Account:: namespace simplifications and cleanup (#2110)

* Flatten Holding model

* Flatten balance model

* Entries domain renames

* Fix valuations reference

* Fix trades stream

* Fix brakeman warnings

* Fix tests

* Replace existing entryable type references in DB

test/models/balance/forward_calculator_test.rb

@@ -0,0 +1,74 @@
+require "test_helper"
+
+class Balance::ForwardCalculatorTest < ActiveSupport::TestCase
+  include EntriesTestHelper
+
+  setup do
+    @account = families(:empty).accounts.create!(
+      name: "Test",
+      balance: 20000,
+      cash_balance: 20000,
+      currency: "USD",
+      accountable: Investment.new
+    )
+  end
+
+  # When syncing forwards, we don't care about the account balance.  We generate everything based on entries, starting from 0.
+  test "no entries sync" do
+    assert_equal 0, @account.balances.count
+
+    expected = [ 0, 0 ]
+    calculated = Balance::ForwardCalculator.new(@account).calculate
+
+    assert_equal expected, calculated.map(&:balance)
+  end
+
+  test "valuations sync" do
+    create_valuation(account: @account, date: 4.days.ago.to_date, amount: 17000)
+    create_valuation(account: @account, date: 2.days.ago.to_date, amount: 19000)
+
+    expected = [ 0, 17000, 17000, 19000, 19000, 19000 ]
+    calculated = Balance::ForwardCalculator.new(@account).calculate.sort_by(&:date).map(&:balance)
+
+    assert_equal expected, calculated
+  end
+
+  test "transactions sync" do
+    create_transaction(account: @account, date: 4.days.ago.to_date, amount: -500) # income
+    create_transaction(account: @account, date: 2.days.ago.to_date, amount: 100) # expense
+
+    expected = [ 0, 500, 500, 400, 400, 400 ]
+    calculated = Balance::ForwardCalculator.new(@account).calculate.sort_by(&:date).map(&:balance)
+
+    assert_equal expected, calculated
+  end
+
+  test "multi-entry sync" do
+    create_transaction(account: @account, date: 8.days.ago.to_date, amount: -5000)
+    create_valuation(account: @account, date: 6.days.ago.to_date, amount: 17000)
+    create_transaction(account: @account, date: 6.days.ago.to_date, amount: -500)
+    create_transaction(account: @account, date: 4.days.ago.to_date, amount: -500)
+    create_valuation(account: @account, date: 3.days.ago.to_date, amount: 17000)
+    create_transaction(account: @account, date: 1.day.ago.to_date, amount: 100)
+
+    expected = [ 0, 5000, 5000, 17000, 17000, 17500, 17000, 17000, 16900, 16900 ]
+    calculated = Balance::ForwardCalculator.new(@account).calculate.sort_by(&:date).map(&:balance)
+
+    assert_equal expected, calculated
+  end
+
+  test "multi-currency sync" do
+    ExchangeRate.create! date: 1.day.ago.to_date, from_currency: "EUR", to_currency: "USD", rate: 1.2
+
+    create_transaction(account: @account, date: 3.days.ago.to_date, amount: -100, currency: "USD")
+    create_transaction(account: @account, date: 2.days.ago.to_date, amount: -300, currency: "USD")
+
+    # Transaction in different currency than the account's main currency
+    create_transaction(account: @account, date: 1.day.ago.to_date, amount: -500, currency: "EUR") # €500 * 1.2 = $600
+
+    expected = [ 0, 100, 400, 1000, 1000 ]
+    calculated = Balance::ForwardCalculator.new(@account).calculate.sort_by(&:date).map(&:balance)
+
+    assert_equal expected, calculated
+  end
+end