/*

    Copyright (C) 2016 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    This is the content script injected into web pages. Once the DOM has loaded on the web page that this content script is injected into, it sends a message to the Safari App Extension, and gets a response with the words to replace and what to replace them with. Once it gets the response, it traverses the DOM and performs the replacements.

*/

// Wait for the DOM to load before dispatching a message to the app extension's Swift code.

document.addEventListener("DOMContentLoaded", function(event) {

    safari.extension.dispatchMessage("GetWordsAndReplacements");

});

// Listens for messages sent from the app extension's Swift code.

safari.self.addEventListener("message", messageHandler);

function messageHandler(event)

{

    if (event.name === "WordsAndReplacements") {

        // The userInfo of the call to -[SFSafariPage dispatchMessageToScriptWithName:userInfo:].

        var wordReplacementMap = event.message;

        for (var wordToReplace in wordReplacementMap) {

            replace(document.body, wordToReplace, wordReplacementMap[wordToReplace]);

        }

    }

}

function replace(node, word, replacement) {

    switch (node.nodeType)

    {

        case Node.ELEMENT_NODE:

            // We don't want to replace text in an input field or textarea.

            if (node.tagName.toLowerCase() === "input" || node.tagName.toLowerCase() === "textarea") {

                return;

            }

            // For other types of element nodes, we explicitly fall through to iterate over their children.

        case Node.DOCUMENT_NODE:

        case Node.DOCUMENT_FRAGMENT_NODE:

            // If the node is a container node, iterate over all the children and recurse into them.

            var child = node.firstChild;

            var next = undefined;

            while (child) {

                next = child.nextSibling;

                replace(child, word, replacement);

                child = next;

            }

            break;

        case Node.TEXT_NODE:

            // If the node is a text node, perform the text replacement.

            replaceTextInTextNode(node, word, replacement);

            break;

    }

}

function replaceTextInTextNode(textNode, word, replacement) {

    // Skip over nodes that aren't text nodes.

    if (textNode.nodeType !== Node.TEXT_NODE)

        return;

    // And text nodes that don't have any text.

    if (!textNode.nodeValue.length)

        return;

    // Generate a regular expression object to perform the replacement.

    var expressionForWordToReplace = new RegExp(word, "gi");

    var nodeValue = textNode.nodeValue;

    var newNodeValue = nodeValue.replace(expressionForWordToReplace, replacement);

    // Perform the replacement in the DOM if the regular expression had any effect.

    if (nodeValue !== newNodeValue) {

        textNode.nodeValue = newNodeValue;

    }

}