// Copyright 2014 The Flutter 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_test/flutter_test.dart';

const Color kSelectedColor = Color(0xFF00FF00);
const Color kUnselectedColor = Colors.transparent;

Widget buildFrame(TabController tabController, { Color? color, Color? selectedColor, double indicatorSize = 12.0 }) {
  return Localizations(
    locale: const Locale('en', 'US'),
    delegates: const <LocalizationsDelegate<dynamic>>[
      DefaultMaterialLocalizations.delegate,
      DefaultWidgetsLocalizations.delegate,
    ],
    child: Directionality(
      textDirection: TextDirection.ltr,
      child: Theme(
        data: ThemeData(colorScheme: const ColorScheme.light().copyWith(secondary: kSelectedColor)),
        child: SizedBox.expand(
          child: Center(
            child: SizedBox(
              width: 400.0,
              height: 400.0,
              child: Column(
                children: <Widget>[
                  TabPageSelector(
                    controller: tabController,
                    color: color,
                    selectedColor: selectedColor,
                    indicatorSize: indicatorSize,
                  ),
                  Flexible(
                    child: TabBarView(
                      controller: tabController,
                      children: const <Widget>[
                        Center(child: Text('0')),
                        Center(child: Text('1')),
                        Center(child: Text('2')),
                      ],
                    ),
                  ),
                ],
              ),
            ),
          ),
        ),
      ),
    ),
  );
}

List<Color> indicatorColors(WidgetTester tester) {
  final Iterable<TabPageSelectorIndicator> indicators = tester.widgetList(
    find.descendant(
      of: find.byType(TabPageSelector),
      matching: find.byType(TabPageSelectorIndicator),
    ),
  );
  return indicators.map<Color>((TabPageSelectorIndicator indicator) => indicator.backgroundColor).toList();
}

void main() {
  testWidgets('PageSelector responds correctly to setting the TabController index', (WidgetTester tester) async {
    final TabController tabController = TabController(
      vsync: const TestVSync(),
      length: 3,
    );
    await tester.pumpWidget(buildFrame(tabController));

    expect(tabController.index, 0);
    expect(indicatorColors(tester), const <Color>[kSelectedColor, kUnselectedColor, kUnselectedColor]);

    tabController.index = 1;
    await tester.pump();
    expect(tabController.index, 1);
    expect(indicatorColors(tester), const <Color>[kUnselectedColor, kSelectedColor, kUnselectedColor]);

    tabController.index = 2;
    await tester.pump();
    expect(tabController.index, 2);
    expect(indicatorColors(tester), const <Color>[kUnselectedColor, kUnselectedColor, kSelectedColor]);
  });

  testWidgets('PageSelector responds correctly to TabController.animateTo()', (WidgetTester tester) async {
    final TabController tabController = TabController(
      vsync: const TestVSync(),
      length: 3,
    );
    await tester.pumpWidget(buildFrame(tabController));

    expect(tabController.index, 0);
    expect(indicatorColors(tester), const <Color>[kSelectedColor, kUnselectedColor, kUnselectedColor]);

    tabController.animateTo(1, duration: const Duration(milliseconds: 200));
    await tester.pump();
    // Verify that indicator 0's color is becoming increasingly transparent,
    // and indicator 1's color is becoming increasingly opaque during the
    // 200ms animation. Indicator 2 remains transparent throughout.
    await tester.pump(const Duration(milliseconds: 10));
    List<Color> colors = indicatorColors(tester);
    expect(colors[0].alpha, greaterThan(colors[1].alpha));
    expect(colors[2], kUnselectedColor);
    await tester.pump(const Duration(milliseconds: 175));
    colors = indicatorColors(tester);
    expect(colors[0].alpha, lessThan(colors[1].alpha));
    expect(colors[2], kUnselectedColor);
    await tester.pumpAndSettle();
    expect(tabController.index, 1);
    expect(indicatorColors(tester), const <Color>[kUnselectedColor, kSelectedColor, kUnselectedColor]);

    tabController.animateTo(2, duration: const Duration(milliseconds: 200));
    await tester.pump();
    // Same animation test as above for indicators 1 and 2.
    await tester.pump(const Duration(milliseconds: 10));
    colors = indicatorColors(tester);
    expect(colors[1].alpha, greaterThan(colors[2].alpha));
    expect(colors[0], kUnselectedColor);
    await tester.pump(const Duration(milliseconds: 175));
    colors = indicatorColors(tester);
    expect(colors[1].alpha, lessThan(colors[2].alpha));
    expect(colors[0], kUnselectedColor);
    await tester.pumpAndSettle();
    expect(tabController.index, 2);
    expect(indicatorColors(tester), const <Color>[kUnselectedColor, kUnselectedColor, kSelectedColor]);
  });

