// 1. audio can only be played on user interact in many OS.
// 2. on iOS audio will only preload after playing (and of course after user interact)
//    So we may mute the audio element and play it to make it preload(Based on Solution1)
// 3. in some situation, image even need to be append to DOM to make it actually load.


// We have generatly 2 solution
// 1. use XHR to ensure everything goes right (easier to implement, but potential memory issue)
// 2. use Element to load everything (hard way, but likely to use less resource)
// For who ever implement this, try your best

export class ResourceLoader {
    constructor(option: {
        baseUrl?: string
    }) {
        // 1. remember all session created
        // 2. feed them
    }
    public baseUrl: string
    createSession(): ResourceLoaderSession {
        throw new Error("Not implemented")
    }
    get<T = HTMLImageElement>(name: string): T {
        throw new Error("Not implemented")
    }
}

// Manage the loading procedure(Spawning load workers, deciding implementation, etc...)
export interface ResourceLoaderSession {
    readonly loader: ResourceLoader
    events: Leaf.EventEmitter<{
        start
        progress: {
            perc: string // like "36.5%"
            down: number
            total: number
        }
        finish
        error: Error
    }>
    // Now every thing can load
    userIsInteracting()
    load(callback: (err?: Error) => void)
    add(name: string, uri: string, type: "image" | "video" | "audio"): this
}
export class XHRResourceLoaderSession implements ResourceLoaderSession {
}
export class ElementResourceLoaderSession implements ResourceLoaderSession {
}

// usage
// const rl = new ResourceLoader()
// let session = rl.createSession({baseUrl:Meta.cdnBase + "/resource/"})
// session.add("myImage","test.jpg")   // default to image
//    .add("myVideo","test.mp4","video")
//    .add(...)
//    .load((err)=>{})
// session.events.listenBy(sb, progress,()=>{
//    //updateUI
//})
//
// // after loaded
// this.VM.src = rl.get("myImage")