// Needs URLSearchParams polyfilled for IE

(function () {
    // Selector for the iframe element embedding Readium
    var readiumIframe = document.querySelector('iframe');

    // It's a good idea to focus on the Readium frame.
    // This bring it in keyboard focus right away.
    readiumIframe.focus();

    // Used to hook into the iframe hosting Readium
    // after it 'unloads' its initial empty document
    // and begins to load the actual document.
    readiumIframe.contentWindow.addEventListener('unload', function () {
        setTimeout(function () {
            bindToIframe(readiumIframe);
        }, 0);
    });

    function bindToIframe(iframe) {
        // Bring the appropriate search (query) params and fragment
        // from the top window URL to the iframe window URL
        setIframeWindowSearchParams(window, iframe.contentWindow);

        getReadium(iframe.contentWindow, function (ReadiumSDK, reader) {
            reader.on(ReadiumSDK.Events.PAGINATION_CHANGED, function () {
                // Execute after all pagination changed event handlers
                setTimeout(function () {

                    // Bring the appropriate search (query) params and fragment
                    // from the iframe window URL to the top window URL
                    setTopWindowSearchParams(window, iframe.contentWindow);
                }, 0);
            });
        });
    }

    function getReadium(iframeWindow, callback) {
        var readiumSdkVar;

        // Intercept the global ReadiumSDK object assignment using a property.
        // This works because this will run before the Readium script is executed.
        Object.defineProperty(iframeWindow, 'ReadiumSDK', {
            get: function () {
                return readiumSdkVar;
            },
            set: function (ReadiumSDK) {
                if (!readiumSdkVar) {
                    ReadiumSDK.once(ReadiumSDK.Events.READER_INITIALIZED, function (reader) {
                        callback(ReadiumSDK, reader);
                    });
                }
                readiumSdkVar = ReadiumSDK;
            }
        });
    }

    function setIframeWindowSearchParams(topWindow, iframeWindow) {
        iframeWindow.location.hash = topWindow.location.hash;
        var iframeUrlSearchParams = new URLSearchParams(iframeWindow.location.search);
        var topWindowSearchParams = new URLSearchParams(topWindow.location.search);
        if (topWindowSearchParams.has('goto')) {
            iframeUrlSearchParams.set('goto', topWindowSearchParams.get('goto'));
        }
        var newUrl = iframeWindow.location.pathname + '?' + iframeUrlSearchParams.toString() + topWindow.location.hash;
        iframeWindow.history.replaceState({}, '', newUrl);
    }

    function setTopWindowSearchParams(topWindow, iframeWindow) {
        var iframeUrlSearchParams = new URLSearchParams(iframeWindow.location.search);
        if (iframeUrlSearchParams.has('goto')) {
            var topWindowSearchParams = new URLSearchParams(topWindow.location.search);
            topWindowSearchParams.delete('goto');
            var topWindowSearchParamsString = topWindowSearchParams.toString();
            if (topWindowSearchParamsString.length) {
                topWindowSearchParamsString = topWindowSearchParamsString + '&';
            }
            topWindowSearchParamsString = topWindowSearchParamsString + 'goto=' + encodeURI(iframeUrlSearchParams.get('goto'));
            var newUrl = topWindow.location.pathname + '?' + topWindowSearchParamsString;
            topWindow.history.replaceState({}, '', newUrl);
        }
    }
})();