using Npgsql.BackendMessages;
using Npgsql.Internal.TypeHandling;
using Npgsql.PostgresTypes;

namespace Npgsql.Internal.TypeHandlers.NumericHandlers;

/// <summary>
/// A type handler for the PostgreSQL real data type.
/// </summary>
/// <remarks>
/// See https://www.postgresql.org/docs/current/static/datatype-numeric.html.
///
/// The type handler API allows customizing Npgsql's behavior in powerful ways. However, although it is public, it
/// should be considered somewhat unstable, and may change in breaking ways, including in non-major releases.
/// Use it at your own risk.
/// </remarks>
public partial class SingleHandler : NpgsqlSimpleTypeHandler<float>, INpgsqlSimpleTypeHandler<double>
{
    public SingleHandler(PostgresType pgType) : base(pgType) {}

    #region Read

    /// <inheritdoc />
    public override float Read(NpgsqlReadBuffer buf, int len, FieldDescription? fieldDescription = null)
        => buf.ReadSingle();

    double INpgsqlSimpleTypeHandler<double>.Read(NpgsqlReadBuffer buf, int len, FieldDescription? fieldDescription)
        => Read(buf, len, fieldDescription);

    #endregion Read

    #region Write

    /// <inheritdoc />
    public int ValidateAndGetLength(double value, NpgsqlParameter? parameter)         => 4;
    /// <inheritdoc />
    public override int ValidateAndGetLength(float value, NpgsqlParameter? parameter) => 4;

    /// <inheritdoc />
    public void Write(double value, NpgsqlWriteBuffer buf, NpgsqlParameter? parameter)         => buf.WriteSingle((float)value);
    /// <inheritdoc />
    public override void Write(float value, NpgsqlWriteBuffer buf, NpgsqlParameter? parameter) => buf.WriteSingle(value);

    #endregion Write
}

partial class SingleHandler
{
    public override int ValidateObjectAndGetLength(object value, ref NpgsqlLengthCache? lengthCache, NpgsqlParameter? parameter)
        => value switch
        {

            Single converted => ((INpgsqlSimpleTypeHandler<Single>)this).ValidateAndGetLength(converted, parameter),

            Double converted => ((INpgsqlSimpleTypeHandler<Double>)this).ValidateAndGetLength(converted, parameter),


            _ => throw new InvalidCastException($"Can't write CLR type {value.GetType()} with handler type SingleHandler")
        };

    public override Task WriteObjectWithLength(object? value, NpgsqlWriteBuffer buf, NpgsqlLengthCache? lengthCache, NpgsqlParameter? parameter, bool async, CancellationToken cancellationToken = default)
        => value switch
        {

            Single converted => WriteWithLength(converted, buf, lengthCache, parameter, async, cancellationToken),

            Double converted => WriteWithLength(converted, buf, lengthCache, parameter, async, cancellationToken),


            DBNull => WriteWithLength(DBNull.Value, buf, lengthCache, parameter, async, cancellationToken),
            null => WriteWithLength(DBNull.Value, buf, lengthCache, parameter, async, cancellationToken),
            _ => throw new InvalidCastException($"Can't write CLR type {value.GetType()} with handler type SingleHandler")
        };
}