import { PropertyBinding } from './PropertyBinding.js';
import * as MathUtils from '../math/MathUtils.js';

/**
 *
 * A group of objects that receives a shared animation state.
 *
 * Usage:
 *
 *  - Add objects you would otherwise pass as 'root' to the
 *    constructor or the .clipAction method of AnimationMixer.
 *
 *  - Instead pass this object as 'root'.
 *
 *  - You can also add and remove objects later when the mixer
 *    is running.
 *
 * Note:
 *
 *    Objects of this class appear as one object to the mixer,
 *    so cache control of the individual objects must be done
 *    on the group.
 *
 * Limitation:
 *
 *  - The animated properties must be compatible among the
 *    all objects in the group.
 *
 *  - A single property can either be controlled through a
 *    target group or directly, but not both.
 */

class AnimationObjectGroup {
	constructor() {
		this.uuid = MathUtils.generateUUID();

		// cached objects followed by the active ones
		this._objects = Array.prototype.slice.call(arguments);

		this.nCachedObjects_ = 0; // threshold
		// note: read by PropertyBinding.Composite

		const indices = {};
		this._indicesByUUID = indices; // for bookkeeping

		for (let i = 0, n = arguments.length; i !== n; ++i) {
			indices[arguments[i].uuid] = i;
		}

		this._paths = []; // inside: string
		this._parsedPaths = []; // inside: { we don't care, here }
		this._bindings = []; // inside: Array< PropertyBinding >
		this._bindingsIndicesByPath = {}; // inside: indices in these arrays

		const scope = this;

		this.stats = {
			objects: {
				get total() {
					return scope._objects.length;
				},
				get inUse() {
					return this.total - scope.nCachedObjects_;
				},
			},
			get bindingsPerObject() {
				return scope._bindings.length;
			},
		};
	}

	add() {
		const objects = this._objects,
			indicesByUUID = this._indicesByUUID,
			paths = this._paths,
			parsedPaths = this._parsedPaths,
			bindings = this._bindings,
			nBindings = bindings.length;

		let knownObject = undefined,
			nObjects = objects.length,
			nCachedObjects = this.nCachedObjects_;

		for (let i = 0, n = arguments.length; i !== n; ++i) {
			const object = arguments[i],
				uuid = object.uuid;
			let index = indicesByUUID[uuid];

			if (index === undefined) {
				// unknown object -> add it to the ACTIVE region

				index = nObjects++;
				indicesByUUID[uuid] = index;
				objects.push(object);

				// accounting is done, now do the same for all bindings

				for (let j = 0, m = nBindings; j !== m; ++j) {
					bindings[j].push(new PropertyBinding(object, paths[j], parsedPaths[j]));
				}
			} else if (index < nCachedObjects) {
				knownObject = objects[index];

				// move existing object to the ACTIVE region

				const firstActiveIndex = --nCachedObjects,
					lastCachedObject = objects[firstActiveIndex];

				indicesByUUID[lastCachedObject.uuid] = index;
				objects[index] = lastCachedObject;

				indicesByUUID[uuid] = firstActiveIndex;
				objects[firstActiveIndex] = object;

				// accounting is done, now do the same for all bindings

				for (let j = 0, m = nBindings; j !== m; ++j) {
					const bindingsForPath = bindings[j],
						lastCached = bindingsForPath[firstActiveIndex];

					let binding = bindingsForPath[index];

					bindingsForPath[index] = lastCached;

					if (binding === undefined) {
						// since we do not bother to create new bindings
						// for objects that are cached, the binding may
						// or may not exist

						binding = new PropertyBinding(object, paths[j], parsedPaths[j]);
					}

					bindingsForPath[firstActiveIndex] = binding;
				}
			} else if (objects[index] !== knownObject) {
				console.error(
					'THREE.AnimationObjectGroup: Different objects with the same UUID ' +
						'detected. Clean the caches or recreate your infrastructure when reloading scenes.'
				);
			} // else the object is already where we want it to be
		} // for arguments

		this.nCachedObjects_ = nCachedObjects;
	}

	remove() {
		const objects = this._objects,
			indicesByUUID = this._indicesByUUID,
			bindings = this._bindings,
			nBindings = bindings.length;

		let nCachedObjects = this.nCachedObjects_;

		for (let i = 0, n = arguments.length; i !== n; ++i) {
			const object = arguments[i],
				uuid = object.uuid,
				index = indicesByUUID[uuid];

			if (index !== undefined && index >= nCachedObjects) {
				// move existing object into the CACHED region

				const lastCachedIndex = nCachedObjects++,
					firstActiveObject = objects[lastCachedIndex];

				indicesByUUID[firstActiveObject.uuid] = index;
				objects[index] = firstActiveObject;

				indicesByUUID[uuid] = lastCachedIndex;
				objects[lastCachedIndex] = object;

