Balance sheet cache layer, non-blocking sync UI (#2356)

* Balance sheet cache layer with cache-busting

* Update family cache timestamps during Sync

* Less blocking sync loaders

* Consolidate family data caching key logic

* Fix turbo stream broadcasts

* Remove dev delay

* Add back account group sorting

app/models/balance_sheet/account_totals.rb

@@ -0,0 +1,63 @@
+class BalanceSheet::AccountTotals
+  def initialize(family, sync_status_monitor:)
+    @family = family
+    @sync_status_monitor = sync_status_monitor
+  end
+
+  def asset_accounts
+    @asset_accounts ||= account_rows.filter { |t| t.classification == "asset" }
+  end
+
+  def liability_accounts
+    @liability_accounts ||= account_rows.filter { |t| t.classification == "liability" }
+  end
+
+  private
+    attr_reader :family, :sync_status_monitor
+
+    AccountRow = Data.define(:account, :converted_balance, :is_syncing) do
+      def syncing? = is_syncing
+
+      # Allows Rails path helpers to generate URLs from the wrapper
+      def to_param = account.to_param
+      delegate_missing_to :account
+    end
+
+    def active_accounts
+      @active_accounts ||= family.accounts.active.with_attached_logo
+    end
+
+    def account_rows
+      @account_rows ||= query.map do |account_row|
+        AccountRow.new(
+          account: account_row,
+          converted_balance: account_row.converted_balance,
+          is_syncing: sync_status_monitor.account_syncing?(account_row)
+        )
+      end
+    end
+
+    def cache_key
+      family.build_cache_key(
+        "balance_sheet_account_rows",
+        invalidate_on_data_updates: true
+      )
+    end
+
+    def query
+      @query ||= Rails.cache.fetch(cache_key) do
+        active_accounts
+          .joins(ActiveRecord::Base.sanitize_sql_array([
+            "LEFT JOIN exchange_rates ON exchange_rates.date = ? AND accounts.currency = exchange_rates.from_currency AND exchange_rates.to_currency = ?",
+            Date.current,
+            family.currency
+          ]))
+          .select(
+            "accounts.*",
+            "SUM(accounts.balance * COALESCE(exchange_rates.rate, 1)) as converted_balance"
+          )
+          .group(:classification, :accountable_type, :id)
+          .to_a
+      end
+    end
+end