using XCEngine;
using XCEngine.Rendering;

namespace XCEngine.Rendering.Universal
{
    internal sealed class UniversalMainSceneBlock
    {
        private const string kMainLightShadowsKeyword =
            "XC_MAIN_LIGHT_SHADOWS";
        private readonly DrawObjectsPass m_drawOpaqueObjectsPass =
            new DrawObjectsPass(
                RenderPassEvent.RenderOpaques,
                SceneRenderPhase.Opaque,
                RendererListDesc.CreateDefault(
                    RendererListType.Opaque));
        private readonly DrawSkyboxPass m_drawSkyboxPass =
            new DrawSkyboxPass();
        private readonly DrawObjectsPass m_drawTransparentObjectsPass =
            new DrawObjectsPass(
                RenderPassEvent.RenderTransparents,
                SceneRenderPhase.Transparent,
                RendererListDesc.CreateDefault(
                    RendererListType.Transparent));

        public void ConfigureRenderSceneSetup(
            RenderSceneSetupContext context)
        {
            if (context == null)
            {
                return;
            }

            context.SetEnvironmentNone();
            context.ClearGlobalShaderKeywords();

            Camera camera = context.camera;
            if (ShouldUseSkyboxEnvironment(
                    context,
                    camera))
            {
                if (camera.hasSkyboxMaterial)
                {
                    context.UseCameraSkyboxMaterial();
                }
                else
                {
                    context.SetProceduralSkybox(
                        camera.skyboxTopColor,
                        camera.skyboxHorizonColor,
                        camera.skyboxBottomColor);
                }
            }

            context.SetGlobalShaderKeyword(
                kMainLightShadowsKeyword,
                context.hasMainDirectionalShadow);
        }

        public void EnqueueRenderPasses(
            ScriptableRenderer renderer,
            UniversalMainSceneData mainScene)
        {
            if (renderer == null ||
                mainScene == null)
            {
                return;
            }

            if (mainScene.renderOpaque)
            {
                EnqueueOpaquePasses(
                    renderer,
                    mainScene);
            }

            if (mainScene.renderSkybox)
            {
                EnqueueSkyboxPasses(
                    renderer,
                    mainScene);
            }

            if (mainScene.renderTransparent)
            {
                EnqueueTransparentPasses(
                    renderer,
                    mainScene);
            }
        }

        private void EnqueueOpaquePasses(
            ScriptableRenderer renderer,
            UniversalMainSceneData mainScene)
        {
            m_drawOpaqueObjectsPass.Configure(
                mainScene.opaquePassEvent,
                SceneRenderPhase.Opaque,
                mainScene.opaqueRendererListDesc,
                mainScene.opaqueDrawingSettings);
            renderer.EnqueuePass(m_drawOpaqueObjectsPass);
        }

        private void EnqueueSkyboxPasses(
            ScriptableRenderer renderer,
            UniversalMainSceneData mainScene)
        {
            m_drawSkyboxPass.Configure(
                mainScene.skyboxPassEvent);
            renderer.EnqueuePass(m_drawSkyboxPass);
        }

        private void EnqueueTransparentPasses(
            ScriptableRenderer renderer,
            UniversalMainSceneData mainScene)
        {
            m_drawTransparentObjectsPass.Configure(
                mainScene.transparentPassEvent,
                SceneRenderPhase.Transparent,
                mainScene.transparentRendererListDesc,
                mainScene.transparentDrawingSettings);
            renderer.EnqueuePass(
                m_drawTransparentObjectsPass);
        }

        private static bool ShouldUseSkyboxEnvironment(
            RenderSceneSetupContext context,
            Camera camera)
        {
            if (context == null ||
                camera == null ||
                !context.hasMainSceneDepthAttachment ||
                (context.clearFlags & RenderClearFlags.Color) == 0 ||
                !camera.skyboxEnabled)
            {
                return false;
            }

            return camera.projectionType ==
                   CameraProjectionType.Perspective;
        }
    }
}