Feature: Add "amount type" configuration column for CSV imports (#1947)

* Rough draft

* Schema conflict update

* Implement signage

* Update system tests

* Lint fixes

app/models/import.rb

@@ -10,6 +10,8 @@ class Import < ApplicationRecord
     "1,234"    => { separator: "",  delimiter: "," }   # Zero-decimal currencies like JPY
   }.freeze
 
+  AMOUNT_TYPE_STRATEGIES = %w[signed_amount custom_column].freeze
+
   belongs_to :family
   belongs_to :account, optional: true
 
@@ -27,8 +29,9 @@ class Import < ApplicationRecord
   }, validate: true, default: "pending"
 
   validates :type, inclusion: { in: TYPES }
+  validates :amount_type_strategy, inclusion: { in: AMOUNT_TYPE_STRATEGIES }
   validates :col_sep, inclusion: { in: SEPARATORS.map(&:last) }
-  validates :signage_convention, inclusion: { in: SIGNAGE_CONVENTIONS }
+  validates :signage_convention, inclusion: { in: SIGNAGE_CONVENTIONS }, allow_nil: true
   validates :number_format, presence: true, inclusion: { in: NUMBER_FORMATS.keys }
 
   has_many :rows, dependent: :destroy

app/models/import/row.rb

@@ -44,7 +44,19 @@ class Import::Row < ApplicationRecord
 
     # In the Maybe system, positive amounts == "outflows", so we must reverse signage
     def apply_transaction_signage_convention(value)
-      value * (import.signage_convention == "inflows_positive" ? -1 : 1)
+      if import.amount_type_strategy == "signed_amount"
+        value * (import.signage_convention == "inflows_positive" ? -1 : 1)
+      elsif import.amount_type_strategy == "custom_column"
+        inflow_value = import.amount_type_inflow_value
+
+        if entity_type == inflow_value
+          value * -1
+        else
+          value
+        end
+      else
+        raise "Unknown amount type strategy for import: #{import.amount_type_strategy}"
+      end
     end
 
     def required_columns

app/models/trade_import.rb

@@ -31,6 +31,7 @@ class TradeImport < Import
           ),
         )
       end
+
       Trade.import!(trades, recursive: true)
     end
   end

app/models/transaction_import.rb

@@ -48,6 +48,12 @@ class TransactionImport < Import
     base
   end
 
+  def selectable_amount_type_values
+    return [] if entity_type_col_label.nil?
+
+    csv_rows.map { |row| row[entity_type_col_label] }.uniq
+  end
+
   def csv_template
     template = <<-CSV
       date*,amount*,name,currency,category,tags,account,notes