using System;
using System.Collections.Generic;
using System.Linq;

namespace UnityEngine.Experimental.Rendering.HDPipeline
{
    public class HDUtils
    {
        public const RendererConfiguration k_RendererConfigurationBakedLighting = RendererConfiguration.PerObjectLightProbe | RendererConfiguration.PerObjectLightmaps | RendererConfiguration.PerObjectLightProbeProxyVolume;

        public static List<RenderPipelineMaterial> GetRenderPipelineMaterialList()
        {
            var baseType = typeof(RenderPipelineMaterial);
            var assembly = baseType.Assembly;

            var types = assembly.GetTypes()
                .Where(t => t.IsSubclassOf(baseType))
                .Select(Activator.CreateInstance)
                .Cast<RenderPipelineMaterial>()
                .ToList();

            // Note: If there is a need for an optimization in the future of this function, user can
            // simply fill the materialList manually by commenting the code abode and returning a
            // custom list of materials they use in their game.
            //
            // return new List<RenderPipelineMaterial>
            // {
            //    new Lit(),
            //    new Unlit(),
            //    ...
            // };

            return types;
        }

        public static Matrix4x4 GetViewProjectionMatrix(Matrix4x4 worldToViewMatrix, Matrix4x4 projectionMatrix)
        {
            // The actual projection matrix used in shaders is actually massaged a bit to work across all platforms
            // (different Z value ranges etc.)
            var gpuProj = GL.GetGPUProjectionMatrix(projectionMatrix, false);
            var gpuVP = gpuProj *  worldToViewMatrix * Matrix4x4.Scale(new Vector3(1.0f, 1.0f, -1.0f)); // Need to scale -1.0 on Z to match what is being done in the camera.wolrdToCameraMatrix API.

            return gpuVP;
        }

        // Helper to help to display debug info on screen
        static float s_OverlayLineHeight = -1.0f;
        public static void NextOverlayCoord(ref float x, ref float y, float overlayWidth, float overlayHeight, float width)
        {
            x += overlayWidth;
            s_OverlayLineHeight = Mathf.Max(overlayHeight, s_OverlayLineHeight);
            // Go to next line if it goes outside the screen.
            if (x + overlayWidth > width)
            {
                x = 0;
                y -= s_OverlayLineHeight;
                s_OverlayLineHeight = -1.0f;
            }
        }
    }
}