#
#       ActiveFacts CQL Parser.
#       Parse rules relating to ValueType definitions.
#
# Copyright (c) 2009 Clifford Heath. Read the LICENSE file.
#
module ActiveFacts
  module CQL
    grammar ValueTypes
      rule value_type
        s each?
        s term_definition_name
        m1:mapping_pragmas
        # REVISIT: ORM2 would allow (subtype_prefix term)?
        written_as
        any? s
        base:(term/implicit_value_type_name) s
        value_type_parameters
        u:in_units?
        a:auto_assignment?
        c:context_note?
        r:(value_constraint enforcement)?
        m2:mapping_pragmas
        c2:context_note?
        s ';' s
        {
          def ast
            name = term_definition_name.value
            params = value_type_parameters.values
            value_constraint = nil
            unless r.empty? 
              value_constraint = Compiler::ValueConstraint.new(r.value_constraint.ast, r.enforcement.ast)
            end
            units = u.empty? ? [] : u.units.value
            auto_assigned_at = a.empty? ? nil : a.auto_assigned_at
            pragmas = m1.value+m2.value
            context_note = !c.empty? ? c.ast : (!c2.empty? ? c2.ast : nil)
            Compiler::ValueType.new name, base.value, params, units, value_constraint, pragmas, context_note, auto_assigned_at
          end
        }
      end

      rule in_units
        in S units
      end

      # A ValueType name that might not yet have been identified or registered as a Term
      # REVISIT: We'd like to support multi-word terms here (cannot include "where", "and", or anything that could follow in the value_type definition)
      # REVISIT: We'd like these to be forward-referenced ObjectTypes too, not immediately created as ValueTypes
      rule implicit_value_type_name
        id
        {
          def node_type; :term; end
        }
      end

      rule value_type_parameters
        '(' s tpl:type_parameter_list? ')' s
          { def values; tpl.empty? ? [] : tpl.values; end }
        / s
          { def values; []; end }
      end

      rule type_parameter_list
        head:number s tail:( ',' s number s )*
        {
          def values
            [head.value, *tail.elements.map{|i| i.number.value}]
          end
        }
      end

      rule unit_definition
        u:(
          s coeff:unit_coefficient? base:units? s o:unit_offset?
          conversion
          singular:unit_name s plural:('/' s p:unit_name s)?
        /
          s singular:unit_name s plural:('/' s p:unit_name s)?
          conversion
          coeff:unit_coefficient? base:units? s o:unit_offset?
        )
        q:(approximately '' / ephemera s url )? s
        ';'
        {
          def ast
            singular = u.singular.text_value
            plural = u.plural.text_value.empty? ? nil : u.plural.p.text_value 
            if u.coeff.empty?
              raise "Unit definition requires either a coefficient or an ephemera URL" unless q.respond_to?(:ephemera)
              numerator,denominator = 1, 1
            else
              numerator, denominator = *u.coeff.ast
            end
            offset = u.o.text_value.empty? ? 0 : u.o.value
            bases = u.base.empty? ? [] : u.base.value
            approximately = q.respond_to?(:approximately) || u.conversion.approximate?
            ephemera = q.respond_to?(:ephemera) ? q.url.text_value : nil
            Compiler::Unit.new singular, plural, numerator, denominator, offset, bases, approximately, ephemera
          end
        }
      end

      rule unit_name
        id
        {
          def node_type; :unit; end
        }
      end


      rule unit_coefficient
        numerator:number denominator:(s '/' s number)? s
        {
          def ast
            [ numerator.text_value,
              (denominator.text_value.empty? ? "1" : denominator.number.text_value)
            ]
          end
        }
      end

      rule unit_offset
        sign:[-+] s number s
        { def value
            sign.text_value == '-' ? "-"+number.text_value : number.text_value
          end
        }
      end

      # In a unit definition, we may use undefined base units; this is the only way to get fundamental units
      rule units
        !non_unit maybe_unit s tail:(!non_unit maybe_unit s)* div:('/' s maybe_unit s tail:(!non_unit maybe_unit s)*)?
        { def value
            tail.elements.inject([maybe_unit.value]) { |a, e| a << e.maybe_unit.value } +
              (div.text_value.empty? ? [] : div.tail.elements.inject([div.maybe_unit.inverse]) { |a, e| a << e.maybe_unit.inverse })
          end
        }
      end

      rule non_unit
        restricted_to / conversion / approximately / ephemera / auto_assignment
      end

      rule unit
        maybe_unit &{|s| input.context.unit?(s[0].unit_name.text_value) }
      end

      rule maybe_unit
        unit_name pow:('^' '-'? [0-9])?
        { def value
            [unit_name.text_value, pow.text_value.empty? ? 1 : Integer(pow.text_value[1..-1])]
          end
          def inverse
            a = value
            a[1] = -a[1]
            a
          end
        }
      end

      rule value_constraint
        restricted_to restricted_values c:context_note?
        {
          def ast
            v = restricted_values.values
            c[:context_note] = c.ast unless c.empty?
            v
          end
        }
        # REVISIT: "where the possible value/s of that <Term> is/are value (, ...)"
      end

      rule restricted_values
        range_list s u:units?
        {
          def values
            { :ranges => range_list.ranges,
              :units => u.empty? ? nil : u.value
            }
          end
        }
        /
        regular_expression
        {
          def values
            { :regular_expression => contents }
          end
        }
      end

      rule range_list
        '{' s
          head:range s tail:( ',' s range )*
        '}' s
        {
          def ranges
            [head.value, *tail.elements.map{|e| e.range.value }]
          end
        }
      end

    end
  end
end