dart/lib/components/slidelist.dart

// Copyright 2015 The Vanadium 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/widgets.dart';
import 'package:flutter/material.dart';

import '../models/all.dart' as model;
import '../stores/store.dart';
import '../styles/common.dart' as style;

import '../utils/keyvalue.dart';

// SlideListPage is the full page view of the list of slides for a deck.
class SlideListPage extends StatelessComponent {
  String _deckId;
  String _title;

  SlideListPage(this._deckId, this._title);
  Widget build(BuildContext context) {
    return new Scaffold(
        toolBar: new ToolBar(
            left: new IconButton(
                icon: 'navigation/arrow_back',
                onPressed: () => Navigator.of(context).pop()),
            center: new Text(_title)),
        body: new Material(child: new SlideList(_deckId)));
  }
}

// SlideList is scrollable list view of slides for a deck.
class SlideList extends StatefulComponent {
  final String deckId;
  SlideList(this.deckId);

  _SlideListState createState() => new _SlideListState();
}

class _SlideListState extends State<SlideList> {
  _SlideListState();
  Store _store = new Store.singleton();
  List<model.Slide> _slides = new List<model.Slide>();

  void updateSlides(List<model.Slide> slides) {
    setState(() {
      _slides = slides;
    });
  }

  void initState() {
    super.initState();
    _store.getAllSlides(config.deckId).then(updateSlides);
  }

  Widget build(BuildContext context) {
    // Create a list of <SlideNumber, Slide> pairs.
    List<KeyValue<String, model.Slide>> slidesWithPosition = [];
    for (var i = 0; i < _slides.length; i++) {
      slidesWithPosition.add(new KeyValue(i.toString(), _slides[i]));
    }
    return new ScrollableList(
        itemExtent: style.Size.listHeight,
        items: slidesWithPosition,
        itemBuilder: (context, kv) => _buildSlide(context, kv.key, kv.value));
  }
}

// TODO(aghassemi): Is this approach okay? Check with Flutter team.
// Builder gets called a lot by the ScrollableList and building RawImage
// is expensive so we cache.
// Expando is a weak map so this does not effect GC.
Expando<Widget> weakSlideCache = new Expando<Widget>();
Widget _buildSlide(BuildContext context, String key, model.Slide slideData) {
  var cachedWidget = weakSlideCache[slideData];
  if (cachedWidget != null) {
    return cachedWidget;
  }

  var thumbnail;
  if (slideData.image != null) {
    thumbnail = new RawImage(
        height: style.Size.listHeight,
        bytes: new Uint8List.fromList(slideData.image),
        fit: ImageFit.cover);
  } else {
    // TODO(aghassemi): Replace with a proper default thumbnail.
    thumbnail = new Text('No Slide Image');
  }
  thumbnail = new Flexible(child: thumbnail);

  var title = new Text('Slide $key', style: style.Text.subTitleStyle);
  var notes = new Text(
      'This is the teaser slide. It should be memorable and descriptive');
  var titleAndNotes = new Flexible(
      child: new Container(
          child: new Column([title, notes], alignItems: FlexAlignItems.start),
          padding: style.Spacing.normalPadding));

  var card = new Container(
      child: new Card(child: new Row([thumbnail, titleAndNotes])),
      margin: style.Spacing.listItemMargin);

  var listItem = new InkWell(key: new Key(key), child: card);

  weakSlideCache[slideData] = listItem;
  return listItem;
}