My solution to the challenge

.gitignore

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+node_modules

modules/suggestions_functions.js

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+//Converts TSV file to JSON for easier data manipulation
+function tsvJSON(tsv) {
+  const lines = tsv.split('\n');
+  const headers = lines.slice(0, 1)[0].split('\t');
+  return lines.slice(1, lines.length).map(line => {
+    const data = line.split('\t');
+    return headers.reduce((obj, nextKey, index) => {
+      obj[nextKey] = data[index];
+      return obj;
+    }, {});
+  });
+}
+
+
+function name_comparison(city_name,query,lat,lng){
+  const namearr = city_name.split('')
+  const queryarr = query.split('')
+  const distance = getEditDistance(city_name,query)
+  const score = lat && lng ? ((namearr.length - distance)/namearr.length)/2 : ((namearr.length - distance)/namearr.length)     //if(there are lat and lng params.then cap the score to 0.5(since the other half will be calculated from the distance given from the lat and lng))
+  return score
+
+}
+
+// Algorithm that calculates the difference between 2 strings(Levenshtein distance)
+function getEditDistance(a, b){
+  if(a.length == 0) return b.length;
+  if(b.length == 0) return a.length;
+  let matrix = [];
+  for(let i = 0; i <= b.length; i++){
+    matrix[i] = [i];
+  }
+  for(let j = 0; j <= a.length; j++){
+    matrix[0][j] = j;
+  }
+  for(let i = 1; i <= b.length; i++){
+    for(let j = 1; j <= a.length; j++){
+      if(b.charAt(i-1) == a.charAt(j-1)){
+        matrix[i][j] = matrix[i-1][j-1];
+      } else {
+        matrix[i][j] = Math.min(matrix[i-1][j-1] + 1, // substitution
+                                Math.min(matrix[i][j-1] + 1, // insertion
+                                         matrix[i-1][j] + 1)); // deletion
+      }
+    }
+  }
+  return (matrix[b.length][a.length]); // returns an integer,0 if strings are identical n if they are not nE(0,+infinite)
+};
+
+
+//Parallel sorting of two arrays based in one condition
+
+function swap(arr,i){
+  const temp = arr[i]
+  arr[i] = arr[i+1]
+  arr[i+1] = temp
+}
+
+
+function bubble_Sort(a,b,method)
+{
+    let swapp;
+    let n = a.length-1;
+    let x=a;
+    do {
+        swapp = false;
+        for (let i=0; i < n; i++)
+        {   if(method === 'descending'){
+                  if (x[i] <= x[i+1]){
+                     swap(x,i)
+                     swap(b,i)
+                     swapp = true
+                  }
+        }else{
+            if (x[i] >= x[i+1]){
+              swap(x,i)
+              swap(b,i)
+              swapp = true;
+            }
+          }
+        }
+        n--;
+    } while (swapp);
+ return x;
+}
+
+
+//Algorithm that calculates the avg distance to travel from LAT1-LNG1 to LAT2-LNG2
+//Math-Formula: https://www.movable-type.co.uk/scripts/latlong.html
+function distance(lat1, lon1, lat2, lon2, unit) {
+	if ((lat1 == lat2) && (lon1 == lon2)) {
+		return 0;
+	}
+	else {
+		const radlat1 = Math.PI * lat1/180;
+		const radlat2 = Math.PI * lat2/180;
+		const theta = lon1-lon2;
+		const radtheta = Math.PI * theta/180;
+		let dist = Math.sin(radlat1) * Math.sin(radlat2) + Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
+		if (dist > 1) {
+			dist = 1;
+		}
+		dist = Math.acos(dist);
+		dist = dist * 180/Math.PI;
+		dist = dist * 60 * 1.1515;
+		if (unit=="K") { dist = dist * 1.609344 }
+		if (unit=="N") { dist = dist * 0.8684 }
+		return dist;
+	}
+}
+
+
+module.exports = {
+  tsvJSON,
+  name_comparison,
+  getEditDistance,
+  swap,
+  bubble_Sort,
+  distance
+}

