module Sass::Tree
  # A static node reprenting a CSS property.
  #
  # @see Sass::Tree
  class AttrNode < Node
    # The name of the property.
    #
    # @return [String]
    attr_accessor :name

    # The value of the property,
    # either a plain string or a SassScript parse tree.
    #
    # @return [String, Script::Node]
    attr_accessor :value

    # @param name [String] See \{#name}
    # @param value [String] See \{#value}
    # @param options [Hash<Symbol, Object>] An options hash;
    #   see [the Sass options documentation](../../Sass.html#sass_options)
    def initialize(name, value, options)
      @name = name
      @value = value
      super(options)
    end

    # Compares the names and values of two properties.
    #
    # @param other [Object] The object to compare with
    # @return [Boolean] Whether or not this node and the other object
    #   are the same
    def ==(other)
      self.class == other.class && name == other.name && value == other.value && super
    end

    # Computes the CSS for the Property.
    #
    # @param tabs [Fixnum] The level of indentation for the CSS
    # @param parent_name [String] The name of the parent property (e.g. `text`) or nil
    # @return [String] The resulting CSS
    def to_s(tabs, parent_name = nil)
      if value[-1] == ?;
        raise Sass::SyntaxError.new("Invalid attribute: #{declaration.dump} (This isn't CSS!).", @line)
      end
      real_name = name
      real_name = "#{parent_name}-#{real_name}" if parent_name
      
      if value.empty? && children.empty?
        raise Sass::SyntaxError.new("Invalid attribute: #{declaration.dump}.", @line)
      end
      
      join_string = case @style
                    when :compact; ' '
                    when :compressed; ''
                    else "\n"
                    end
      spaces = '  ' * (tabs - 1)
      to_return = ''
      if !value.empty?
        to_return << "#{spaces}#{real_name}:#{@style == :compressed ? '' : ' '}#{value};#{join_string}"
      end
      
      children.each do |kid|
        to_return << kid.to_s(tabs, real_name) << join_string
      end
      
      (@style == :compressed && parent_name) ? to_return : to_return[0...-1]
    end

    protected

    # Runs any SassScript that may be embedded in the property.
    #
    # @param environment [Sass::Environment] The lexical environment containing
    #   variable and mixin values
    def perform!(environment)
      @name = interpolate(@name, environment)
      @value = @value.is_a?(String) ? interpolate(@value, environment) : @value.perform(environment).to_s
      super
    end

    # Returns an error message if the given child node is invalid,
    # and false otherwise.
    #
    # {AttrNode} only allows other {AttrNode}s and {CommentNode}s as children.
    # @param child [Tree::Node] A potential child node
    # @return [String] An error message if the child is invalid, or nil otherwise
    def invalid_child?(child)
      if !child.is_a?(AttrNode) && !child.is_a?(CommentNode)
        "Illegal nesting: Only attributes may be nested beneath attributes."
      end
    end

    private

    def declaration
      ":#{name} #{value}"
    end
  end
end