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

namespace JdeScoping.DataSync.Tests.Etl.Transformers;

public class ColumnRenameTransformerTests
{
    [Fact]
    public void GetName_ReturnsRenamedColumn()
    {
        var source = CreateMockReader(new[] { "OldName", "Other" });
        var transformer = new ColumnRenameTransformer(("OldName", "NewName"));
        var reader = transformer.Transform(source);
        Assert.Equal("NewName", reader.GetName(0));
        Assert.Equal("Other", reader.GetName(1));
    }

    [Fact]
    public void GetOrdinal_FindsByNewName()
    {
        var source = CreateMockReader(new[] { "OldName", "Other" });
        var transformer = new ColumnRenameTransformer(("OldName", "NewName"));
        var reader = transformer.Transform(source);
        Assert.Equal(0, reader.GetOrdinal("NewName"));
    }

    [Fact]
    public void GetOrdinal_OldName_ThrowsIndexOutOfRange()
    {
        var source = CreateMockReader(new[] { "OldName", "Other" });
        var transformer = new ColumnRenameTransformer(("OldName", "NewName"));
        var reader = transformer.Transform(source);
        Assert.Throws<IndexOutOfRangeException>(() => reader.GetOrdinal("OldName"));
    }

    [Fact]
    public void FieldCount_Unchanged()
    {
        var source = CreateMockReader(new[] { "OldName", "Other" });
        var transformer = new ColumnRenameTransformer(("OldName", "NewName"));
        var reader = transformer.Transform(source);
        Assert.Equal(2, reader.FieldCount);
    }

    [Fact]
    public void MultipleRenames_AllApplied()
    {
        var source = CreateMockReader(new[] { "A", "B", "C" });
        var transformer = new ColumnRenameTransformer(("A", "Alpha"), ("C", "Charlie"));
        var reader = transformer.Transform(source);
        Assert.Equal("Alpha", reader.GetName(0));
        Assert.Equal("B", reader.GetName(1));
        Assert.Equal("Charlie", reader.GetName(2));
    }

    [Fact]
    public void OnInitialize_RenameCollision_ThrowsInvalidOperationException()
    {
        // Arrange - renaming A to B when B already exists
        var transformer = new ColumnRenameTransformer(("A", "B"));
        var source = CreateMockReader(new[] { "A", "B", "C" });

        // Act & Assert
        var ex = Assert.Throws<InvalidOperationException>(() =>
            transformer.Transform(source));
        Assert.Contains("A", ex.Message);
        Assert.Contains("B", ex.Message);
        Assert.Contains("collision", ex.Message.ToLower());
    }

    [Fact]
    public void OnInitialize_PreExistingDuplicates_ThrowsInvalidOperationException()
    {
        // Arrange - source has duplicate column names (case-insensitive)
        var transformer = new ColumnRenameTransformer();
        var source = CreateMockReaderWithDuplicates(new[] { "Name", "name" });

        // Act & Assert
        Assert.Throws<InvalidOperationException>(() =>
            transformer.Transform(source));
    }

    private static IDataReader CreateMockReader(string[] columns)
    {
        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);
        }
        return reader;
    }

    private static IDataReader CreateMockReaderWithDuplicates(string[] columns)
    {
        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]);
        }
        return reader;
    }
}