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 * modification, are permitted provided that the following conditions are met:
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 *       notice, this list of conditions and the following disclaimer.
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 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
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 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
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 */

using System;
using System.IO;
using OpenSim.Framework;
using OpenSim.Region.Framework.Interfaces;
using OpenSim.Region.Framework.Scenes;

namespace OpenSim.Region.CoreModules.World.Terrain.FileLoaders
{
    public class LLRAW : ITerrainLoader
    {
        public struct HeightmapLookupValue : IComparable<HeightmapLookupValue>
        {
            public ushort Index;
            public float Value;

            public HeightmapLookupValue(ushort index, float value)
            {
                Index = index;
                Value = value;
            }

            public int CompareTo(HeightmapLookupValue val)
            {
                return Value.CompareTo(val.Value);
            }
        }

        /// <summary>Lookup table to speed up terrain exports</summary>
        HeightmapLookupValue[] LookupHeightTable;

        public LLRAW()
        {
        }

        private void BuildLookupHeightTable()
        {
            LookupHeightTable = new HeightmapLookupValue[256 * 256];

            for (int i = 0; i < 256; i++)
            {
                for (int j = 0; j < 256; j++)
                {
                    LookupHeightTable[i + (j * 256)] = new HeightmapLookupValue((ushort)(i + (j * 256)), (float)((double)i * ((double)j / 128.0d)));
                }
            }
            Array.Sort<HeightmapLookupValue>(LookupHeightTable);
        }

        #region ITerrainLoader Members

        public ITerrainChannel LoadFile(string filename)
        {
            FileInfo file = new FileInfo(filename);

            ITerrainChannel channel;

            using (FileStream s = file.Open(FileMode.Open, FileAccess.Read))
                channel = LoadStream(s);

            return channel;
        }

        public ITerrainChannel LoadFile(string filename, int offsetX, int offsetY, int fileWidth, int fileHeight, int sectionWidth, int sectionHeight)
        {
            TerrainChannel retval = new TerrainChannel(sectionWidth, sectionHeight);

            FileInfo file = new FileInfo(filename);

            using (FileStream s = file.Open(FileMode.Open, FileAccess.Read))
            using (BinaryReader bs = new BinaryReader(s))
            {
                int currFileYOffset = fileHeight - 1;

                // if our region isn't on the first Y section of the areas to be landscaped, then
                // advance to our section of the file
                while (currFileYOffset > offsetY)
                {
                    // read a whole strip of regions
                    int heightsToRead = sectionHeight * (fileWidth * sectionWidth);
                    bs.ReadBytes(heightsToRead * 13); // because there are 13 fun channels
                    currFileYOffset--;
                }

                // got to the Y start offset within the file of our region
                // so read the file bits associated with our region
                int y;

                // for each Y within our Y offset
                for (y = sectionHeight - 1; y >= 0; y--)
                {
                    int currFileXOffset = 0;

                    // if our region isn't the first X section of the areas to be landscaped, then
                    // advance the stream to the X start pos of our section in the file
                    // i.e. eat X upto where we start
                    while (currFileXOffset < offsetX)
                    {
                        bs.ReadBytes(sectionWidth * 13);
                        currFileXOffset++;
                    }

                    // got to our X offset, so write our regions X line
                    int x;
                    for (x = 0; x < sectionWidth; x++)
                    {
                        // Read a strip and continue
                        retval[x, y] = bs.ReadByte() * (bs.ReadByte() / 128.0f);
                        bs.ReadBytes(11);
                    }
                    // record that we wrote it
                    currFileXOffset++;

