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

test/models/account/balance_calculator_test.rb

@@ -0,0 +1,156 @@
+require "test_helper"
+
+class Account::BalanceCalculatorTest < ActiveSupport::TestCase
+  include Account::EntriesTestHelper
+
+  setup do
+    @account = families(:empty).accounts.create!(
+      name: "Test",
+      balance: 20000,
+      cash_balance: 20000,
+      currency: "USD",
+      accountable: Investment.new
+    )
+  end
+
+  # When syncing backwards, we start with the account balance and generate everything from there.
+  test "reverse no entries sync" do
+    assert_equal 0, @account.balances.count
+
+    expected = [ @account.balance ]
+    calculated = Account::BalanceCalculator.new(@account).calculate(reverse: true)
+
+    assert_equal expected, calculated.map(&:balance)
+  end
+
+  # When syncing forwards, we don't care about the account balance.  We generate everything based on entries, starting from 0.
+  test "forward no entries sync" do
+    assert_equal 0, @account.balances.count
+
+    expected = [ 0 ]
+    calculated = Account::BalanceCalculator.new(@account).calculate
+
+    assert_equal expected, calculated.map(&:balance)
+  end
+
+  test "forward 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 = Account::BalanceCalculator.new(@account).calculate.sort_by(&:date).map(&:balance)
+
+    assert_equal expected, calculated
+  end
+
+  test "reverse 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 = [ 17000, 17000, 19000, 19000, 20000, 20000 ]
+    calculated = Account::BalanceCalculator.new(@account).calculate(reverse: true).sort_by(&:date).map(&:balance)
+
+    assert_equal expected, calculated
+  end
+
+  test "forward 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 = Account::BalanceCalculator.new(@account).calculate.sort_by(&:date).map(&:balance)
+
+    assert_equal expected, calculated
+  end
+
+  test "reverse 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 = [ 19600, 20100, 20100, 20000, 20000, 20000 ]
+    calculated = Account::BalanceCalculator.new(@account).calculate(reverse: true).sort_by(&:date).map(&:balance)
+
+    assert_equal expected, calculated
+  end
+
+  test "reverse 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 = [ 12000, 17000, 17000, 17000, 16500, 17000, 17000, 20100, 20000, 20000 ]
+    calculated = Account::BalanceCalculator.new(@account).calculate(reverse: true) .sort_by(&:date).map(&:balance)
+
+    assert_equal expected, calculated
+  end
+
+  test "forward 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 = Account::BalanceCalculator.new(@account).calculate.sort_by(&:date).map(&:balance)
+
+    assert_equal expected, calculated
+  end
+
+  test "investment balance sync" do
+    @account.update!(cash_balance: 18000)
+
+    # Transactions represent deposits / withdrawals from the brokerage account
+    # Ex: We deposit $20,000 into the brokerage account
+    create_transaction(account: @account, date: 2.days.ago.to_date, amount: -20000)
+
+    # Trades either consume cash (buy) or generate cash (sell).  They do NOT change total balance, but do affect composition of cash/holdings.
+    # Ex: We buy 20 shares of MSFT at $100 for a total of $2000
+    create_trade(securities(:msft), account: @account, date: 1.day.ago.to_date, qty: 20, price: 100)
+
+    holdings = [
+      Account::Holding.new(date: Date.current, security: securities(:msft), amount: 2000),
+      Account::Holding.new(date: 1.day.ago.to_date, security: securities(:msft), amount: 2000),
+      Account::Holding.new(date: 2.days.ago.to_date, security: securities(:msft), amount: 0)
+    ]
+
+    expected = [ 0, 20000, 20000, 20000 ]
+    calculated_backwards = Account::BalanceCalculator.new(@account, holdings: holdings).calculate(reverse: true).sort_by(&:date).map(&:balance)
+    calculated_forwards = Account::BalanceCalculator.new(@account, holdings: holdings).calculate.sort_by(&:date).map(&:balance)
+
+    assert_equal calculated_forwards, calculated_backwards
+    assert_equal expected, calculated_forwards
+  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 = Account::BalanceCalculator.new(@account).calculate.sort_by(&:date).map(&:balance)
+
+    assert_equal expected, calculated
+  end
+
+  private
+    def create_holding(date:, security:, amount:)
+      Account::Holding.create!(
+        account: @account,
+        security: security,
+        date: date,
+        qty: 0, # not used
+        price: 0, # not used
+        amount: amount,
+        currency: @account.currency
+      )
+    end
+end