import { Nullable } from "types";
import { Material, InternalTexture } from "Materials";
import { PostProcess } from "PostProcess";
import { Engine } from "Engine";
import { Scene } from "scene";
import { VertexBuffer } from "Mesh";
    /**
	 * PostProcessManager is used to manage one or more post processes or post process pipelines
     * See https://doc.babylonjs.com/how_to/how_to_use_postprocesses
     */
    export class PostProcessManager {
        private _scene: Scene;
        private _indexBuffer: Nullable<WebGLBuffer>;
        private _vertexBuffers: { [key: string]: Nullable<VertexBuffer> } = {};

        /**
         * Creates a new instance PostProcess
         * @param scene The scene that the post process is associated with.
         */
        constructor(scene: Scene) {
            this._scene = scene;
        }

        private _prepareBuffers(): void {
            if (this._vertexBuffers[VertexBuffer.PositionKind]) {
                return;
            }

            // VBO
            var vertices = [];
            vertices.push(1, 1);
            vertices.push(-1, 1);
            vertices.push(-1, -1);
            vertices.push(1, -1);

            this._vertexBuffers[VertexBuffer.PositionKind] = new VertexBuffer(this._scene.getEngine(), vertices, VertexBuffer.PositionKind, false, false, 2);

            this._buildIndexBuffer();
        }

        private _buildIndexBuffer(): void {
            // Indices
            var indices = [];
            indices.push(0);
            indices.push(1);
            indices.push(2);

            indices.push(0);
            indices.push(2);
            indices.push(3);

            this._indexBuffer = this._scene.getEngine().createIndexBuffer(indices);
        }

        /**
         * Rebuilds the vertex buffers of the manager.
         * @hidden
         */
        public _rebuild(): void {
            let vb = this._vertexBuffers[VertexBuffer.PositionKind];

            if (!vb) {
                return;
            }
            vb._rebuild();
            this._buildIndexBuffer();
        }

        // Methods
        /**
         * Prepares a frame to be run through a post process.
         * @param sourceTexture The input texture to the post procesess. (default: null)
         * @param postProcesses An array of post processes to be run. (default: null)
         * @returns True if the post processes were able to be run.
         * @hidden
         */
        public _prepareFrame(sourceTexture: Nullable<InternalTexture> = null, postProcesses: Nullable<PostProcess[]> = null): boolean {
            let camera = this._scene.activeCamera;
            if (!camera) {
                return false;
            }

            var postProcesses = postProcesses || (<Nullable<PostProcess[]>>camera._postProcesses.filter((pp) => { return pp != null; }));

            if (!postProcesses || postProcesses.length === 0 || !this._scene.postProcessesEnabled) {
                return false;
            }

            postProcesses[0].activate(camera, sourceTexture, postProcesses !== null && postProcesses !== undefined);
            return true;
        }

        /**
         * Manually render a set of post processes to a texture.
         * @param postProcesses An array of post processes to be run.
         * @param targetTexture The target texture to render to.
         * @param forceFullscreenViewport force gl.viewport to be full screen eg. 0,0,textureWidth,textureHeight
         * @param faceIndex defines the face to render to if a cubemap is defined as the target
         * @param lodLevel defines which lod of the texture to render to
         */
        public directRender(postProcesses: PostProcess[], targetTexture: Nullable<InternalTexture> = null, forceFullscreenViewport = false, faceIndex = 0, lodLevel = 0): void {
            var engine = this._scene.getEngine();

            for (var index = 0; index < postProcesses.length; index++) {
                if (index < postProcesses.length - 1) {
                    postProcesses[index + 1].activate(this._scene.activeCamera, targetTexture);
                } else {
                    if (targetTexture) {
                        engine.bindFramebuffer(targetTexture, faceIndex, undefined, undefined, forceFullscreenViewport, undefined, lodLevel);
                    } else {
                        engine.restoreDefaultFramebuffer();
                    }
                }

                var pp = postProcesses[index];
                var effect = pp.apply();

                if (effect) {
                    pp.onBeforeRenderObservable.notifyObservers(effect);

                    // VBOs
                    this._prepareBuffers();
                    engine.bindBuffers(this._vertexBuffers, this._indexBuffer, effect);

                    // Draw order
                    engine.drawElementsType(Material.TriangleFillMode, 0, 6);

                    pp.onAfterRenderObservable.notifyObservers(effect);
                }
            }

            // Restore depth buffer
            engine.setDepthBuffer(true);
            engine.setDepthWrite(true);
        }

        /**
         * Finalize the result of the output of the postprocesses.
         * @param doNotPresent If true the result will not be displayed to the screen.
         * @param targetTexture The target texture to render to.
         * @param faceIndex The index of the face to bind the target texture to.
         * @param postProcesses The array of post processes to render.
         * @param forceFullscreenViewport force gl.viewport to be full screen eg. 0,0,textureWidth,textureHeight (default: false)
         * @hidden
         */
        public _finalizeFrame(doNotPresent?: boolean, targetTexture?: InternalTexture, faceIndex?: number, postProcesses?: Array<PostProcess>, forceFullscreenViewport = false): void {
            let camera = this._scene.activeCamera;

            if (!camera) {
                return;
            }

            postProcesses = postProcesses || <Array<PostProcess>>camera._postProcesses.filter((pp) => { return pp != null; });
            if (postProcesses.length === 0 || !this._scene.postProcessesEnabled) {
                return;
            }
            var engine = this._scene.getEngine();

            for (var index = 0, len = postProcesses.length; index < len; index++) {
                var pp = postProcesses[index];

                if (index < len - 1) {
                    pp._outputTexture = postProcesses[index + 1].activate(camera, targetTexture);
                } else {
                    if (targetTexture) {
                        engine.bindFramebuffer(targetTexture, faceIndex, undefined, undefined, forceFullscreenViewport);
                        pp._outputTexture = targetTexture;
                    } else {
                        engine.restoreDefaultFramebuffer();
                        pp._outputTexture = null;
                    }
                }

                if (doNotPresent) {
                    break;
                }

                var effect = pp.apply();

                if (effect) {
                    pp.onBeforeRenderObservable.notifyObservers(effect);

                    // VBOs
                    this._prepareBuffers();
                    engine.bindBuffers(this._vertexBuffers, this._indexBuffer, effect);

                    // Draw order
                    engine.drawElementsType(Material.TriangleFillMode, 0, 6);

                    pp.onAfterRenderObservable.notifyObservers(effect);
                }
            }

            // Restore states
            engine.setDepthBuffer(true);
            engine.setDepthWrite(true);
            engine.setAlphaMode(Engine.ALPHA_DISABLE);
        }

        /**
         * Disposes of the post process manager.
         */
        public dispose(): void {
            var buffer = this._vertexBuffers[VertexBuffer.PositionKind];
            if (buffer) {
                buffer.dispose();
                this._vertexBuffers[VertexBuffer.PositionKind] = null;
            }

            if (this._indexBuffer) {
                this._scene.getEngine()._releaseBuffer(this._indexBuffer);
                this._indexBuffer = null;
            }
        }
    }