create-dan/template/src/dan/assets/loaders/loader.js

Dan frameworks

import { addInCache, removeFromCache } from '../cache'

// Loader status
const LoaderAssetStatus = {
    Waiting: 0,
    Progress: 1,
    Complete: 2,
    Error: 3
}

/**
 * Loader abstract class
 * @param {String} header  - Adress (URL, function, ...)
 * @param {Object} options - Options (cache, size)
 */
class LoaderAsset {
    constructor(header, { size = 1, cache = false, attributes = null, priority = 9999999 }) {
        this.header = header
        this.priority = priority
        this.body = null
        this.size = size
        this.status = LoaderAssetStatus.Waiting
        this._cache = cache
        this._fetch = null
        this.attributes = attributes
        this._loading = {}
        this.loading = new Promise((resolve, reject) => {
            this._loading.resolve = resolve
            this._loading.reject = reject
        })

        // Cache
        this.cache = cache
    }

    /**
     * Start loading
     */
    load() {
        this.status = LoaderAssetStatus.Progress

        // Already loaded
        if (this.status === LoaderAssetStatus.Complete) {
            this._loading.resolve(this.body)
        }
        else {
            // Start
            if (this._fetch === null) {
                this._fetch = this.fetch()
            }

            // Wait
            this._fetch.then((body) => {
                // Complete
                this.status = LoaderAssetStatus.Complete
                this.body = body

                // Attributes
                if(typeof body === 'object') {
                    for(let id in this.attributes) {
                        if(body[id] === undefined) {
                            body[id] = this.attributes[id]
                        }
                    }
                }

                this._loading.resolve(body)
            }).catch((error) => {
                // Error
                this.status = LoaderAssetStatus.Error
                this.body = null
                this._loading.reject(error)
            })
        }

        return this.loading
    }

    /**
     * Fetch the body asset
     */
    fetch() {
        return new Promise(function (resolve, reject) {
            reject('fetch() is not impleted')
        })
    }

    /**
     * Get cache status
     * @returns {Boolean}
     */
    get cache() {
        return this._cache
    }

    /**
     * Set cache status
     * @param {Boolean} cache - Cache status
     */
    set cache(cache) {
        // Add
        if (cache) {
            addInCache(this.id, this)
        }
        // Remove
        else {
            removeFromCache(this.id, this)
        }

        this._cache = cache
    }
}

export default LoaderAsset
export { LoaderAsset, LoaderAssetStatus }