Programming Excercise

web1&2(challenge).js

/*
Exercise:

Write a web based math engine. It should take the form of a running web service 
that takes in a single parameter GET or POST* called “values”, which is a 
JSON-formatted list of numbers. The response should be a JSON dictionary with 
two values, the “sum” and the “product”.

Example input: “values” = [1, 4, 7, -2] (will be either a url param for a GET 
or a post param for POST)

Example output: {“sum”: 10, “product”: -56}

* POST is optional

(Extra Challenge:)

Write an additional endpoint to query the history with a second parameter asking 
how far back you want to go.

Should return a list of JSON objects formatted like the following:

                [{"ip": "127.0.0.1", "timestamp": 2011-06-09T17:46:21, "values": [1, 4, 7, -2], "sum": 10, "product": -56},
                {"ip": "127.0.0.1", "timestamp": 2011-06-09T17:25:23, "values": [1, 4, 7, -2], "sum": 10, "product": -56},
                {"ip": ...}, 
                {"ip": ...}, ...]
*/

/*
* Instructions on the second exercise were a bit
* fuzzy, but from what I understood:
*
* '/history' endpoint recieves a JSON which
* contains a javascript Date object (instructions
* weren't clear as to what type of parameter was
* sent), wich is used to filter history up to, and
* including, that point.
*/

var express = require('express');
var bodyParser = require('body-parser');
var app = express();
var history = new Array();

app.use(bodyParser());

app.get('/mathengine', function(request, response){
  response.send(200, sumProductJSON(request));
});

app.post('/mathengine', function(request, response){
  response.send(200, sumProductJSON(request));
});

app.get('/history', function(request, response){
  response.send(200, filterHistory(request));
});

app.post('/history', function(request, response){
  response.send(200, filterHistory(request));
});

app.listen(80, function(){
  console.log("Started on port 80...");
});

function sumProductJSON(request){
  var values = request.query.values;
  if(!values){
    values = request.body.values;
  }
  var sum=0;
  var product=1;
  for(var i=0; i<values.length;i++){
    sum+=parseInt(values[i]);
    product*=values[i];
  }
  addToHistory(values, sum, product, request.connection.remoteAddress);
  return ({ "sum":sum, "product":product});
}

function addToHistory(values, sum, product, address){
  var record = {
    "ip":address,
    "timestamp": new Date().toISOString(),
    "values":values,
    "sum" : sum,
    "product" : product
  };
  history.push(record);
  /*
  * For the sake of simplicity and proof-of-concept, I used an
  * array. In practice, something like Redis can be used, and
  * just stringify the JSON object before storing it:
  *
  * var redis = require('redis').createClient();
  * redis.lpush('history', JSON.stringify(record));
  */
}

function filterHistory(request){
  history.reverse();
  var date = request.query.date;
  if(!date){
    date = request.body.date;
  }
  var sorted = new Array();
  for(var i=0;i<history.length;i++){
    var bench = new Date(date);
    var current = new Date(history[i].timestamp);
    if(bench > current){
      break;
    }
    sorted.push(history[i]);
  }
  return sorted;
}