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

namespace CodeWalker.GameFiles
{
    public class ResourceBuilder
    {
        protected const int RESOURCE_IDENT = 0x37435352;
        protected const int BASE_SIZE = 0x2000;
        private const int SKIP_SIZE = 16;//512;//256;//64;
        private const int ALIGN_SIZE = 16;//512;//64;

        public class ResourceBuilderBlock
        {
            public IResourceBlock Block;
            public long Length;

            public ResourceBuilderBlock(IResourceBlock block)
            {
                Block = block;
                Length = block?.BlockLength ?? 0;
            }
        }
        public class ResourceBuilderBlockSet
        {
            public bool IsSystemSet = false;
            public ResourceBuilderBlock RootBlock = null;
            public LinkedList<ResourceBuilderBlock> BlockList = new LinkedList<ResourceBuilderBlock>();
            public Dictionary<ResourceBuilderBlock, LinkedListNode<ResourceBuilderBlock>> BlockDict = new Dictionary<ResourceBuilderBlock, LinkedListNode<ResourceBuilderBlock>>();

            public int Count => BlockList.Count;

            public ResourceBuilderBlockSet(IList<IResourceBlock> blocks, bool sys)
            {
                IsSystemSet = sys;
                if (sys && (blocks.Count > 0))
                {
                    RootBlock = new ResourceBuilderBlock(blocks[0]);
                }
                var list = new List<ResourceBuilderBlock>();
                int start = sys ? 1 : 0;
                for (int i = start; i < blocks.Count; i++)
                {
                    var bb = new ResourceBuilderBlock(blocks[i]);
                    list.Add(bb);
                }
                list.Sort((a, b) => b.Length.CompareTo(a.Length));
                foreach (var bb in list)
                {
                    var ln = BlockList.AddLast(bb);
                    BlockDict[bb] = ln;
                }
            }

            public ResourceBuilderBlock FindBestBlock(long maxSize)
            {
                var n = BlockList.First;
                while ((n != null) && (n.Value.Length > maxSize))
                {
                    n = n.Next;
                }
                return n?.Value;
            }

            public ResourceBuilderBlock TakeBestBlock(long maxSize)
            {
                var r = FindBestBlock(maxSize);
                if (r != null)
                {
                    if (BlockDict.TryGetValue(r, out LinkedListNode<ResourceBuilderBlock> ln))
                    {
                        BlockList.Remove(ln);
                        BlockDict.Remove(r);
                    }
                }
                return r;
            }

        }

        public static void GetBlocks(IResourceBlock rootBlock, out IList<IResourceBlock> sys, out IList<IResourceBlock> gfx)
        {
            var systemBlocks = new HashSet<IResourceBlock>();
            var graphicBlocks = new HashSet<IResourceBlock>();
            var processed = new HashSet<IResourceBlock>();


            void addBlock(IResourceBlock block)
            {
                if (block is IResourceSystemBlock)
                {
                    if (!systemBlocks.Contains(block)) systemBlocks.Add(block);
                }
                else if(block is IResourceGraphicsBlock)
                {
                    if (!graphicBlocks.Contains(block)) graphicBlocks.Add(block);
                }
            }
            void addChildren(IResourceBlock block)
            {
                if (block is IResourceSystemBlock sblock)
                {
                    var references = sblock.GetReferences();
                    foreach (var reference in references)
                    {
                        if (!processed.Contains(reference))
                        {
                            processed.Add(reference);
                            addBlock(reference);
                            addChildren(reference);
                        }
                    }
                    var parts = sblock.GetParts();
                    foreach (var part in parts)
                    {
                        addChildren(part.Item2);
                    }
                }
            }

            addBlock(rootBlock);
            addChildren(rootBlock);


            sys = new List<IResourceBlock>();
            foreach (var s in systemBlocks)
            {
                sys.Add(s);
            }
            gfx = new List<IResourceBlock>();
            foreach (var s in graphicBlocks)
            {
                gfx.Add(s);
            }
        }

