# Context management

require 'fileutils'
#require 'ontomde-core/exceptions.rb'

#Internal use.
#
#Used for storing context.
class WarningHash < Hash

  #Returns context value associated to key.
  #Raises an error if key is not found.
  # Returns default, when context is undefined for key, and a default value is provided.
  #if value is missing, key is return when context[:contextReturnKeyIfEmpty] is true. (feature used by web inspector) 
  def [](key,default=Object.class)
    val=super(key)
    return val unless val.nil?
    #Note: Object.class is used as a magic number.
    return default unless default==Object.class
    return "#{key}" if context[:contextReturnKeyIfEmpty,false]
    raise Warning.new(), <<FINCODE
Evaluation interrompue:
La session ne contient pas la variable :#{key}.
L'exemple de code suivant permet de definir une variable de contexte:

  votre code
  mtk_context(:#{key}=>'valeur'){
     votre code
     puts context[:#{key}]
     votre code
     }
FINCODE
  end
  def get(key)
    return self[key] if self.include?(key)
    return nil
  end
end

module Mrdf_Model
  @@context=WarningHash.new()

  def context
    return @@context
  end

  # Similar to mtk_context but preserves already defined context.
  # Used to provide a default context.
  def mtk_default_context(*additional_context,&block)
    filtered_context=Array.new
    additional_context.each { |item| item.each { |k,v|
        next if @@context.include?(k)
        filtered_context << item
      }}
    mtk_context(*filtered_context,&block)
  end

  #Defines context variables for use in block passed as parameter.
  #Existing context variable are redefined. (cf. mtk_default_context )
  #When exiting block, previously defined context variables are restored.
  #
  #Example 1:
  #  mtk_context( :build => "build\", :option => true) {
  #     your-code
  #     puts context[:build]
  #     your-code
  #     puts context[:option]
  #     your-code
  #  }
  #
  #Example 2:
  #  mtk_context( :build => "BUILD_ONE\") {
  #       your-code
  #       puts context[:build] # BUILD_ONE
  #    mtk_context( :build => "NEW_DIR", :option => true) {
  #       your-code
  #       puts context[:build] # NEW_DIR\
  #       your-code
  #       puts context[:option]
  #       your-code
  #    }
  #    puts context[:build] # BUILD_ONE
  #  }
  def mtk_context(*additional_context,&block)
    context_save=@@context
    @@context=context_save.clone
    additional_context.each { |item| item.each { |k,v|
        @@context[k]=v
      }}
    yield
    @@context=context_save
    return nil
  end

end

module Mrdf_Resource

  # returns current context
  def context
    return @rdf_model.context
  end

  # cf: Mrdf_Model::mtk_context
  def mtk_context(*args,&block)
    return @rdf_model.mtk_context(*args,&block)
  end
  #
  # cf: Mrdf_Model::mtk_default_context
  def mtk_default_context(*args,&block)
    return @rdf_model.mtk_default_context(*args,&block)
  end

end