Xoom Exchange Rate Trend - Draws a graph indicating the exchange rate trend of Xoom.com Online Money Transfer Website.

XoomXChangeRateTrendGraph.gs

/**
 * Services combined together:
 * ~Yahoo Pipes~, Gmail, Google App Script, GDrive, Google Charts
 * 
 * This is a Google App Script Web App that draws a Column Graph highlighting the current and historical exchange rate trend of 
 * Xoom Money Transfer. Created this simple app to keep an eye on the $ to Rupee up/down trend.
 * Has a related excel sheet also.
 * 
 * Output (snapshot): https://plus.google.com/photos/108969069990423509081/albums/6115274347350257297?authkey=CKOFv9-t77O4kAE
 * 
 * How to (re)use this script:
 * - Go to Google Drive (https:\\drive.google.com)
 * - Create a new Spreadsheet
 * - Go to Tools -> Script Editor menu
 * - Copy and paste this entire script in the script file (eg. in Code.gs file)
 * 
 * One time Configuration:
 * - You need to replace the dummy SPREADSHEETID with your newly created SpreadSheetID
 *   Run getId() method in Google App Script and check logs to get the SpreadSheetID
 * - You will need to grant permission to Google Drive (for spreadsheet update), external requests (to use ~yahoo pipes URL~ Google Apps Script) and Gmail (to pull old historical XOOM data from gmail).
 *
 * Optionally configure the trigger in the App script to run the updateDailyXchangeDataToSpreadsheet() method everyday (for eg at 4-5 PM everyday)
 * 
 * You can specify the number of days of data you want to see in the chart by passing p=value as query param in the Web App link
 * https://script.google.com/macros/s/AKfycbwUeHXu5p4WkHZg4oKsHx6BlN8OIHHIu2xxxx-xxxxx-xxxxx/dev?p=25
 * 
 */

/**
 Has a related excel sheet also.
*/

var DEFAULTNOOFDAYS = 25, //if no parameter specified in WebApp URL
    QUERIEDNOOFDAYS = 0,
    SPREADSHEETID = 'YOUR_SPREADSHEET_ID_GOES_HERE';

/*
 * Fetch daily xoom rates and update in a spreadsheet. Use web service to then respond back a Column Chart to highlight the trend.
 */
function updateDailyXchangeDataToSpreadsheet() {
  var sheet   = SpreadsheetApp.getActiveSheet(),  
      lastRow = sheet.getLastRow(); //need to append data at the end  
  
  var rate = getDailyXchangeRateFromXoom(),
      date = new Date();
  
 sheet.getRange(lastRow+1,1).setValue(Utilities.formatDate(date, "GMT", "MM/dd/yyyy"));
 sheet.getRange(lastRow+1,2).setValue(rate);
}

/*
 * Fetch today's exchange rate from Xoom's website
 */
function getDailyXchangeRateFromXoom() {
  var html = UrlFetchApp.fetch('https://www.xoom.com/india/fees-fx').getContentText();
  var doc = XmlService.parse(html);
  var html = doc.getRootElement();
  var menu = getElementsByClassName(html, 'cp-grn-highlight')[0]; //Exchange rate usually in the first child
  var output = XmlService.getPrettyFormat().format(menu);
  
  return menu.getText().replace('1 USD = ', '').replace(' INR', '').trim().substring(0,5); 
}

/*
 * Locates an HTML Dom element by ClassName
 */
function getElementsByClassName(element, classToFind) {  
  var data = [];
  var descendants = element.getDescendants();
  descendants.push(element);  
  for(i in descendants) {
    var elt = descendants[i].asElement();
    if(elt != null) {
      var classes = elt.getAttribute('class');
      if(classes != null) {
        classes = classes.getValue();
        if(classes == classToFind) data.push(elt);
        else {
          classes = classes.split(' ');
          for(j in classes) {
            if(classes[j] == classToFind) {
              data.push(elt);
              break;
            }
          }
        }
      }
    }
  }
  return data;
}

/**
 * To access the spreadsheet data from a web app you must create/save the sspreadsheet id. 
 * This method must be run manually once by the user for the webapp to get data from the spreadsheet properly
 */
function getId() {  
  var ui = SpreadsheetApp.getUi(),
      id = SpreadsheetApp.getActiveSpreadsheet().getId();
  
  Logger.log(id);  
  SpreadsheetApp.getUi().alert(id);
}

function getXchangeDataFromSpreadSheet(noOfDays) {
  var sheet = SpreadsheetApp.openById(SPREADSHEETID),
       data = sheet.getDataRange().getValues().reverse(),
       arrExchngRates = [];
  
