using UnityEngine;
using System.Collections.Generic;

public class TextureCache2D : TextureCache
{
	private Texture2DArray cache;

	public override void TransferToSlice(int sliceIndex, Texture texture)
	{
		bool mismatch = (cache.width != texture.width) || (cache.height != texture.height);

		if (texture is Texture2D)
		{
			mismatch |= (cache.format != (texture as Texture2D).format);
		}

		if (mismatch)
		{
			Debug.LogErrorFormat(texture, "Texture size or format of \"{0}\" doesn't match renderloop settings (should be {1}x{2} {3})",
				texture.name, cache.width, cache.height, cache.format);
			return;
		}

		Graphics.CopyTexture(texture, 0, cache, sliceIndex);
	}

	public override Texture GetTexCache()
	{
		return cache;
	}

	public bool AllocTextureArray(int numTextures, int width, int height, TextureFormat format, bool isMipMapped)
	{
		bool res = AllocTextureArray(numTextures);
		m_numMipLevels = GetNumMips(width, height);

		cache = new Texture2DArray(width, height, numTextures, format, isMipMapped);
		cache.hideFlags = HideFlags.HideAndDontSave;
		cache.wrapMode = TextureWrapMode.Clamp;

		return res;
	}

	public void Release()
	{
		Texture.DestroyImmediate(cache);      // do I need this?
	}
}

public class TextureCacheCubemap : TextureCache
{
	private CubemapArray cache;

	public override void TransferToSlice(int sliceIndex, Texture texture)
	{
		bool mismatch = (cache.width != texture.width) || (cache.height != texture.height);

		if (texture is Cubemap)
		{
			mismatch |= (cache.format != (texture as Cubemap).format);
		}

		if (mismatch)
		{
			Debug.LogErrorFormat(texture, "Texture size or format of \"{0}\" doesn't match renderloop settings (should be {1}x{2} {3})",
				texture.name, cache.width, cache.height, cache.format);
			return;
		}

		for (int f = 0; f < 6; f++)
			Graphics.CopyTexture(texture, f, cache, 6 * sliceIndex + f);
	}

	public override Texture GetTexCache()
	{
		return cache;
	}

	public bool AllocTextureArray(int numCubeMaps, int width, TextureFormat format, bool isMipMapped)
	{
		bool res = AllocTextureArray(6 * numCubeMaps);
		m_numMipLevels = GetNumMips(width, width);

		cache = new CubemapArray(width, numCubeMaps, format, isMipMapped);
		cache.hideFlags = HideFlags.HideAndDontSave;
		cache.wrapMode = TextureWrapMode.Clamp;

		return res;
	}

	public void Release()
	{
		Texture.DestroyImmediate(cache);      // do I need this?
	}
}


abstract public class TextureCache : Object
{
	protected int m_numMipLevels;

	public static int ms_GlobalTextureCacheVersion = 0;
	public int m_TextureCacheVersion = 0;

#if UNITY_EDITOR
	internal class AssetReloader : UnityEditor.AssetPostprocessor
	{
		void OnPostprocessTexture(Texture texture)
		{
			ms_GlobalTextureCacheVersion++;
		}
	}
	private AssetReloader m_assetReloader;
#endif

	private struct SSliceEntry
	{
		public uint TexID;
		public uint CountLRU;
	};

	private int m_numTextures;
	private int[] m_SortedIdxArray;
	private SSliceEntry[] m_SliceArray;
	
	Dictionary<uint, int> m_locatorInSliceArray;

	private static uint g_MaxFrameCount = unchecked((uint)(-1));
	private static uint g_InvalidTexID = (uint)0;

	public int FetchSlice(Texture texture)
	{
		uint TexID = (uint)texture.GetInstanceID();

		//assert(TexID!=g_InvalidTexID);
		if (TexID == g_InvalidTexID) return 0;

		bool bSwapSlice = false;
		bool bFoundAvailOrExistingSlice = false;
		int sliceIndex = -1;

		// search for existing copy
		if (m_locatorInSliceArray.ContainsKey(TexID))
		{
			if (m_TextureCacheVersion != ms_GlobalTextureCacheVersion)
			{
				m_locatorInSliceArray.Remove(TexID);
				m_TextureCacheVersion++;
				Debug.Assert(m_TextureCacheVersion <= ms_GlobalTextureCacheVersion);
			}
			else
			{
				sliceIndex = m_locatorInSliceArray[TexID];
				bFoundAvailOrExistingSlice = true;
			}
			//assert(m_SliceArray[sliceIndex].TexID==TexID);
		}

		// If no existing copy found in the array
		if (!bFoundAvailOrExistingSlice)
		{
			// look for first non zero entry. Will by the least recently used entry
			// since the array was pre-sorted (in linear time) in NewFrame()
			bool bFound = false;
			int j = 0, idx = 0;
			while ((!bFound) && j < m_numTextures)
			{
				idx = m_SortedIdxArray[j];
				if (m_SliceArray[idx].CountLRU == 0) ++j;       // if entry already snagged by a new texture in this frame then ++j
				else bFound = true;
			}

			if (bFound)
			{
				// if we are replacing an existing entry delete it from m_locatorInSliceArray.
				if (m_SliceArray[idx].TexID != g_InvalidTexID)
				{
					m_locatorInSliceArray.Remove(m_SliceArray[idx].TexID);
				}

				m_locatorInSliceArray.Add(TexID, idx);
				m_SliceArray[idx].TexID = TexID;

				sliceIndex = idx;
				bFoundAvailOrExistingSlice = true;
				bSwapSlice = true;
			}
		}


