# Copyright (C) 2011 RightScale, Inc, All Rights Reserved Worldwide.
#
# THIS PROGRAM IS CONFIDENTIAL AND PROPRIETARY TO RIGHTSCALE
# AND CONSTITUTES A VALUABLE TRADE SECRET. Any unauthorized use,
# reproduction, modification, or disclosure of this program is
# strictly prohibited. Any use of this program by an authorized
# licensee is strictly subject to the terms and conditions,
# including confidentiality obligations, set forth in the applicable
# License Agreement between RightScale.com, Inc. and
# the licensee

module RightConf

  # DSL implementation
  class Language

    # List of configurators resulting from parsing a configuration
    attr_reader :configurators

    # Errors generated by configurators validations if any
    attr_reader :validation_errors

    # Load given file and run content to retrieve configurators
    #
    # === Parameters
    # file(String):: Path to file being loaded
    #
    # === Result
    # lang(Language):: Instance initialized from file
    def self.load(file)
      begin
        content = IO.read(file)
      rescue Exception => e
        raise "Failed to load '#{file}': #{e.message}"
      end
      parse(content)
    end

    # Parse given configuration text
    #
    # === Parameters
    # content(String):: Content to be parsed
    #
    # === Result
    # lang(Language):: Instance initialized from content
    def self.parse(content)
      lang = new
      lang.instance_eval(content)
      lang
    end

    protected

    # Initialize configurators and validation errors lists
    # Do not call directly, instead call 'load'
    def initialize
      @configurators = Array.new
      @validation_errors = Array.new
    end

    # Each missing method should correspond to a configurator section.
    # Such sections consist of a block which gets eval'ed in the contect of the
    # corresponding configurator instance.
    #
    # === Parameters
    # meth(Symbol):: Method symbol, should be a configurator
    # args(Array):: List of arguments
    # blk(Proc):: Block to be evaled in configurator context
    #
    # === Return
    # true:: Always return true
    def method_missing(meth, *args, &blk)
      if blk 
        klass = ConfiguratorRegistry[meth]
        if klass
          configurator = klass.new(*args)
          configurator.instance_eval(&blk)
          error = configurator.validate
          @validation_errors << error if error
          @configurators << configurator
        else
          @validation_errors << "Unknown configurator '#{meth}'"
        end
      else
        @validation_errors << "Invalid syntax, expecting block after '#{meth}'"
      end
      true
    end

  end
end