node_in_action_3_4_2

random_story.js

var fs = require('fs')
, request = require('request')
, htmlparser = require('htmlparser');

var tasks = [
	function  () {
		var configFileName = './rss_feeds.txt';
		fs.exists(configFileName, function  (exists) {
			if (!exists) {
				next('Create a list of RSS feeds in the file ./rss_feeds.txt');
			} else {
				next(false, configFileName);
			}
		});
	},
	function  (configFileName) {
		fs.readFile(configFileName, function  (err, feedList) {
			if (err) {
				next(err.message);
			} else {
				feedList = feedList.toString().replace(/^\s+|\s+$/g, '').split("\n");
				var random = Math.floor(Math.random() * feedList.length);
				next(false, feedList[random])
			}
		});
	},
	function  (feedUrl) {
		request({uri: feedUrl}, function  (err, response, body) {
			if (err) {
				next(err.message);
			} else if(response.statusCode == 200) {
				next(false, body);
			} else {
				next('Abnormal request status code.');
			}
		});
	},
	function  (rss) {
		var handler = new htmlparser.RssHandler();
		var parser = new htmlparser.Parser(handler);
		parser.parseComplete(rss);
		if (handler.dom.items.length) {
			var item = handler.dom.items.shift();
			console.log(item.title);
			console.log(item.link);
		} else {
			next('No RSS items found.');
		}
	}
];

function next(err, result) {
	if (err) throw new Error(err);

	var currentTask = tasks.shift();
	if (currentTask) {
		currentTask(result);
	}
}

next();