Add Budget::Phase model, spec and factory

Create a new Budget::Phase model that:
* Stablishes a relation with its budget
* Stablishes relation with two other Budget::Phases (previous and next)
* Validates basic dates range, kind and description rules.
* Adds scopes to get the ones enabled as well as each individual phase

Create a factory that generates a basic and valid Budget::Phase

Create a model spec that checks kind, date range and budget validations.

app/models/budget/phase.rb

@@ -0,0 +1,31 @@
+class Budget
+  class Phase < ActiveRecord::Base
+
+    belongs_to :budget
+    belongs_to :next_phase, class_name: 'Budget::Phase', foreign_key: :next_phase_id
+    has_one :prev_phase, class_name: 'Budget::Phase', foreign_key: :next_phase_id
+
+    validates :budget, presence: true
+    validates :kind, presence: true, uniqueness: { scope: :budget }, inclusion: { in: Budget::PHASES }
+    validates :description, length: { maximum: Budget.description_max_length }
+    validate :dates_range_valid?
+
+    scope :enabled,           -> { where(enabled: true) }
+    scope :drafting,          -> { find_by_kind('drafting') }
+    scope :accepting,         -> { find_by_kind('accepting')}
+    scope :reviewing,         -> { find_by_kind('reviewing')}
+    scope :selecting,         -> { find_by_kind('selecting')}
+    scope :valuating,         -> { find_by_kind('valuating')}
+    scope :publishing_prices, -> { find_by_kind('publishing_prices')}
+    scope :balloting,         -> { find_by_kind('balloting')}
+    scope :reviewing_ballots, -> { find_by_kind('reviewing_ballots')}
+    scope :finished,          -> { find_by_kind('finished')}
+
+    def dates_range_valid?
+      if starts_at.present? && ends_at.present? && starts_at >= ends_at
+        errors.add(:starts_at, I18n.t('budgets.phases.errors.dates_range_invalid'))
+      end
+    end
+
+  end
+end

config/locales/en/budgets.yml

@@ -158,3 +158,6 @@ en:
       accepted: "Accepted spending proposal: "
       discarded: "Discarded spending proposal: "
       incompatibles: Incompatibles
+    phases:
+      errors:
+        dates_range_invalid: "Start date can't be equal or later than End date"

config/locales/es/budgets.yml

@@ -158,3 +158,6 @@ es:
       accepted: 'Propuesta de inversión aceptada: '
       discarded: 'Propuesta de inversión descartada: '
       incompatibles: Incompatibles
+    phases:
+      errors:
+        dates_range_invalid: "La fecha de comienzo no puede ser igual o superior a la de finalización"

spec/factories.rb

@@ -341,7 +341,16 @@ FactoryBot.define do
       feasibility "feasible"
       valuation_finished true
     end
+  end
 
+  factory :budget_phase, class: 'Budget::Phase' do
+    budget
+    kind        :balloting
+    summary     Faker::Lorem.sentence(3)
+    description Faker::Lorem.sentence(10)
+    starts_at   Date.yesterday
+    ends_at     Date.tomorrow
+    enabled     true
   end
 
   factory :image do

spec/models/budget/phase_spec.rb

@@ -0,0 +1,44 @@
+require 'rails_helper'
+
+describe Budget::Phase do
+
+  let(:budget) { create(:budget) }
+
+  describe "validates" do
+    it "is not valid without a budget" do
+      expect(build(:budget_phase, budget: nil)).not_to be_valid
+    end
+
+    describe "kind validations" do
+      it "is not valid without a kind" do
+        expect(build(:budget_phase, kind: nil)).not_to be_valid
+      end
+
+      it "is not valid with a kind not in valid budget phases" do
+        expect(build(:budget_phase, kind: 'invalid_phase_kind')).not_to be_valid
+      end
+
+      it "is not valid with the same kind as another budget's phase" do
+        create(:budget_phase, budget: budget)
+
+        expect(build(:budget_phase, budget: budget)).not_to be_valid
+      end
+    end
+
+    describe "#dates_range_valid?" do
+      it "is valid when start & end dates are different & consecutive" do
+        expect(build(:budget_phase, starts_at: Date.today, ends_at: Date.tomorrow)).to be_valid
+      end
+
+      it "is not valid when dates are equal" do
+        expect(build(:budget_phase, starts_at: Date.today, ends_at: Date.today)).not_to be_valid
+      end
+
+      it "is not valid when start date is later than end date" do
+        expect(build(:budget_phase, starts_at: Date.tomorrow, ends_at: Date.today)).not_to be_valid
+      end
+    end
+
+  end
+
+end