/// <reference path="../../../../../dist/preview release/babylon.d.ts"/>

module BABYLON.GLTF2.Loader.Extensions {
    const NAME = "MSFT_lod";

    interface IMSFTLOD {
        ids: number[];
    }

    /**
     * [Specification](https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/MSFT_lod)
     */
    export class MSFT_lod implements IGLTFLoaderExtension {
        /** The name of this extension. */
        public readonly name = NAME;

        /** Defines whether this extension is enabled. */
        public enabled = true;

        /**
         * Maximum number of LODs to load, starting from the lowest LOD.
         */
        public maxLODsToLoad = Number.MAX_VALUE;

        /**
         * Observable raised when all node LODs of one level are loaded.
         * The event data is the index of the loaded LOD starting from zero.
         * Dispose the loader to cancel the loading of the next level of LODs.
         */
        public onNodeLODsLoadedObservable = new Observable<number>();

        /**
         * Observable raised when all material LODs of one level are loaded.
         * The event data is the index of the loaded LOD starting from zero.
         * Dispose the loader to cancel the loading of the next level of LODs.
         */
        public onMaterialLODsLoadedObservable = new Observable<number>();

        private _loader: GLTFLoader;

        private _nodeIndexLOD: Nullable<number> = null;
        private _nodeSignalLODs = new Array<Deferred<void>>();
        private _nodePromiseLODs = new Array<Array<Promise<any>>>();

        private _materialIndexLOD: Nullable<number> = null;
        private _materialSignalLODs = new Array<Deferred<void>>();
        private _materialPromiseLODs = new Array<Array<Promise<any>>>();

        /** @hidden */
        constructor(loader: GLTFLoader) {
            this._loader = loader;
        }

        /** @hidden */
        public dispose() {
            delete this._loader;

            this._nodeIndexLOD = null;
            this._nodeSignalLODs.length = 0;
            this._nodePromiseLODs.length = 0;

            this._materialIndexLOD = null;
            this._materialSignalLODs.length = 0;
            this._materialPromiseLODs.length = 0;

            this.onMaterialLODsLoadedObservable.clear();
            this.onNodeLODsLoadedObservable.clear();
        }

        /** @hidden */
        public onReady(): void {
            for (let indexLOD = 0; indexLOD < this._nodePromiseLODs.length; indexLOD++) {
                const promise = Promise.all(this._nodePromiseLODs[indexLOD]).then(() => {
                    if (indexLOD !== 0) {
                        this._loader.endPerformanceCounter(`Node LOD ${indexLOD}`);
                    }

                    this._loader.log(`Loaded node LOD ${indexLOD}`);
                    this.onNodeLODsLoadedObservable.notifyObservers(indexLOD);

                    if (indexLOD !== this._nodePromiseLODs.length - 1) {
                        this._loader.startPerformanceCounter(`Node LOD ${indexLOD + 1}`);
                        if (this._nodeSignalLODs[indexLOD]) {
                            this._nodeSignalLODs[indexLOD].resolve();
                        }
                    }
                });

                this._loader._completePromises.push(promise);
            }

            for (let indexLOD = 0; indexLOD < this._materialPromiseLODs.length; indexLOD++) {
                const promise = Promise.all(this._materialPromiseLODs[indexLOD]).then(() => {
                    if (indexLOD !== 0) {
                        this._loader.endPerformanceCounter(`Material LOD ${indexLOD}`);
                    }

                    this._loader.log(`Loaded material LOD ${indexLOD}`);
                    this.onMaterialLODsLoadedObservable.notifyObservers(indexLOD);

                    if (indexLOD !== this._materialPromiseLODs.length - 1) {
                        this._loader.startPerformanceCounter(`Material LOD ${indexLOD + 1}`);
                        if (this._materialSignalLODs[indexLOD]) {
                            this._materialSignalLODs[indexLOD].resolve();
                        }
                    }
                });

                this._loader._completePromises.push(promise);
            }
        }

        /** @hidden */
        public loadNodeAsync(context: string, node: INode, assign: (babylonTransformNode: TransformNode) => void): Nullable<Promise<TransformNode>> {
            return GLTFLoader.LoadExtensionAsync<IMSFTLOD, TransformNode>(context, node, this.name, (extensionContext, extension) => {
                let firstPromise: Promise<TransformNode>;

                const nodeLODs = this._getLODs(extensionContext, node, this._loader.gltf.nodes, extension.ids);
                this._loader.logOpen(`${extensionContext}`);

                for (let indexLOD = 0; indexLOD < nodeLODs.length; indexLOD++) {
                    const nodeLOD = nodeLODs[indexLOD];

                    if (indexLOD !== 0) {
                        this._nodeIndexLOD = indexLOD;
                        this._nodeSignalLODs[indexLOD] = this._nodeSignalLODs[indexLOD] || new Deferred();
                    }

                    const assign = (babylonTransformNode: TransformNode) => { babylonTransformNode.setEnabled(false); };
                    const promise = this._loader.loadNodeAsync(`#/nodes/${nodeLOD.index}`, nodeLOD, assign).then((babylonMesh) => {
                        if (indexLOD !== 0) {
                            // TODO: should not rely on _babylonMesh
                            const previousNodeLOD = nodeLODs[indexLOD - 1];
                            if (previousNodeLOD._babylonTransformNode) {
                                previousNodeLOD._babylonTransformNode.dispose();
                                delete previousNodeLOD._babylonTransformNode;
                                this._disposeUnusedMaterials();
                            }
                        }

