// 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/gestures.dart';
import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  group('text contrast guideline', () {
    testWidgets('black text on white background - Text Widget - direct style', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(
        const Text(
          'this is a test',
          style: TextStyle(fontSize: 14.0, color: Colors.black),
        ),
      ));
      await expectLater(tester, meetsGuideline(textContrastGuideline));
      handle.dispose();
    });

    testWidgets('white text on black background - Text Widget - direct style', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(
        Container(
          width: 200.0,
          height: 200.0,
          color: Colors.black,
          child: const Text(
            'this is a test',
            style: TextStyle(fontSize: 14.0, color: Colors.white),
          ),
        ),
      ));
      await expectLater(tester, meetsGuideline(textContrastGuideline));
      handle.dispose();
    });

    testWidgets('black text on white background - Text Widget - inherited style', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(
        DefaultTextStyle(
          style: const TextStyle(fontSize: 14.0, color: Colors.black),
          child: Container(
            color: Colors.white,
            child: const Text('this is a test'),
          ),
        ),
      ));
      await expectLater(tester, meetsGuideline(textContrastGuideline));
      handle.dispose();
    });

    testWidgets('white text on black background - Text Widget - inherited style', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(
        DefaultTextStyle(
          style: const TextStyle(fontSize: 14.0, color: Colors.white),
          child: Container(
            width: 200.0,
            height: 200.0,
            color: Colors.black,
            child: const Text('this is a test'),
          ),
        ),
      ));
      await expectLater(tester, meetsGuideline(textContrastGuideline));
      handle.dispose();
    });

    testWidgets('Material text field - amber on amber', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(MaterialApp(
        home: Scaffold(
          body: Container(
            width: 200.0,
            height: 200.0,
            color: Colors.amberAccent,
            child: TextField(
              style: const TextStyle(color: Colors.amber),
              controller: TextEditingController(text: 'this is a test'),
            ),
          ),
        ),
      ));
      await expectLater(tester, doesNotMeetGuideline(textContrastGuideline));
      handle.dispose();
    });

    testWidgets('Material text field - default style', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(MaterialApp(
          home: Scaffold(
            body: Center(
              child: SizedBox(
                width: 100,
                child: TextField(
                  controller: TextEditingController(text: 'this is a test'),
                ),
              ),
            ),
          ),
        ),
      );
      await tester.idle();
      await expectLater(tester, meetsGuideline(textContrastGuideline));
      handle.dispose();
    });

    testWidgets('yellow text on yellow background fails with correct message', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(
        Container(
          width: 200.0,
          height: 200.0,
          color: Colors.yellow,
          child: const Text(
            'this is a test',
            style: TextStyle(fontSize: 14.0, color: Colors.yellowAccent),
          ),
        ),
      ));
      final Evaluation result = await textContrastGuideline.evaluate(tester);
      expect(result.passed, false);
      expect(result.reason,
        'SemanticsNode#4(Rect.fromLTRB(300.0, 200.0, 500.0, 400.0), label: "this is a test",'
        ' textDirection: ltr):\nExpected contrast ratio of at least '
        '4.5 but found 1.17 for a font size of 14.0. The '
        'computed light color was: Color(0xfffafafa), The computed dark color was:'
        ' Color(0xffffeb3b)\n'
        'See also: https://www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contrast-contrast.html');
      handle.dispose();
    });

    testWidgets('label without corresponding text is skipped', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(
        Semantics(
          label: 'This is not text',
          container: true,
          child: const SizedBox(
            width: 200.0,
            height: 200.0,
            child: Placeholder(),
          ),
        ),
      ));

      final Evaluation result = await textContrastGuideline.evaluate(tester);
      expect(result.passed, true);
      handle.dispose();
    });

    testWidgets('offscreen text is skipped', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(
        Stack(
          children: <Widget>[
            Positioned(
              left: -300.0,
              child: Container(
                width: 200.0,
                height: 200.0,
                color: Colors.yellow,
                child: const Text(
                  'this is a test',
                  style: TextStyle(fontSize: 14.0, color: Colors.yellowAccent),
                ),
              ),
            ),
          ],
        )
      ));

