import "package:flutter/material.dart";

import "../main.dart";
import "../models.dart";
import "../format.dart";
import "../theme.dart";

/// Admin-only screen to manage user accounts: list, create, change role,
/// reset password, delete. The API enforces the real access control and the
/// last-admin / self-delete guards; the UI mirrors them to avoid dead actions.
class AdminUsersScreen extends StatefulWidget {
  const AdminUsersScreen({super.key});
  @override
  State<AdminUsersScreen> createState() => _AdminUsersScreenState();
}

class _AdminUsersScreenState extends State<AdminUsersScreen> {
  late Future<List<AdminUser>> _future;

  @override
  void initState() {
    super.initState();
    _future = apiClient.listUsers();
  }

  void _reload() => setState(() => _future = apiClient.listUsers());

  String? get _myId => authService.user?.id;

  void _snack(String msg) =>
      ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text(msg)));

  Future<void> _changeRole(AdminUser u, String role) async {
    try {
      await apiClient.updateUser(u.id, role: role);
      _reload();
    } catch (e) {
      _snack("$e");
    }
  }

  Future<void> _resetPassword(AdminUser u) async {
    final controller = TextEditingController();
    final saved = await showDialog<bool>(
      context: context,
      builder: (ctx) => AlertDialog(
        title: Text("Reset password — ${u.email}"),
        content: TextField(
          controller: controller,
          autofocus: true,
          decoration: const InputDecoration(
            labelText: "New password (min 8)",
            border: OutlineInputBorder(),
          ),
        ),
        actions: [
          TextButton(onPressed: () => Navigator.pop(ctx, false), child: const Text("Cancel")),
          FilledButton(onPressed: () => Navigator.pop(ctx, true), child: const Text("Set password")),
        ],
      ),
    );
    if (saved != true) return;
    try {
      await apiClient.setUserPassword(u.id, controller.text);
      _snack("Password updated.");
    } catch (e) {
      _snack("$e");
    }
  }

  Future<void> _delete(AdminUser u) async {
    final confirmed = await showDialog<bool>(
      context: context,
      builder: (ctx) => AlertDialog(
        title: const Text("Delete user?"),
        content: Text("Delete ${u.name.isEmpty ? u.email : u.name}? This cannot be undone."),
        actions: [
          TextButton(onPressed: () => Navigator.pop(ctx, false), child: const Text("Cancel")),
          FilledButton(
            style: FilledButton.styleFrom(backgroundColor: DriverVault.danger),
            onPressed: () => Navigator.pop(ctx, true),
            child: const Text("Delete"),
          ),
        ],
      ),
    );
    if (confirmed != true) return;
    try {
      await apiClient.deleteUser(u.id);
      _reload();
    } catch (e) {
      _snack("$e");
    }
  }