        public static void AssignPositions(IList<IResourceBlock> blocks, uint basePosition, out RpfResourcePageFlags pageFlags)
        {
            if ((blocks.Count > 0) && (blocks[0] is Meta))
            {
                //use naive packing strategy for Meta resources, due to crashes caused by the improved packing
                AssignPositionsForMeta(blocks, basePosition, out pageFlags);
                return;
            }

            var sys = (basePosition == 0x50000000);

            long pad(long p)
            {
                return ((ALIGN_SIZE - (p % ALIGN_SIZE)) % ALIGN_SIZE);
            }

            long largestBlockSize = 0; // find largest structure
            long startPageSize = BASE_SIZE;// 0x2000; // find starting page size
            long totalBlockSize = 0;
            foreach (var block in blocks)
            {
                var blockLength = block.BlockLength;
                totalBlockSize += blockLength;
                totalBlockSize += pad(totalBlockSize);
                if (largestBlockSize < blockLength)
                {
                    largestBlockSize = blockLength;
                }
            }
            while (startPageSize < largestBlockSize)
            {
                startPageSize *= 2;
            }


            pageFlags = new RpfResourcePageFlags();
            var pageSizeMult = 1;

            while (true)
            {
                if (blocks.Count == 0) break;

                var blockset = new ResourceBuilderBlockSet(blocks, sys);
                var rootblock = blockset.RootBlock;
                var currentPosition = 0L;
                var currentPageSize = startPageSize;
                var currentPageStart = 0L;
                var currentPageSpace = startPageSize;
                var currentRemainder = totalBlockSize;
                var pageCount = 1;
                var pageCounts = new uint[9];
                var pageCountIndex = 0;
                var targetPageSize = Math.Max(65536 * pageSizeMult, startPageSize >> (sys ? 5 : 2));
                var minPageSize = Math.Max(512 * pageSizeMult, Math.Min(targetPageSize, startPageSize) >> 4);
                var baseShift = 0u;
                var baseSize = 512;
                while (baseSize < minPageSize)
                {
                    baseShift++;
                    baseSize *= 2;
                    if (baseShift >= 0xF) break;
                }
                var baseSizeMax = baseSize << 8;
                var baseSizeMaxTest = startPageSize;
                while (baseSizeMaxTest < baseSizeMax)
                {
                    pageCountIndex++;
                    baseSizeMaxTest *= 2;
                }
                pageCounts[pageCountIndex] = 1;

                while (true)
                {
                    var isroot = sys && (currentPosition == 0);
                    var block = isroot ? rootblock : blockset.TakeBestBlock(currentPageSpace);
                    var blockLength = block?.Length ?? 0;
                    if (block != null)
                    {
                        //add this block to the current page.
                        block.Block.FilePosition = basePosition + currentPosition;
                        var opos = currentPosition;
                        currentPosition += blockLength;
                        currentPosition += pad(currentPosition);
                        var usedspace = currentPosition - opos;
                        currentPageSpace -= usedspace;
                        currentRemainder -= usedspace;//blockLength;// 

                    }
                    else if (blockset.Count > 0)
                    {
                        //allocate a new page
                        currentPageStart += currentPageSize;
                        currentPosition = currentPageStart;
                        block = blockset.FindBestBlock(long.MaxValue); //just find the biggest block
                        blockLength = block?.Length ?? 0;
                        while (blockLength <= (currentPageSize >> 1))//determine best new page size
                        {
                            if (currentPageSize <= minPageSize) break;
                            if (pageCountIndex >= 8) break;
                            if ((currentPageSize <= targetPageSize) && (currentRemainder >= (currentPageSize - minPageSize))) break;

