//Subject
class Graphic {
    protected _fileName = ""

    constructor(fileName: string) {
        this._fileName = fileName
    }

    getFileName() {
        return this._fileName
    }
}

//RealSubject
class Picture extends Graphic { 
    constructor(fileName: string) {
        super(fileName)
    }

    //Request()
    draw() {
        console.log("draw " + this._fileName)
    }
}

//Proxy
class ImageProxy extends Graphic { 
    private _image: Picture = undefined

    constructor(fileName: string) {
        super(fileName)
    }

    getImage() {
        if (this._image == undefined) {
            this._image = new Picture(this._fileName)
        }
        return this._image
    }

    draw() {
        this.getImage().draw()
    }
}

//Client
let proxy = new ImageProxy("1.png")
//operation without creating a RealSubject
let fileName = proxy.getFileName()
//forwarded to the RealSubject
proxy.draw()

console.log("fileName is", fileName)