server.js

var express = require('express');
var app = express();

var request = require('request');

var fs = require('fs');
var mkdirp = require('mkdirp').mkdirp;

var buslines;
fs.readFile('data/buslines.json', 'utf8', function (err, data) {
  if (err) throw err;
  buslines = JSON.parse(data);
});

var stops;
fs.readFile('data/stops.json', 'utf8', function (err, data) {
  if (err) throw err;
  stops = JSON.parse(data);
});

app.get('/route', function(req, res) {
	if (buslines == undefined) {
		res.status(500).send('Buslines not loaded.');
	} else if (stops == undefined) {
		res.status(500).send('Stops not loaded.');
	} else {
		var allBuses = {};

		buslines.forEach(function (busRoute, i) {
			getRouteData(busRoute, function (r) {
				if (r.error || r.response.matches[0] == undefined) {
					allBuses[busRoute] = false;
				} else {
					allBuses[busRoute] = r.response;
					var rte_dirs = r.response.matches[0].directions;
					[0, 1].forEach(function (rd, i) {
						if (rte_dirs[i] !== undefined) {
							var rd = rte_dirs[i],
									props = {},
									keys = Object.keys(rd);

							keys.forEach(function (key, i) {
								if (key !== 'shape' && key !== 'polylines')
									props[key] = rd[key];
							});

							var dirObj = { 
								"type": "FeatureCollection",
							  "features": [],
							  "properties": {
							  	"stops": null
							  }
							};

							rte_dirs[i].shape.forEach(function (ea) {
						    var feat = {
						    	"type": "Feature",
						      "geometry": ea,
						      "properties": props,
						    }
						    dirObj.features.push(feat);
							});

							// create updated locations for stops
							var s = getRteStops(busRoute);
							if (s == undefined || s == null) {
								console.log("Failed stops data join for route id: " + busRoute);
							} else {
								dirObj.properties.stops = s;
							  dirObj.features.forEach(function (shape, i) {
							  	dirObj.features[i].properties['stops'] = null;
							    var relStops = getRelevantStops(shape, s[i]);
							   	if (relStops !== undefined && relStops.length > 0) {
							   		var allignedStops = calcStopsAlligned(shape, relStops);
							   		dirObj.features[i].properties['stops'] = allignedStops;
							   	}
							  });
							}

							var rte_path = 'geojsons/' + busRoute;
							mkdirp(rte_path, function (err) {
							  if (err) { 
							  	console.error('Failed to make file path. Error: ' + err);
							  } else {
							  	rte_path = rte_path + '/' + busRoute + '_dir' + i + '.geojson';
							  	var dostr = JSON.stringify(dirObj);
							  	fs.writeFile(rte_path, dostr, function (err) {
							  		if (err) {
							  			console.error('Failed to write file. Error: ' + err);
							  		}
							  	});
							  }
							});
						} else {
							console.log('Route direction ' + rd + ' was undefined for route: ' + busRoute);
						}
					});
				}

				if (i == buslines.length - 1) {
					res.status(200).send(allBuses);
				}
			});
		});
	}
});

app.get('/route/:route', function(req, res) {
	var busRoute = req.params.route;

	if (busRoute == undefined)
		res.status(400).send(Error('No bus route included.'));

	getRouteData(busRoute, function (r) {
		if (r.error) {
			res.status(500).send(r.response);
		} else {
			res.status(200).send(r.response);
		}
	});
})

app.listen('8080')
console.log('Up and running on port 8080...');

exports = module.exports = app;



// utilities
var getRteStops = function (busRoute) {
	var stopnames = Object.keys(stops);
	var f = busRoute.split(/[^A-Za-z0-9]/)[0].toUpperCase();
	if (stopnames.indexOf(f) > -1) {
		return stops[f];
	} else {
		var sel = null;
		stopnames.forEach(function (s) {
			if (s.indexOf(f) > -1 && s.split(/[^A-Za-z0-9]/)[0] == f) { sel = s; }
		});
		return stops[sel];
	}
};


var getRouteData = function (busRoute, cb) {
	var url = 'http://bustime.mta.info/api/search?q=' + busRoute;

	request(url, function(error, response, data){
		if(error){
			cb({error: true, response: response});
		} else {
			var data = JSON.parse(data).searchResults;

			if (data.empty) {
				cb({error: true, response: response});
			} else {
				var route = data.matches[0];

				if (route !== undefined) {
					if (route.directions[0] !== undefined) {
						route.directions[0].shape = [];
						route.directions[0].polylines.forEach(function (pl, i) {
							route.directions[0].shape.push(decodePolyline(pl));
						});
					}

					if (route.directions[1] !== undefined) {
						route.directions[1].shape = [];
						route.directions[1].polylines.forEach(function (pl, i) {
							route.directions[1].shape.push(decodePolyline(pl));
						});
					}