  //code here looks weird. Little explanation is needed
  //if noOfDays passed in query parameter is valid and less than no of records in spreadsheet, use it, 
  //otherwise use the DEFAULTNOOFDAYS
  if (noOfDays === null || noOfDays === '' || noOfDays < 1 ) {
    noOfDays = DEFAULTNOOFDAYS; //if noofdays invalid in query string, set it to default value
  }
  
  var len = noOfDays > data.length ? DEFAULTNOOFDAYS : noOfDays; //noOfDays > DEFAULTNOOFDAYS > data.length
  
  QUERIEDNOOFDAYS = len; //to be displayed on chart title   
  
  for (var i = 0; i < len; i++) {
    arrExchngRates.push([getDateMonth(data[i][0]), data[i][1]]);
  }    
   return arrExchngRates;
}

/**
 * Respond back with the chart when the WebApp URL is invoked
 */
function doGet(e) {  
 //if URL has today parameter, return today's rate instead of graph
 if (e.parameters["today"]) {
  return ContentService.createTextOutput(JSON.stringify({rate:getDailyXchangeRateFromXoom()})).setMimeType(ContentService.MimeType.JSON);
 }
  
  var noOfDays = e.parameters["p"];
  Logger.log(noOfDays); //input param from query string p=20
  
  var dataTable = Charts.newDataTable()      
        .addColumn(Charts.ColumnType.STRING, "Dates")
        .addColumn(Charts.ColumnType.NUMBER, "Rates");
        
  var arrExchngRates = getXchangeDataFromSpreadSheet(noOfDays).reverse();
  //Logger.log(arrExchngRates);
  for (var i = 0; i < arrExchngRates.length; i++) {
    dataTable.addRow(arrExchngRates[i]);    
  }
  dataTable.build(); 
  
  var textStyleBuilder = Charts.newTextStyle().setFontSize(10),
      style = textStyleBuilder.build();

  // Build the chart.
  var chart = Charts.newColumnChart()
    .setDataTable(dataTable)      
    .setColors(["rgb(66, 133, 244)"])      
    .setDimensions(950, 400)      
    .setXAxisTitle("Date")      
    .setYAxisTitle("Rupees")      
    .setTitle("Xoom Exchange Rate Trend ("+QUERIEDNOOFDAYS+" Days)")
    .setLegendTextStyle(style)
    .setXAxisTextStyle(style)    
    .build();
 
  // Add our chart to the UI and return it so that we can publish  
  // this UI as a service and access it via a URL.
  var ui = UiApp.createApplication();  
  ui.add(chart);  
  return ui;
}

function getDateMonth(dateString) {
  var dateArray = dateString.split("/");
  var year = dateArray[2];
  var day = dateArray[1];
  var month = dateArray[0];
  return day + "/" + month;
}

/**
 * Run this method once to pull all historical Xoom Rates from your Gmail Inbox into the spreadsheet
 */
function updateOldXchangeDataToSpreadsheet() {
  var sheet   = SpreadsheetApp.getActiveSheet(),
      lastRow = sheet.getLastRow();
  
  // Which Gmail Label should be searched? you can specify Inbox, Sent, etc.
  // Not mandatory, but specifying a subset (like search only within xoom filter) makes the response faster
  var label   = 'xoom'; //This is a label defined in Gmail to filter all mails with subject 'Today at Xoom'
 
  // Retrieve all threads of the specified label
  var threads = GmailApp.search("in:" + label);
  threads = threads.reverse();
  
  for (var i = 0; i < threads.length; i++) {
    
    var messages = threads[i].getMessages();
    for (var m = 0; m < messages.length; m++) {
      var msg = messages[m],
          xchngRate = msg.getSubject().substring(9,14); //Subject is in format: "Rupee at 61.30 Today at Xoom"
       
      sheet.getRange(lastRow+1+i,1).setValue(msg.getDate());
      sheet.getRange(lastRow+1+i,2).setValue(xchngRate);
    }
  }  
}

Under function getDailyXchangeRateFromXoom()
while html parsing at below line of code
var doc = XmlService.parse(html);

I am getting error "The entity name must immediately follow the '&' in the entity reference."

Looks like below fetch call is getting incomplete html
var html = UrlFetchApp.fetch('https://www.xoom.com/india/fees-fx').getContentText();

Below is the html