		// wrap up
		//assert(bFoundAvailOrExistingSlice);
		if (bFoundAvailOrExistingSlice)
		{
			m_SliceArray[sliceIndex].CountLRU = 0;      // mark slice as in use this frame

			if (bSwapSlice) // if this was a miss
			{
				// transfer new slice to sliceIndex from source texture
				TransferToSlice(sliceIndex, texture);
			}
		}

		return sliceIndex;
	}

	public void NewFrame()
	{
		int numNonZeros = 0;
		int[] tmpBuffer = new int[m_numTextures];
		for (int i = 0; i < m_numTextures; i++)
		{
			tmpBuffer[i] = m_SortedIdxArray[i];     // copy buffer
			if (m_SliceArray[m_SortedIdxArray[i]].CountLRU != 0) ++numNonZeros;
		}
		int nonZerosBase = 0, zerosBase = 0;
		for (int i = 0; i < m_numTextures; i++)
		{
			if (m_SliceArray[tmpBuffer[i]].CountLRU == 0)
			{
				m_SortedIdxArray[zerosBase + numNonZeros] = tmpBuffer[i];
				++zerosBase;
			}
			else
			{
				m_SortedIdxArray[nonZerosBase] = tmpBuffer[i];
				++nonZerosBase;
			}
		}

		for (int i = 0; i < m_numTextures; i++)
		{
			if (m_SliceArray[i].CountLRU < g_MaxFrameCount) ++m_SliceArray[i].CountLRU;     // next frame
		}

		//for(int q=1; q<m_numTextures; q++)
		//    assert(m_SliceArray[m_SortedIdxArray[q-1]].CountLRU>=m_SliceArray[m_SortedIdxArray[q]].CountLRU);
	}

	public TextureCache()
	{
		m_numTextures = 0;
		m_numMipLevels = 0;
	}

	public virtual void TransferToSlice(int sliceIndex, Texture texture)
	{
	}

	public virtual Texture GetTexCache()
	{
		return null;
	}

	protected bool AllocTextureArray(int numTextures)
	{
		if (numTextures > 0)
		{
			m_SliceArray = new SSliceEntry[numTextures];
			m_SortedIdxArray = new int[numTextures];
			m_locatorInSliceArray = new Dictionary<uint, int>();

			m_numTextures = numTextures;
			for (int i = 0; i < m_numTextures; i++)
			{
				m_SliceArray[i].CountLRU = g_MaxFrameCount;         // never used before
				m_SliceArray[i].TexID = g_InvalidTexID;
				m_SortedIdxArray[i] = i;
			}
		}

		//return m_SliceArray != NULL && m_SortedIdxArray != NULL && numTextures > 0;
		return numTextures > 0;
	}

	// should not really be used in general. Assuming lights are culled properly entries will automatically be replaced efficiently.
	public void RemoveEntryFromSlice(Texture texture)
	{
		uint TexID = (uint)texture.GetInstanceID();

		//assert(TexID!=g_InvalidTexID);
		if (TexID == g_InvalidTexID) return;

		// search for existing copy
		if (m_locatorInSliceArray.ContainsKey(TexID))
		{
			int sliceIndex = m_locatorInSliceArray[TexID];

			//assert(m_SliceArray[sliceIndex].TexID==TexID);

			// locate entry sorted by uCountLRU in m_pSortedIdxArray
			bool bFoundIdxSortLRU = false;
			int i = 0;
			while ((!bFoundIdxSortLRU) && i < m_numTextures)
			{
				if (m_SortedIdxArray[i] == sliceIndex) bFoundIdxSortLRU = true;
				else ++i;
			}

			if (bFoundIdxSortLRU)
			{
				// relocate sliceIndex to front of m_pSortedIdxArray since uCountLRU will be set to maximum.
				for (int j = 0; j < i; j++) { m_SortedIdxArray[j + 1] = m_SortedIdxArray[j]; }
				m_SortedIdxArray[0] = sliceIndex;

				// delete from m_locatorInSliceArray and m_pSliceArray.
				m_locatorInSliceArray.Remove(TexID);
				m_SliceArray[sliceIndex].CountLRU = g_MaxFrameCount;            // never used before
				m_SliceArray[sliceIndex].TexID = g_InvalidTexID;
			}
		}

	}

	protected int GetNumMips(int width, int height)
	{
		return GetNumMips(width > height ? width : height);
	}

	protected int GetNumMips(int dim)
	{
		uint uDim = (uint)dim;
		int iNumMips = 0;
		while (uDim > 0)
		{ ++iNumMips; uDim >>= 1; }
		return iNumMips;
	}
}