                            currentPageSize = currentPageSize >> 1;
                            pageCountIndex++;
                        }
                        currentPageSpace = currentPageSize;
                        pageCounts[pageCountIndex]++;
                        pageCount++;
                    }
                    else
                    {
                        break;
                    }
                }


                pageFlags = new RpfResourcePageFlags(pageCounts, baseShift);

                if ((pageCount == pageFlags.Count) && (pageFlags.Size >= currentPosition)) //make sure page counts fit in the flags value
                {
                    break;
                }

                startPageSize *= 2;
                pageSizeMult *= 2;
            }

        }

        public static void AssignPositionsForMeta(IList<IResourceBlock> blocks, uint basePosition, out RpfResourcePageFlags pageFlags)
        {
            // find largest structure
            long largestBlockSize = 0;
            foreach (var block in blocks)
            {
                if (largestBlockSize < block.BlockLength)
                    largestBlockSize = block.BlockLength;
            }

            // find minimum page size
            long currentPageSize = 0x2000;
            while (currentPageSize < largestBlockSize)
                currentPageSize *= 2;

            long currentPageCount;
            long currentPosition;
            while (true)
            {
                currentPageCount = 0;
                currentPosition = 0;

                // reset all positions
                foreach (var block in blocks)
                    block.FilePosition = -1;

                foreach (var block in blocks)
                {
                    if (block.FilePosition != -1)
                        throw new Exception("Block was already assigned a position!");

                    // check if new page is necessary...
                    // if yes, add a new page and align to it
                    long maxSpace = currentPageCount * currentPageSize - currentPosition;
                    if (maxSpace < (block.BlockLength + SKIP_SIZE))
                    {
                        currentPageCount++;
                        currentPosition = currentPageSize * (currentPageCount - 1);
                    }

                    // set position
                    block.FilePosition = basePosition + currentPosition;
                    currentPosition += block.BlockLength; // + SKIP_SIZE; //is padding everywhere really necessary??

                    // align...
                    if ((currentPosition % ALIGN_SIZE) != 0)
                        currentPosition += (ALIGN_SIZE - (currentPosition % ALIGN_SIZE));
                }

                // break if everything fits...
                if (currentPageCount < 128)
                    break;

                currentPageSize *= 2;
            }

            pageFlags = new RpfResourcePageFlags(RpfResourceFileEntry.GetFlagsFromBlocks((uint)currentPageCount, (uint)currentPageSize, 0));

        }


        public static byte[] Build(ResourceFileBase fileBase, int version, bool compress = true)
        {

            fileBase.FilePagesInfo = new ResourcePagesInfo();

            IList<IResourceBlock> systemBlocks;
            IList<IResourceBlock> graphicBlocks;
            GetBlocks(fileBase, out systemBlocks, out graphicBlocks);
            
            RpfResourcePageFlags systemPageFlags;
            AssignPositions(systemBlocks, 0x50000000, out systemPageFlags);
            
            RpfResourcePageFlags graphicsPageFlags;
            AssignPositions(graphicBlocks, 0x60000000, out graphicsPageFlags);


            fileBase.FilePagesInfo.SystemPagesCount = (byte)systemPageFlags.Count;
            fileBase.FilePagesInfo.GraphicsPagesCount = (byte)graphicsPageFlags.Count;


            var systemStream = new MemoryStream();
            var graphicsStream = new MemoryStream();
            var resourceWriter = new ResourceDataWriter(systemStream, graphicsStream);

            resourceWriter.Position = 0x50000000;
            foreach (var block in systemBlocks)
            {
                resourceWriter.Position = block.FilePosition;

                var pos_before = resourceWriter.Position;
                block.Write(resourceWriter);
                var pos_after = resourceWriter.Position;

                if ((pos_after - pos_before) != block.BlockLength)
                {
                    throw new Exception("error in system length");
                }
            }

            resourceWriter.Position = 0x60000000;
            foreach (var block in graphicBlocks)
            {
                resourceWriter.Position = block.FilePosition;

                var pos_before = resourceWriter.Position;
                block.Write(resourceWriter);
                var pos_after = resourceWriter.Position;

