Basic Account Balance Sync Algorithm (#501)

* Sketch out sync interface

* Add basic account sync algorithm

* Update logic for final balance in series

* Remove start_date concept

* Clean up tests

* Improve clarity of test

* Update app/models/account.rb

Co-authored-by: Rob Zolkos <rob@zolkos.com>
Signed-off-by: Zach Gollwitzer <zach.gollwitzer@gmail.com>

* Update app/models/transaction.rb

Co-authored-by: Rob Zolkos <rob@zolkos.com>
Signed-off-by: Zach Gollwitzer <zach.gollwitzer@gmail.com>

* Update app/models/valuation.rb

Co-authored-by: Rob Zolkos <rob@zolkos.com>
Signed-off-by: Zach Gollwitzer <zach.gollwitzer@gmail.com>

* Re-organize code, simplify job interface

* Consolidate balance calculations

* More cleanup

---------

Signed-off-by: Zach Gollwitzer <zach.gollwitzer@gmail.com>
Co-authored-by: Rob Zolkos <rob@zolkos.com>

app/jobs/account_balance_sync_job.rb

@@ -1,74 +0,0 @@
-class AccountBalanceSyncJob < ApplicationJob
-  queue_as :default
-
-  # Naive implementation of the perform method (will be refactored to handle transactions later)
-  def perform(account_id:, valuation_date:, sync_type:, sync_action:)
-    account = Account.find(account_id)
-
-    account.status = "SYNCING"
-    account.save!
-
-    case sync_type
-    when "valuation"
-      case sync_action
-      when "update"
-        handle_valuation_update(account: account, valuation_date: valuation_date)
-      when "destroy"
-        handle_valuation_destroy(account: account, valuation_date: valuation_date)
-      else
-        logger.error "Unsupported sync_action: #{sync_action} for sync_type: #{sync_type}"
-      end
-    else
-      logger.error "Unsupported sync_type: #{sync_type}"
-    end
-
-    sync_current_account_balance(account)
-
-    account.status = "OK"
-    account.save!
-  end
-
-  private
-
-    def sync_current_account_balance(account)
-      today_balance = account.balances.find_or_initialize_by(date: Date.current)
-      today_balance.update(balance: account.converted_balance)
-    end
-
-    def handle_valuation_update(account:, valuation_date:)
-      updated_valuation = account.valuations.find_by(date: valuation_date)
-
-      return unless updated_valuation
-
-      update_period_start = valuation_date
-      update_period_end = (account.valuations.where("date > ?", valuation_date).order(:date).first&.date || Date.current) - 1.day
-
-      balances_to_upsert = (update_period_start..update_period_end).map do |date|
-        { date: date, balance: updated_valuation.value, created_at: Time.current, updated_at: Time.current }
-      end
-
-      account.balances.upsert_all(balances_to_upsert, unique_by: :index_account_balances_on_account_id_and_date)
-
-      logger.info "Upserted balances for account #{account.id} from #{update_period_start} to #{update_period_end}"
-    end
-
-    def handle_valuation_destroy(account:, valuation_date:)
-      prior_valuation = account.valuations.where("date < ?", valuation_date).order(:date).last
-      period_start = prior_valuation&.date
-      period_end = (account.valuations.where("date > ?", valuation_date).order(:date).first&.date || Date.current) - 1.day
-
-      if prior_valuation
-        balances_to_upsert = (period_start..period_end).map do |date|
-          { date: date, balance: prior_valuation.value, created_at: Time.current, updated_at: Time.current }
-        end
-
-        account.balances.upsert_all(balances_to_upsert, unique_by: :index_account_balances_on_account_id_and_date)
-        logger.info "Upserted balances for account #{account.id} from #{period_start} to #{period_end}"
-      else
-        delete_count = account.balances.where(date: period_start..period_end).delete_all
-        logger.info "Deleted #{delete_count} balances for account #{account.id} from #{period_start} to #{period_end}"
-      end
-    rescue => e
-      logger.error "Sync failed after valuation destroy operation on account #{account.id} with message: #{e.message}"
-    end
-end

