Investment Portfolio Sync (#974)

* Add investment portfolio models

* Add portfolio to demo data

* Setup initial tests

* Rough sketch of sync logic

* Clean up trade sync logic

* Add trade validation

* Integrate trades into sync process

app/models/account/holding/syncer.rb

@@ -0,0 +1,96 @@
+class Account::Holding::Syncer
+  attr_reader :warnings
+
+  def initialize(account, start_date: nil)
+    @account = account
+    @warnings = []
+    @sync_date_range = calculate_sync_start_date(start_date)..Date.current
+    @portfolio = {}
+
+    load_prior_portfolio if start_date
+  end
+
+  def run
+    holdings = []
+
+    sync_date_range.each do |date|
+      holdings += build_holdings_for_date(date)
+    end
+
+    upsert_holdings holdings
+  end
+
+  private
+
+    attr_reader :account, :sync_date_range
+
+    def sync_entries
+      @sync_entries ||= account.entries
+                               .account_trades
+                               .includes(entryable: :security)
+                               .where("date >= ?", sync_date_range.begin)
+                               .order(:date)
+    end
+
+    def build_holdings_for_date(date)
+      trades = sync_entries.select { |trade| trade.date == date }
+
+      @portfolio = generate_next_portfolio(@portfolio, trades)
+
+      @portfolio.map do |isin, holding|
+        price = Security::Price.find_by!(date: date, isin: isin).price
+
+        account.holdings.build \
+          date: date,
+          security_id: holding[:security_id],
+          qty: holding[:qty],
+          price: price,
+          amount: price * holding[:qty]
+      end
+    end
+
+    def generate_next_portfolio(prior_portfolio, trade_entries)
+      trade_entries.each_with_object(prior_portfolio) do |entry, new_portfolio|
+        trade = entry.account_trade
+
+        price = trade.price
+        prior_qty = prior_portfolio.dig(trade.security.isin, :qty) || 0
+        new_qty = prior_qty + trade.qty
+
+        new_portfolio[trade.security.isin] = {
+          qty: new_qty,
+          price: price,
+          amount: new_qty * price,
+          security_id: trade.security_id
+        }
+      end
+    end
+
+    def upsert_holdings(holdings)
+      current_time = Time.now
+      holdings_to_upsert = holdings.map do |holding|
+        holding.attributes
+               .slice("date", "currency", "qty", "price", "amount", "security_id")
+               .merge("updated_at" => current_time)
+      end
+
+      account.holdings.upsert_all(holdings_to_upsert, unique_by: %i[account_id security_id date currency])
+    end
+
+    def load_prior_portfolio
+      prior_day_holdings = account.holdings.where(date: sync_date_range.begin - 1.day)
+
+      prior_day_holdings.each do |holding|
+        @portfolio[holding.security.isin] = {
+          qty: holding.qty,
+          price: holding.price,
+          amount: holding.amount,
+          security_id: holding.security_id
+        }
+      end
+    end
+
+    def calculate_sync_start_date(start_date)
+      start_date || account.entries.account_trades.order(:date).first.try(:date) || Date.current
+    end
+end