Deposit, Withdrawal, and Interest Transactions for Investment View (#1075)

* Trade and Transaction builders

* Consolidate logic

* Remove redundant fields from trade form

* Add deposit, withdrawal, and interest form controls

app/models/account/transaction_builder.rb

@@ -0,0 +1,63 @@
+class Account::TransactionBuilder
+  include ActiveModel::Model
+
+  TYPES = %w[ income expense interest transfer_in transfer_out ].freeze
+
+  attr_accessor :type, :amount, :date, :account, :transfer_account_id
+
+  validates :type, :amount, :date, presence: true
+  validates :type, inclusion: { in: TYPES }
+
+  def save
+    if valid?
+      transfer? ? create_transfer : create_transaction
+    end
+  end
+
+  private
+
+    def transfer?
+      %w[transfer_in transfer_out].include?(type)
+    end
+
+    def create_transfer
+      return create_unlinked_transfer(account.id, signed_amount) unless transfer_account_id
+
+      from_account_id = type == "transfer_in" ? transfer_account_id : account.id
+      to_account_id = type == "transfer_in" ? account.id : transfer_account_id
+
+      outflow = create_unlinked_transfer(from_account_id, signed_amount.abs)
+      inflow = create_unlinked_transfer(to_account_id, signed_amount.abs * -1)
+
+      Account::Transfer.create! entries: [ outflow, inflow ]
+
+      inflow
+    end
+
+    def create_unlinked_transfer(account_id, amount)
+      build_entry(account_id, amount, marked_as_transfer: true).tap(&:save!)
+    end
+
+    def create_transaction
+      build_entry(account.id, signed_amount).tap(&:save!)
+    end
+
+    def build_entry(account_id, amount, marked_as_transfer: false)
+      Account::Entry.new \
+        account_id: account_id,
+        amount: amount,
+        currency: account.currency,
+        date: date,
+        marked_as_transfer: marked_as_transfer,
+        entryable: Account::Transaction.new
+    end
+
+    def signed_amount
+      case type
+      when "expense", "transfer_out"
+        amount.to_d
+      else
+        amount.to_d * -1
+      end
+    end
+end