      final Evaluation result = await textContrastGuideline.evaluate(tester);
      expect(result.passed, true);
      handle.dispose();
    });

    testWidgets('Disabled button is excluded from text contrast guideline', (WidgetTester tester) async {
      // Regression test https://github.com/flutter/flutter/issues/94428
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(
        _boilerplate(
          ElevatedButton(
            onPressed: null,
            child: Container(
              width: 200.0,
              height: 200.0,
              color: Colors.yellow,
              child: const Text(
                'this is a test',
                style: TextStyle(fontSize: 14.0, color: Colors.yellowAccent),
              ),
            ),
          ),
        )
      );
      await expectLater(tester, meetsGuideline(textContrastGuideline));
      handle.dispose();
    });
  });

  group('custom minimum contrast guideline', () {
    Widget _icon({IconData icon = Icons.search, required Color color, required Color background}) {
      return Container(
        padding: const EdgeInsets.all(8.0),
        color: background,
        child: Icon(icon, color: color),
      );
    }

    Widget _text({String text = 'Text', required Color color, required Color background}) {
      return Container(
        padding: const EdgeInsets.all(8.0),
        color: background,
        child: Text(text, style: TextStyle(color: color)),
      );
    }

    Widget _row(List<Widget> widgets) => _boilerplate(Row(children: widgets));

    final Finder _findIcons = find.byWidgetPredicate((Widget widget) => widget is Icon);
    final Finder _findTexts = find.byWidgetPredicate((Widget widget) => widget is Text);
    final Finder _findIconsAndTexts = find.byWidgetPredicate((Widget widget) => widget is Icon || widget is Text);

    testWidgets('Black icons on white background', (WidgetTester tester) async {
      await tester.pumpWidget(_row(<Widget>[
        _icon(color: Colors.black, background: Colors.white),
        _icon(color: Colors.black, background: Colors.white),
      ]));

      await expectLater(tester, meetsGuideline(CustomMinimumContrastGuideline(finder: _findIcons)));
    });

    testWidgets('Black icons on black background', (WidgetTester tester) async {
      await tester.pumpWidget(_row(<Widget>[
        _icon(color: Colors.black, background: Colors.black),
        _icon(color: Colors.black, background: Colors.black),
      ]));

      await expectLater(tester, doesNotMeetGuideline(CustomMinimumContrastGuideline(finder: _findIcons)));
    });

    testWidgets('White icons on black background ("dark mode")', (WidgetTester tester) async {
      await tester.pumpWidget(_row(<Widget>[
        _icon(color: Colors.white, background: Colors.black),
        _icon(color: Colors.white, background: Colors.black),
      ]));

      await expectLater(tester, meetsGuideline(CustomMinimumContrastGuideline(finder: _findIcons)));
    });

    testWidgets('Using different icons', (WidgetTester tester) async {
      await tester.pumpWidget(_row(<Widget>[
        _icon(color: Colors.black, background: Colors.white, icon: Icons.more_horiz),
        _icon(color: Colors.black, background: Colors.white, icon: Icons.description),
        _icon(color: Colors.black, background: Colors.white, icon: Icons.image),
        _icon(color: Colors.black, background: Colors.white, icon: Icons.beach_access),
      ]));

      await expectLater(tester, meetsGuideline(CustomMinimumContrastGuideline(finder: _findIcons)));
    });

    testWidgets('One invalid instance fails entire test', (WidgetTester tester) async {
      await tester.pumpWidget(_row(<Widget>[
        _icon(color: Colors.black, background: Colors.white),
        _icon(color: Colors.black, background: Colors.black),
      ]));

      await expectLater(tester, doesNotMeetGuideline(CustomMinimumContrastGuideline(finder: _findIcons)));
    });

