require 'psych/handler'
module Psych
###
# This class works in conjunction with Psych::Parser to build an in-memory
# parse tree that represents a YAML document.
#
# == Example
#
# parser = Psych::Parser.new Psych::TreeBuilder.new
# parser.parse('--- foo')
# tree = parser.handler.root
#
# See Psych::Handler for documentation on the event methods used in this
# class.
class TreeBuilder < Psych::Handler
# Returns the root node for the built tree
attr_reader :root
# Create a new TreeBuilder instance
def initialize
@stack = []
@last = nil
@root = nil
end
%w{
Sequence
Mapping
}.each do |node|
class_eval %{
def start_#{node.downcase}(anchor, tag, implicit, style)
n = Nodes::#{node}.new(anchor, tag, implicit, style)
@last.children << n
push n
end
def end_#{node.downcase}
pop
end
}
end
###
# Handles start_document events with +version+, +tag_directives+,
# and +implicit+ styling.
#
# See Psych::Handler#start_document
def start_document version, tag_directives, implicit
n = Nodes::Document.new version, tag_directives, implicit
@last.children << n
push n
end
###
# Handles end_document events with +version+, +tag_directives+,
# and +implicit+ styling.
#
# See Psych::Handler#start_document
def end_document implicit_end = !streaming?
@last.implicit_end = implicit_end
pop
end
def start_stream encoding
@root = Nodes::Stream.new(encoding)
push @root
end
def end_stream
pop
end
def scalar value, anchor, tag, plain, quoted, style
s = Nodes::Scalar.new(value,anchor,tag,plain,quoted,style)
@last.children << s
s
end
def alias anchor
@last.children << Nodes::Alias.new(anchor)
end
private
def push value
@stack.push value
@last = value
end
def pop
x = @stack.pop
@last = @stack.last
x
end
end
end