				// accounting is done, now do the same for all bindings

				for (let j = 0, m = nBindings; j !== m; ++j) {
					const bindingsForPath = bindings[j],
						firstActive = bindingsForPath[lastCachedIndex],
						binding = bindingsForPath[index];

					bindingsForPath[index] = firstActive;
					bindingsForPath[lastCachedIndex] = binding;
				}
			}
		} // for arguments

		this.nCachedObjects_ = nCachedObjects;
	}

	// remove & forget
	uncache() {
		const objects = this._objects,
			indicesByUUID = this._indicesByUUID,
			bindings = this._bindings,
			nBindings = bindings.length;

		let nCachedObjects = this.nCachedObjects_,
			nObjects = objects.length;

		for (let i = 0, n = arguments.length; i !== n; ++i) {
			const object = arguments[i],
				uuid = object.uuid,
				index = indicesByUUID[uuid];

			if (index !== undefined) {
				delete indicesByUUID[uuid];

				if (index < nCachedObjects) {
					// object is cached, shrink the CACHED region

					const firstActiveIndex = --nCachedObjects,
						lastCachedObject = objects[firstActiveIndex],
						lastIndex = --nObjects,
						lastObject = objects[lastIndex];

					// last cached object takes this object's place
					indicesByUUID[lastCachedObject.uuid] = index;
					objects[index] = lastCachedObject;

					// last object goes to the activated slot and pop
					indicesByUUID[lastObject.uuid] = firstActiveIndex;
					objects[firstActiveIndex] = lastObject;
					objects.pop();

					// accounting is done, now do the same for all bindings

					for (let j = 0, m = nBindings; j !== m; ++j) {
						const bindingsForPath = bindings[j],
							lastCached = bindingsForPath[firstActiveIndex],
							last = bindingsForPath[lastIndex];

						bindingsForPath[index] = lastCached;
						bindingsForPath[firstActiveIndex] = last;
						bindingsForPath.pop();
					}
				} else {
					// object is active, just swap with the last and pop

					const lastIndex = --nObjects,
						lastObject = objects[lastIndex];

					if (lastIndex > 0) {
						indicesByUUID[lastObject.uuid] = index;
					}

					objects[index] = lastObject;
					objects.pop();

					// accounting is done, now do the same for all bindings

					for (let j = 0, m = nBindings; j !== m; ++j) {
						const bindingsForPath = bindings[j];

						bindingsForPath[index] = bindingsForPath[lastIndex];
						bindingsForPath.pop();
					}
				} // cached or active
			} // if object is known
		} // for arguments

		this.nCachedObjects_ = nCachedObjects;
	}

	// Internal interface used by befriended PropertyBinding.Composite:

	subscribe_(path, parsedPath) {
		// returns an array of bindings for the given path that is changed
		// according to the contained objects in the group

		const indicesByPath = this._bindingsIndicesByPath;
		let index = indicesByPath[path];
		const bindings = this._bindings;

		if (index !== undefined) return bindings[index];

		const paths = this._paths,
			parsedPaths = this._parsedPaths,
			objects = this._objects,
			nObjects = objects.length,
			nCachedObjects = this.nCachedObjects_,
			bindingsForPath = new Array(nObjects);

		index = bindings.length;

		indicesByPath[path] = index;

		paths.push(path);
		parsedPaths.push(parsedPath);
		bindings.push(bindingsForPath);

		for (let i = nCachedObjects, n = objects.length; i !== n; ++i) {
			const object = objects[i];
			bindingsForPath[i] = new PropertyBinding(object, path, parsedPath);
		}

		return bindingsForPath;
	}

	unsubscribe_(path) {
		// tells the group to forget about a property path and no longer
		// update the array previously obtained with 'subscribe_'

		const indicesByPath = this._bindingsIndicesByPath,
			index = indicesByPath[path];

		if (index !== undefined) {
			const paths = this._paths,
				parsedPaths = this._parsedPaths,
				bindings = this._bindings,
				lastBindingsIndex = bindings.length - 1,
				lastBindings = bindings[lastBindingsIndex],
				lastBindingsPath = path[lastBindingsIndex];

			indicesByPath[lastBindingsPath] = index;

			bindings[index] = lastBindings;
			bindings.pop();

			parsedPaths[index] = parsedPaths[lastBindingsIndex];
			parsedPaths.pop();

			paths[index] = paths[lastBindingsIndex];
			paths.pop();
		}
	}
}

AnimationObjectGroup.prototype.isAnimationObjectGroup = true;

export { AnimationObjectGroup };