				}

				cb({error: false, response: data});
			}
		}
	});
};


var decodePolyline = function(encoded) {
  var len = encoded.length,
  		index = 0,
  		array = [],
  		lat = 0,
  		lng = 0;

  while (index < len) {
    var b,
    		shift = 0,
    		result = 0;
    
    do {
      b = encoded.charCodeAt(index++) - 63;
      result |= (b & 0x1f) << shift;
      shift += 5;
    } while (b >= 0x20);

    var dlat = ((result & 1) ? ~(result >> 1) : (result >> 1));
    lat += dlat;

    shift = 0;
    result = 0;

    do {
      b = encoded.charCodeAt(index++) - 63;
      result |= (b & 0x1f) << shift;
      shift += 5;
    } while (b >= 0x20);

    var dlng = ((result & 1) ? ~(result >> 1) : (result >> 1));
    lng += dlng;

    array.push([lng * 1e-5, lat * 1e-5]);
  }

  return { "type": "LineString", "coordinates": array };
};


function getRelevantStops (shape, stops) {
	if (stops == undefined) {
		return undefined;
	}
  var pts = shape.geometry.coordinates;
  var rel = [];
  pts.forEach(function (aft, i) {
    var best = { s: null, d: null };
    Object.keys(stops).forEach(function (stop) {
      var s = stops[stop],
          l = s.location;
      if (s !== undefined && s.location !== undefined) {
	      var d = calcDist(l[0], l[1], aft[1], aft[0]);

	      if ((i > 0 && d < 100) && (best.d == null || d < best.d)) {
	        // compare distances with point in the middle versus with the point after the two points
	        var bef = pts[i - 1],
	            distNo = calcDist(bef[0], bef[1], aft[1], aft[0]) + calcDist(aft[0], aft[1], l[1], l[0]),
	            distYes = calcDist(bef[0], bef[1], l[1], l[0]) + calcDist(l[0], l[1], aft[1], aft[0]);

	        if (distYes < distNo) {
	          best.s = s;
	          best.d = d;
	        }
	      }
      }
    });
    if (best.s !== null) {
      rel.push(best.s);
    }
  });
  return rel;
};

function calcStopsAlligned (shape, stops) {
  var pts = shape.geometry.coordinates,
      adjStops = [];

  stops.forEach(function (s) {
    var best = {d: null, dp: null, ll: null},
        l = s.location; 
    pts.forEach(function (aft, i) {
      var d = calcDist(l[0], l[1], aft[1], aft[0]);
      if ((i > 0 && d < 100) && (best.d == null || d < best.d)) {
        var bef = pts[i - 1],

            A = calcDist(l[0], l[1], aft[1], aft[0]),
            B = calcDist(bef[1], bef[0], l[0], l[1]),
            F = calcDist(bef[1], bef[0], aft[1], aft[0]),

            z = Math.acos((F * F + B * B - A *A)/(2 * B * F)),
            C = B * Math.cos(z),

            verB = F * Math.sin(z),
            horB = F * Math.cos(z),
            verS = C * Math.sin(z),
            horS = C * Math.cos(z),

            lat = bef[1] - ((bef[1] - aft[1]) * (verS / verB)),
            lng = (aft[0] - bef[0]) * (horS / horB) + bef[0];

        best.d = d;
        best.dp = calcDist(bef[1], bef[0], l[0], l[1]);
        best.ll = [lat, lng];
      }
    });
    adjStops.push({adjusted: best.ll, original: s});
  });
  return adjStops;
};

function calcDist (lat1, lng1, lat2, lng2) {
  var R = 6371000,
      rad = (Math.PI / 180),
      x = (lng2 - lng1) * rad,
      y = (lat2 - lat1) * rad;
  return R * Math.sqrt((x * x) + (y * y));
};