//libassetloader.js

(async function() {
    if(typeof XMLHttpRequest!="function") {
        if(typeof loadfail=="function") {
            loadfail("libassetloader.js: XMLHttpRequest(type of "+(typeof XMLHttpRequest)+") is not a function");
        } else {
            window.alert("libassetloader.js: XMLHttpRequest(type of "+(typeof XMLHttpRequest)+") is not a function");
        }
        return;
    }
    if(typeof Blob!="function") {
        if(typeof loadfail=="function") {
            loadfail("libassetloader.js: Blob(type of "+(typeof Blob)+") is not a function");
        } else {
            window.alert("libassetloader.js: Blob(type of "+(typeof Blob)+") is not a function");
        }
        return;
    }
    if(typeof URL!="function") {
        if(typeof loadfail=="function") {
            loadfail("libassetloader.js: URL(type of "+(typeof URL)+") is not a function");
        } else {
            window.alert("libassetloader.js: URL(type of "+(typeof URL)+") is not a function");
        }
        return;
    }

    var AssetManager= {};

    // map http url -> blob url
    AssetManager.loadedAssets= {};

    AssetManager.loading_count=0;

    AssetManager.loadWithCache=async function(pth) {
        if(pth in AssetManager.loadedAssets) {
            return Promise.resolve(AssetManager.loadedAssets[pth]);
        }
        return AssetManager.do_fetch_res(pth);
    };

    AssetManager.do_fetch_res=async function(pth) {
        var resolve;
        var reject;
        var ret=new Promise(function(s, r) {
            resolve=s;
            reject=r;
        });
        var xhr=new XMLHttpRequest();

        xhr.responseType = "blob";

        var onreadystatechange=async function() {
            if(xhr.readyState!=XMLHttpRequest.DONE) {
                return;
            }
            removelisteners();
            AssetManager.loading_count--;
            if(xhr.status!=200) {
                onfail();
                return;
            }
            AssetManager.loadedAssets[pth]=URL.createObjectURL(xhr.response);
            console.debug("asset "+pth+" loaded from source.");
            resolve(AssetManager.loadedAssets[pth]);
            return;
        };

        var onfail=function() {
            removelisteners();
            xhr.abort();
            window.loadfail("asset "+pth+" load failed");
            reject("asset "+pth+" load failed");
        };

        var removelisteners=function() {
            xhr.removeEventListener("readystatechange", onreadystatechange);
            xhr.removeEventListener("error", onfail);
            xhr.removeEventListener("abort", onfail);
        };

        xhr.addEventListener("readystatechange", onreadystatechange);
        xhr.addEventListener("error", onfail);
        xhr.addEventListener("abort", onfail);

        xhr.open("GET", pth, true);
        xhr.send();

        AssetManager.loading_count++;
        return ret;
    };

    AssetManager.isDone=function() {
        return AssetManager.loading_count==0;
    };

    AssetManager.waitAll=async function() {
        return new Promise(function(resolve, reject) {
            var i;
            i=setInterval(function() {
                if(AssetManager.loading_count==0) {
                    clearInterval(i);
                    resolve();
                }
            }, 100);
        });
    };

    window.AssetManager=AssetManager;

})();