require 'set'
require 'sass/script/string'
require 'sass/script/number'
require 'sass/script/color'
require 'sass/script/functions'
require 'sass/script/unary_operation'

module Sass::Script
  # A SassScript parse node representing a binary operation,
  # such as `!a + !b` or `"foo" + 1`.
  class Operation < Node
    # @param operand1 [Script::Node] The parse-tree node
    #   for the right-hand side of the operator
    # @param operand2 [Script::Node] The parse-tree node
    #   for the left-hand side of the operator
    # @param operator [Symbol] The operator to perform.
    #   This should be one of the binary operator names in {Lexer::OPERATORS}
    def initialize(operand1, operand2, operator)
      @operand1 = operand1
      @operand2 = operand2
      @operator = operator
    end

    # @return [String] A human-readable s-expression representation of the operation
    def inspect
      "(#{@operator.inspect} #{@operand1.inspect} #{@operand2.inspect})"
    end

    # Evaluates the operation.
    #
    # @param environment [Sass::Environment] The environment in which to evaluate the SassScript
    # @return [Literal] The SassScript object that is the value of the operation
    # @raise [Sass::SyntaxError] if the operation is undefined for the operands
    def perform(environment)
      literal1 = @operand1.perform(environment)
      literal2 = @operand2.perform(environment)
      begin
        res = literal1.send(@operator, literal2)
        res.options = environment.options
        res
      rescue NoMethodError => e
        raise e unless e.name.to_s == @operator.to_s
        raise Sass::SyntaxError.new("Undefined operation: \"#{literal1} #{@operator} #{literal2}\".")
      end
    end

    # Returns the operands for this operation.
    #
    # @return [Array<Node>]
    # @see Node#children
    def children
      [@operand1, @operand2]
    end
  end
end