using System;
using System.Runtime.InteropServices;
using VM.IPP;

namespace VM.Mathematics.SignalProcessing
{
	public unsafe class MedianFilterSampleCode
	{
		public static float[] MedianFilter(float[] input, int size)
		{
			if (input == null)
				throw new ArgumentNullException();

			if (input.Length <= 0)
				throw new ArgumentException("Input array must have length longer than zero.");

			if (input.Length <= size)
				throw new ArgumentException("Input array must be longer then or equal to mask size.");

			if (size < 3)
				throw new ArgumentException("Size must be bigger then 3.");

			if (size % 2 == 0)
				throw new ArgumentException("Size must be odd.");

			// Allocate output
			float[] output = new float[input.Length];

			// Find buffer size
			int bSize = 0;
			int errCode = 0;
			errCode = ippsFilterMedianGetBufferSize(size, IppDataType.ipp32f, &bSize);
			ErrorHandling.HandleReturnValue(errCode);
			byte[] buffer = new byte[bSize];

			// Make delay line for input
			var delayLen = size - 1;
			float[] dlySrc = new float[delayLen];
			for (int i = 0; i < delayLen; i++)
			{
				dlySrc[i] = input[i];
			}

			// Make delay line for output
			float[] dlyDst = new float[delayLen];
			for (int i = 0; i < delayLen; i++)
			{
				dlyDst[i] = input[input.Length - (delayLen - i)];
			}

			// Do the actual filtering
			errCode = 0;
			fixed (float* pDlySrc = &dlySrc[0])
			fixed (float* pDlyDst = &dlyDst[0])
			fixed (float* pInput = &input[0])
			fixed (float* pOutput = &output[0])
			fixed (byte* pBuffer = &buffer[0])
			{
				errCode = ippsFilterMedian_32f(pInput, pOutput, input.Length, size, pDlySrc, pDlyDst, pBuffer);
			}
			ErrorHandling.HandleReturnValue(errCode);

			return output;
		}
		
		[DllImport(IppDllNames.IPPSDLL, EntryPoint = "ippsFilterMedianGetBufferSize")]
		private static extern int ippsFilterMedianGetBufferSize(int maskSize, IppDataType dataType, int* pBufferSize);

		[DllImport(IppDllNames.IPPSDLL, EntryPoint = "ippsFilterMedian_32f")]
		private static extern int ippsFilterMedian_32f(float* pSrc, float* pDst, int len, int maskSize, float* pDlySrc, float* pDlyDst, byte* pBuffer);
	}
}