module AmbitiousSeeder
  class Railtie < Rails::Railtie
    rake_tasks do
      load 'tasks/ambitious_seeder.rake'
    end
  end

  class NoSeedUpError < Exception
  end

  class NoSeedDownError < Exception
  end
  
  module Seeder
    def self.up(seeds)
      self.initialize_schema_seeds_table
            
      if seeds.kind_of?(Array)
        seeds.each { |seed| self.up(seed) }
        return
      end

      seed = seeds

      return if seed_already_up?(seed)

      begin
        seed.send(:up)
      rescue AmbitiousSeeder::NoSeedUpError
        abort "No upwards method for #{seed}!"
      end

      record_seed(seed)
    end
    
    def self.down(seed)
      self.initialize_schema_seeds_table

      return unless seed_already_up?(seed)

      begin
        seed.send(:down)
      rescue AmbitiousSeeder::NoSeedDownError
        abort "No downwards method for #{seed}!"
      end

      expunge_seed(seed)
    end
    
    private
    def self.db
      @db ||= setup_db
    end
    
    def self.setup_db
      ActiveRecord::Base.configurations = Rails.application.config.database_configuration
      ActiveRecord::Base.establish_connection(ActiveRecord::Base.configurations[Rails.env])
      ActiveRecord::Base.connection      
    end
    
    def self.seeds_table_name
      'schema_seeds'      
    end
    
    def self.seeds_table
      Arel::Table.new(seeds_table_name)
    end
    
    def self.initialize_schema_seeds_table
      seeds_table = seeds_table_name
      unless db.table_exists?(seeds_table)
        db.create_table(seeds_table, :id => false) do |table|
          table.column :seed, :string, :null => false
        end
      end
    end
    
    def self.seed_already_up?(seed)
      self.completed_seeds.include? seed.seed_name
    end

    def self.record_seed(seed)
      seeds_table.insert seeds_table["seed"] => seed.seed_name
    end
    
    def self.expunge_seed(seed)
      seeds_table.where(seeds_table["seed"].eq(seed.seed_name)).delete
    end
    
    def self.completed_seeds
      db.select_values(seeds_table.project(seeds_table['seed']).to_sql)
    end   
  end
  
  class Seed
    def self.seed_name
      self.to_s.gsub(/seed$/i, '').underscore
    end
    
    def self.up
      raise AmbitiousSeeder::NoSeedUpError
    end
    
    def self.down
      raise AmbitiousSeeder::NoSeedDownError
    end    
  end  
end