Add basic limiting & ordering to payments API

app/controllers/api/v0/payments_controller.rb

@@ -1,6 +1,42 @@
 class Api::V0::PaymentsController < Api::V0::BaseController
+  ALLOWED_ORDER_BY_ATTRIBUTES = ['created_at', 'updated_at', 'ct_payment_id', 'status']
+
   def index
     campaign = Campaign.find_by_id!(params[:campaign_id])
-    render json: campaign.payments
+    resource = ApiResource.new(campaign.payments, params)
+    resource.apply_filters!    
+
+    render json: resource.relation
   end
-end
+
+  private
+
+  class ApiResource < Struct.new(:relation, :params)
+    def apply_filters!
+      self.relation = apply_limit!(relation) if apply_limit?
+      self.relation = apply_order!(relation) if apply_order?
+    end
+
+    def apply_limit!(relation)
+      relation.limit(params[:limit])
+    end
+
+    def apply_order!(relation)
+      relation.order("#{params[:order_by]} #{order_direction}")
+    end
+
+    def apply_order?
+      String(params[:order_by]).in?(ALLOWED_ORDER_BY_ATTRIBUTES)
+    end
+
+    def apply_limit?
+      params[:limit].present?
+    end
+
+    private
+
+    def order_direction
+      params[:order_direction] == 'asc' ? 'asc' : 'desc'
+    end
+  end
+end

spec/controllers/api/v0/payments_controller_spec.rb

@@ -8,19 +8,93 @@
 
     let(:campaign) { create(:campaign) }
     let!(:first_payment) { create(:payment, campaign: campaign) }
-    let!(:second_payment) { create(:payment, campaign: campaign) }
 
-    subject { get :index, campaign_id: campaign.id, api_key: api_key }
+    def api_params(params={})
+      {campaign_id: campaign.id, api_key: api_key}.merge(params)
+    end
+
+    subject { get :index, api_params }
+
+    before do
+      PaymentSerializer.should_receive(:new).with(first_payment, anything)
+      .and_return(double("serializer", serializable_hash: {payment: 1}))
+    end
+
+    context 'for multiple records' do
+      let!(:second_payment) { create(:payment, campaign: campaign) }
+      before do
+
+        PaymentSerializer.should_receive(:new).with(second_payment, anything)
+        .and_return(double("serializer", serializable_hash: {payment: 2}))
+
+      end
+      it 'lists ALL of the payments for the campaign' do
+
+        subject
+
+        json = JSON.parse(response.body)
+        json.should == [{'payment' => 1}, {'payment' => 2}]
+      end
+      context 'ordering' do
+        let(:order) { '' }
+        let(:order_by) { 'created_at' }
+
+        subject { get :index, api_params(order_direction: order, order_by: order_by) }
+
+        it 'defaults to descending' do
+          subject
+
+          json = JSON.parse(response.body)
+          json.should == [{'payment' => 2}, {'payment' => 1}]
+        end
+
+        context 'ascending' do
+          let(:order) { 'asc' }
+
+          it 'respects the sort order' do
+            subject
+
+            json = JSON.parse(response.body)
+            json.should == [{'payment' => 1}, {'payment' => 2}]
+          end
+        end
+
+        context 'descending' do
+          let(:order) { 'desc' }
+
+          it 'respects the sort order' do
+            subject
+
+            json = JSON.parse(response.body)
+            json.should == [{'payment' => 2}, {'payment' => 1}]
+          end
+        end
+
+        context 'when ordering by a fake column' do
+          let(:order_by) { 'foobar' }
+
+          it 'returns the default order' do
+            subject
+
+
+            json = JSON.parse(response.body)
+            json.should == [{'payment' => 1}, {'payment' => 2}]
+          end
+        end
+      end
+    end
+
+    context 'limiting' do
+      let(:limit) { 1 }
 
-    it 'lists ALL of the payments for the campaign' do
-      serializer_double = double("serializer", serializable_hash: {payment: true})
-      PaymentSerializer.should_receive(:new).with(first_payment, anything).and_return(serializer_double)
-      PaymentSerializer.should_receive(:new).with(second_payment, anything).and_return(serializer_double)
+      subject { get :index, api_params(limit: limit) }
 
-      subject
+      it 'limits the objects returned' do
+        subject
 
-      json = JSON.parse(response.body)
-      json.should == [{'payment' => true}, {'payment' => true}]
+        JSON.parse(response.body).size.should == 1
+      end
     end
   end
 end
+