using System.Data;

namespace Connected.Interop
{
	public static class TypeSystem
	{
		public static bool IsInteger(Type type)
		{
			var nnType = type.GetNonNullableType();

			return GetTypeCode(nnType) switch
			{
				TypeCode.SByte or TypeCode.Int16 or TypeCode.Int32 or TypeCode.Int64 or TypeCode.Byte or TypeCode.UInt16 or TypeCode.UInt32 or TypeCode.UInt64 => true,
				_ => false,
			};
		}

		public static TypeCode GetTypeCode(Type type)
		{
			if (type.IsEnum)
				return GetTypeCode(Enum.GetUnderlyingType(type));

			if (type == typeof(bool))
				return TypeCode.Boolean;
			else if (type == typeof(byte))
				return TypeCode.Byte;
			else if (type == typeof(sbyte))
				return TypeCode.SByte;
			else if (type == typeof(short))
				return TypeCode.Int16;
			else if (type == typeof(ushort))
				return TypeCode.UInt16;
			else if (type == typeof(int))
				return TypeCode.Int32;
			else if (type == typeof(uint))
				return TypeCode.UInt32;
			else if (type == typeof(long))
				return TypeCode.Int64;
			else if (type == typeof(ulong))
				return TypeCode.UInt64;
			else if (type == typeof(float))
				return TypeCode.Single;
			else if (type == typeof(double))
				return TypeCode.Double;
			else if (type == typeof(decimal))
				return TypeCode.Decimal;
			else if (type == typeof(string))
				return TypeCode.String;
			else if (type == typeof(char))
				return TypeCode.Char;
			else if (type == typeof(DateTime))
				return TypeCode.DateTime;
			else
				return TypeCode.Object;
		}

		public static Type ToType(this DbType type)
		{
			return type switch
			{
				DbType.AnsiString or DbType.AnsiStringFixedLength or DbType.String or DbType.StringFixedLength or DbType.Xml => typeof(string),
				DbType.Binary or DbType.Object => typeof(object),
				DbType.Boolean => typeof(bool),
				DbType.Byte => typeof(byte),
				DbType.Int16 => typeof(short),
				DbType.Int32 => typeof(int),
				DbType.SByte => typeof(sbyte),
				DbType.UInt16 => typeof(ushort),
				DbType.UInt32 => typeof(uint),
				DbType.Int64 => typeof(long),
				DbType.UInt64 => typeof(ulong),
				DbType.Currency or DbType.Decimal => typeof(decimal),
				DbType.Double => typeof(double),
				DbType.Single => typeof(float),
				DbType.VarNumeric => typeof(decimal),
				DbType.Date or DbType.DateTime or DbType.DateTime2 or DbType.Time => typeof(DateTime),
				DbType.DateTimeOffset => typeof(DateTimeOffset),
				DbType.Guid => typeof(Guid),
				_ => throw new NotSupportedException(),
			};
		}

		public static DbType ToDbType(this Type? type)
		{
			if (type is null)
				return DbType.Object;

			var underlyingType = type;

			if (underlyingType.IsEnum)
				underlyingType = Enum.GetUnderlyingType(underlyingType);

			if (underlyingType == typeof(char) || underlyingType == typeof(string))
				return DbType.String;
			else if (underlyingType == typeof(byte))
				return DbType.Byte;
			else if (underlyingType == typeof(bool))
				return DbType.Boolean;
			else if (underlyingType == typeof(DateTime) || underlyingType == typeof(DateTimeOffset))
				return DbType.DateTime2;
			else if (underlyingType == typeof(decimal))
				return DbType.Decimal;
			else if (underlyingType == typeof(double))
				return DbType.Double;
			else if (underlyingType == typeof(Guid))
				return DbType.Guid;
			else if (underlyingType == typeof(short))
				return DbType.Int16;
			else if (underlyingType == typeof(int))
				return DbType.Int32;
			else if (underlyingType == typeof(long))
				return DbType.Int64;
			else if (underlyingType == typeof(sbyte))
				return DbType.SByte;
			else if (underlyingType == typeof(float))
				return DbType.Single;
			else if (underlyingType == typeof(TimeSpan))
				return DbType.Time;
			else if (underlyingType == typeof(ushort))
				return DbType.UInt16;
			else if (underlyingType == typeof(uint))
				return DbType.UInt32;
			else if (underlyingType == typeof(ulong))
				return DbType.UInt64;
			else if (underlyingType == typeof(byte[]))
				return DbType.Binary;
			else
				return DbType.String;
		}
	}
}