Add reconciliation manager (#2459)

* Add reconciliation manager

* Fix notes editing

app/models/account/reconcileable.rb

@@ -0,0 +1,16 @@
+module Account::Reconcileable
+  extend ActiveSupport::Concern
+
+  def create_reconciliation(balance:, date:, dry_run: false)
+    reconciliation_manager.reconcile_balance(balance: balance, date: date, dry_run: dry_run)
+  end
+
+  def update_reconciliation(existing_valuation_entry, balance:, date:, dry_run: false)
+    reconciliation_manager.reconcile_balance(balance: balance, date: date, existing_valuation_entry: existing_valuation_entry, dry_run: dry_run)
+  end
+
+  private
+    def reconciliation_manager
+      @reconciliation_manager ||= Account::ReconciliationManager.new(self)
+    end
+end

app/models/account/reconciliation_manager.rb

@@ -0,0 +1,90 @@
+class Account::ReconciliationManager
+  attr_reader :account
+
+  def initialize(account)
+    @account = account
+  end
+
+  # Reconciles balance by creating a Valuation entry. If existing valuation is provided, it will be updated instead of creating a new one.
+  def reconcile_balance(balance:, date: Date.current, dry_run: false, existing_valuation_entry: nil)
+    old_balance_components = old_balance_components(reconciliation_date: date, existing_valuation_entry: existing_valuation_entry)
+    prepared_valuation = prepare_reconciliation(balance, date, existing_valuation_entry)
+
+    unless dry_run
+      prepared_valuation.save!
+      account.sync_later
+    end
+
+    ReconciliationResult.new(
+      success?: true,
+      old_cash_balance: old_balance_components[:cash_balance],
+      old_balance: old_balance_components[:balance],
+      new_cash_balance: derived_cash_balance(date: date, total_balance: prepared_valuation.amount),
+      new_balance: prepared_valuation.amount,
+      error_message: nil
+    )
+  rescue => e
+    ReconciliationResult.new(
+      success?: false,
+      error_message: e.message
+    )
+  end
+
+  private
+    # Returns before -> after OR error message
+    ReconciliationResult = Struct.new(
+      :success?,
+      :old_cash_balance,
+      :old_balance,
+      :new_cash_balance,
+      :new_balance,
+      :error_message,
+      keyword_init: true
+    )
+
+    def prepare_reconciliation(balance, date, existing_valuation)
+      valuation_record = existing_valuation ||
+                         account.entries.valuations.find_by(date: date) || # In case of conflict, where existing valuation is not passed as arg, but one exists
+                         account.entries.build(
+                                  name: Valuation.build_reconciliation_name(account.accountable_type),
+                                  entryable: Valuation.new(kind: "reconciliation")
+                                )
+
+      valuation_record.assign_attributes(
+        date: date,
+        amount: balance,
+        currency: account.currency
+      )
+
+      valuation_record
+    end
+
+    def derived_cash_balance(date:, total_balance:)
+      balance_components_for_reconciliation_date = get_balance_components_for_date(date)
+
+      return nil unless balance_components_for_reconciliation_date[:balance] && balance_components_for_reconciliation_date[:cash_balance]
+
+      # We calculate the existing non-cash balance, which for investments would represents "holdings" for the date of reconciliation
+      # Since the user is setting "total balance", we have to subtract the existing non-cash balance from the total balance to get the new cash balance
+      existing_non_cash_balance = balance_components_for_reconciliation_date[:balance] - balance_components_for_reconciliation_date[:cash_balance]
+
+      total_balance - existing_non_cash_balance
+    end
+
+    def old_balance_components(reconciliation_date:, existing_valuation_entry: nil)
+      if existing_valuation_entry
+        get_balance_components_for_date(existing_valuation_entry.date)
+      else
+        get_balance_components_for_date(reconciliation_date)
+      end
+    end
+
+    def get_balance_components_for_date(date)
+      balance_record = account.balances.find_by(date: date, currency: account.currency)
+
+      {
+        cash_balance: balance_record&.cash_balance,
+        balance: balance_record&.balance
+      }
+    end
+end