// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

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

import 'drawer.dart';
import 'item.dart';

const double _kFlexibleSpaceMaxHeight = 256.0;

List<GalleryItem> _itemsWithCategory(String category) {
  return kAllGalleryItems.where((GalleryItem item) => item.category == category).toList();
}

final List<GalleryItem> _demoItems = _itemsWithCategory('Demos');
final List<GalleryItem> _componentItems = _itemsWithCategory('Components');
final List<GalleryItem> _styleItems = _itemsWithCategory('Style');

class GalleryHome extends StatefulWidget {
  GalleryHome({
    Key key,
    this.useLightTheme,
    this.onThemeChanged,
    this.timeDilation,
    this.onTimeDilationChanged,
    this.showPerformanceOverlay,
    this.onShowPerformanceOverlayChanged
  }) : super(key: key) {
    assert(onThemeChanged != null);
    assert(onTimeDilationChanged != null);
    assert(onShowPerformanceOverlayChanged != null);
  }

  final bool useLightTheme;
  final ValueChanged<bool> onThemeChanged;

  final double timeDilation;
  final ValueChanged<double> onTimeDilationChanged;

  final bool showPerformanceOverlay;
  final ValueChanged<bool> onShowPerformanceOverlayChanged;

  @override
  GalleryHomeState createState() => new GalleryHomeState();
}

class GalleryHomeState extends State<GalleryHome> {
  final Key _homeKey = new ValueKey<String>("Gallery Home");
  final List<Widget> _listItems = <Widget>[];

  @override
  void initState() {
    super.initState();

    // The first item in the list just exists to occupy the space behind
    // the flexible app bar. As it's scrolled out of the way, the app bar's
    // height will shrink.
    final double statusBarHeight = (MediaQuery.of(context)?.padding ?? EdgeInsets.zero).top;
    _listItems.add(new SizedBox(height: _kFlexibleSpaceMaxHeight + statusBarHeight));

    final ThemeData themeData = Theme.of(context);
    final TextStyle headerStyle = themeData.textTheme.body2.copyWith(color: themeData.primaryColor);
    String category;
    for (GalleryItem galleryItem in kAllGalleryItems) {
      if (category != galleryItem.category) {
        if (category != null)
          _listItems.add(new Divider());
        _listItems.add(
          new Container(
            height: 48.0,
            padding: const EdgeInsets.only(left: 16.0),
            child: new Align(
              alignment: FractionalOffset.centerLeft,
              child: new Text(galleryItem.category, style: headerStyle)
            )
          )
        );
        category = galleryItem.category;
      }
      _listItems.add(galleryItem);
    }
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      key: _homeKey,
      drawer: new GalleryDrawer(
        useLightTheme: config.useLightTheme,
        onThemeChanged: config.onThemeChanged,
        timeDilation: config.timeDilation,
        onTimeDilationChanged: config.onTimeDilationChanged,
        showPerformanceOverlay: config.showPerformanceOverlay,
        onShowPerformanceOverlayChanged: config.onShowPerformanceOverlayChanged
      ),
      appBar: new AppBar(
        expandedHeight: _kFlexibleSpaceMaxHeight,
        flexibleSpace: new FlexibleSpaceBar(
          background: new Image(
            image: new AssetImage('packages/flutter_gallery_assets/appbar_background.jpg'),
            fit: ImageFit.cover,
            height: _kFlexibleSpaceMaxHeight
          ),
          title: new Text('Flutter gallery')
        )
      ),
      appBarBehavior: AppBarBehavior.under,
      body: new Block(children: _listItems)
    );
  }
}