Plaid sync domain improvements (#2267)

Breaks our Plaid sync process out into more manageable classes. Notably, this moves the sync process to a distinct, 2-step flow:

1. Import stage - we first make API calls and import Plaid data to "mirror" tables
2. Processing stage - read the raw data, apply business rules, build internal domain models and sync balances

This provides several benefits:

- Plaid syncs can now be "replayed" without fetching API data again
- Mirror tables provide better audit and debugging capabilities
- Eliminates the "all or nothing" sync behavior that is currently in place, which is brittle

test/models/plaid_account/processor_test.rb

@@ -0,0 +1,172 @@
+require "test_helper"
+
+class PlaidAccount::ProcessorTest < ActiveSupport::TestCase
+  setup do
+    @plaid_account = plaid_accounts(:one)
+  end
+
+  test "processes new account and assigns attributes" do
+    Account.destroy_all # Clear out internal accounts so we start fresh
+
+    expect_default_subprocessor_calls
+
+    @plaid_account.update!(
+      plaid_id: "test_plaid_id",
+      plaid_type: "depository",
+      plaid_subtype: "checking",
+      current_balance: 1000,
+      available_balance: 1000,
+      currency: "USD",
+      name: "Test Plaid Account",
+      mask: "1234"
+    )
+
+    assert_difference "Account.count" do
+      PlaidAccount::Processor.new(@plaid_account).process
+    end
+
+    @plaid_account.reload
+
+    account = Account.order(created_at: :desc).first
+    assert_equal "Test Plaid Account", account.name
+    assert_equal @plaid_account.id, account.plaid_account_id
+    assert_equal "checking", account.subtype
+    assert_equal 1000, account.balance
+    assert_equal 1000, account.cash_balance
+    assert_equal "USD", account.currency
+    assert_equal "Depository", account.accountable_type
+    assert_equal "checking", account.subtype
+  end
+
+  test "processing is idempotent with updates and enrichments" do
+    expect_default_subprocessor_calls
+
+    assert_equal "Plaid Depository Account", @plaid_account.account.name
+    assert_equal "checking", @plaid_account.account.subtype
+
+    @plaid_account.account.update!(
+      name: "User updated name",
+      subtype: "savings",
+      balance: 2000 # User cannot override balance.  This will be overridden by the processor on next processing
+    )
+
+    @plaid_account.account.lock_attr!(:name)
+    @plaid_account.account.lock_attr!(:subtype)
+    @plaid_account.account.lock_attr!(:balance) # Even if balance somehow becomes locked, Plaid ignores it and overrides it
+
+    assert_no_difference "Account.count" do
+      PlaidAccount::Processor.new(@plaid_account).process
+    end
+
+    @plaid_account.reload
+
+    assert_equal "User updated name", @plaid_account.account.name
+    assert_equal "savings", @plaid_account.account.subtype
+    assert_equal @plaid_account.current_balance, @plaid_account.account.balance # Overriden by processor
+  end
+
+  test "account processing failure halts further processing" do
+    Account.any_instance.stubs(:save!).raises(StandardError.new("Test error"))
+
+    PlaidAccount::Transactions::Processor.any_instance.expects(:process).never
+    PlaidAccount::Investments::TransactionsProcessor.any_instance.expects(:process).never
+    PlaidAccount::Investments::HoldingsProcessor.any_instance.expects(:process).never
+
+    expect_no_investment_balance_calculator_calls
+    expect_no_liability_processor_calls
+
+    assert_raises(StandardError) do
+      PlaidAccount::Processor.new(@plaid_account).process
+    end
+  end
+
+  test "product processing failure reports exception and continues processing" do
+    PlaidAccount::Transactions::Processor.any_instance.stubs(:process).raises(StandardError.new("Test error"))
+
+    # Subsequent product processors still run
+    expect_investment_product_processor_calls
+
+    assert_nothing_raised do
+      PlaidAccount::Processor.new(@plaid_account).process
+    end
+  end
+
+  test "calculates balance using BalanceCalculator for investment accounts" do
+    @plaid_account.update!(plaid_type: "investment")
+
+    PlaidAccount::Investments::BalanceCalculator.any_instance.expects(:balance).returns(1000).once
+    PlaidAccount::Investments::BalanceCalculator.any_instance.expects(:cash_balance).returns(1000).once
+
+    PlaidAccount::Processor.new(@plaid_account).process
+  end
+
+  test "processes credit liability data" do
+    expect_investment_product_processor_calls
+    expect_no_investment_balance_calculator_calls
+    expect_depository_product_processor_calls
+
+    @plaid_account.update!(plaid_type: "credit", plaid_subtype: "credit card")
+
+    PlaidAccount::Liabilities::CreditProcessor.any_instance.expects(:process).once
+    PlaidAccount::Liabilities::MortgageProcessor.any_instance.expects(:process).never
+    PlaidAccount::Liabilities::StudentLoanProcessor.any_instance.expects(:process).never
+
+    PlaidAccount::Processor.new(@plaid_account).process
+  end
+
+  test "processes mortgage liability data" do
+    expect_investment_product_processor_calls
+    expect_no_investment_balance_calculator_calls
+    expect_depository_product_processor_calls
+
+    @plaid_account.update!(plaid_type: "loan", plaid_subtype: "mortgage")
+
+    PlaidAccount::Liabilities::CreditProcessor.any_instance.expects(:process).never
+    PlaidAccount::Liabilities::MortgageProcessor.any_instance.expects(:process).once
+    PlaidAccount::Liabilities::StudentLoanProcessor.any_instance.expects(:process).never
+
+    PlaidAccount::Processor.new(@plaid_account).process
+  end
+
+  test "processes student loan liability data" do
+    expect_investment_product_processor_calls
+    expect_no_investment_balance_calculator_calls
+    expect_depository_product_processor_calls
+
+    @plaid_account.update!(plaid_type: "loan", plaid_subtype: "student")
+
+    PlaidAccount::Liabilities::CreditProcessor.any_instance.expects(:process).never
+    PlaidAccount::Liabilities::MortgageProcessor.any_instance.expects(:process).never
+    PlaidAccount::Liabilities::StudentLoanProcessor.any_instance.expects(:process).once
+
+    PlaidAccount::Processor.new(@plaid_account).process
+  end
+
+  private
+    def expect_investment_product_processor_calls
+      PlaidAccount::Investments::TransactionsProcessor.any_instance.expects(:process).once
+      PlaidAccount::Investments::HoldingsProcessor.any_instance.expects(:process).once
+    end
+
+    def expect_depository_product_processor_calls
+      PlaidAccount::Transactions::Processor.any_instance.expects(:process).once
+    end
+
+    def expect_no_investment_balance_calculator_calls
+      PlaidAccount::Investments::BalanceCalculator.any_instance.expects(:balance).never
+      PlaidAccount::Investments::BalanceCalculator.any_instance.expects(:cash_balance).never
+    end
+
+    def expect_no_liability_processor_calls
+      PlaidAccount::Liabilities::CreditProcessor.any_instance.expects(:process).never
+      PlaidAccount::Liabilities::MortgageProcessor.any_instance.expects(:process).never
+      PlaidAccount::Liabilities::StudentLoanProcessor.any_instance.expects(:process).never
+    end
+
+    def expect_default_subprocessor_calls
+      expect_depository_product_processor_calls
+      expect_investment_product_processor_calls
+      expect_no_investment_balance_calculator_calls
+      expect_no_liability_processor_calls
+    end
+end