Tasks display

app/models/project.rb

@@ -2,17 +2,41 @@
 
 class Project < ApplicationRecord
   validates :name, :code, presence: true
-  validates :code, exclusion: { in: %w[new] }, uniqueness: true
+  validates :code, exclusion: { in: %w[new] }, uniqueness: true, format: { with: /\A[a-z]{2,}\z/ }
 
   has_many :tasks, dependent: :restrict_with_exception
 
   has_rich_text :description
 
-  normalizes :code, with: ->(code) { code.strip.downcase }
+  normalizes :code, with: ->(code) { code.strip.downcase.gsub(/\W+/, '') }
+
+  after_commit :create_tasks_number_sequence, on: :create
+  after_destroy_commit :drop_tasks_number_sequence
 
   def to_param
     return unless id
 
     code
   end
+
+  def tasks_number_sequence_name
+    "_seq_projects__#{code}_tasks_number"
+  end
+
+  def next_task_number
+    result = self.class.connection.exec_query "SELECT NEXT VALUE FOR #{tasks_number_sequence_name} AS task_number"
+    raise "Expected one result, got #{result.count}" unless result.one?
+
+    result.first['task_number']
+  end
+
+  private
+
+  def create_tasks_number_sequence
+    self.class.connection.execute "CREATE SEQUENCE IF NOT EXISTS #{tasks_number_sequence_name} AS INT UNSIGNED"
+  end
+
+  def drop_tasks_number_sequence
+    self.class.connection.execute "DROP SEQUENCE IF EXISTS #{tasks_number_sequence_name}"
+  end
 end