  Future<void> _createUser() async {
    final created = await showModalBottomSheet<bool>(
      context: context,
      isScrollControlled: true,
      builder: (_) => const _CreateUserSheet(),
    );
    if (created == true) _reload();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text("Users")),
      floatingActionButton: FloatingActionButton.extended(
        onPressed: _createUser,
        icon: const Icon(Icons.person_add_alt_1),
        label: const Text("Add user"),
      ),
      body: FutureBuilder<List<AdminUser>>(
        future: _future,
        builder: (context, snap) {
          if (snap.connectionState == ConnectionState.waiting) {
            return const Center(child: CircularProgressIndicator());
          }
          if (snap.hasError) {
            return Center(child: Text("${snap.error}"));
          }
          final users = snap.data ?? [];
          final adminCount = users.where((u) => u.role == "admin").length;
          return ListView.separated(
            padding: const EdgeInsets.all(12),
            itemCount: users.length,
            separatorBuilder: (_, __) => const Divider(height: 1),
            itemBuilder: (context, i) {
              final u = users[i];
              final isSelf = u.id == _myId;
              final lastAdmin = u.role == "admin" && adminCount <= 1;
              return ListTile(
                contentPadding: const EdgeInsets.symmetric(horizontal: 4),
                title: Row(
                  children: [
                    Flexible(child: Text(u.email, overflow: TextOverflow.ellipsis)),
                    if (isSelf)
                      const Padding(
                        padding: EdgeInsets.only(left: 6),
                        child: Text("(you)", style: TextStyle(color: Colors.grey, fontSize: 12)),
                      ),
                  ],
                ),
                subtitle: Text(
                  "${u.name.isEmpty ? '—' : u.name} · ${formatDate(DateTime.tryParse(u.created))}",
                  style: const TextStyle(fontSize: 12),
                ),
                trailing: Row(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    DropdownButton<String>(
                      value: u.role == "admin" ? "admin" : "user",
                      underline: const SizedBox.shrink(),
                      // Disable demoting the last admin.
                      onChanged: lastAdmin ? null : (v) => v == null ? null : _changeRole(u, v),
                      items: const [
                        DropdownMenuItem(value: "user", child: Text("user")),
                        DropdownMenuItem(value: "admin", child: Text("admin")),
                      ],
                    ),
                    PopupMenuButton<String>(
                      onSelected: (choice) {
                        if (choice == "password") _resetPassword(u);
                        if (choice == "delete") _delete(u);
                      },
                      itemBuilder: (_) => [
                        const PopupMenuItem(value: "password", child: Text("Reset password")),
                        PopupMenuItem(
                          value: "delete",
                          // Can't delete yourself or the last admin.
                          enabled: !isSelf && !lastAdmin,
                          child: const Text("Delete", style: TextStyle(color: DriverVault.danger)),
                        ),
                      ],
                    ),
                  ],
                ),
              );
            },
          );
        },
      ),
    );
  }
}

class _CreateUserSheet extends StatefulWidget {
  const _CreateUserSheet();
  @override
  State<_CreateUserSheet> createState() => _CreateUserSheetState();
}

class _CreateUserSheetState extends State<_CreateUserSheet> {
  final _email = TextEditingController();
  final _name = TextEditingController();
  final _password = TextEditingController();
  String _role = "user";
  bool _saving = false;
  String? _error;

  @override
  void dispose() {
    _email.dispose();
    _name.dispose();
    _password.dispose();
    super.dispose();
  }

  Future<void> _save() async {
    setState(() {
      _saving = true;
      _error = null;
    });
    try {
      await apiClient.createUser(
        email: _email.text.trim(),
        password: _password.text,
        name: _name.text.trim(),
        role: _role,
      );
      if (mounted) Navigator.pop(context, true);
    } catch (e) {
      setState(() => _error = e.toString());
    } finally {
      if (mounted) setState(() => _saving = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: EdgeInsets.only(
        left: 16,
        right: 16,
        top: 16,
        bottom: MediaQuery.of(context).viewInsets.bottom + 16,
      ),
      child: Column(
        mainAxisSize: MainAxisSize.min,
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          const Text("Add a user",
              style: TextStyle(fontSize: 18, fontWeight: FontWeight.w600)),
          const SizedBox(height: 12),
          if (_error != null)
            Padding(
              padding: const EdgeInsets.only(bottom: 8),
              child: Text(_error!, style: const TextStyle(color: DriverVault.danger)),
            ),
          TextField(
            controller: _email,
            keyboardType: TextInputType.emailAddress,
            decoration: const InputDecoration(labelText: "Email", border: OutlineInputBorder()),
          ),
          const SizedBox(height: 8),
          TextField(
            controller: _name,
            decoration: const InputDecoration(labelText: "Name", border: OutlineInputBorder()),
          ),
          const SizedBox(height: 8),
          Row(
            children: [
              Expanded(
                child: TextField(
                  controller: _password,
                  decoration: const InputDecoration(
                    labelText: "Password (min 8)",
                    border: OutlineInputBorder(),
                  ),
                ),
              ),
              const SizedBox(width: 8),
              DropdownButton<String>(
                value: _role,
                onChanged: (v) => setState(() => _role = v ?? "user"),
                items: const [
                  DropdownMenuItem(value: "user", child: Text("user")),
                  DropdownMenuItem(value: "admin", child: Text("admin")),
                ],
              ),
            ],
          ),
          const SizedBox(height: 12),
          SizedBox(
            width: double.infinity,
            child: FilledButton(
              onPressed: _saving ? null : _save,
              child: Text(_saving ? "Creating…" : "Create user"),
            ),
          ),
        ],
      ),
    );
  }
}