content_twitter.js

var Api = require('rosette-api');
var TWITTER_TWEET_TEXT_CLASS = "tweet-text"; //css class name of tweet text
var TWITTER_TWEET_CONTAINER_CLASS = "tweet"; //css class name of tweet text container
var requests = [];

// given a sentiment score (from -.5 to .5), return an html color representing that sentiment
var sentimentColor = function(sentiment) {
    var color = '';
    if (sentiment < -0.5) { // dark red
        color = '#d07e7e';
    }
    else if (sentiment < -0.3) { // medium red
        color = '#eec1c1';
    }
    else if (sentiment < -0.1) { // light red
        color = '#e7c3c3';
    }
    else if (sentiment < 0.01) { // grey
        color = '#F8F8F8';
    }
    else if (sentiment < 0.1) { // light green
        color = '#cfe7be';
    }
    else if (sentiment < 0.3) { // medium green
        color = '#DEEED4';
    }
    else { // dark green
        color = '#ACD093';
    }
    return color;
};

// given a sentiment response from the Rosette API and a text container, 
// set the outer container's background color according to its
// calculated sentiment
function getSentimentAndColor(resp, container) {
    var pos = 0;
    var neg = 0;
    // necessary becuase response returns positive and negative confidence
    // in a different order depending on dominant sentiment (positive or negative)
    if (resp.document.label == "pos") {
        pos = resp.document.confidence;
    } else if (resp.document.label == "neg") {
        neg = resp.document.confidence;
    }

    var posVal = parseFloat(pos);
    var negVal = parseFloat(neg);

    container.style.backgroundColor = sentimentColor(posVal-negVal);
}

// given some text, return a rating from -2 to 2 representing the sentiment
var setBackgroundColor = function(text, container) {
    chrome.storage.local.get('rosetteKey', function (result) {
        if (result.rosetteKey != null) {

        var apiSent = new Api(result.rosetteKey, 'https://api.rosette.com/rest/v1/');
        var endpoint = "sentiment";
        apiSent.parameters.content = JSON.stringify(text);
        apiSent.parameters.language = "eng";
         var appHeader = [];
          appHeader[0] = "X-RosetteAPI-App"
          appHeader[1] = "chrome-extension-sentiment";
          apiSent.parameters.customHeaders = [appHeader];

        apiSent.rosette(endpoint, function(err, res){
          if(err){
            console.log(err);
          } else {
            getSentimentAndColor(res, container);
          }
        });

        }
    });
    
};

// returns true of element has class cls
var hasClass = function(element, cls) {
    return (' ' + element.className + ' ').indexOf(' ' + cls + ' ') > -1;
};

// given a tweet element, return the container element
var getTweetContainer = function(tweet) {
    var container = tweet;
    while(!hasClass(container, TWITTER_TWEET_CONTAINER_CLASS) && container.parentNode) {
        container = container.parentNode;
    }
    return container;
};

// main function for filling in the colors corresponding to different sentiments on a twitter page
var fillSentiment = function() {
    var tweets = document.getElementsByClassName(TWITTER_TWEET_TEXT_CLASS);
    
    // first make sure there are new entries to analyze
    var newEntries = false;
    for (var i in tweets) {
        var tweet = tweets[i];
        if(!tweet.getAttribute || tweet.getAttribute("rosette")) {
            continue;
        }
        newEntries = true;
        break;
    }
    if (!newEntries)
        return;
    
    for (var i in tweets) {
        var tweet = tweets[i];
        if(!tweet.getAttribute || tweet.getAttribute("rosette")) {
            continue;
        }
        tweet.setAttribute("rosette", "1");
        // analyze new entries
        var text = tweet.innerText;
        var container = getTweetContainer(tweet);
        setBackgroundColor(text, container);
    }
};

//listen for when DOM is changed by AJAX calls
var react = function(evt) {
    // don't run right away. Rather wait a second so requests get batch sent
    setTimeout(function() {
        fillSentiment();
    }, 1000);
}
document.addEventListener("DOMNodeInserted", react);

// reload page when facebook checkbox is unchecked
chrome.storage.onChanged.addListener(function (changes, areaName) {
    if (changes.siteSelectors && changes.siteSelectors.newValue.indexOf("tsa") === -1) {
        document.removeEventListener("DOMNodeInserted", react);
        location.reload();
    }
});

// NOTE: The content_fb.js file in this repo contains the
// most elegant structure for sending non-concurrent XMLHttpRequests (to avoid 429 errors)
// out of all the Chrome extension examples.