Plaid portfolio sync algorithm and calculation improvements (#1526)

* Start tests rework

* Cash balance on schema

* Add reverse syncer

* Reverse balance sync with holdings

* Reverse holdings sync

* Reverse holdings sync should work with only trade entries

* Consolidate brokerage cash

* Add forward sync option

* Update new balance info after syncs

* Intraday balance calculator and sync fixes

* Show only balance for trade entries

* Tests passing

* Update Gemfile.lock

* Cleanup, performance improvements

* Remove account reloads for reliable sync outputs

* Simplify valuation view logic

* Special handling for Plaid cash holding

app/models/account/balance_calculator.rb

@@ -0,0 +1,121 @@
+class Account::BalanceCalculator
+  def initialize(account, holdings: nil)
+    @account = account
+    @holdings = holdings || []
+  end
+
+  def calculate(reverse: false, start_date: nil)
+    cash_balances = reverse ? reverse_cash_balances : forward_cash_balances
+
+    cash_balances.map do |balance|
+      holdings_value = converted_holdings.select { |h| h.date == balance.date }.sum(&:amount)
+      balance.balance = balance.balance + holdings_value
+      balance
+    end
+  end
+
+  private
+    attr_reader :account, :holdings
+
+    def oldest_date
+      converted_entries.first ? converted_entries.first.date - 1.day : Date.current
+    end
+
+    def reverse_cash_balances
+      prior_balance = account.cash_balance
+
+      Date.current.downto(oldest_date).map do |date|
+        entries_for_date = converted_entries.select { |e| e.date == date }
+        holdings_for_date = converted_holdings.select { |h| h.date == date }
+
+        valuation = entries_for_date.find { |e| e.account_valuation? }
+
+        current_balance = if valuation
+          # To get this to a cash valuation, we back out holdings value on day
+          valuation.amount - holdings_for_date.sum(&:amount)
+        else
+          transactions = entries_for_date.select { |e| e.account_transaction? || e.account_trade? }
+
+          calculate_balance(prior_balance, transactions)
+        end
+
+        balance_record = Account::Balance.new(
+          account: account,
+          date: date,
+          balance: valuation ? current_balance : prior_balance,
+          cash_balance: valuation ? current_balance : prior_balance,
+          currency: account.currency
+        )
+
+        prior_balance = current_balance
+
+        balance_record
+      end
+    end
+
+    def forward_cash_balances
+      prior_balance = 0
+      current_balance = nil
+
+      oldest_date.upto(Date.current).map do |date|
+        entries_for_date = converted_entries.select { |e| e.date == date }
+        holdings_for_date = converted_holdings.select { |h| h.date == date }
+
+        valuation = entries_for_date.find { |e| e.account_valuation? }
+
+        current_balance = if valuation
+          # To get this to a cash valuation, we back out holdings value on day
+          valuation.amount - holdings_for_date.sum(&:amount)
+        else
+          transactions = entries_for_date.select { |e| e.account_transaction? || e.account_trade? }
+
+          calculate_balance(prior_balance, transactions, inverse: true)
+        end
+
+        balance_record = Account::Balance.new(
+          account: account,
+          date: date,
+          balance: current_balance,
+          cash_balance: current_balance,
+          currency: account.currency
+        )
+
+        prior_balance = current_balance
+
+        balance_record
+      end
+    end
+
+    def converted_entries
+      @converted_entries ||= @account.entries.order(:date).to_a.map do |e|
+        converted_entry = e.dup
+        converted_entry.amount = converted_entry.amount_money.exchange_to(
+          account.currency,
+          date: e.date,
+          fallback_rate: 1
+        ).amount
+        converted_entry.currency = account.currency
+        converted_entry
+      end
+    end
+
+    def converted_holdings
+      @converted_holdings ||= holdings.map do |h|
+        converted_holding = h.dup
+        converted_holding.amount = converted_holding.amount_money.exchange_to(
+          account.currency,
+          date: h.date,
+          fallback_rate: 1
+        ).amount
+        converted_holding.currency = account.currency
+        converted_holding
+      end
+    end
+
+    def calculate_balance(prior_balance, transactions, inverse: false)
+      flows = transactions.sum(&:amount)
+      negated = inverse ? account.asset? : account.liability?
+      flows *= -1 if negated
+      prior_balance + flows
+    end
+end