    testWidgets('White on different colors, passing', (WidgetTester tester) async {
      await tester.pumpWidget(_row(<Widget>[
        _icon(color: Colors.white, background: Colors.red[800]!, icon: Icons.more_horiz),
        _icon(color: Colors.white, background: Colors.green[800]!, icon: Icons.description),
        _icon(color: Colors.white, background: Colors.blue[800]!, icon: Icons.image),
        _icon(color: Colors.white, background: Colors.purple[800]!, icon: Icons.beach_access),
      ]));

      await expectLater(tester, meetsGuideline(CustomMinimumContrastGuideline(finder: _findIcons)));
    });

    testWidgets('White on different colors, failing', (WidgetTester tester) async {
      await tester.pumpWidget(_row(<Widget>[
        _icon(color: Colors.white, background: Colors.red[200]!, icon: Icons.more_horiz),
        _icon(color: Colors.white, background: Colors.green[400]!, icon: Icons.description),
        _icon(color: Colors.white, background: Colors.blue[600]!, icon: Icons.image),
        _icon(color: Colors.white, background: Colors.purple[800]!, icon: Icons.beach_access),
      ]));

      await expectLater(tester, doesNotMeetGuideline(CustomMinimumContrastGuideline(finder: _findIcons)));
    });

    testWidgets('Absence of icons, passing', (WidgetTester tester) async {
      await tester.pumpWidget(_row(<Widget>[]));

      await expectLater(tester, meetsGuideline(CustomMinimumContrastGuideline(finder: _findIcons)));
    });

    testWidgets('Absence of icons, passing - 2nd test', (WidgetTester tester) async {
      await tester.pumpWidget(_row(<Widget>[
        _text(color: Colors.black, background: Colors.white),
        _text(color: Colors.black, background: Colors.black),
      ]));

      await expectLater(tester, meetsGuideline(CustomMinimumContrastGuideline(finder: _findIcons)));
    });

    testWidgets('Guideline ignores widgets of other types', (WidgetTester tester) async {
      await tester.pumpWidget(_row(<Widget>[
        _icon(color: Colors.black, background: Colors.white),
        _icon(color: Colors.black, background: Colors.white),
        _text(color: Colors.black, background: Colors.white),
        _text(color: Colors.black, background: Colors.black),
      ]));

      await expectLater(tester, meetsGuideline(CustomMinimumContrastGuideline(finder: _findIcons)));
      await expectLater(tester, doesNotMeetGuideline(CustomMinimumContrastGuideline(finder: _findTexts)));
      await expectLater(tester, doesNotMeetGuideline(CustomMinimumContrastGuideline(finder: _findIconsAndTexts)));
    });

    testWidgets('Custom minimum ratio - Icons', (WidgetTester tester) async {
      await tester.pumpWidget(_row(<Widget>[
        _icon(color: Colors.blue, background: Colors.white),
        _icon(color: Colors.black, background: Colors.white),
      ]));

      await expectLater(tester, doesNotMeetGuideline(CustomMinimumContrastGuideline(finder: _findIcons)));
      await expectLater(tester, meetsGuideline(CustomMinimumContrastGuideline(finder: _findIcons, minimumRatio: 3.0)));
    });

    testWidgets('Custom minimum ratio - Texts', (WidgetTester tester) async {
      await tester.pumpWidget(_row(<Widget>[
        _text(color: Colors.blue, background: Colors.white),
        _text(color: Colors.black, background: Colors.white),
      ]));

      await expectLater(tester, doesNotMeetGuideline(CustomMinimumContrastGuideline(finder: _findTexts)));
      await expectLater(tester, meetsGuideline(CustomMinimumContrastGuideline(finder: _findTexts, minimumRatio: 3.0)));
    });

    testWidgets('Custom minimum ratio - Different standards for icons and texts', (WidgetTester tester) async {
      await tester.pumpWidget(_row(<Widget>[
        _icon(color: Colors.blue, background: Colors.white),
        _icon(color: Colors.black, background: Colors.white),
        _text(color: Colors.blue, background: Colors.white),
        _text(color: Colors.black, background: Colors.white),
      ]));

      await expectLater(tester, doesNotMeetGuideline(CustomMinimumContrastGuideline(finder: _findIcons)));
      await expectLater(tester, meetsGuideline(CustomMinimumContrastGuideline(finder: _findTexts, minimumRatio: 3.0)));
    });

