using SFML.Graphics;
using System.Diagnostics;

namespace Otter {
    /// <summary>
    /// NOT YET SUPPORTED
    /// Very WIP class, probably internal for Otter, don't use it yet.
    /// </summary>
    class SpriteBatch {

        RenderStates renderStates = RenderStates.Default;

        public int MaxSprites = 100;

        public int DrawCount { get; private set; }

        VertexArray vertexArray = new VertexArray(PrimitiveType.Quads);

        bool drawing;

        Stopwatch stopwatch;
        public SpriteBatch() {
        }

        public void Begin() {
            if (drawing == false) {
                drawing = true;
                vertexArray.Clear();
                DrawCount = 0;
                stopwatch = Stopwatch.StartNew();
            }
        }

        public void SetTexture(Texture texture) {

        }

        public void SetShader(Shader shader) {

        }

        public void SetBlendMode(BlendMode blend) {

        }

        public void Draw(VertexArray vertices, RenderStates states) {
            if (!drawing) return;

            // Render states have changed, so flush and clear.
            if (!CompareStates(renderStates, states)) {
                Flush();
                vertexArray.Clear();
                renderStates = states;
            }

            // Exceeding maximum sprites, so flush and clear.
            if (DrawCount >= MaxSprites) {
                Flush();
                DrawCount = 0;
                vertexArray.Clear();
            }

            // Apply the transform to the four points
            var transform = states.Transform;
            
            // Append the vertices
            for (uint i = 0; i < vertices.VertexCount; i++) {
                var vertex = vertices[i];
                var pos = transform.TransformPoint(vertex.Position.X, vertex.Position.Y);
                vertex.Position.X = pos.X;
                vertex.Position.Y = pos.Y;
                vertexArray.Append(vertex);
            }

            DrawCount++;
            // I think that's it?
        }

        bool CompareStates(RenderStates a, RenderStates b) {
            if (a.Texture != b.Texture) return false;
            if (a.Shader != b.Shader) return false;
            if (a.BlendMode != b.BlendMode) return false;
            // Dont care about transform right now.
      
            return true;
        }

        public void SetRenderState(RenderStates states) {
            renderStates = states;
        }

        public void End() {
            if (drawing) {
                drawing = false;
                Flush();
                vertexArray.Clear();
                //Console.WriteLine("Spritebatch took {0}ms", stopwatch.ElapsedMilliseconds);
            }
        }

        void Flush() {
            if (vertexArray.VertexCount > 0) {
                renderStates.Transform = Transform.Identity;
                Otter.Draw.Spritebatch(vertexArray, renderStates);
            }
        }

    }
}