use deterministic string colors for other city names

Author: thepiwo

app/components/map.js

@@ -96,11 +96,22 @@ function getCityColor(team) {
         'Köln': '#6b5aac'
     };
 
-    return colorlist[team.event.city] ? colorlist[team.event.city] : randomColor();
+    return colorlist[team.event.city] ? colorlist[team.event.city] : stringColor(team.event.city);
 }
 
-function randomColor() {
-    return '#' + Math.floor(Math.random() * 16777215).toString(16);
+function stringColor(string) {
+    var hash = 0;
+    if (string.length === 0) return hash;
+    for (var i = 0; i < string.length; i++) {
+        hash = string.charCodeAt(i) + ((hash << 5) - hash);
+        hash = hash & hash;
+    }
+    var color = '#';
+    for (var j = 0; j < 3; j++) {
+        var value = (hash >> (j * 8)) & 255;
+        color += ('00' + value.toString(16)).substr(-2);
+    }
+    return color;
 }
 
 function colorGradientByWeight(color1, color2, weight) {