Net worth calculation (#508)

* Add classification generated column to account

* Add basic net worth calculation

* Add net worth tests

* Fix lint errors

app/models/family.rb

@@ -2,4 +2,66 @@ class Family < ApplicationRecord
   has_many :users, dependent: :destroy
   has_many :accounts, dependent: :destroy
   has_many :transactions, through: :accounts
+
+  def net_worth
+    accounts.sum("CASE WHEN classification = 'asset' THEN balance ELSE -balance END")
+  end
+
+  def assets
+    accounts.where(classification: "asset").sum(:balance)
+  end
+
+  def liabilities
+    accounts.where(classification: "liability").sum(:balance)
+  end
+
+  def net_worth_series(period = nil)
+    query = accounts.joins(:balances)
+      .select("account_balances.date, SUM(CASE WHEN accounts.classification = 'asset' THEN account_balances.balance ELSE -account_balances.balance END) AS balance, 'USD' as currency")
+      .group("account_balances.date")
+      .order("account_balances.date ASC")
+
+    if period && period.date_range
+      query = query.where("account_balances.date BETWEEN ? AND ?", period.date_range.begin, period.date_range.end)
+    end
+
+    MoneySeries.new(
+      query,
+      { trend_type: "asset" }
+    )
+  end
+
+  def asset_series(period = nil)
+    query = accounts.joins(:balances)
+      .select("account_balances.date, SUM(account_balances.balance) AS balance, 'asset' AS classification, 'USD' AS currency")
+      .group("account_balances.date")
+      .order("account_balances.date ASC")
+      .where(classification: "asset")
+
+    if period && period.date_range
+      query = query.where("account_balances.date BETWEEN ? AND ?", period.date_range.begin, period.date_range.end)
+    end
+
+    MoneySeries.new(
+      query,
+      { trend_type: "asset" }
+    )
+  end
+
+  def liability_series(period = nil)
+    query = accounts.joins(:balances)
+      .select("account_balances.date, SUM(account_balances.balance) AS balance, 'liability' AS classification, 'USD' AS currency")
+      .group("account_balances.date")
+      .order("account_balances.date ASC")
+      .where(classification: "liability")
+
+    if period && period.date_range
+      query = query.where("account_balances.date BETWEEN ? AND ?", period.date_range.begin, period.date_range.end)
+    end
+
+    MoneySeries.new(
+      query,
+      { trend_type: "liability" }
+    )
+  end
 end