Add indexer service (equivalent of Dereferencer, but named more accurately)

app/assets/javascripts/admin/services/indexer.js.coffee

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+# Convert an array of objects into a hash, indexed by the objects' ids
+#
+# producers = [{id: 1, name: 'one'}, {id: 2, name: 'two'}]
+# Indexer.index producers
+# -> {1: {id: 1, name: 'one'}, 2: {id: 2, name: 'two'}}
+
+angular.module("ofn.admin").factory 'Indexer', ->
+  new class Indexer
+    index: (data) ->
+      index = []
+      for e in data
+        index[e.id] = e
+      index

spec/javascripts/unit/admin/services/indexer_spec.js.coffee

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+describe "indexer", ->
+  Indexer = null
+
+  beforeEach ->
+    module "ofn.admin"
+
+  beforeEach inject (_Indexer_) ->
+    Indexer = _Indexer_
+
+  it "indexes an array of objects by id", ->
+    objects = [{id: 1, name: 'one'}, {id: 2, name: 'two'}]
+    index = Indexer.index objects
+    expect(index).toEqual({1: {id: 1, name: 'one'}, 2: {id: 2, name: 'two'}})