feat(find): Update find algorithm to use index file

finding timezone now relies on generated index file and associated directory strucuture of geojson

files organized according to recursive quadtree.

lib/find.js

@@ -1,26 +1,121 @@
+var fs = require('fs')
+
 var inside = require('turf-inside'),
   moment = require('moment-timezone'),
   point = require('turf-point')
 
 var tzData = require('../data/index.json')
 
-var getTimezone = function(lat, lng) {
-  var pt = point([lng, lat])
+var getTimezone = function(lat, lon) {
+
+  lat = parseFloat(lat)
+  lon = parseFloat(lon)
+
+  // validate latitude
+  if(isNaN(lat) || lat > 90 || lat < -90) {
+    var err = new Error('Invalid latitude: ' + lat)
+    throw err
+  }
+
+  // validate longitude
+  if(isNaN(lon) || lon > 180 || lon < -180) {
+    var err = new Error('Invalid longitude: ' + lon)
+    throw err
+  }
+
+  // fix edges of the world
+  if(lat === 90) {
+    lat = 89.9999
+  } else if(lat === -90) {
+    lat = -89.9999
+  }
+
+  if(lon === 180) {
+    lon = 179.9999
+  } else if(lon === -180) {
+    lon = -179.9999
+  }
+
+  var pt = point([lon, lat]),
+    quadData = {
+      top: 90,
+      bottom: -90,
+      left: -180,
+      right: 180,
+      midLat: 0,
+      midLon: 0
+    },
+    quadPos = '',
+    curTzData = tzData.lookup
+
+  while(true) {
+
+    // calculate next quadtree position 
+    var nextQuad
+    if(lat >= quadData.midLat && lon >= quadData.midLon) {
+      nextQuad = 'a'
+      quadData.bottom = quadData.midLat
+      quadData.left = quadData.midLon
+    } else if(lat >= quadData.midLat && lon < quadData.midLon) {
+      nextQuad = 'b'
+      quadData.bottom = quadData.midLat
+      quadData.right = quadData.midLon
+    } else if(lat < quadData.midLat && lon < quadData.midLon) {
+      nextQuad = 'c'
+      quadData.top = quadData.midLat
+      quadData.right = quadData.midLon
+    } else {
+      nextQuad = 'd'
+      quadData.top = quadData.midLat
+      quadData.left = quadData.midLon
+    }
+
+    //console.log(nextQuad)
+    curTzData = curTzData[nextQuad]
+    //console.log()
+    quadPos += nextQuad
+
+    // analyze result of current depth
+    if(curTzData === 'f') {
+      console.log('looking up tz from file', quadPos)
+      // exact boundaries saved in file
+      // parse geojson for exact boundaries
+      var filepath = quadPos.split('').join('/'),
+        geoJson = require('../data/' + filepath + '/geo.json')
+
+      for (var i = 0; i < geoJson.features.length; i++) {
+        if(inside(pt, geoJson.features[i])) {
+          return geoJson.features[i].properties.TZID
+        }
+      }
 
-  for (var i = 0; i < tzData.features.length; i++) {
-    if(inside(pt, tzData.features[i])) {
-      return tzData.features[i].properties.TZID
+      // not within subarea, therefore no valid timezone
+      return null
+    } else if(curTzData === -1) {
+      console.log('no timezone at index')
+      // no timezone at this gps location
+      return null
+    } else if(typeof curTzData === 'number') {
+      // exact match found
+      console.log('exact match at index')
+      return tzData.timezones[curTzData[nextQuad]]
+    } else if(typeof curTzData !== 'object') {
+      // not another nested quad index, throw error
+      var err = new Error('Unexpected data type')
+      throw err
     }
+
+    // calculate next quadtree depth data
+    quadData.midLat = (quadData.top + quadData.bottom) / 2
+    quadData.midLon = (quadData.left + quadData.right) / 2
   }
 
-  return null
-
 }
 
 module.exports = {
   timezone: getTimezone,
-  timezoneMoment: function(lat, lng, timeString) {
-    var tzName = getTimezone(lat, lng)
+  timezoneMoment: function(lat, lon, timeString) {
+    var tzName = getTimezone(lat, lon)
     if(!tzName) {
       return tzName
     }