Moved Formula to separate model

app/models/formula.rb

@@ -0,0 +1,58 @@
+class Formula < ActiveRecord::Base
+  include BodyTracking::FormulaBuilder
+
+  attr_reader :parts, :quantities
+
+  belongs_to :quantity, inverse_of: :formula, required: true
+
+  validates :code, presence: true
+  validate do
+    parse.each { |message, params| errors.add(:code, message, params) }
+  end
+
+  after_initialize do
+    if new_record?
+      self.zero_nil = true if self.zero_nil.nil?
+    end
+  end
+
+  private
+
+  def parse
+    parser = FormulaBuilder.new(self.code)
+    identifiers, parts = parser.parse
+    errors = parser.errors
+
+    quantities = Quantity.where(project: self.quantity.project, name: identifiers)
+    quantities_names = quantities.pluck(:name)
+    (identifiers - quantities_names).each do |q|
+      errors << [:unknown_quantity, {quantity: q}]
+    end
+
+    @parts, @quantities = parts, quantities.to_a if errors.empty?
+    errors
+  end
+
+  def calculate(inputs)
+    quantities = inputs.map { |q, v| [q.name, v.transpose[0]] }.to_h
+    length = quantities.values.first.length
+
+    raise(InvalidFormula, 'Invalid formula') unless self.valid?
+    raise InvalidInputs unless quantities.values.all? { |v| v.length == length }
+
+    args = []
+    @parts.each do |p|
+      code = p[:type] == :indexed ?
+        "length.times.map { |index| #{p[:content]} }" : p[:content]
+      args << get_binding(quantities, args, length).eval(code)
+    end
+    args.last.map { |v| [v, nil] }
+  rescue Exception => e
+    puts e.message
+    [[nil, nil]] * length
+  end
+
+  def get_binding(quantities, args, length)
+    binding
+  end
+end

app/models/quantity.rb

@@ -1,6 +1,4 @@
 class Quantity < ActiveRecord::Base
-  include BodyTracking::Formula
-
   enum domain: {
     diet: 0,
     measurement: 1,
@@ -18,12 +16,16 @@ class Quantity < ActiveRecord::Base
   has_and_belongs_to_many :column_views
   has_many :readouts
 
+  has_one :formula, inverse_of: :quantity, dependent: :destroy, validate: true
+  accepts_nested_attributes_for :formula, allow_destroy: true, reject_if: proc { |attrs|
+    attrs['code'].blank?
+  }
+
   validates :name, presence: true, uniqueness: {scope: :project_id}
   validates :domain, inclusion: {in: domains.keys}
   validate if: -> { parent.present? } do
     errors.add(:parent, :parent_domain_mismatch) unless domain == parent.domain
   end
-  validates :formula, formula: {allow_nil: true}
 
   after_initialize do
     if new_record?
@@ -31,8 +33,6 @@ class Quantity < ActiveRecord::Base
     end
   end
 
-  delegate :valid?, :quantities, :calculate, to: :f_obj, prefix: :formula, allow_nil: true
-
   def movable?(direction)
     case direction
     when :up
@@ -58,10 +58,4 @@ class Quantity < ActiveRecord::Base
 
     quantities
   end
-
-  private
-
-  def f_obj
-    Formula.new(self.project, self.formula) if self.formula?
-  end
 end