opendata.js

/*
    This module has functions used to interface with the Penn OpenData API.
    It allows for rate-limiting requests and granular error reporting.
    The main function is RateLimitReq.
*/

module.exports = function(rpm) {
    var request = require('request');
    var parse = require('./parse.js');
    var config;
    try {
        config = require('./config.js');
    } catch (err) { // If there is no config file
        config = {};
        config.requestAB = process.env.REQUESTAB;
        config.requestAT = process.env.REQUESTAT;
    }
    var opendata = {};

    if (config.IFTTTKey) {
        var IFTTTMaker = require('iftttmaker')(config.IFTTTKey);
    }
    function SendError(errmsg) { // Send an email to Ben through IFTTT when there is a server error
        if (config.IFTTTKey) {
            IFTTTMaker.send('PCSError', errmsg).then(function () {
            }).catch(function (error) {
              console.log('The error request could not be sent:', error);
            });
        }
    }

    // Send requests to the API and deal with the result
    function SendPennReq(url, resultType, res, ODkeyInd) {
        // Choose the auth bearer and token pair to use based on ODkeyInd
        var AB = config.requestAB[ODkeyInd];
        var AT = config.requestAT[ODkeyInd];
        // Send the request
        request({
            uri: url,
            method: "GET",headers: {"Authorization-Bearer": AB, "Authorization-Token": AT}, // Send authorization headers
            timeout: 19000,
        }, function(error, response, body) {

            if (error || response.statusCode >= 500) {
                // This is triggered if the OpenData API returns an error or never responds
                console.log(JSON.stringify(response));
                console.log('OpenData Request failed:', url, error);
                SendError('OpenData Request failed');
                res.statusCode = 512; // Reserved error code to tell front end that its a Penn InTouch problem, not a PCS problem
                return res.send('PCSERROR: request failed');
            }

            var parsedRes, rawResp = {};
            try { // Try to make body into valid JSON
                rawResp = JSON.parse(body);
                if (rawResp.statusCode) {
                    SendError('Status Code');
                    res.statusCode = 512; // Reserved error code to tell front end that its a Penn InTouch problem, not a PCS problem
                    return res.send('status code error');
                }
            } catch(err) { // Could not parse the JSON for some reason
                console.log('Resp parse error ' + err);
                SendError('Parse Error!!!');
                console.log(JSON.stringify(response));
                return res.send({});
            }

            try {
                if (rawResp.service_meta.error_text) { // If the API returned an error in its response
                    console.log('Resp Err: ' + rawResp.service_meta.error_text);
                    SendError('Error Text');
                    res.statusCode = 513; // Reserved error code to tell front end that its a Penn InTouch problem, not a PCS problem
                    return res.send(rawResp.service_meta.error_text);
                }
                parsedRes = rawResp.result_data;
            } catch(err) {
                console.log(err);
                SendError('Other Error!!!');
                res.statusCode = 500;
                return res.send(err);
            }

            // Route the parsed response to the correct function
            RouteAPIResp(resultType, parsedRes, res);
        });
    }

    function RouteAPIResp(resultType, parsedRes, res) { // Send the raw data to the appropriate formatting function
        var resultTypes = {
            deptSearch: parse.CourseList,
            numbSearch: parse.SectionList,
            sectSearch: parse.SectionInfo,
            schedInfo:  parse.SchedInfo,
            registrar:  parse.RecordRegistrar
        };

        var searchResponse;
        if (resultType in resultTypes) {
            searchResponse = resultTypes[resultType](parsedRes);
        } else {
            searchResponse = {};
        }
        if (res.send) {return res.send(JSON.stringify(searchResponse));} // return correct info
    }

    // Delay a requests the necessary amount of time before sending it to the API
    if (!rpm) {rpm = 95;}

    opendata.RateLimitReq = function(url, resultType, res, lastRT, ODkeyInd) {
        // lastRT is the timestamp of the last sent request using this auth key

        var period = 60000 / rpm;
        var now = new Date().getTime();
        var diff = now - lastRT; // how long ago was the last request point
        var delay = (period - diff) * (diff < period); // How long to delay the request (if diff is > period, no need to delay)
        var lastRequestTime = now+delay; // Update the latest request timestamp (will be a future timestamp if a delay is added)

        setTimeout(function() {
            SendPennReq(url, resultType, res, ODkeyInd) ;// Send the request after the delay
        }, delay);
        return lastRequestTime; // Return the latest request time for recording.
    };

    return opendata;
};