Initial commit

app/models/operation.rb

@@ -0,0 +1,96 @@
+# frozen_string_literal: true
+
+# {Operation} provides generic methods for the accounting operations
+# models.
+# @abstract
+class Operation < ApplicationRecord
+  belongs_to :reference, polymorphic: true
+  belongs_to :currency, foreign_key: :currency_id
+  belongs_to :account, class_name: 'Operations::Account',
+             foreign_key: :code, primary_key: :code
+
+  validates :credit, :debit, numericality: { greater_than_or_equal_to: 0 }
+  validates :currency, :code, presence: true
+
+  validate do
+    errors.add(:account, 'account doesn\'t exist') unless account
+  end
+
+  validate do
+    unless account&.currency_type == currency&.type
+      errors.add(:currency, 'type and account currency type don\'t match')
+    end
+  end
+
+  validate do
+    unless account&.type == self.class.operation_type
+      errors.add(:base, 'Account type and operation type don\'t match')
+    end
+  end
+
+  self.abstract_class = true
+
+  # Returns operation amount with sign.
+  def amount
+    credit.zero? ? -debit : credit
+  end
+
+  class << self
+    def operation_type
+      name.demodulize.downcase
+    end
+
+    def credit!(amount:, currency:, kind: :main, **opt)
+      return if amount.zero?
+
+      opt[:code] ||= Operations::Account.find_by(
+        type:          operation_type,
+        kind:          kind,
+        currency_type: currency.type
+      ).code
+
+      opt.merge(credit: amount, currency_id: currency.id)
+         .yield_self { |attr| new(attr) }
+         .tap(&:save!)
+    end
+
+    def debit!(amount:, currency:, kind: :main, **opt)
+      return if amount.zero?
+
+      opt[:code] ||= Operations::Account.find_by(
+        type:          operation_type,
+        kind:          kind,
+        currency_type: currency.type
+      ).code
+
+      opt.merge(debit: amount, currency_id: currency.id)
+         .yield_self { |attr| new(attr) }
+         .tap(&:save!)
+    end
+
+    def transfer!(amount:, currency:, from_kind:, to_kind:, **opt)
+      params = opt.merge(amount: amount, currency: currency)
+
+      [
+        debit!(params.merge(kind: from_kind)),
+        credit!(params.merge(kind: to_kind))
+      ]
+    end
+
+    def balance(currency: nil, created_at_from: nil, created_at_to: nil)
+      if currency.blank?
+        db_balances = all
+        db_balances = db_balances.where('created_at > ?', created_at_from) if created_at_from.present?
+        db_balances = db_balances.where('created_at < ?', created_at_to) if created_at_to.present?
+        db_balances = db_balances.group(:currency_id)
+                                 .sum('credit - debit')
+
+        Currency.ids.map(&:to_sym).each_with_object({}) do |id, memo|
+          memo[id] = db_balances[id.to_s] || 0
+        end
+      else
+        where(currency: currency).sum('credit - debit')
+      end
+    end
+  end
+end