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

app/models/holding/reverse_calculator.rb

@@ -0,0 +1,38 @@
+class Holding::ReverseCalculator < Holding::BaseCalculator
+  private
+    # Reverse calculators will use the existing holdings as a source of security ids and prices
+    # since it is common for a provider to supply "current day" holdings but not all the historical
+    # trades that make up those holdings.
+    def portfolio_cache
+      @portfolio_cache ||= Holding::PortfolioCache.new(account, use_holdings: true)
+    end
+
+    def calculate_holdings
+      current_portfolio = generate_starting_portfolio
+      previous_portfolio = {}
+
+      holdings = []
+
+      Date.current.downto(account.start_date).each do |date|
+        today_trades = portfolio_cache.get_trades(date: date)
+        previous_portfolio = transform_portfolio(current_portfolio, today_trades, direction: :reverse)
+        holdings += build_holdings(current_portfolio, date)
+        current_portfolio = previous_portfolio
+      end
+
+      holdings
+    end
+
+    # Since this is a reverse sync, we start with today's holdings
+    def generate_starting_portfolio
+      holding_quantities = empty_portfolio
+
+      todays_holdings = account.holdings.where(date: Date.current)
+
+      todays_holdings.each do |holding|
+        holding_quantities[holding.security_id] = holding.qty
+      end
+
+      holding_quantities
+    end
+end