BigIntegerExtensions.cs

namespace Texnomic.Types.Extensions;

/// <summary>
/// Extension methods for <see cref="BigInteger"/> values.
/// </summary>
public static class BigIntegerExtensions
{
    extension(BigInteger Value)
    {
        /// <summary>Converts the value to a <see cref="BigDecimal"/> with an implicit denominator of one.</summary>
        public BigDecimal ToBigDecimal() => new(Value);

        /// <summary>Converts the value to a <see cref="BigDecimal"/> scaled by <paramref name="Denominator"/>.</summary>
        public BigDecimal ToBigDecimal(BigInteger Denominator) => new(Value, Denominator);

        /// <summary>Encodes the value into its minimal unsigned byte representation.</summary>
        public byte[] ToBytes(bool IsBigEndian = true)
            => Value.ToByteArray(Value.Sign >= 0, IsBigEndian);

        /// <summary>
        /// Attempts to encode the value into <paramref name="Destination"/> as unsigned bytes.
        /// </summary>
        public bool TryWriteBytes(Span<byte> Destination, out int BytesWritten, bool IsBigEndian = true)
            => Value.TryWriteBytes(Destination, out BytesWritten, isUnsigned: Value.Sign >= 0, isBigEndian: IsBigEndian);

        /// <summary>Formats the value as a lowercase hexadecimal string with leading zeros stripped.</summary>
        public string AsHex(bool Prefixed = true)
        {
            if (Value.Sign == -1)
            {
                var Hex = $"{BigInteger.Abs(Value):x}".TrimStart('0');

                return Prefixed ? $"0x{Hex}" : Hex;
            }
            else
            {
                var Hex = $"{Value:x}".TrimStart('0');

                return Prefixed ? $"0x{Hex}" : Hex;
            }
        }

        /// <summary>
        /// Formats the value as a fixed-width lowercase hexadecimal string with exactly
        /// <c>Width * 2</c> hex characters, left-padded with zero nibbles.
        /// </summary>
        public string AsPaddedHex(int Width, bool Prefixed = true)
            => Value.ToBytes(IsBigEndian: true).AsPaddedHex(Width, Prefixed);
    }
}