// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using Microsoft.AspNetCore.Razor.Language;
using Microsoft.VisualStudio.Test;
using Xunit;

namespace Microsoft.VisualStudio.Text
{
    public class TextContentChangedEventArgsExtensionsTest
    {
        [Fact]
        public void TextChangeOccurred_NoChanges_ReturnsFalse()
        {
            // Arrange
            var before = new StringTextSnapshot(string.Empty);
            var after = new StringTextSnapshot(string.Empty);
            var testArgs = new TestTextContentChangedEventArgs(before, after);

            // Act
            var result = testArgs.TextChangeOccurred(out var changeInformation);

            // Assert
            Assert.False(result);
        }

        [Fact]
        public void TextChangeOccurred_CancelingChanges_ReturnsFalse()
        {
            // Arrange
            var before = new StringTextSnapshot("by");
            before.Version.Changes.Add(new TestTextChange(new SourceChange(0, 2, "hi")));
            before.Version.Changes.Add(new TestTextChange(new SourceChange(0, 2, "by")));
            var after = new StringTextSnapshot("by");
            var testArgs = new TestTextContentChangedEventArgs(before, after);

            // Act
            var result = testArgs.TextChangeOccurred(out var changeInformation);

            // Assert
            Assert.False(result);
        }

        [Fact]
        public void TextChangeOccurred_SingleChange_ReturnsTrue()
        {
            // Arrange
            var before = new StringTextSnapshot("by");
            var firstChange = new TestTextChange(new SourceChange(0, 2, "hi"));
            before.Version.Changes.Add(firstChange);
            var after = new StringTextSnapshot("hi");
            var testArgs = new TestTextContentChangedEventArgs(before, after);

            // Act
            var result = testArgs.TextChangeOccurred(out var changeInformation);

            // Assert
            Assert.True(result);
            Assert.Same(firstChange, changeInformation.firstChange);
            Assert.Equal(firstChange, changeInformation.lastChange);
            Assert.Equal("hi", changeInformation.newText);
            Assert.Equal("by", changeInformation.oldText);
        }

        [Fact]
        public void TextChangeOccurred_MultipleChanges_ReturnsTrue()
        {
            // Arrange
            var before = new StringTextSnapshot("by by");
            var firstChange = new TestTextChange(new SourceChange(0, 2, "hi"));
            before.Version.Changes.Add(firstChange);
            var lastChange = new TestTextChange(new SourceChange(3, 2, "hi"));
            before.Version.Changes.Add(lastChange);
            var after = new StringTextSnapshot("hi hi");
            var testArgs = new TestTextContentChangedEventArgs(before, after);

            // Act
            var result = testArgs.TextChangeOccurred(out var changeInformation);

            // Assert
            Assert.True(result);
            Assert.Same(firstChange, changeInformation.firstChange);
            Assert.Equal(lastChange, changeInformation.lastChange);
            Assert.Equal("hi hi", changeInformation.newText);
            Assert.Equal("by by", changeInformation.oldText);
        }

        private class TestTextContentChangedEventArgs : TextContentChangedEventArgs
        {
            public TestTextContentChangedEventArgs(ITextSnapshot before, ITextSnapshot after)
                : base(before, after, EditOptions.DefaultMinimalChange, null)
            {
            }
        }
    }
}