Add filter logic for overview page

common/model.js

@@ -0,0 +1,43 @@
+
+export const groupByQuadrants = (items) => (
+  items.reduce((quadrants, item) => ({
+    ...quadrants,
+    [item.quadrant]: addItemToQuadrant(quadrants[item.quadrant], item),
+  }), {})
+);
+
+export const groupByRing = (items) => (
+  items.reduce((rings, item) => ({
+    ...rings,
+    [item.ring]: addItemToList(rings[item.ring], item),
+  }), {})
+);
+
+export const groupByFirstLetter = (items) => {
+  const index = items.reduce((letterIndex, item) => ({
+    ...letterIndex,
+    [getFirstLetter(item)]: addItemToList(letterIndex[getFirstLetter(item)], item),
+  }), {});
+
+  return Object.keys(index).sort().map((letter) => ({
+    letter,
+    items: index[letter],
+  }));
+}
+
+const addItemToQuadrant = (quadrant = {}, item) => ({
+  ...quadrant,
+  [item.ring]: addItemToRing(quadrant[item.ring], item),
+});
+
+const addItemToList = (list = [], item) => ([
+  ...list,
+  item,
+]);
+
+const addItemToRing = (ring = [], item) => ([
+  ...ring,
+  item,
+]);
+
+export const getFirstLetter = (item) => item.title.substr(0,1).toUpperCase();