using System.Data;
using JdeScoping.DataSync.Etl.Transformers;
using NSubstitute;

namespace JdeScoping.DataSync.Tests.Etl.Transformers;

public class ColumnDropTransformerTests
{
    [Fact]
    public void FieldCount_ExcludesDroppedColumns()
    {
        var source = CreateMockReader(new[] { "Id", "Name", "DropMe", "Value" });
        var transformer = new ColumnDropTransformer("DropMe");
        var reader = transformer.Transform(source);
        Assert.Equal(3, reader.FieldCount);
    }

    [Fact]
    public void GetName_SkipsDroppedColumns()
    {
        var source = CreateMockReader(new[] { "Id", "Name", "DropMe", "Value" });
        var transformer = new ColumnDropTransformer("DropMe");
        var reader = transformer.Transform(source);
        Assert.Equal("Id", reader.GetName(0));
        Assert.Equal("Name", reader.GetName(1));
        Assert.Equal("Value", reader.GetName(2));
    }

    [Fact]
    public void GetOrdinal_ReturnsRemappedOrdinal()
    {
        var source = CreateMockReader(new[] { "Id", "Name", "DropMe", "Value" });
        var transformer = new ColumnDropTransformer("DropMe");
        var reader = transformer.Transform(source);
        Assert.Equal(0, reader.GetOrdinal("Id"));
        Assert.Equal(1, reader.GetOrdinal("Name"));
        Assert.Equal(2, reader.GetOrdinal("Value"));
    }

    [Fact]
    public void GetOrdinal_DroppedColumn_ThrowsIndexOutOfRange()
    {
        var source = CreateMockReader(new[] { "Id", "Name", "DropMe", "Value" });
        var transformer = new ColumnDropTransformer("DropMe");
        var reader = transformer.Transform(source);
        Assert.Throws<IndexOutOfRangeException>(() => reader.GetOrdinal("DropMe"));
    }

    [Fact]
    public void GetValue_ReturnsCorrectValues()
    {
        var source = CreateMockReader(new[] { "Id", "Name", "DropMe", "Value" }, new object[] { 1, "Test", "Dropped", 42 });
        source.Read().Returns(true);
        var transformer = new ColumnDropTransformer("DropMe");
        var reader = transformer.Transform(source);
        reader.Read();
        Assert.Equal(1, reader.GetValue(0));
        Assert.Equal("Test", reader.GetValue(1));
        Assert.Equal(42, reader.GetValue(2));
    }

    [Fact]
    public void MultipleDroppedColumns_AllExcluded()
    {
        var source = CreateMockReader(new[] { "Id", "Drop1", "Name", "Drop2", "Value" });
        var transformer = new ColumnDropTransformer("Drop1", "Drop2");
        var reader = transformer.Transform(source);
        Assert.Equal(3, reader.FieldCount);
        Assert.Equal("Id", reader.GetName(0));
        Assert.Equal("Name", reader.GetName(1));
        Assert.Equal("Value", reader.GetName(2));
    }

    [Fact]
    public void MapOrdinal_DroppedColumn_MapsCorrectly()
    {
        // Arrange - drop column B (ordinal 1), so C becomes ordinal 1
        var source = CreateMockReader(new[] { "A", "B", "C" });
        var transformer = new ColumnDropTransformer("B");
        transformer.Transform(source);

        // Act - transformed ordinal 1 should map to source ordinal 2 (C)
        var result = transformer.MapOrdinal(1, source);

        // Assert
        Assert.Equal(2, result);
    }

    private static IDataReader CreateMockReader(string[] columns, object[]? values = null)
    {
        var reader = Substitute.For<IDataReader>();
        reader.FieldCount.Returns(columns.Length);
        for (int i = 0; i < columns.Length; i++)
        {
            var index = i;
            reader.GetName(index).Returns(columns[index]);
            reader.GetOrdinal(columns[index]).Returns(index);
            if (values != null) reader.GetValue(index).Returns(values[index]);
        }
        return reader;
    }
}