#
#       ActiveFacts CQL Parser.
#       Parse rules relating to high-level CQL definitions and constraints.
#
# Copyright (c) 2009 Clifford Heath. Read the LICENSE file.
#
module ActiveFacts
  module CQL
    grammar CQL
      include LexicalRules
      include Expressions
      include Terms
      include ObjectTypes
      include ValueTypes
      include FactTypes
      include Context

      rule cql_file
        s seq:definition*
        {
          def definitions
            seq.elements.map{|e|
                e.value rescue $stderr.puts "Can't call value() on #{e.inspect}"
              }
          end
        }
      end

      # Each definition has an ast() method that returns an instance of a subclass of Compiler::Definition
      rule definition
	definition_body s
	{
	  def ast
	    definition_body.ast
	  end

	  def body
	    definition_body.text_value
	  end
	}
      end

      rule definition_body
        vocabulary_definition
        / import_definition
        / prescan           # Always fails, but its side-effects are needed in the following
        / constraint
        / unit_definition   # REVISIT: Move this above the prescan?
        / object_type
	/ query
	/ s ';' s { def ast; nil; end }
      end

      rule vocabulary_definition
        s vocabulary S vocabulary_name s ';'
        {
	  def ast
	    Compiler::Vocabulary.new(vocabulary_name.value)
	  end
        }
      end

      rule vocabulary_name
	id
	{ def node_type; :vocabulary; end }
      end

      rule import_definition
        s import S vocabulary_name alias_list ';'
        {
	  def ast
	    Compiler::Import.new(import.input.parser, vocabulary_name.value, alias_list.value)
	  end
        }
      end

      # REVISIT: Need a way to define equivalent readings for fact types here (and in the metamodel)
      rule alias_list
        ( s ',' s alias S aliased_from:alias_term S as S alias_to:alias_term s )*
        {
          def value
            elements.inject({}){|h, e| h[e.aliased_from.value] = e.alias_to; h }
          end
        }
      end

      rule alias_term
	id
	{ def node_type; :term; end }
      end

      rule constraint
        subset_constraint /
        equality_constraint /
        set_constraint /
        presence_constraint
        # REVISIT: / value_constraint
      end

      rule enforcement
	s '(' s otherwise s action s a:agent? s ')' s
	  {
	    def ast; Compiler::Enforcement.new(action.text_value, a.empty? ? nil : a.text_value); end
	  }
	/
	''
	  {
	    def ast; nil; end
	  }
      end

      # An enforcement action, like SMS, email, log, alarm, etc.
      rule action
	id
      end

      # presence constraint:
      rule presence_constraint
	(each_occurs_in_clauses / either_or)
        {
	  def ast
	    Compiler::PresenceConstraint.new c, enforcement.ast, clauses_ast, role_list_ast, quantifier_ast
	  end
	}
      end

      # set (exclusion, mandatory exclusion, complex equality) constraint
      rule set_constraint
	(for_each_how_many / either_or_not_both)
          {
	    def ast
	      Compiler::SetExclusionConstraint.new c, enforcement.ast, clauses_ast, role_list_ast, quantifier_ast
	    end
	  }
      end

      rule subset_constraint
        (a_only_if_b / if_b_then_a)
        {
	  def ast
	    Compiler::SubsetConstraint.new c, enforcement.ast, [clauses.ast, r2.ast]
	  end
	}
      end

      rule equality_constraint
	if_and_only_if
        {
	  def ast
	    all_clauses = [clauses.ast, *tail.elements.map{|e| e.clauses.ast }]
	    Compiler::SetEqualityConstraint.new c, enforcement.ast, all_clauses
	  end
	}
      end

    end
  end
end