                        babylonMesh.setEnabled(true);
                        return babylonMesh;
                    });

                    if (indexLOD === 0) {
                        firstPromise = promise;
                    }
                    else {
                        this._nodeIndexLOD = null;
                    }

                    this._nodePromiseLODs[indexLOD] = this._nodePromiseLODs[indexLOD] || [];
                    this._nodePromiseLODs[indexLOD].push(promise);
                }

                this._loader.logClose();
                return firstPromise!;
            });
        }

        /** @hidden */
        public _loadMaterialAsync(context: string, material: IMaterial, babylonMesh: Mesh, babylonDrawMode: number, assign: (babylonMaterial: Material) => void): Nullable<Promise<Material>> {
            // Don't load material LODs if already loading a node LOD.
            if (this._nodeIndexLOD) {
                return null;
            }

            return GLTFLoader.LoadExtensionAsync<IMSFTLOD, Material>(context, material, this.name, (extensionContext, extension) => {
                let firstPromise: Promise<Material>;

                const materialLODs = this._getLODs(extensionContext, material, this._loader.gltf.materials, extension.ids);
                this._loader.logOpen(`${extensionContext}`);

                for (let indexLOD = 0; indexLOD < materialLODs.length; indexLOD++) {
                    const materialLOD = materialLODs[indexLOD];

                    if (indexLOD !== 0) {
                        this._materialIndexLOD = indexLOD;
                    }

                    const promise = this._loader._loadMaterialAsync(`#/materials/${materialLOD.index}`, materialLOD, babylonMesh, babylonDrawMode, (babylonMaterial) => {
                        if (indexLOD === 0) {
                            assign(babylonMaterial);
                        }
                    }).then((babylonMaterial) => {
                        if (indexLOD !== 0) {
                            assign(babylonMaterial);

                            // TODO: should not rely on _data
                            const previousDataLOD = materialLODs[indexLOD - 1]._data!;
                            if (previousDataLOD[babylonDrawMode]) {
                                previousDataLOD[babylonDrawMode].babylonMaterial.dispose();
                                delete previousDataLOD[babylonDrawMode];
                            }
                        }

                        return babylonMaterial;
                    });

                    if (indexLOD === 0) {
                        firstPromise = promise;
                    }
                    else {
                        this._materialIndexLOD = null;
                    }

                    this._materialPromiseLODs[indexLOD] = this._materialPromiseLODs[indexLOD] || [];
                    this._materialPromiseLODs[indexLOD].push(promise);
                }

                this._loader.logClose();
                return firstPromise!;
            });
        }

        /** @hidden */
        public _loadUriAsync(context: string, uri: string): Nullable<Promise<ArrayBufferView>> {
            // Defer the loading of uris if loading a material or node LOD.
            if (this._materialIndexLOD !== null) {
                this._loader.log(`deferred`);
                const previousIndexLOD = this._materialIndexLOD - 1;
                this._materialSignalLODs[previousIndexLOD] = this._materialSignalLODs[previousIndexLOD] || new Deferred<void>();
                return this._materialSignalLODs[previousIndexLOD].promise.then(() => {
                    return this._loader.loadUriAsync(context, uri);
                });
            }
            else if (this._nodeIndexLOD !== null) {
                this._loader.log(`deferred`);
                const previousIndexLOD = this._nodeIndexLOD - 1;
                this._nodeSignalLODs[previousIndexLOD] = this._nodeSignalLODs[previousIndexLOD] || new Deferred<void>();
                return this._nodeSignalLODs[this._nodeIndexLOD - 1].promise.then(() => {
                    return this._loader.loadUriAsync(context, uri);
                });
            }

            return null;
        }

        /**
         * Gets an array of LOD properties from lowest to highest.
         */
        private _getLODs<T>(context: string, property: T, array: ArrayLike<T> | undefined, ids: number[]): T[] {
            if (this.maxLODsToLoad <= 0) {
                throw new Error("maxLODsToLoad must be greater than zero");
            }

            const properties = new Array<T>();

            for (let i = ids.length - 1; i >= 0; i--) {
                properties.push(ArrayItem.Get(`${context}/ids/${ids[i]}`, array, ids[i]));
                if (properties.length === this.maxLODsToLoad) {
                    return properties;
                }
            }

            properties.push(property);
            return properties;
        }

        private _disposeUnusedMaterials(): void {
            // TODO: should not rely on _data
            const materials = this._loader.gltf.materials;
            if (materials) {
                for (const material of materials) {
                    if (material._data) {
                        for (const drawMode in material._data) {
                            const data = material._data[drawMode];
                            if (data.babylonMeshes.length === 0) {
                                data.babylonMaterial.dispose(false, true);
                                delete material._data[drawMode];
                            }
                        }
                    }
                }
            }
        }
    }

    GLTFLoader.RegisterExtension(NAME, (loader) => new MSFT_lod(loader));
}