module Picnic
  # Provides an interface for accessing your Picnic app's configuration file.
  #
  # Usage example:
  #
  #   # Load the configuration from /etc/foo/config.yml
  #   Conf.load('foo')
  #
  #   # The contents of config.yml is now available as follows:
  #   puts Conf[:server]
  #   puts Conf[:authentication][:username]
  #   # ... etc.
  class Conf
    $CONF ||= HashWithIndifferentAccess.new
    $CONF[:log] ||= HashWithIndifferentAccess.new
    $CONF[:log][:file]  ||= STDOUT
    $CONF[:log][:level] ||= 'DEBUG'
    $CONF[:uri_path]    ||= "/"
    
    # Read a configuration option.
    #
    # For example:
    #   puts Conf[:server]
    def self.[](key)
      $CONF[key]
    end
    
    # Another way of reading a configuration option.
    #
    # The following statements are equivalent:
    #   puts Conf[:server]
    #   puts Conf.server
    def self.method_missing(method, *args)
      self[method]
    end
    
    # Returns the path to your application's example config file.
    #
    # The example config file should be in the root directory of
    # your application's distribution package and should be called
    # <tt>config.example.yml</tt>. This file is used as a template
    # for your app's configuration, to be customized by the end
    # user. 
    def self.example_config_file_path
      if $APP_PATH
        app_path = File.expand_path($APP_PATH)
      else
        caller.last =~ /^(.*?):\d+$/
        app_path = File.dirname(File.expand_path($1))
      end
      app_path+'/../config.example.yml'
    end
    
    # Copies the example config file into the appropriate
    # configuration directory.
    #
    # +app+:: The name of your application. For example: <tt>foo</tt>
    # +dest_conf_file:: The path where the example conf file should be copied to.
    #                   For example: <tt>/etc/foo/config.yml</tt>
    def self.copy_example_config_file(app, dest_conf_file)
      require 'fileutils'
          
      example_conf_file = example_config_file_path
      
      puts "\n#{app.to_s.upcase} SERVER HAS NOT YET BEEN CONFIGURED!!!\n"
      puts "\nAttempting to copy sample configuration from '#{example_conf_file}' to '#{dest_conf_file}'...\n"
      
      unless File.exists? example_conf_file 
        puts "\nThe example conf file does not exist! The author of #{app} may have forgotten to include it. You'll have to create the config file manually.\n"
        exit 2
      end
      
      begin
        dest_conf_file_dir = File.dirname(dest_conf_file)
        FileUtils.mkpath(dest_conf_file_dir) unless File.exists? dest_conf_file_dir
        FileUtils.cp(example_conf_file, dest_conf_file)
      rescue Errno::EACCES
        puts "\nIt appears that you do not have permissions to create the '#{dest_conf_file}' file. Try running this command using sudo (as root).\n"
        exit 2
      rescue => e
        puts "\nFor some reason the '#{dest_conf_file}' file could not be created (#{e})."
        puts "You'll have to copy the file manually. Use '#{example_conf_file}' as a template.\n"  
        exit 2
      end
      
      puts "\nA sample configuration has been created for you in '#{dest_conf_file}'. Please edit this file to" +
        " suit your needs and then run #{app} again.\n"
      exit 1
    end
    
    # Loads the configuration from the yaml file for the given app.
    #
    # <tt>app</tt> should be the name of your app; for example: <tt>foo</tt>.
    #
    # By default, the configuration will be loaded from <tt>/etc/<app>/config.yml</tt>.
    # You can override this by setting a global <tt>$CONFIG_FILE</tt> variable.
    def self.load(app)
      
      conf_file = $CONFIG_FILE || "/etc/#{app.to_s.downcase}/config.yml"
      
      puts "Loading configuration for #{app} from '#{conf_file}'..."
      
      begin
        conf_file = etc_conf = conf_file
        unless File.exists? conf_file 
          # can use local config.yml file in case we're running non-gem installation
          conf_file = File.dirname(File.expand_path(__FILE__))+"/../../config.yml"
        end
      
        unless File.exists? conf_file  
          copy_example_config_file(app, etc_conf)
        end
        
        loaded_conf = HashWithIndifferentAccess.new(YAML.load_file(conf_file))
        
        if $CONF
          $CONF = HashWithIndifferentAccess.new($CONF)
          $CONF = $CONF.merge(loaded_conf)
        else
          $CONF = loaded_conf
        end
        
        $CONF[:log][:file] = STDOUT unless $CONF[:log][:file]
        
      rescue
          raise "Your #{app} configuration may be invalid."+
            " Please double-check check your config.yml file."+
            " Make sure that you are using spaces instead of tabs for your indentation!!" +
            "\n\nTHE UNDERLYING ERROR WAS:\n#{$!}"
      end
    end
  end
end