module ag.grid {

    export class TemplateService {

        templateCache:any = {};
        waitingCallbacks:any = {};
        $scope: any;

        init($scope: any) {
            this.$scope = $scope;
        }

        // returns the template if it is loaded, or null if it is not loaded
        // but will call the callback when it is loaded
        getTemplate(url: any, callback: any) {

            var templateFromCache = this.templateCache[url];
            if (templateFromCache) {
                return templateFromCache;
            }

            var callbackList = this.waitingCallbacks[url];
            var that = this;
            if (!callbackList) {
                // first time this was called, so need a new list for callbacks
                callbackList = [];
                this.waitingCallbacks[url] = callbackList;
                // and also need to do the http request
                var client = new XMLHttpRequest();
                client.onload = function () {
                    that.handleHttpResult(this, url);
                };
                client.open("GET", url);
                client.send();
            }

            // add this callback
            if (callback) {
                callbackList.push(callback);
            }

            // caller needs to wait for template to load, so return null
            return null;
        }

        handleHttpResult(httpResult: any, url: any) {

            if (httpResult.status !== 200 || httpResult.response === null) {
                console.warn('Unable to get template error ' + httpResult.status + ' - ' + url);
                return;
            }

            // response success, so process it
            this.templateCache[url] = httpResult.response;

            // inform all listeners that this is now in the cache
            var callbacks = this.waitingCallbacks[url];
            for (var i = 0; i < callbacks.length; i++) {
                var callback = callbacks[i];
                // we could pass the callback the response, however we know the client of this code
                // is the cell renderer, and it passes the 'cellRefresh' method in as the callback
                // which doesn't take any parameters.
                callback();
            }

            if (this.$scope) {
                var that = this;
                setTimeout(function () {
                    that.$scope.$apply();
                }, 0);
            }
        }
    }
}