module Mm2ep
  module Depend
    class TreeExpr
      def compute
        raise NotImplementedError
      end
    end

    class TreeValue
      def value
        raise "No value for #{@name}" if @value.nil?
        @value
      end

      def to_s
        raise NotImplementedError
      end
    end

    class VarValue < TreeValue
      def initialize str
        @name = str
        @value = nil
      end

      def to_s
        "var:#{@name}<-(#{@value})"
      end
    end

    class NumberValue < TreeValue
      def initialize str
        @value = str.to_i
      end

      def to_s
        "number:#{@value}"
      end
    end

    class StringValue < TreeValue
      def initialize str
        @value = str
      end

      def to_s
        "string:\"#{@value}\""
      end
    end

    class BoolValue < TreeValue
      def initialize str
        @value = case str
                 when /true/i then true
                 when /false/i then false
                 end

      end

      def to_s
        "bool:#{@value}"
      end
    end

    class AndOp < TreeExpr
      def initialize expr1, expr2
          @expr1 = expr1
          @expr2 = expr2
      end

      def compute
        # binding.pry
        return @expr1.compute && @expr2.compute
      end

      def to_s
        "( #{@expr1.to_s} ) AND ( #{@expr2.to_s} )"
      end
    end

    class OrOp
      def initialize expr1, expr2
          @expr1 = expr1
          @expr2 = expr2
      end

      def compute
        return @expr1.compute || @expr2.compute
      end

      def to_s
        "( #{@expr1.to_s} ) OR ( #{@expr2.to_s} )"
      end
    end

    class NotOp
      def initialize expr
        @expr = expr
      end

      def compute
        return ! @expr.compute
      end

      def to_s
        "NOT ( #{@expr.to_s} )"
      end
    end

    class EqOp
      def initialize lval, rval
        @lval = lval
        @rval = rval
      end

      def compute
        return if @lval.value == @rval.value
      end

      def to_s
        "#{@lval.to_s} = #{@rval.to_s}"
      end
    end

    class Parser < Rly::Yacc

      precedence :left, 'OR_OP'
      precedence :left, 'AND_OP'
      precedence :left, 'EQ_OP'
      precedence :left, 'L_PAR', 'R_PAR'
      precedence :right, :UMINUS

      rule 'statement : expr' do |st, e|
        st.value = e.value
      end

      rule 'expr : VAR' do |ex, l|
        ex.value = EqOp.new(
          VarExpr.new(l.value),
          BoolValue.new('true')
        )
      end

      rule 'expr : T_BOOL' do |ex, l|
        ex.value = BoolValue.new(l.value.to_s)
      end

      rule 'expr : F_BOOL' do |ex, l|
        ex.value = BoolValue.new(l.value.to_s)
      end

      rule 'expr : NOT_OP expr %prec UMINUS' do |ex, l, e|
        ex.value = NotOp.new(e.value)
      end

      rule 'expr : expr AND_OP expr' do |ex, l, e, r|
        ex.value = AndOp.new(l.value, r.value)
      end

      rule 'expr : expr OR_OP expr' do |ex, l, e, r|
        ex.value = OrOp.new(l.value, r.value)
      end
      rule 'expr : L_PAR expr R_PAR' do |ex, l, e, r|
        ex.value = e.value
      end

      rule 'expr : VAR EQ_OP F_BOOL' do |ex, v, eq, n|
        ex.value = EqOp.new(
          VarValue.new(v.value.to_s),
          BoolValue.new(n.value)
        )
      end

      rule 'expr : VAR EQ_OP T_BOOL' do |ex, v, eq, n|
        ex.value = EqOp.new(
          VarValue.new(v.value.to_s),
          BoolValue.new(n.value)
        )
      end

      rule 'expr : VAR EQ_OP STRING' do |ex, v, eq, n|
        ex.value = EqOp.new(
          VarValue.new(v.value.to_s),
          StringValue.new(n.value)
        )
      end

      rule 'expr : VAR EQ_OP NUMBER' do |ex, v, eq, n|
        ex.value = EqOp.new(
          VarValue.new(v.value.to_s),
          NumberValue.new(n.value)
        )
      end

    end # class
  end # module
end # module