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require "forwardable"
module OpenGraphReader
class Parser
# A Graph to represent OpenGraph tags.
class Graph
# A node in the graph.
Node = Struct.new(:name, :content) do
extend Forwardable
include Enumerable
# The parent node.
#
# @return [Node, nil]
attr_accessor :parent
# @!method empty?
# Does this node have any children?
#
# @return [Bool]
def_delegators :children, :empty?
# Children of this node.
def children
@children ||= []
end
# Iterate over all children.
#
# @yield [Node]
def each(&block)
children.each do |child|
yield child
child.each(&block)
end
end
# Add children.
#
# @param [Node] node
def << node
node.parent = self
children << node
end
# Get node's namespace.
#
# @return [String]
def namespace
parent.fullname if parent
end
# Get node's namespace as array.
#
# @return [Array<String>]
def path
@path ||= fullname.split(":")
end
# Get node's full name.
#
# @return [String]
def fullname
@fullname ||= [namespace, name].compact.join(":")
@fullname unless @fullname.empty?
end
end
extend Forwardable
include Enumerable
# The initial node.
#
# @return [Node, nil]
attr_reader :root
# @!method empty?
# Does this graph have any nodes?
#
# @return [Bool]
def_delegators :root, :empty?
# Create new graph.
def initialize
@root = Node.new
end
# Iterate through all nodes that have a value.
#
# @yield [Node]
def each
root.each do |child|
yield child if child.content
end
end
# Fetch first node's value.
#
# @param [String] property The fully qualified name, for example <tt>og:type</tt>.
# @param [String] default The default in case the a value is not found.
# @yield Return a default in case the value is not found. Supersedes the default parameter.
# @return [String, Bool, Integer, Float, DateTime, nil]
def fetch property, default=nil
node = find_by(property)
return yield if node.nil? && block_given?
return default if node.nil?
node.content
end
# Fetch first node
#
# @param [String] property The fully qualified name, for example <tt>og:type</tt>.
# @return [Node, nil]
def find_by property
property = normalize_property property
find {|node| node.fullname == property }
end
# Fetch all nodes
#
# @param [String] property The fully qualified name, for example <tt>og:type</tt>.
# @return [Array<Node>]
def select_by property
property = normalize_property property
select {|node| node.fullname == property }
end
def find_or_create_path path
path.inject(root) {|node, name|
child = node.children.reverse.find {|child| child.name == name }
unless child
child = Node.new name
node << child
end
child
}
end
private
def normalize_property property
property.is_a?(Enumerable) ? property.join(":") : property
end
end
end
end
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