final isSelf = member.account == _selfAccount;
        return ListTile(
          leading: CircleAvatar(
            child: Text(
              member.account.substring(0, 1).toUpperCase(),
            ),
          ),
          title: Text(
            isSelf ? '${member.account}${l10n.selfMarker}' : member.account,
          ),
          subtitle: Text(member.displayName),
          trailing: Row(
            mainAxisSize: MainAxisSize.min,
            children: [
              _RoleChip(role: member.role),
              if (_canRemove(member))
                IconButton(
                  tooltip: l10n.removeMember,
                  icon: const Icon(Icons.person_remove_outlined),
                  onPressed: () => _remove(member),
                ),
            ],
          ),
        );
      },
    );
  }
}

/// 角色标签：owner 附星标（创建者徽标）。
class _RoleChip extends StatelessWidget {
  const _RoleChip({required this.role});

  final MemberRole role;

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    final theme = Theme.of(context);
    final owner = role == MemberRole.owner;
    return Container(
      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 2),
      decoration: BoxDecoration(
        color: owner
            ? theme.colorScheme.tertiaryContainer
            : theme.colorScheme.surfaceContainerHighest,
        borderRadius: BorderRadius.circular(999),
      ),
      child: Row(
        mainAxisSize: MainAxisSize.min,
        children: [
          if (owner)
            Icon(
              Icons.star,
              size: 12,
              color: theme.colorScheme.onTertiaryContainer,
            ),
          if (owner) const SizedBox(width: 4),
          Text(
            owner ? l10n.roleOwner : l10n.roleCollaborator,
            style: theme.textTheme.labelSmall?.copyWith(
              color: owner
                  ? theme.colorScheme.onTertiaryContainer
                  : theme.colorScheme.onSurfaceVariant,
            ),
          ),
        ],
      ),
    );
  }
}