/* @license
 * Copyright 2020 Google LLC. All Rights Reserved.
 * Licensed under the Apache License, Version 2.0 (the 'License');
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an 'AS IS' BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import {FrontSide, Material, Mesh, MeshStandardMaterial, Object3D, Sphere} from 'three';
import {GLTF} from 'three/examples/jsm/loaders/GLTFLoader.js';

import {$clone, $prepare, $preparedGLTF, GLTFInstance, PreparedGLTF} from '../GLTFInstance.js';

import {CorrelatedSceneGraph} from './correlated-scene-graph.js';

const $correlatedSceneGraph = Symbol('correlatedSceneGraph');

interface PreparedModelViewerGLTF extends PreparedGLTF {
  [$correlatedSceneGraph]?: CorrelatedSceneGraph;
}

/**
 * This specialization of GLTFInstance collects all of the processing needed
 * to prepare a model and to clone it making special considerations for
 * <model-viewer> use cases.
 */
export class ModelViewerGLTFInstance extends GLTFInstance {
  /**
   * @override
   */
  protected static[$prepare](source: GLTF) {
    const prepared = super[$prepare](source) as PreparedModelViewerGLTF;

    if (prepared[$correlatedSceneGraph] == null) {
      prepared[$correlatedSceneGraph] = CorrelatedSceneGraph.from(prepared);
    }

    const {scene} = prepared;

    const nullSphere = new Sphere(undefined, Infinity);

    scene.traverse((node: Object3D) => {
      // Set a high renderOrder while we're here to ensure the model
      // always renders on top of the skysphere
      node.renderOrder = 1000;

      // Three.js seems to cull some animated models incorrectly. Since we
      // expect to view our whole scene anyway, we turn off the frustum
      // culling optimization here.
      node.frustumCulled = false;
      // Animations for objects without names target their UUID instead. When
      // objects are cloned, they get new UUIDs which the animation can't
      // find. To fix this, we assign their UUID as their name.
      if (!node.name) {
        node.name = node.uuid;
      }
      const mesh = node as Mesh;
      if (mesh.isMesh) {
        mesh.castShadow = true;
        if ((mesh as any).isSkinnedMesh) {
          // Akin to disablig frustum culling above, we have to also manually
          // disable the bounds to make raycasting correct for skinned meshes.
          mesh.geometry.boundingSphere = nullSphere;
          // The bounding box is set in GLTFLoader by the accessor bounds, which
          // are not updated with animation.
          mesh.geometry.boundingBox = null;
        }

        const material = mesh.material as MeshStandardMaterial;
        // This makes shadows better for non-manifold meshes
        material.shadowSide = FrontSide;
      }
    });

    return prepared;
  }

  get correlatedSceneGraph() {
    return (
        this[$preparedGLTF] as PreparedModelViewerGLTF)[$correlatedSceneGraph]!;
  }

  /**
   * @override
   */
  [$clone](): PreparedGLTF {
    const clone: PreparedModelViewerGLTF = super[$clone]();
    const sourceUUIDToClonedMaterial = new Map<string, Material>();

    clone.scene.traverse((node: Object3D) => {
      // Materials aren't cloned when cloning meshes; geometry
      // and materials are copied by reference. This is necessary
      // for the same model to be used twice with different
      // scene-graph operations.
      if ((node as Mesh).isMesh) {
        const mesh = node as Mesh;
        const material = mesh.material as MeshStandardMaterial;
        if (material != null) {
          if (sourceUUIDToClonedMaterial.has(material.uuid)) {
            mesh.material = sourceUUIDToClonedMaterial.get(material.uuid)!;
            return;
          }

          mesh.material = material.clone() as MeshStandardMaterial;
          sourceUUIDToClonedMaterial.set(material.uuid, mesh.material);
        }
      }
    });

    // Cross-correlate the scene graph by relying on information in the
    // current scene graph; without this step, relationships between the
    // Three.js object graph and the glTF scene graph will be lost.
    clone[$correlatedSceneGraph] =
        CorrelatedSceneGraph.from(clone, this.correlatedSceneGraph);

    return clone;
  }
}