app/jobs/account_sync_job.rb

@@ -0,0 +1,7 @@
+class AccountSyncJob < ApplicationJob
+  queue_as :default
+
+  def perform(account)
+    account.sync
+  end
+end

app/models/account.rb

@@ -1,4 +1,6 @@
 class Account < ApplicationRecord
+  include Syncable
+
   broadcasts_refreshes
   belongs_to :family
   has_many :balances, class_name: "AccountBalance"

app/models/account/balance_calculator.rb

@@ -0,0 +1,38 @@
+class Account::BalanceCalculator
+    def initialize(account)
+      @account = account
+    end
+
+    def daily_balances(start_date = nil)
+      calc_start_date = [ start_date, @account.effective_start_date ].compact.max
+
+      valuations = @account.valuations.where("date >= ?", calc_start_date).order(:date).select(:date, :value)
+      transactions = @account.transactions.where("date > ?", calc_start_date).order(:date).select(:date, :amount)
+      oldest_entry = [ valuations.first, transactions.first ].compact.min_by(&:date)
+
+      net_transaction_flows = transactions.sum(&:amount)
+      implied_start_balance = oldest_entry.is_a?(Valuation) ? oldest_entry.value : @account.balance + net_transaction_flows
+
+      prior_balance = implied_start_balance
+      calculated_balances = ((calc_start_date + 1.day)...Date.current).map do |date|
+        valuation = valuations.find { |v| v.date == date }
+
+        if valuation
+            current_balance = valuation.value
+        else
+            current_day_net_transaction_flows = transactions.select { |t| t.date == date }.sum(&:amount)
+            current_balance = prior_balance - current_day_net_transaction_flows
+        end
+
+        prior_balance = current_balance
+
+        { date: date, balance: current_balance, updated_at: Time.current }
+      end
+
+      [
+        { date: calc_start_date, balance: implied_start_balance, updated_at: Time.current },
+        *calculated_balances,
+        { date: Date.current, balance: @account.balance, updated_at: Time.current } # Last balance must always match "source of truth"
+      ]
+    end
+end

app/models/account/syncable.rb

@@ -0,0 +1,26 @@
+module Account::Syncable
+    extend ActiveSupport::Concern
+
+    def sync_later
+        AccountSyncJob.perform_later self
+    end
+
+    def sync
+        update!(status: "SYNCING")
+        synced_daily_balances = Account::BalanceCalculator.new(self).daily_balances
+        self.balances.upsert_all(synced_daily_balances, unique_by: :index_account_balances_on_account_id_and_date)
+        self.balances.where("date < ?", effective_start_date).delete_all
+        update!(status: "OK")
+    rescue => e
+        update!(status: "ERROR")
+        Rails.logger.error("Failed to sync account #{id}: #{e.message}")
+    end
+
+    # The earliest date we can calculate a balance for
+    def effective_start_date
+        first_valuation_date = self.valuations.order(:date).pluck(:date).first
+        first_transaction_date = self.transactions.order(:date).pluck(:date).first
+
+        [ first_valuation_date, first_transaction_date&.prev_day ].compact.min || Date.current
+    end
+end

app/models/transaction.rb

@@ -1,3 +1,11 @@
 class Transaction < ApplicationRecord
   belongs_to :account
+
+  after_commit :sync_account
+
+  private
+
+    def sync_account
+      self.account.sync_later
+    end
 end

app/models/valuation.rb

@@ -1,20 +1,14 @@
 class Valuation < ApplicationRecord
   belongs_to :account
 
-  after_commit :sync_account_balances, on: [ :create, :update ]
-  after_destroy :sync_account_balances_after_destroy
+  after_commit :sync_account
 
   def trend(previous)
     Trend.new(value, previous&.value)
   end
 
   private
-
-    def sync_account_balances_after_destroy
-      AccountBalanceSyncJob.perform_later(account_id: account_id, valuation_date: date, sync_type: "valuation", sync_action: "destroy")
-    end
-
-    def sync_account_balances
-      AccountBalanceSyncJob.perform_later(account_id: account_id, valuation_date: date, sync_type: "valuation", sync_action: "update")
+    def sync_account
+      self.account.sync_later
     end
 end