grade.js

#!/usr/bin/env node
/*
Automatically grade files for the presence of specified HTML tags/attributes.
Uses commander.js and cheerio. Teaches command line application development
and basic DOM parsing.

References:

 + cheerio
   - https://github.com/MatthewMueller/cheerio
   - http://encosia.com/cheerio-faster-windows-friendly-alternative-jsdom/
   - http://maxogden.com/scraping-with-node.html

 + commander.js
   - https://github.com/visionmedia/commander.js
   - http://tjholowaychuk.com/post/9103188408/commander-js-nodejs-command-line-interfaces-made-easy

 + JSON
   - http://en.wikipedia.org/wiki/JSON
   - https://developer.mozilla.org/en-US/docs/JSON
   - https://developer.mozilla.org/en-US/docs/JSON#JSON_in_Firefox_2
*/

var fs = require('fs');
var program = require('commander');
var cheerio = require('cheerio');
var sys = require('util');
var rest = require('restler');


var CHECKSFILE_DEFAULT = "checks.json";

var assertFileExists = function(infile) {
    var instr = infile.toString();
    if(!fs.existsSync(instr)) {
        console.log("%s does not exist. Exiting.", instr);
        process.exit(1); // http://nodejs.org/api/process.html#process_process_exit_code
    }
    return instr;
};

var assertURLExists = function(url) {
     var urlStr = url.toString();
     rest.get(urlStr).on('complete', function(data, response) {
	if(response.statusCode == 200) {
		checkJson = checkHtml(data, program.checks);
    		var outJson = JSON.stringify(checkJson, null, 4);
    		console.log(outJson);
	}
	else {
		console.log("%s doesn't exist.", urlStr);
		process.exit(1); 
	}
       });

};

   

var cheerioHtmlFile = function(htmlfile) {
    return cheerio.load(fs.readFileSync(htmlfile));
};

var loadChecks = function(checksfile) {
    return JSON.parse(fs.readFileSync(checksfile));
};

var checkHtmlFile = function(htmlfile, checksfile) {
    $ = cheerioHtmlFile(htmlfile);
    var checks = loadChecks(checksfile).sort();
    var out = {};
    for(var ii in checks) {
        var present = $(checks[ii]).length > 0;
        out[checks[ii]] = present;
    }
    return out;
};

var checkHtml = function(html, checksfile) {
    $ = cheerio.load(html);
    var checks = loadChecks(checksfile).sort();
    var out = {};
    for(var ii in checks) {
        var present = $(checks[ii]).length > 0;
        out[checks[ii]] = present;
    }
    return out;
  
}

var clone = function(fn) {
    // Workaround for commander.js issue.
    // http://stackoverflow.com/a/6772648
    return fn.bind({});
};

if(require.main == module) {
    program
        .option('-c, --checks <check_file>', 'Path to checks.json', clone(assertFileExists), CHECKSFILE_DEFAULT)
        .option('-f, --file <html_file>', 'Path to index.html', clone(assertFileExists))
	.option('-u, --url <url_path>', 'Path to remote html file')
        .parse(process.argv);
    var checkJson;
    if(program.file) {
	checkJson = checkHtmlFile(program.file, program.checks);
    	var outJson = JSON.stringify(checkJson, null, 4);
    	console.log(outJson);
    }
    else if(program.url) {
	assertURLExists(program.url);
    }
    else {
	console.log("You must supply either --file <html_file> or --url <url_path> to command line inputs");
	process.exit(1);	
    }
} else {
    exports.checkHtmlFile = checkHtmlFile;
    exports.checkHtml = checkHtml;
}