package.json

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+{
+  "name": "backend-coding-challenge",
+  "version": "1.0.0",
+  "description": "(inspired by https://github.com/busbud/coding-challenge-backend-c)",
+  "main": "server.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1",
+    "start": "node server.js",
+    "heroku-postbuild":"npm install"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/NickKarvounakis/backend-coding-challenge.git"
+  },
+  "author": "",
+  "license": "ISC",
+  "bugs": {
+    "url": "https://github.com/NickKarvounakis/backend-coding-challenge/issues"
+  },
+  "homepage": "https://github.com/NickKarvounakis/backend-coding-challenge#readme",
+  "dependencies": {
+    "compression": "^1.7.4",
+    "d3": "^5.9.7",
+    "d3-fetch": "^1.1.2",
+    "express": "^4.17.1",
+    "morgan": "^1.9.1",
+    "node-fetch": "^2.6.0"
+  }
+}

routes/suggestions.js

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+const express = require('express')
+const router = express.Router()
+const fs = require('fs')
+const model = require('../modules/suggestions_functions')
+
+
+
+function cities(json,query,lat,lng){
+  let object = []
+  let scores = []
+  let distances = []
+  let counter = 0
+  json.forEach((city,index) => {
+    if(city.name){
+      if((city.name.toLowerCase()).includes(query.toLowerCase())){
+        const score = model.name_comparison(city.name,query,lat,lng)
+        const dist = model.distance(lat,lng,city.lat,city.long)
+        scores.push(score)
+        object.push({ name:`${city.name}, ${city.admin1}, ${city.tz}`, latitude:city.lat, longitude:city.long, score:scores[counter]})
+        distances.push(dist)
+        counter++
+      }
+      else { //checks the alt-names for every city if there wasn't a match with the name
+          if(city.alt_name){
+            const alt = city.alt_name.split(',')
+             for(let i=0;i<alt.length-1;i++){
+              if((alt[i].toLowerCase()).includes(query.toLowerCase())){
+                const scorex = model.name_comparison(alt[i],query,lat,lng)
+                const distx = model.distance(lat,lng,city.lat,city.long)
+                scores.push(scorex)
+                object.push({ name:`${city.name}, ${city.admin1}, ${city.tz}`, latitude:city.lat, longitude:city.long, score:scores[counter]})
+                distances.push(distx)
+                counter++
+                break;
+            }
+        }}
+      }
+    }
+  })
+  //if(lat and lng query parameters are passed)
+  if(lat && lng){
+    model.bubble_Sort(distances,object)
+    for(let i=distances.length-1; i >=  0; i--){
+      object[distances.length - (i+1)]['score'] += (i+1)/(distances.length * 2)
+      scores[distances.length - (i+1)] += (i+1)/(distances.length * 2)
+    }
+  }
+  else{
+    model.bubble_Sort(scores,object,'descending')
+  }
+  return object
+}
+
+
+
+router.get('/',(req,res,next) => {
+  const query = req.query.q
+  if(!query)
+    res.json({ message: 'You need to enter a valid query' })
+  const lat = req.query.latitude
+  const lng = req.query.longitude
+  const tsv =  fs.readFileSync('./data/cities_canada-usa.tsv',{ encoding: 'utf8' });
+  const json =  model.tsvJSON(tsv)
+  const response =  cities(json,query,lat,lng)
+  res.json({ suggestions:response })
+})
+
+
+
+module.exports = router

server.js

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+const express = require('express')
+const {createServer} = require('http')
+const compression = require('compression')
+const morgan = require('morgan')
+const path = require('path')
+
+const app = express()
+const dev = app.get('env') !== 'production'
+
+if(!dev){
+  app.disable('x-powered-by')
+  app.use(compression())
+  app.use(morgan('common'))
+}else {
+  app.use(morgan('dev'))
+}
+
+app.use(express.json())
+
+app.get('/',(req,res) => {
+  res.send({ message: 'Enter /suggestions?q=<<CITYNAMEHERE>> to get started' })
+})
+
+const SuggestionRouter = require('./routes/suggestions')
+app.use('/suggestions',SuggestionRouter)
+
+app.get('*', function(req, res){
+  res.statusCode = 404
+  res.json({ message: 'Error,route not found',statusCode: res.statusCode });
+});
+
+
+const server = createServer(app)
+const normalizePort = port => parseInt(port, 10)
+const PORT = normalizePort(process.env.PORT || 3000)
+
+server.listen(PORT,(err) => {
+  if(err) throw err
+  console.log('SERVER STARTED')
+})