  });

  group('tap target size guideline', () {
    testWidgets('Tappable box at 48 by 48', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(
        SizedBox(
          width: 48.0,
          height: 48.0,
          child: GestureDetector(
            onTap: () { },
          ),
        ),
      ));
      await expectLater(tester, meetsGuideline(androidTapTargetGuideline));
      handle.dispose();
    });

    testWidgets('Tappable box at 47 by 48', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(
        SizedBox(
          width: 47.0,
          height: 48.0,
          child: GestureDetector(
            onTap: () { },
          ),
        ),
      ));
      await expectLater(tester, doesNotMeetGuideline(androidTapTargetGuideline));
      handle.dispose();
    });

    testWidgets('Tappable box at 48 by 47', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(
        SizedBox(
          width: 48.0,
          height: 47.0,
          child: GestureDetector(
            onTap: () { },
          ),
        ),
      ));
      await expectLater(tester, doesNotMeetGuideline(androidTapTargetGuideline));
      handle.dispose();
    });

    testWidgets('Tappable box at 48 by 48 shrunk by transform', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(
        Transform.scale(
          scale: 0.5, // should have new height of 24 by 24.
          child: SizedBox(
            width: 48.0,
            height: 48.0,
            child: GestureDetector(
              onTap: () { },
            ),
          ),
        ),
      ));
      await expectLater(tester, doesNotMeetGuideline(androidTapTargetGuideline));
      handle.dispose();
    });

    testWidgets('Too small tap target fails with the correct message', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(
        SizedBox(
          width: 48.0,
          height: 47.0,
          child: GestureDetector(
            onTap: () { },
          ),
        ),
      ));
      final Evaluation result = await androidTapTargetGuideline.evaluate(tester);
      expect(result.passed, false);
      expect(result.reason,
        'SemanticsNode#4(Rect.fromLTRB(376.0, 276.5, 424.0, 323.5), actions: [tap]): expected tap '
        'target size of at least Size(48.0, 48.0), but found Size(48.0, 47.0)\n'
        'See also: https://support.google.com/accessibility/android/answer/7101858?hl=en');
      handle.dispose();
    });

    testWidgets('Box that overlaps edge of window is skipped', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      final Widget smallBox = SizedBox(
        width: 48.0,
        height: 47.0,
        child: GestureDetector(
          onTap: () { },
        ),
      );
      await tester.pumpWidget(
        MaterialApp(
          home: Stack(
            children: <Widget>[
              Positioned(
                left: 0.0,
                top: -1.0,
                child: smallBox,
              ),
            ],
          ),
        ),
      );

      final Evaluation overlappingTopResult = await androidTapTargetGuideline.evaluate(tester);
      expect(overlappingTopResult.passed, true);

      await tester.pumpWidget(
        MaterialApp(
          home: Stack(
            children: <Widget>[
              Positioned(
                left: -1.0,
                top: 0.0,
                child: smallBox,
              ),
            ],
          ),
        ),
      );

      final Evaluation overlappingLeftResult = await androidTapTargetGuideline.evaluate(tester);
      expect(overlappingLeftResult.passed, true);

      await tester.pumpWidget(
        MaterialApp(
          home: Stack(
            children: <Widget>[
              Positioned(
                bottom: -1.0,
                child: smallBox,
              ),
            ],
          ),
        ),
      );

      final Evaluation overlappingBottomResult = await androidTapTargetGuideline.evaluate(tester);
      expect(overlappingBottomResult.passed, true);

