# Used in the pipeline:commit:configure:database Rake task to transform a YAML
# file containing common elements from an ActiveRecord database.yml
# configuration into a YAML file containing a section for each specified
# database environment. It names the databases according to the environment as
# well as a client ID. The client ID ensures that multiple build agents can run
# tests at the same time even when using a central DB server.
#
# Example call:
#   template = ProjectdxPipeline::DatabaseConfigurationTemplate.new('config/database.pipeline.yml')
#   template.render_to_file('config/database.yml')
#
# Example template YAML file:
#   ---
#   adapter: postgresql
#   username: postgres_user
#   password: blahblahblah
#   host: db.example.com
#   encoding: UTF8
#   min_messages: warning
#   database_prefix: an_awesome_app
#   pool: 5
#   environments:
#     - development
#     - test
#
class ProjectdxPipeline::DatabaseConfigurationTemplate
  # the common database config data shared by all environments
  attr_accessor :config_data

  # an array containing the names of each database environment to be configured
  attr_accessor :environments

  # a string that will prefix the name of each database
  attr_accessor :database_prefix

  # a string that will suffix the name of each database, defaults to the
  # hostname of the machine on which this code is running, but will remove the
  # "rf-pdx-" prefix and the "(.dyn).renewfund.com" suffix, and it will truncate
  # the result to be no longer than 63 characters due to PostgreSQL's limitation
  # on the lenght of database names.
  attr_accessor :client_id

  # Instantiates a new configuration template. If a +template_file+ is
  # specified, it will be loaded as a YAML file and used to read in the
  # configuration data for the template.
  def initialize(template_file = nil)
    @config_data = {}
    if template_file
      @config_data = self.class.read_template(template_file)
      @client_id = @config_data.delete('client_id')
      @database_prefix = @config_data.delete('database_prefix')
      @environments = @config_data.delete('environments')
    end
  end

  # returns a Hash containing the ActiveRecord configuration data for all
  # environments
  def configuration
    environments.inject({}) do |config, env_name|
      config[env_name] = @config_data.dup
      config[env_name]['database'] = database_name(env_name)
      config
    end
  end

  # Writes the ActiveRecord configuration data (i.e. config/database.yml) to the
  # specified file path
  def render_to_file(path)
    File.open(path, 'w') do |f|
      YAML.dump(configuration, f)
    end
  end

  def database_name(environment) #:nodoc:
    "#{database_prefix}-#{environment}-#{client_id}"
  end

  def client_id #:nodoc:
    @client_id ||= begin
                     client_id = Socket.gethostname.gsub(/\W/, '_')
                     client_id.sub!(/^rf_pdx_/, '')
                     client_id.sub!(/(_dyn)?_renewfund_com$/, '')
                     client_id.slice(0..62)
                   end
  end

  def self.read_template(template_file) #:nodoc:
    YAML.load_file(template_file)
  end
end