index.js

var request = require('request');
var cheerio = require('cheerio');
var url     = require('url');

function search(options, callback) {

  var session = request.defaults({ jar : true });
  var host = options.host || 'www.google.com';
  var solver = options.solver;
  var params = options.params || {};
  var results = [];

  params.hl = params.hl || options.lang || 'en';

  if(options.age) params.tbs = 'qdr:' + options.age;
  if(options.query) params.q = options.query;

  params.start = params.start || 0;

  getPage(params, function onPage(err, body) {
    if(err) {
      if(err.code !== 'ECAPTCHA' || !solver) return callback(err);

      solveCaptcha(err.location, function(err, page) {
        if(err) return callback(err);
        onPage(null, page);
      });

      return;
    }

    var currentResults = extractResults(body);

    var newResults = currentResults.filter(function(result) {
      return results.indexOf(result) === -1;
    });

    newResults.forEach(function(result) {
      callback(null, result['url'], result);
    });

    if(newResults.length === 0) {
      return;
    }

    results = results.concat(newResults);

    if(!options.limit || results.length < options.limit) {
      params.start = results.length;
      getPage(params, onPage);
    }
  });


  function getPage(params, callback) {
    session.get({
        uri: 'https://' + host + '/search',
        qs: params,
        followRedirect: false
      }, 
      function(err, res) {
        if(err) return callback(err);

        if(res.statusCode === 302) {
          var parsed = url.parse(res.headers.location, true);

          if(parsed.pathname !== '/search') {
            var err = new Error('Captcha');
            err.code = 'ECAPTCHA';
            err.location = res.headers.location;
            this.abort();
            return callback(err);
          } else {
            session.get({
              uri: res.headers.location,
              qs: params,
              followRedirect: false
            }, function(err, res) {
              if(err) return callback(err);
              callback(null, res.body);
            });
            return;
          }
        }

        callback(null, res.body);
      }
    );
  }

  function extractResults(body) {
    var results = [];
    var $ = cheerio.load(body);

    $('#search .g').each(function(i, elem) {
      var item = {};

      var elemUrl = $(this).find("h3 a");
      var elemMeta = $(this).find(".slp");
      var elemDesc = $(this).find(".st");
      var parsedUrl = url.parse(elemUrl.attr("href"), true);
      if (parsedUrl.pathname === '/url') {
        item['url'] = parsedUrl.query.q;
      }
      item['title'] = elemUrl.text();
      item['meta'] = elemMeta.text();
      item['desc'] = elemDesc.text();

      results.push(item);
    });    

    return results;
  }

  function solveCaptcha(captchaUrl, callback) {

    var tmp = url.parse(captchaUrl);
    var baseUrl = url.format({
      protocol: tmp.protocol,
      hostname: tmp.host,
    });

    // Fetch captcha page
    session.get(captchaUrl, function(err, res) {
      if(err) return callback(err);

      var $ = cheerio.load(res.body);
      var captchaId = $('input[name=id]').attr('value');
      var continueUrl = $('input[name=continue]').attr('value');
      var formAction = $('form').attr('action');
      var imgSrc = $('img').attr('src');

      // Fetch captcha image
      session.get({uri: baseUrl + imgSrc, encoding: null}, function(err, res) {
        if(err) return callback(err);

        // Send to solver
        solver.solve(res.body, function(err, id, solution) {
          if(err) return callback(err);

          // Try solution
          session.get({
              uri: baseUrl + '/sorry/' + formAction,
              qs: {
                id: captchaId,
                captcha: solution,
                continue: continueUrl
              }
            }, 
            function(err, res) {
              if(res.statusCode !== 200) return callback(new Error('Captcha decoding failed'));
              callback(null, res.body);
            }
          );

        });

      });

    });

  }

}

module.exports.search = search;