/**
 * Selection.js
 *
 * @author realor
 */

import { Application } from '../ui/Application.js'
import * as THREE from '../lib/three.module.js'

class Selection {
    constructor(application, notify = false) {
        this.application = application
        this._objects = new Set()
        this.notify = notify
    }

    get iterator() {
        return this._objects.values()
    }

    get object() {
        // returns the first object in selection
        let objects = this._objects
        return objects.size === 0 ? null : objects.values().next().value
    }

    get objects() {
        return Array.from(this._objects)
    }

    get roots() {
        // returns the top selected objects
        let roots = []
        let iterator = this._objects.values()
        let item = iterator.next()
        while (!item.done) {
            let object = item.value
            if (this.isRoot(object)) {
                roots.push(object)
            }
            item = iterator.next()
        }
        return roots
    }

    contains(object) {
        return this._objects.has(object)
    }

    isRoot(object) {
        // is root if object is selected but no ancestor is selected
        let root = this._objects.has(object)
        let parent = object.parent
        while (parent && root) {
            root = !this._objects.has(parent)
            parent = parent.parent
        }
        return root
    }

    isEmpty() {
        return this._objects.size === 0
    }

    get size() {
        return this._objects.size
    }

    set(...objects) {
        this._objects.clear()
        this._add(objects)
        if (this.notify) this._notifyListeners()
    }

    add(...objects) {
        this._add(objects)
        if (this.notify) this._notifyListeners()
    }

    remove(...objects) {
        let size = this._objects.size

        for (let object of objects) {
            this._objects.delete(object)
        }

        if (size !== this._objects.size) {
            if (this.notify) this._notifyListeners()
        }
    }

    clear() {
        if (this._objects.size > 0) {
            this._objects.clear()
            if (this.notify) this._notifyListeners()
        }
    }

    _add(objects) {
        for (let i = 0; i < objects.length; i++) {
            let object = objects[i]
            if (object instanceof THREE.Object3D) {
                this._objects.add(object)
            }
        }
    }

    _notifyListeners() {
        let selectionEvent = { type: 'changed', objects: this.objects }
        this.application.notifyEventListeners('selection', selectionEvent)
    }
}

export { Selection }