using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DVBServices
{
	internal class Utils
	{
		/// <summary>
		/// Convert a string of bytes to a hex string.
		/// </summary>
		/// <param name="inputChars">The string to be converted.</param>
		/// <returns>The string of hex characters.</returns>
		public static string ConvertToHex(byte[] inputChars)
		{
			return (ConvertToHex(inputChars, inputChars.Length));
		}

		/// <summary>
		/// Convert a string of bytes to a hex string.
		/// </summary>
		/// <param name="inputChars">The array holding the bytes to be converted.</param>
		/// <param name="length">The number of byte to be converted.</param>
		/// <returns>The string of hex characters.</returns>
		public static string ConvertToHex(byte[] inputChars, int length)
		{
			return (ConvertToHex(inputChars, 0, length));
		}

		/// <summary>
		/// Convert a string of bytes to a hex string.
		/// </summary>
		/// <param name="inputChars">The array holding the bytes to be converted.</param>
		/// <param name="offset">The the offset to the first byte to be converted.</param> 
		/// <param name="length">The number of byte to be converted.</param>
		/// <returns>The string of hex characters.</returns>
		public static string ConvertToHex(byte[] inputChars, int offset, int length)
		{
			char[] outputChars = new char[length * 2];
			int outputIndex = 0;

			for (int inputIndex = 0; inputIndex < length; inputIndex++)
			{
				int hexByteLeft = inputChars[offset] >> 4;
				int hexByteRight = inputChars[offset] & 0x0f;

				outputChars[outputIndex] = getHex(hexByteLeft);
				outputChars[outputIndex + 1] = getHex(hexByteRight);

				outputIndex += 2;
				offset++;
			}

			return ("0x" + new string(outputChars));
		}

		private static char getHex(int value)
		{
			if (value < 10)
				return ((char)('0' + value));

			return ((char)('a' + (value - 10)));
		}
	}
}