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crawler.js
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crawler.js
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'use strict';
var mongo = require('mongodb'),
jsdom = require('jsdom'),
async = require('async'),
Twitter = require('easy-tweet');
var getMongoCollection = function (url, collectionName) {
return function (callback) {
mongo.MongoClient.connect(url, { native_parser:true }, function(err, db) {
db.collection(collectionName, callback);
});
};
};
var loadWindow = function (url) {
return function (callback) {
jsdom.env({
url: url,
done: function (err, window) {
if (err) callback(err);
else {
jsdom.jQueryify(window, 'http://code.jquery.com/jquery-2.1.1.js', function () {
callback(null, window);
});
}
}
});
};
};
var queryPages = function (pages) {
return function (callback) {
async.mapSeries(pages, function (page, done) {
loadWindow(page.url).then(function (window) {
page.query(window, function (items) {
window.close();
done(null, items)
});
})
}, callback);
};
};
var saveAndTweet = function (collection, twitterClient, item) {
return function (callback) {
collection.insert(item, function(err, result){
twitterClient.tweet(item.content);
callback(err);
});
};
};
var processQueryResults = function (err, results) {
var processResult = function (item, done) {
var id = item.identifier;
collection.findOne({ identifier: id }, function (err, doc) {
if(!doc) {
saveAndTweet(collection, twitterClient, item).then(done);
} else {
done();
}
});
};
// iterate over query results from a page
var pageResultIterator = function (pageItems, done){
async.each(pageItems, processResult, done);
};
var closeDB = function (err) {
collection.db.close();
callback(err);
}
// iterate over query results
async.each(results, pageResultIterator, closeDB);
};
// options = {
// mongoDB: {
// url: string,
// collection: string
// },
// twitter: {
// api_key: string,
// api_secret: string,
// access_token: string,
// access_token_secret: string
// },
// pages: [
// {
// url: string,
// query: function(window, callback)
// }
// ]
// }
var Crawler = function (options) {
var _twitterClient = new Twitter(
options.twitter.api_key,
options.twitter.api_secret,
options.twitter.access_token,
options.twitter.access_token_secret
);
Object.defineProperties(this, {
options: {
value: options
},
twitterClient: {
value: _twitterClient
}
});
};
Crawler.prototype.run = function() {
var options = this.options;
var twitterClient = this.twitterClient;
var getQueryResults = queryPages(options.pages);
var getCollection = getMongoCollection(options.mongoDB.url, options.mongoDB.collection);
var getTwitterClient = function() { return twitterClient; };
async.parallel([ getQueryResults, getCollection, getTwitterClient ], processQueryResults);
};
module.exports = Crawler;