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

import '../../core/theme/app_colors.dart';
import '../../core/widgets/app_icon.dart';
import '../../core/widgets/app_icon_image.dart';
import '../../core/widgets/pressable.dart';
import '../../data/models/app_entry.dart';
import '../home/launcher_controller.dart';

/// Every launchable app, with real icons and a search field. The header is
/// page content; there is no persistent app bar.
class AllAppsScreen extends StatefulWidget {
  const AllAppsScreen({super.key});

  @override
  State<AllAppsScreen> createState() => _AllAppsScreenState();
}

class _AllAppsScreenState extends State<AllAppsScreen> {
  final _search = TextEditingController();
  String _query = '';

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (mounted) context.read<LauncherController>().loadApps(force: true);
    });
  }

  @override
  void dispose() {
    _search.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final colors = context.colors;
    final theme = Theme.of(context);
    final launcher = context.watch<LauncherController>();
    final query = _query.trim().toLowerCase();
    final apps = launcher.apps
        .where(
          (app) => query.isEmpty || app.label.toLowerCase().contains(query),
        )
        .toList(growable: false);

    return Scaffold(
      backgroundColor: colors.canvas,
      body: Container(
        decoration: homeBackground(colors, Theme.of(context).brightness),
        child: SafeArea(
          child: Padding(
            padding: const EdgeInsets.fromLTRB(36, 24, 36, 16),
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Row(
                  children: [
                    _BackButton(onTap: () => Navigator.of(context).pop()),
                    const SizedBox(width: 18),
                    Expanded(
                      child: Column(
                        crossAxisAlignment: CrossAxisAlignment.start,
                        children: [
                          Text(
                            'All apps',
                            style: theme.textTheme.headlineLarge,
                          ),
                          const SizedBox(height: 2),
                          Text(
                            '${apps.length} installed ${apps.length == 1 ? 'app' : 'apps'}'
                            ' · hold an app to add it to Home',
                            maxLines: 1,
                            overflow: TextOverflow.ellipsis,
                            style: theme.textTheme.bodySmall?.copyWith(
                              color: colors.inkMuted,
                            ),
                          ),
                        ],
                      ),
                    ),
                    SizedBox(
                      width: 300,
                      child: TextField(
                        controller: _search,
                        onChanged: (value) => setState(() => _query = value),
                        style: theme.textTheme.bodyMedium,
                        decoration: InputDecoration(
                          hintText: 'Search apps',
                          isDense: true,
                          prefixIcon: Padding(
                            padding: const EdgeInsets.only(left: 2),
                            child: AppIcon(
                              'assets/icons/search.svg',
                              size: 18,
                              color: colors.inkFaint,
                            ),
                          ),
                        ),
                      ),
                    ),
                  ],
                ),
                const SizedBox(height: 24),
                Expanded(child: _buildBody(context, launcher, apps)),
              ],
            ),
          ),
        ),
      ),
    );
  }

  Widget _buildBody(
    BuildContext context,
    LauncherController launcher,
    List<AppEntry> apps,
  ) {
    final colors = context.colors;
    final theme = Theme.of(context);

    if (apps.isEmpty && launcher.isLoadingApps) {
      return Center(
        child: SizedBox(
          width: 30,
          height: 30,
          child: CircularProgressIndicator(
            strokeWidth: 2.4,
            color: colors.accent,
          ),
        ),
      );
    }

    if (apps.isEmpty && launcher.appsError != null) {
      return Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Text(
              'Could not read installed apps.',
              style: theme.textTheme.bodyLarge,
            ),
            const SizedBox(height: 12),
            TextButton(
              onPressed: () => launcher.loadApps(force: true),
              child: const Text('Try again'),
            ),
          ],
        ),
      );
    }

    if (apps.isEmpty) {
      return Center(
        child: Text(
          'No apps match “${_query.trim()}”.',
          style: theme.textTheme.bodyMedium?.copyWith(color: colors.inkMuted),
        ),
      );
    }

    return GridView.builder(
      padding: const EdgeInsets.only(bottom: 20),
      gridDelegate: const SliverGridDelegateWithMaxCrossAxisExtent(
        maxCrossAxisExtent: 162,
        mainAxisExtent: 150,
        crossAxisSpacing: 12,
        mainAxisSpacing: 12,
      ),
      itemCount: apps.length,
      itemBuilder: (context, index) {
        final app = apps[index];
        return Pressable(
          semanticLabel:
              '${app.label}. Tap to open. Long press to add to Home.',
          onTap: () => _launch(app),
          onLongPress: () => _addToHome(app),
          child: Container(
            decoration: BoxDecoration(
              color: colors.surface,
              borderRadius: BorderRadius.circular(24),
              border: Border.all(color: colors.border),
            ),
            padding: const EdgeInsets.fromLTRB(12, 16, 12, 12),
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [
                AppIconImage(bytes: app.icon, size: 46),
                const SizedBox(height: 10),
                Text(
                  app.label,
                  maxLines: 2,
                  overflow: TextOverflow.ellipsis,
                  textAlign: TextAlign.center,
                  style: theme.textTheme.bodySmall?.copyWith(
                    color: colors.ink,
                    fontWeight: FontWeight.w500,
                  ),
                ),
              ],
            ),
          ),
        );
      },
    );
  }

  Future<void> _addToHome(AppEntry app) async {
    final launcher = context.read<LauncherController>();
    final error = await launcher.addPinnedApp(app);
    if (!mounted) return;
    final message = error ?? '${app.label} added to Home';
    ScaffoldMessenger.of(context)
        .showSnackBar(SnackBar(content: Text(message)));
  }

  Future<void> _launch(AppEntry app) async {
    final launcher = context.read<LauncherController>();
    final error = await launcher.launchAppEntry(app);
    if (!mounted) return;
    if (error != null) {
      ScaffoldMessenger.of(context)
          .showSnackBar(SnackBar(content: Text(error)));
      return;
    }
    // Pressing Home should land on the dashboard, not on All apps.
    Navigator.of(context).popUntil((route) => route.isFirst);
  }
}

class _BackButton extends StatelessWidget {
  const _BackButton({required this.onTap});

  final VoidCallback onTap;

  @override
  Widget build(BuildContext context) {
    final colors = context.colors;
    return Pressable(
      onTap: onTap,
      semanticLabel: 'Back',
      pressedScale: 0.92,
      child: Container(
        width: 46,
        height: 46,
        decoration: BoxDecoration(
          color: colors.surface,
          shape: BoxShape.circle,
          border: Border.all(color: colors.border),
        ),
        alignment: Alignment.center,
        child: AppIcon(
          'assets/icons/arrow-left.svg',
          size: 20,
          color: colors.ink,
        ),
      ),
    );
  }
}