whoward/cadenza

# frozen_string_literal: true

module Cadenza
  # The {VariableNode} holds a variable name (identifier) which it can render
  # the value of given a {Context} with the name defined in it's variable stack.
  class VariableNode
    include TreeNode

    # @return [String] the name given to this variable
    attr_accessor :identifier

    # @return [Array] a list of Node objects passed to the {#value} for use in a
    #         function variable.  See {Context#define_function}.
    attr_accessor :parameters

    # creates a new {VariableNode} with the name given.
    # @param [String] identifier see {#identifier}
    # @param [Array] parameters see {#parameters}
    def initialize(identifier, parameters = [])
      @identifier = identifier
      @parameters = parameters
    end

    # @param [Context] context
    # @return [Object] looks up and returns the value of this variable in the
    #                  given {Context}
    def eval(context)
      value = context.lookup(@identifier)

      if value.is_a? Proc
        args = parameters.map { |p| p.eval(context) }
        value = value.call(context, *args)
      end

      value
    end

    # @param [VariableNode] other
    # @return [Boolean] if the given {VariableNode} is equivalent by value to
    #                   this node.
    def ==(other)
      identifier == other.identifier && parameters == other.parameters
    end
  end
end