Merge pull request #146 from cobudget/refactor/simplify-group-balance

Move Group balance calculation to Group model

app/models/group.rb

@@ -51,8 +51,16 @@ def add_member(user)
     memberships.create!(member: user, is_admin: false)
   end
 
+  def total_allocations
+    allocations.sum(:amount)
+  end
+
+  def total_contributions
+    Contribution.where(bucket_id: buckets.map(&:id)).sum(:amount)
+  end
+
   def balance
-    memberships.map { |m| m.balance }.reduce(:+) || 0
+    (total_allocations - total_contributions).floor || 0
   end
 
   def formatted_balance

spec/models/group_spec.rb

@@ -1,10 +1,10 @@
 require 'rails_helper'
 
 RSpec.describe Group, :type => :model do
-	describe "#add_admin(user)" do
+  describe "#add_admin(user)" do
     context "user already member of group" do
       it "makes the user an admin of group" do
-        make_user_group_member 
+        make_user_group_member
         group.add_admin(user)
         expect(group.memberships.find_by(member: user, is_admin: true)).to be_truthy
       end
@@ -16,16 +16,53 @@
         user = create(:user)
         group.add_admin(user)
         expect(group.memberships.find_by(member: user, is_admin: true)).to be_truthy
-  		end
+      end
     end
-	end
+  end
 
-  describe "#balance" do
-    context "if no allocations or contributions" do
-      it "returns 0" do
-        group = create(:group)
-        expect(group.balance).to eq(0)
+  describe "group balance calculations" do
+    subject(:group)  { create(:group) }
+    let(:bucket) { create(:bucket, group: group) }
+
+    describe "#total_allocations" do
+      it "calculates all allocations" do
+        create(:allocation, group: group, amount: 100)
+        create(:allocation, group: group, amount: 100.5)
+        expect(subject.total_allocations).to eq 200.5
+      end
+    end
+
+    describe "#total_contributions" do
+      it "calculates all contributions" do
+        create(:contribution, bucket: bucket, amount: 100)
+        create(:contribution, bucket: bucket, amount: 100)
+        expect(subject.total_contributions).to eq 200
+      end
+    end
+
+    describe "#balance" do
+      context "if no allocations or contributions" do
+        it "returns 0" do
+          expect(subject.balance).to eq(0)
+        end
+      end
+
+      context "with allocations and contributions" do
+        it "calculates the group balance" do
+          create(:allocation, group: group, amount: 500)
+          create(:allocation, group: group, amount: 100)
+          create(:contribution, bucket: bucket, amount: 100)
+          create(:contribution, bucket: bucket, amount: 100)
+          # contribution factory creates an allocation equalling
+          # the contribution amount
+          expect(subject.reload.balance).to eq 600
+        end
+
+        it "rounds the balance down" do
+          create(:allocation, group: group, amount: 500.50)
+          expect(subject.reload.balance).to eq 500
+        end
       end
     end
   end
-end
+end