Fix Plaid cash balance double counting

app/models/balance/reverse_calculator.rb

@@ -21,7 +21,13 @@ class Balance::ReverseCalculator < Balance::BaseCalculator
         if valuation.present?
           @balances << build_balance(date, previous_cash_balance, holdings_value)
         else
-          @balances << build_balance(date, current_cash_balance, holdings_value)
+          # If date is today, we don't distinguish cash vs. total since provider's are inconsistent with treatment
+          # of the cash component.  Instead, just set the balance equal to the "total value" reported by the provider
+          if date == Date.current
+            @balances << build_balance(date, account.balance, 0)
+          else
+            @balances << build_balance(date, current_cash_balance, holdings_value)
+          end
         end
 
         current_cash_balance = previous_cash_balance

app/models/plaid_investment_sync.rb

@@ -11,6 +11,7 @@ class PlaidInvestmentSync
     @securities = securities
 
     PlaidAccount.transaction do
+      normalize_cash_balance!
       sync_transactions!
       sync_holdings!
     end
@@ -19,6 +20,23 @@ class PlaidInvestmentSync
   private
     attr_reader :transactions, :holdings, :securities
 
+    # Plaid considers "brokerage cash" and "cash equivalent holdings" to all be part of "cash balance"
+    # Internally, we DO NOT.
+    # Maybe clearly distinguishes between "brokerage cash" vs. "holdings (i.e. invested cash)"
+    # For this reason, we must back out cash + cash equivalent holdings from the reported cash balance to avoid double counting
+    def normalize_cash_balance!
+      non_cash_holdings = holdings.reject do |h|
+        _internal_security, plaid_security = get_security(h.security_id, securities)
+        plaid_security&.type == "cash"
+      end
+
+      non_cash_holdings_value = non_cash_holdings.sum { |h| h.quantity * h.institution_price }
+
+      plaid_account.account.update!(
+        cash_balance: plaid_account.account.cash_balance - non_cash_holdings_value
+      )
+    end
+
     def sync_transactions!
       transactions.each do |transaction|
         security, plaid_security = get_security(transaction.security_id, securities)

test/models/balance/reverse_calculator_test.rb

@@ -120,4 +120,23 @@ class Balance::ReverseCalculatorTest < ActiveSupport::TestCase
 
     assert_equal expected, calculated
   end
+
+  test "uses provider reported holdings and cash value on current day" do
+    aapl = securities(:aapl)
+
+    # Implied holdings value of $1,000 from provider
+    @account.update!(cash_balance: 19000, balance: 20000)
+
+    # Create a holding that differs in value from provider ($2,000 vs. the $1,000 reported by provider)
+    Holding.create!(date: Date.current, account: @account, security: aapl, qty: 10, price: 100, amount: 2000, currency: "USD")
+    Holding.create!(date: 1.day.ago.to_date, account: @account, security: aapl, qty: 10, price: 100, amount: 2000, currency: "USD")
+
+    # Today reports the provider value.  Yesterday, provider won't give us any data, so we MUST look at the generated holdings value
+    # to calculate the end balance ($19,000 cash + $2,000 holdings = $21,000 total value)
+    expected = [ 21000, 20000 ]
+
+    calculated = Balance::ReverseCalculator.new(@account).calculate.sort_by(&:date).map(&:balance)
+
+    assert_equal expected, calculated
+  end
 end