grader.js

#!/usr/bin/env node

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

var HTMLFILE_DEFAULT = "index.html";
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);
    }
    return instr;
};

var cheerioHtml = function(htmlbuf) {
    return cheerio.load(htmlbuf);
};

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

var checkHtmlFile = function(htmlfile, checksfile) {
    return checkHtml(fs.readFileSync(htmlfile), checksfile);
}

var checkHtml = function(htmlbuf, checksfile) {
    $ = cheerioHtml(htmlbuf);
    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 checkUrl = function(url, checksfile) {
    rest.get(url).on('complete', function(result) {
        if (result instanceof Error) {
            console.log('Error: ' + result.message);
            process.exit(1);
        } else {
            var checkJson = checkHtml(result, checksfile);
            var outJson = JSON.stringify(checkJson, null, 4);
            console.log(outJson);
        }
    });
};

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), HTMLFILE_DEFAULT)
        .option('-u, --url <url>', 'Url to fetch and check')
        .parse(process.argv);
    if (program.url) {
        checkUrl(program.url, program.checks);
    } else {
        var checkJson = checkHtmlFile(program.file, program.checks);
        var outJson = JSON.stringify(checkJson, null, 4);
        console.log(outJson);
    }
} else {
    exports.checkHtmlFile = checkHtmlFile;
}