export function scriptLib(url: string,
                          namespace: string,
                          callback?: (lib: any) => void): void {
    script(url, () => {
        const lib = (window as any)[namespace];
        (window as any)[namespace] = {};
        delete (window as any)[namespace];
        callback && callback(lib);
    });
}

export function script(url: string, callback?: () => void): void {
    const script = document.createElement("script");
    script.type = "text/javascript";
    script.charset = "utf-8";
    script.src = url;
    if ((script as any).readyState) { // IE
        (script as any).onreadystatechange = () => {
            const loaded = (script as any).readyState === "loaded";
            const completed = (script as any).readyState === "complete";
            if (loaded || completed) {
                (script as any).onreadystatechange = null;
                if (typeof callback === "function") {
                    callback();
                }
            }
        };
    } else { // Others
        script.onload = () => {
            if (typeof callback === "function") {
                callback();
            }
        };
    }
    document.getElementsByTagName("head")[0].appendChild(script);
}

export function scripts(urls: string[], callback?: () => void): void {
    urls.reverse();
    let callbackTmp = callback;
    for (let i = 0; i < urls.length; i++) {
        const url = urls[i];
        callbackTmp = (
            (url, callbackTmp) => () =>
                script(url, () => callbackTmp && callbackTmp())
        )(url, callbackTmp);
    }
    callbackTmp && callbackTmp();
}

export function image(url: string, callback?: () => void): void {
    const img = new Image();
    img.src = url;
    if ((img as any).readyState) {
        (img as any).onreadystatechange = () => {
            if (typeof callback === "function") {
                callback();
            }
        };
    } else {
        img.onload = () => {
            if (typeof callback === "function") {
                callback();
            }
        };
    }
}

export function css(url: string, callback?: () => void): void {
    const link = <HTMLLinkElement> document.createElement("link");
    link.type = "text/css";
    link.rel = "stylesheet";
    link.href = url;
    if ((link as any).readyState) {
        (link as any).onreadystatechange = () => {
            if (typeof callback === "function") {
                callback();
            }
        };
    } else {
        link.onload = () => {
            if (typeof callback === "function") {
                callback();
            }
        };
    }
    document.getElementsByTagName("head")[0].appendChild(link);
}