                if ((pos_after - pos_before) != block.BlockLength)
                {
                    throw new Exception("error in graphics length");
                }
            }




            var sysDataSize = (int)systemPageFlags.Size;
            var sysData = new byte[sysDataSize];
            systemStream.Flush();
            systemStream.Position = 0;
            systemStream.Read(sysData, 0, (int)systemStream.Length);


            var gfxDataSize = (int)graphicsPageFlags.Size;
            var gfxData = new byte[gfxDataSize];
            graphicsStream.Flush();
            graphicsStream.Position = 0;
            graphicsStream.Read(gfxData, 0, (int)graphicsStream.Length);



            uint uv = (uint)version;
            uint sv = (uv >> 4) & 0xF;
            uint gv = (uv >> 0) & 0xF;
            uint sf = systemPageFlags.Value + (sv << 28);
            uint gf = graphicsPageFlags.Value + (gv << 28);


            var tdatasize = sysDataSize + gfxDataSize;
            var tdata = new byte[tdatasize];
            Buffer.BlockCopy(sysData, 0, tdata, 0, sysDataSize);
            Buffer.BlockCopy(gfxData, 0, tdata, sysDataSize, gfxDataSize);


            var cdata = compress ? Compress(tdata) : tdata;


            var dataSize = 16 + cdata.Length;
            var data = new byte[dataSize];

            byte[] h1 = BitConverter.GetBytes((uint)0x37435352);
            byte[] h2 = BitConverter.GetBytes((int)version);
            byte[] h3 = BitConverter.GetBytes(sf);
            byte[] h4 = BitConverter.GetBytes(gf);
            Buffer.BlockCopy(h1, 0, data, 0, 4);
            Buffer.BlockCopy(h2, 0, data, 4, 4);
            Buffer.BlockCopy(h3, 0, data, 8, 4);
            Buffer.BlockCopy(h4, 0, data, 12, 4);
            Buffer.BlockCopy(cdata, 0, data, 16, cdata.Length);

            return data;
        }






        public static byte[] AddResourceHeader(RpfResourceFileEntry entry, byte[] data)
        {
            if (data == null) return null;
            byte[] newdata = new byte[data.Length + 16];
            byte[] h1 = BitConverter.GetBytes((uint)0x37435352);
            byte[] h2 = BitConverter.GetBytes(entry.Version);
            byte[] h3 = BitConverter.GetBytes(entry.SystemFlags);
            byte[] h4 = BitConverter.GetBytes(entry.GraphicsFlags);
            Buffer.BlockCopy(h1, 0, newdata, 0, 4);
            Buffer.BlockCopy(h2, 0, newdata, 4, 4);
            Buffer.BlockCopy(h3, 0, newdata, 8, 4);
            Buffer.BlockCopy(h4, 0, newdata, 12, 4);
            Buffer.BlockCopy(data, 0, newdata, 16, data.Length);
            return newdata;
        }


        public static byte[] Compress(byte[] data)
        {
            using (MemoryStream ms = new MemoryStream())
            {
                DeflateStream ds = new DeflateStream(ms, CompressionMode.Compress, true);
                ds.Write(data, 0, data.Length);
                ds.Close();
                byte[] deflated = ms.GetBuffer();
                byte[] outbuf = new byte[ms.Length]; //need to copy to the right size buffer...
                Array.Copy(deflated, outbuf, outbuf.Length);
                return outbuf;
            }
        }
        public static byte[] Decompress(byte[] data)
        {
            using (MemoryStream ms = new MemoryStream(data))
            {
                DeflateStream ds = new DeflateStream(ms, CompressionMode.Decompress);
                MemoryStream outstr = new MemoryStream();
                ds.CopyTo(outstr);
                byte[] deflated = outstr.GetBuffer();
                byte[] outbuf = new byte[outstr.Length]; //need to copy to the right size buffer...
                Array.Copy(deflated, outbuf, outbuf.Length);
                return outbuf;
            }
        }

    }
}