      await tester.pumpWidget(
        MaterialApp(
          home: Stack(
            children: <Widget>[
              Positioned(
                right: -1.0,
                child: smallBox,
              ),
            ],
          ),
        ),
      );

      final Evaluation overlappingRightResult = await androidTapTargetGuideline.evaluate(tester);
      expect(overlappingRightResult.passed, true);
      handle.dispose();
    });

    testWidgets('Does not fail on mergedIntoParent child', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(
        MergeSemantics(
          child: Semantics(
            container: true,
            child: SizedBox(
              width: 50.0,
              height: 50.0,
              child: Semantics(
                container: true,
                child: GestureDetector(
                  onTap: () { },
                  child: const SizedBox(width: 4.0, height: 4.0),
                ),
              ),
            ),
          ),
        )
      ));

      final Evaluation overlappingRightResult = await androidTapTargetGuideline.evaluate(tester);
      expect(overlappingRightResult.passed, true);
      handle.dispose();
    });

    testWidgets('Does not fail on links', (WidgetTester tester) async {
      Widget textWithLink() {
        return Builder(
          builder: (BuildContext context) {
            return RichText(
              text: TextSpan(
                children: <InlineSpan>[
                  const TextSpan(
                    text: 'See examples at ',
                  ),
                  TextSpan(
                    text: 'flutter repo',
                    recognizer: TapGestureRecognizer()
                      ..onTap = () { },
                  ),
                ],
              ),
            );
          },
        );
      }

      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(textWithLink()));

      await expectLater(tester, meetsGuideline(androidTapTargetGuideline));
      handle.dispose();
    });
  });

  group('Labeled tappable node guideline', () {
    testWidgets('Passes when node is labeled', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(Semantics(
        container: true,
        onTap: () { },
        label: 'test',
        child: const SizedBox(width: 10.0, height: 10.0),
      )));
      final Evaluation result = await labeledTapTargetGuideline.evaluate(tester);
      expect(result.passed, true);
      handle.dispose();
    });
    testWidgets('Fails if long-press has no label', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(Semantics(
        container: true,
        onLongPress: () { },
        label: '',
        child: const SizedBox(width: 10.0, height: 10.0),
      )));
      final Evaluation result = await labeledTapTargetGuideline.evaluate(tester);
      expect(result.passed, false);
      handle.dispose();
    });

    testWidgets('Fails if tap has no label', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(Semantics(
        container: true,
        onTap: () { },
        label: '',
        child: const SizedBox(width: 10.0, height: 10.0),
      )));
      final Evaluation result = await labeledTapTargetGuideline.evaluate(tester);
      expect(result.passed, false);
      handle.dispose();
    });

    testWidgets('Passes if tap is merged into labeled node', (WidgetTester tester) async {
      final SemanticsHandle handle = tester.ensureSemantics();
      await tester.pumpWidget(_boilerplate(Semantics(
        container: true,
        onLongPress: () { },
        label: '',
        child: Semantics(
          label: 'test',
          child: const SizedBox(width: 10.0, height: 10.0),
        ),
      )));
      final Evaluation result = await labeledTapTargetGuideline.evaluate(tester);
      expect(result.passed, true);
      handle.dispose();
    });
  });

  testWidgets('regression test for material widget', (WidgetTester tester) async {
    final SemanticsHandle handle = tester.ensureSemantics();
    await tester.pumpWidget(
      MaterialApp(
        theme: ThemeData.light(),
        home: Scaffold(
          backgroundColor: Colors.white,
          body: ElevatedButton(
            style: ElevatedButton.styleFrom(
              primary: const Color(0xFFFBBC04),
              elevation: 0,
            ),
            onPressed: () {},
            child: const Text('Button', style: TextStyle(color: Colors.black)),
        ),
      ),
    ));
    await expectLater(tester, meetsGuideline(textContrastGuideline));
    handle.dispose();
  });
}

Widget _boilerplate(Widget child) {
  return MaterialApp(
    home: Scaffold(body: Center(child: child)),
  );
}