  testWidgets('PageSelector responds correctly to TabBarView drags', (WidgetTester tester) async {
    final TabController tabController = TabController(
      vsync: const TestVSync(),
      initialIndex: 1,
      length: 3,
    );
    await tester.pumpWidget(buildFrame(tabController));

    expect(tabController.index, 1);
    expect(indicatorColors(tester), const <Color>[kUnselectedColor, kSelectedColor, kUnselectedColor]);

    final TestGesture gesture = await tester.startGesture(const Offset(200.0, 200.0));

    // Drag to the left moving the selection towards indicator 2. Indicator 2's
    // opacity should increase and Indicator 1's opacity should decrease.
    await gesture.moveBy(const Offset(-100.0, 0.0));
    await tester.pumpAndSettle();
    List<Color> colors = indicatorColors(tester);
    expect(colors[1].alpha, greaterThan(colors[2].alpha));
    expect(colors[0], kUnselectedColor);

    // Drag back to where we started.
    await gesture.moveBy(const Offset(100.0, 0.0));
    await tester.pumpAndSettle();
    colors = indicatorColors(tester);
    expect(indicatorColors(tester), const <Color>[kUnselectedColor, kSelectedColor, kUnselectedColor]);

    // Drag to the left moving the selection towards indicator 0. Indicator 0's
    // opacity should increase and Indicator 1's opacity should decrease.
    await gesture.moveBy(const Offset(100.0, 0.0));
    await tester.pumpAndSettle();
    colors = indicatorColors(tester);
    expect(colors[1].alpha, greaterThan(colors[0].alpha));
    expect(colors[2], kUnselectedColor);

    // Drag back to where we started.
    await gesture.moveBy(const Offset(-100.0, 0.0));
    await tester.pumpAndSettle();
    colors = indicatorColors(tester);
    expect(indicatorColors(tester), const <Color>[kUnselectedColor, kSelectedColor, kUnselectedColor]);

    // Completing the gesture doesn't change anything
    await gesture.up();
    await tester.pumpAndSettle();
    colors = indicatorColors(tester);
    expect(indicatorColors(tester), const <Color>[kUnselectedColor, kSelectedColor, kUnselectedColor]);

    // Fling to the left, selects indicator 2
    await tester.fling(find.byType(TabBarView), const Offset(-100.0, 0.0), 1000.0);
    await tester.pumpAndSettle();
    expect(indicatorColors(tester), const <Color>[kUnselectedColor, kUnselectedColor, kSelectedColor]);

    // Fling to the right, selects indicator 1
    await tester.fling(find.byType(TabBarView), const Offset(100.0, 0.0), 1000.0);
    await tester.pumpAndSettle();
    expect(indicatorColors(tester), const <Color>[kUnselectedColor, kSelectedColor, kUnselectedColor]);

  });

  testWidgets('PageSelector indicatorColors', (WidgetTester tester) async {
    const Color kRed = Color(0xFFFF0000);
    const Color kBlue = Color(0xFF0000FF);

    final TabController tabController = TabController(
      vsync: const TestVSync(),
      initialIndex: 1,
      length: 3,
    );
    await tester.pumpWidget(buildFrame(tabController, color: kRed, selectedColor: kBlue));

    expect(tabController.index, 1);
    expect(indicatorColors(tester), const <Color>[kRed, kBlue, kRed]);

    tabController.index = 0;
    await tester.pumpAndSettle();
    expect(indicatorColors(tester), const <Color>[kBlue, kRed, kRed]);
  });

  testWidgets('PageSelector indicatorSize', (WidgetTester tester) async {
    final TabController tabController = TabController(
      vsync: const TestVSync(),
      initialIndex: 1,
      length: 3,
    );
    await tester.pumpWidget(buildFrame(tabController, indicatorSize: 16.0));

    final Iterable<Element> indicatorElements = find.descendant(
      of: find.byType(TabPageSelector),
      matching: find.byType(TabPageSelectorIndicator),
    ).evaluate();

    // Indicators get an 8 pixel margin, 16 + 8 = 24.
    for (final Element indicatorElement in indicatorElements)
      expect(indicatorElement.size, const Size(24.0, 24.0));

    expect(tester.getSize(find.byType(TabPageSelector)).height, 24.0);
  });

}