                    // if our region isn't the last X section of the areas to be landscaped, then
                    // advance the stream to the end of this Y column
                    while (currFileXOffset < fileWidth)
                    {
                        // eat the next regions x line
                        bs.ReadBytes(sectionWidth * 13); //The 13 channels again
                        currFileXOffset++;
                    }
                }
            }

            return retval;
        }

        public ITerrainChannel LoadStream(Stream s)
        {
            // The raw format doesn't contain any dimension information.
            // Guess the square dimensions by using the length of the raw file.
            double dimension = Math.Sqrt((double)(s.Length / 13));
            // Regions are always multiples of 256.
            int trimmedDimension = (int)dimension - ((int)dimension % (int)Constants.RegionSize);
            if (trimmedDimension < Constants.RegionSize)
                trimmedDimension = (int)Constants.RegionSize;

            TerrainChannel retval = new TerrainChannel(trimmedDimension, trimmedDimension);

            using (BinaryReader bs = new BinaryReader(s))
            {
                int y;
                for (y = 0; y < retval.Height; y++)
                {
                    int x;
                    for (x = 0; x < retval.Width; x++)
                    {
                        retval[x, (retval.Height - 1) - y] = bs.ReadByte() * (bs.ReadByte() / 128.0f);
                        bs.ReadBytes(11); // Advance the stream to next bytes.
                    }
                }
            }

            return retval;
        }

        public void SaveFile(string filename, ITerrainChannel map)
        {
            FileInfo file = new FileInfo(filename);

            using (FileStream s = file.Open(FileMode.CreateNew, FileAccess.Write))
                SaveStream(s, map);
        }

        public void SaveStream(Stream s, ITerrainChannel map)
        {
            if (LookupHeightTable == null)
                BuildLookupHeightTable();

            using (BinaryWriter binStream = new BinaryWriter(s))
            {
                // Output the calculated raw
                for (int y = 0; y < map.Height; y++)
                {
                    for (int x = 0; x < map.Width; x++)
                    {
                        double t = map[x, (map.Height - 1) - y];
                        //if height is less than 0, set it to 0 as
                        //can't save -ve values in a LLRAW file
                        if (t < 0d)
                        {
                            t = 0d;
                        }

                        int index = 0;

                        // The lookup table is pre-sorted, so we either find an exact match or
                        // the next closest (smaller) match with a binary search
                        index = Array.BinarySearch<HeightmapLookupValue>(LookupHeightTable, new HeightmapLookupValue(0, (float)t));
                        if (index < 0)
                            index = ~index - 1;

                        index = LookupHeightTable[index].Index;

                        byte red = (byte) (index & 0xFF);
                        byte green = (byte) ((index >> 8) & 0xFF);
                        const byte blue = 20;
                        const byte alpha1 = 0;
                        const byte alpha2 = 0;
                        const byte alpha3 = 0;
                        const byte alpha4 = 0;
                        const byte alpha5 = 255;
                        const byte alpha6 = 255;
                        const byte alpha7 = 255;
                        const byte alpha8 = 255;
                        byte alpha9 = red;
                        byte alpha10 = green;

                        binStream.Write(red);
                        binStream.Write(green);
                        binStream.Write(blue);
                        binStream.Write(alpha1);
                        binStream.Write(alpha2);
                        binStream.Write(alpha3);
                        binStream.Write(alpha4);
                        binStream.Write(alpha5);
                        binStream.Write(alpha6);
                        binStream.Write(alpha7);
                        binStream.Write(alpha8);
                        binStream.Write(alpha9);
                        binStream.Write(alpha10);
                    }
                }
            }
            LookupHeightTable = null;
        }

        public string FileExtension
        {
            get { return ".raw"; }
        }

        public virtual void SaveFile(ITerrainChannel m_channel, string filename,
                             int offsetX, int offsetY,
                             int fileWidth, int fileHeight,
                             int regionSizeX, int regionSizeY)
        {
            throw new System.Exception("Not Implemented");
        }

        #endregion

        public override string ToString()
        {
            return "LL/SL RAW";
        }

        //Returns true if this extension is supported for terrain save-tile
        public bool SupportsTileSave()
        {
            return false;
        }
    }
}