using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.IO;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;

namespace MonoGame.Extended.Tiled.Serialization
{
    public class TiledMapLayerModelContent
    {
        private readonly List<VertexPositionTexture> _vertices;
        private readonly List<ushort> _indices;

        public string LayerName { get; }
        public ReadOnlyCollection<VertexPositionTexture> Vertices { get; }
        public ReadOnlyCollection<ushort> Indices { get; }
        public Size2 ImageSize { get; }
        public string TextureAssetName { get; }

        public TiledMapLayerModelContent(string layerName, TiledMapImageContent image)
        {
            LayerName = layerName;
            _vertices = new List<VertexPositionTexture>();
            Vertices = new ReadOnlyCollection<VertexPositionTexture>(_vertices);
            _indices = new List<ushort>();
            Indices = new ReadOnlyCollection<ushort>(_indices);
            ImageSize = new Size2(image.Width, image.Height);
            TextureAssetName = Path.ChangeExtension(image.Source, null);
        }

        public TiledMapLayerModelContent(string layerName, TiledMapTilesetContent tileset)
            : this(layerName, tileset.Image)
        {
        }

        public void AddTileVertices(Point2 position, Rectangle? sourceRectangle = null, TiledMapTileFlipFlags flags = TiledMapTileFlipFlags.None)
        {
            float texelLeft, texelTop, texelRight, texelBottom;
            var sourceRectangle1 = sourceRectangle ?? new Rectangle(0, 0, (int)ImageSize.Width, (int)ImageSize.Height);

            if (sourceRectangle.HasValue)
            {
                var reciprocalWidth = 1f / ImageSize.Width;
                var reciprocalHeight = 1f / ImageSize.Height;
                texelLeft = sourceRectangle1.X * reciprocalWidth;
                texelTop = sourceRectangle1.Y * reciprocalHeight;
                texelRight = (sourceRectangle1.X + sourceRectangle1.Width) * reciprocalWidth;
                texelBottom = (sourceRectangle1.Y + sourceRectangle1.Height) * reciprocalHeight;
            }
            else
            {
                texelLeft = 0;
                texelTop = 0;
                texelBottom = 1;
                texelRight = 1;
            }

            VertexPositionTexture vertexTopLeft, vertexTopRight, vertexBottomLeft, vertexBottomRight;

            vertexTopLeft.Position = new Vector3(position, 0);
            vertexTopRight.Position = new Vector3(position + new Vector2(sourceRectangle1.Width, 0), 0);
            vertexBottomLeft.Position = new Vector3(position + new Vector2(0, sourceRectangle1.Height), 0);
            vertexBottomRight.Position =
                new Vector3(position + new Vector2(sourceRectangle1.Width, sourceRectangle1.Height), 0);

            vertexTopLeft.TextureCoordinate.Y = texelTop;
            vertexTopLeft.TextureCoordinate.X = texelLeft;

            vertexTopRight.TextureCoordinate.Y = texelTop;
            vertexTopRight.TextureCoordinate.X = texelRight;

            vertexBottomLeft.TextureCoordinate.Y = texelBottom;
            vertexBottomLeft.TextureCoordinate.X = texelLeft;

            vertexBottomRight.TextureCoordinate.Y = texelBottom;
            vertexBottomRight.TextureCoordinate.X = texelRight;

            var flipDiagonally = (flags & TiledMapTileFlipFlags.FlipDiagonally) != 0;
            var flipHorizontally = (flags & TiledMapTileFlipFlags.FlipHorizontally) != 0;
            var flipVertically = (flags & TiledMapTileFlipFlags.FlipVertically) != 0;

            if (flipDiagonally)
            {
                FloatHelper.Swap(ref vertexTopRight.TextureCoordinate.X, ref vertexBottomLeft.TextureCoordinate.X);
                FloatHelper.Swap(ref vertexTopRight.TextureCoordinate.Y, ref vertexBottomLeft.TextureCoordinate.Y);
            }

            if (flipHorizontally)
            {
                if (flipDiagonally)
                {
                    FloatHelper.Swap(ref vertexTopLeft.TextureCoordinate.Y, ref vertexTopRight.TextureCoordinate.Y);
                    FloatHelper.Swap(ref vertexBottomLeft.TextureCoordinate.Y, ref vertexBottomRight.TextureCoordinate.Y);
                }
                else
                {
                    FloatHelper.Swap(ref vertexTopLeft.TextureCoordinate.X, ref vertexTopRight.TextureCoordinate.X);
                    FloatHelper.Swap(ref vertexBottomLeft.TextureCoordinate.X, ref vertexBottomRight.TextureCoordinate.X);
                }
            }

            if (flipVertically)
                if (flipDiagonally)
                {
                    FloatHelper.Swap(ref vertexTopLeft.TextureCoordinate.X, ref vertexBottomLeft.TextureCoordinate.X);
                    FloatHelper.Swap(ref vertexTopRight.TextureCoordinate.X, ref vertexBottomRight.TextureCoordinate.X);
                }
                else
                {
                    FloatHelper.Swap(ref vertexTopLeft.TextureCoordinate.Y, ref vertexBottomLeft.TextureCoordinate.Y);
                    FloatHelper.Swap(ref vertexTopRight.TextureCoordinate.Y, ref vertexBottomRight.TextureCoordinate.Y);
                }

            _vertices.Add(vertexTopLeft);
            _vertices.Add(vertexTopRight);
            _vertices.Add(vertexBottomLeft);
            _vertices.Add(vertexBottomRight);

            Debug.Assert(Vertices.Count <= TiledMapHelper.MaximumVerticesPerModel);
        }

        public void AddTileIndices()
        {
            var indexOffset = Vertices.Count;

            Debug.Assert(3 + indexOffset <= TiledMapHelper.MaximumVerticesPerModel);

            _indices.Add((ushort)(0 + indexOffset));
            _indices.Add((ushort)(1 + indexOffset));
            _indices.Add((ushort)(2 + indexOffset));
            _indices.Add((ushort)(1 + indexOffset));
            _indices.Add((ushort)(3 + indexOffset));
            _indices.Add((ushort)(2 + indexOffset));

            Debug.Assert(Indices.Count <= TiledMapHelper.MaximumIndicesPerModel);
        }
    }
}