Basic Portfolio Views (#1000)

* Add holdings tab to account view

* Basic portfolio UI

* Cleanup

* Handle missing holding data

* Remove synced at (implemented in separate pr)

* translations

* Tweak post sync streams

* Remove stale methods from merge conflict

app/models/account/holding.rb

@@ -1,6 +1,46 @@
 class Account::Holding < ApplicationRecord
+  include Monetizable
+
+  monetize :amount
+
   belongs_to :account
   belongs_to :security
 
+  validates :qty, :currency, presence: true
+
   scope :chronological, -> { order(:date) }
+  scope :current, -> { where(date: Date.current).order(amount: :desc) }
+  scope :for, ->(security) { where(security_id: security).order(:date) }
+
+  delegate :name, to: :security
+  delegate :symbol, to: :security
+
+  def weight
+    return nil unless amount
+
+    portfolio_value = account.holdings.current.where.not(amount: nil).sum(&:amount)
+    portfolio_value.zero? ? 1 : amount / portfolio_value * 100
+  end
+
+  # Basic approximation of cost-basis
+  def avg_cost
+    avg_cost = account.holdings.for(security).where("date <= ?", date).average(:price)
+    Money.new(avg_cost, currency)
+  end
+
+  def trend
+    @trend ||= calculate_trend
+  end
+
+  private
+
+    def calculate_trend
+      return nil unless amount_money
+
+      start_amount = qty * avg_cost
+
+      TimeSeries::Trend.new \
+        current: amount_money,
+        previous: start_amount
+    end
 end