// MonoGame - Copyright (C) The MonoGame Team
// This file is subject to the terms and conditions defined in
// file 'LICENSE.txt', which is part of this source code package.

using System;
using Microsoft.Xna.Framework.Graphics;
using PVRTexLibNET;

namespace Microsoft.Xna.Framework.Content.Pipeline.Graphics
{
    /// <summary>
    /// Supports the processing of a texture compressed using ETC1.
    /// </summary>
    public class Etc1BitmapContent : BitmapContent
    {
        byte[] _data;

        /// <summary>
        /// Initializes a new instance of Etc1BitmapContent.
        /// </summary>
        protected Etc1BitmapContent()
            : base()
        {
        }

        /// <summary>
        /// Initializes a new instance of Etc1BitmapContent with the specified width or height.
        /// </summary>
        /// <param name="width">Width in pixels of the bitmap resource.</param>
        /// <param name="height">Height in pixels of the bitmap resource.</param>
        public Etc1BitmapContent(int width, int height)
            : base(width, height)
        {
        }

        public override byte[] GetPixelData()
        {
            return _data;
        }

        public override void SetPixelData(byte[] sourceData)
        {
            int bytesRequired = ((Width + 3) >> 2) * ((Height + 3) >> 2) * SurfaceFormat.RgbEtc1.GetSize();
            if (bytesRequired != sourceData.Length)
                throw new ArgumentException("ETC1 bitmap with width " + Width + " and height " + Height + " needs "
                    + bytesRequired + " bytes. Received " + sourceData.Length + " bytes");

            if (_data == null || _data.Length != bytesRequired)
                _data = new byte[bytesRequired];
            Buffer.BlockCopy(sourceData, 0, _data, 0, bytesRequired);
        }

        protected override bool TryCopyFrom(BitmapContent sourceBitmap, Rectangle sourceRegion, Rectangle destinationRegion)
        {
            SurfaceFormat sourceFormat;
            if (!sourceBitmap.TryGetFormat(out sourceFormat))
                return false;

            // A shortcut for copying the entire bitmap to another bitmap of the same type and format
            if (SurfaceFormat.RgbEtc1 == sourceFormat && (sourceRegion == new Rectangle(0, 0, Width, Height)) && sourceRegion == destinationRegion)
            {
                SetPixelData(sourceBitmap.GetPixelData());
                return true;
            }

            // Destination region copy is not yet supported
            if (destinationRegion != new Rectangle(0, 0, Width, Height))
                return false;

            // If the source is not Vector4 or requires resizing, send it through BitmapContent.Copy
            if (!(sourceBitmap is PixelBitmapContent<Vector4>) || sourceRegion.Width != destinationRegion.Width || sourceRegion.Height != destinationRegion.Height)
            {
                try
                {
                    BitmapContent.Copy(sourceBitmap, sourceRegion, this, destinationRegion);
                    return true;
                }
                catch (InvalidOperationException)
                {
                    return false;
                }
            }

            // Create the texture object in the PVR library
            var sourceData = sourceBitmap.GetPixelData();
            var rgba32F = (PixelFormat)0x2020202061626772; // static const PixelType PVRStandard32PixelType = PixelType('r', 'g', 'b', 'a', 32, 32, 32, 32);
            using (var pvrTexture = PVRTexture.CreateTexture(sourceData, (uint)sourceBitmap.Width, (uint)sourceBitmap.Height, 1,
                rgba32F, true, VariableType.Float, ColourSpace.lRGB))
            {
                // Resize the bitmap if needed
                if ((sourceBitmap.Width != Width) || (sourceBitmap.Height != Height))
                    pvrTexture.Resize((uint)Width, (uint)Height, 1, ResizeMode.Cubic);
                pvrTexture.Transcode(PixelFormat.ETC1, VariableType.UnsignedByte, ColourSpace.lRGB /*, CompressorQuality.ETCMediumPerceptual, true*/);
                var texDataSize = pvrTexture.GetTextureDataSize(0);
                var texData = new byte[texDataSize];
                pvrTexture.GetTextureData(texData, texDataSize);
                SetPixelData(texData);
            }
            return true;
        }

        protected override bool TryCopyTo(BitmapContent destinationBitmap, Rectangle sourceRegion, Rectangle destinationRegion)
        {
            SurfaceFormat destinationFormat;
            if (!destinationBitmap.TryGetFormat(out destinationFormat))
                return false;

            // A shortcut for copying the entire bitmap to another bitmap of the same type and format
            if (SurfaceFormat.RgbEtc1 == destinationFormat && (sourceRegion == new Rectangle(0, 0, Width, Height)) && sourceRegion == destinationRegion)
            {
                destinationBitmap.SetPixelData(GetPixelData());
                return true;
            }

            // No other support for copying from a ETC1 texture yet
            return false;
        }

        /// <summary>
        /// Gets the corresponding GPU texture format for the specified bitmap type.
        /// </summary>
        /// <param name="format">Format being retrieved.</param>
        /// <returns>The GPU texture format of the bitmap type.</returns>
        public override bool TryGetFormat(out SurfaceFormat format)
        {
            format = SurfaceFormat.RgbEtc1;
            return true;
        }

        /// <summary>
        /// Returns a string description of the bitmap.
        /// </summary>
        /// <returns>Description of the bitmap.</returns>
        public override string ToString()
        {
            return "ETC1 " + Width + "x" + Height;
        }
    }
}