using JdeScoping.ConfigManager.Core.Services;

namespace JdeScoping.ConfigManager.Core.Tests.Services;

public class DiffServiceTests
{
    private readonly DiffService _sut;

    public DiffServiceTests()
    {
        _sut = new DiffService();
    }

    [Fact]
    public void GenerateDiff_WithNoChanges_ReturnsEmptyDiff()
    {
        // Arrange
        var original = "line1\nline2\nline3";
        var modified = "line1\nline2\nline3";

        // Act
        var result = _sut.GenerateDiff(original, modified);

        // Assert
        result.HasChanges.ShouldBeFalse();
    }

    [Fact]
    public void GenerateDiff_WithChanges_ReturnsDiffLines()
    {
        // Arrange
        var original = "line1\nline2\nline3";
        var modified = "line1\nmodified\nline3";

        // Act
        var result = _sut.GenerateDiff(original, modified);

        // Assert
        result.HasChanges.ShouldBeTrue();
        result.Lines.ShouldNotBeEmpty();
    }

    [Fact]
    public void GenerateDiff_WithAddedLine_ReportsInsertion()
    {
        // Arrange
        var original = "line1\nline2";
        var modified = "line1\nline2\nline3";

        // Act
        var result = _sut.GenerateDiff(original, modified);

        // Assert
        result.HasChanges.ShouldBeTrue();
        result.Insertions.ShouldBe(1);
        result.Deletions.ShouldBe(0);
        result.Lines.ShouldContain(l => l.Type == DiffLineType.Added && l.Text == "line3");
    }

    [Fact]
    public void GenerateDiff_WithRemovedLine_ReportsDeletion()
    {
        // Arrange
        var original = "line1\nline2\nline3";
        var modified = "line1\nline3";

        // Act
        var result = _sut.GenerateDiff(original, modified);

        // Assert
        result.HasChanges.ShouldBeTrue();
        result.Deletions.ShouldBe(1);
        result.Lines.ShouldContain(l => l.Type == DiffLineType.Removed && l.Text == "line2");
    }

    [Fact]
    public void GenerateDiff_WithModifiedLine_ReportsAdditionAndDeletion()
    {
        // Arrange
        var original = "line1\noriginal\nline3";
        var modified = "line1\nchanged\nline3";

        // Act
        var result = _sut.GenerateDiff(original, modified);

        // Assert
        result.HasChanges.ShouldBeTrue();
        result.Insertions.ShouldBeGreaterThan(0);
        result.Deletions.ShouldBeGreaterThan(0);
    }

    [Fact]
    public void GenerateDiff_WithEmptyOriginal_ReportsAllAsInsertions()
    {
        // Arrange
        var original = "";
        var modified = "line1\nline2";

        // Act
        var result = _sut.GenerateDiff(original, modified);

        // Assert
        result.HasChanges.ShouldBeTrue();
        result.Insertions.ShouldBeGreaterThan(0);
        result.Deletions.ShouldBe(0);
    }

    [Fact]
    public void GenerateDiff_WithEmptyModified_ReportsAllAsDeletions()
    {
        // Arrange
        var original = "line1\nline2";
        var modified = "";

        // Act
        var result = _sut.GenerateDiff(original, modified);

        // Assert
        result.HasChanges.ShouldBeTrue();
        result.Insertions.ShouldBe(0);
        result.Deletions.ShouldBeGreaterThan(0);
    }

    [Fact]
    public void GenerateDiff_LineNumbers_AreCorrectForUnchangedLines()
    {
        // Arrange
        var original = "line1\nline2\nline3";
        var modified = "line1\nline2\nline3";

        // Act
        var result = _sut.GenerateDiff(original, modified);

        // Assert
        var firstLine = result.Lines.First();
        firstLine.OldLineNumber.ShouldBe(1);
        firstLine.NewLineNumber.ShouldBe(1);
    }

    [Fact]
    public void GenerateDiff_AddedLine_HasNullOldLineNumber()
    {
        // Arrange
        var original = "line1";
        var modified = "line1\nline2";

        // Act
        var result = _sut.GenerateDiff(original, modified);

        // Assert
        var addedLine = result.Lines.FirstOrDefault(l => l.Type == DiffLineType.Added);
        addedLine.ShouldNotBeNull();
        addedLine.OldLineNumber.ShouldBeNull();
        addedLine.NewLineNumber.ShouldNotBeNull();
    }

    [Fact]
    public void GenerateDiff_RemovedLine_HasNullNewLineNumber()
    {
        // Arrange
        var original = "line1\nline2";
        var modified = "line1";

        // Act
        var result = _sut.GenerateDiff(original, modified);

        // Assert
        var removedLine = result.Lines.FirstOrDefault(l => l.Type == DiffLineType.Removed);
        removedLine.ShouldNotBeNull();
        removedLine.OldLineNumber.ShouldNotBeNull();
        removedLine.NewLineNumber.ShouldBeNull();
    }
}