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/**

* Copyright 2015 The AMP HTML Authors. All Rights Reserved.

*

* Licensed under the Apache License, Version 2.0 (the "License");

* you may not use this file except in compliance with the License.

* You may obtain a copy of the License at

*

* http://www.apache.org/licenses/LICENSE-2.0

*

* Unless required by applicable law or agreed to in writing, software

* distributed under the License is distributed on an "AS-IS" BASIS,

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* See the License for the specific language governing permissions and

* limitations under the License.

*/

import {dev} from './log';

import {parseUrl} from './url';

/**

* Allows listening for message from the iframe. Returns an unlisten

* function to remove the listener.

*

* @param {!Element} iframe.

* @param {string} typeOfMessage.

* @param {function(!Object)} callback Called when a message of this type

* arrives for this iframe.

* @param {boolean=} opt_is3P set to true if the iframe is 3p.

* @return {!Unlisten}

*/

export function listen(iframe, typeOfMessage, callback, opt_is3P) {

dev.assert(iframe.src, 'only iframes with src supported');

dev.assert(!iframe.parentNode, 'cannot register events on an attached ' +

'iframe. It will cause hair-pulling bugs like #2942');

const origin = parseUrl(iframe.src).origin;

let win = iframe.ownerDocument.defaultView;

const sentinel = getSentinel_(opt_is3P);

let unlisten;

let listener = function(event) {

// If this iframe no longer has a contentWindow is was removed

// from the DOM. Unlisten immediately as we can never again receive

// messages for it (

if (!iframe.contentWindow) {

unlisten();

return;

}

if (event.origin != origin) {

return;

}

if (event.source != iframe.contentWindow) {

return;

}

if (!event.data) {

return;

}

const data = parseIfNeeded(event.data, opt_is3P);

if (data.sentinel != sentinel) {

return;

}

if (data.type != typeOfMessage) {

return;

}

callback(data);

};

win.addEventListener('message', listener);

return unlisten = function() {

if (listener) {

win.removeEventListener('message', listener);

// Make sure references to the unlisten function do not keep

// alive too much.

listener = null;

iframe = null;

win = null;

callback = null;

}

};

}

/**

* Allows listening for a message from the iframe and then removes the listener

*

* @param {!Element} iframe.

* @param {string} typeOfMessage.

* @param {function(!Object)} callback Called when a message of this type

* arrives for this iframe.

* @param {boolean=} opt_is3P set to true if the iframe is 3p.

* @return {!Unlisten}

*/

export function listenOnce(iframe, typeOfMessage, callback, opt_is3P) {

const unlisten = listen(iframe, typeOfMessage, data => {

unlisten();

return callback(data);

}, opt_is3P);

return unlisten;

}

/**

* Posts a message to the iframe.

* @param {!Element} element The iframe.

* @param {string} type Type of the message.

* @param {!Object} object Message payload.

* @param {string} targetOrigin origin of the target.

* @param {boolean=} opt_is3P set to true if the iframe is 3p.

*/

export function postMessage(iframe, type, object, targetOrigin, opt_is3P) {

if (!iframe.contentWindow) {

return;

}

object.type = type;

object.sentinel = getSentinel_(opt_is3P);

if (opt_is3P) {

// Serialize ourselves because that is much faster in Chrome.

object = 'amp-' + JSON.stringify(object);

}

iframe.contentWindow./*OK*/postMessage(object, targetOrigin);

}

/**

* Gets the sentinel string.

* @param {boolean=} opt_is3P set to true if the iframe is 3p.

* @returns {string} Sentinel string.

* @private

*/

function getSentinel_(opt_is3P) {

return opt_is3P ? 'amp-$internalRuntimeToken$' : 'amp';

}

/**

* Json parses event.data if it needs to be

* @param {boolean=} opt_is3P set to true if the iframe is 3p.

* @returns {!Object} object message

* @private

*/

function parseIfNeeded(data, opt_is3P) {

const shouldBeParsed = typeof data === 'string'

&& data.charAt(0) === '{'

&& !opt_is3P;

if (shouldBeParsed) {

try {

data = JSON.parse(data);

} catch (e) {

log.warn('Postmessage could not be parsed. ' +

'Is it in a valid JSON format?', e);

}

}

return data;

}