require 'strscan'
module HTML
class Conditions < Hash
def initialize(hash)
super()
hash = { :content => hash } unless Hash === hash
hash = keys_to_symbols(hash)
hash.each do |k,v|
case k
when :tag, :content then
# keys are valid, and require no further processing
when :attributes then
hash[k] = keys_to_strings(v)
when :parent, :child, :ancestor, :descendant
hash[k] = Conditions.new(v)
when :children
hash[k] = v = keys_to_symbols(v)
v.each do |k,v2|
case k
when :count, :greater_than, :less_than
# keys are valid, and require no further processing
when :only
v[k] = Conditions.new(v2)
else
raise "illegal key #{k.inspect} => #{v2.inspect}"
end
end
else
raise "illegal key #{k.inspect} => #{v.inspect}"
end
end
update hash
end
private
def keys_to_strings(hash)
hash.keys.inject({}) do |h,k|
h[k.to_s] = hash[k]
h
end
end
def keys_to_symbols(hash)
hash.keys.inject({}) do |h,k|
raise "illegal key #{k.inspect}" unless k.respond_to?(:to_sym)
h[k.to_sym] = hash[k]
h
end
end
end
# The base class of all nodes, textual and otherwise, in an HTML document.
class Node
# The array of children of this node. Not all nodes have children.
attr_reader :children
# The parent node of this node. All nodes have a parent, except for the
# root node.
attr_reader :parent
# The line number of the input where this node was begun
attr_reader :line
# The byte position in the input where this node was begun
attr_reader :position
# Create a new node as a child of the given parent.
def initialize(parent, line=0, pos=0)
@parent = parent
@children = []
@line, @position = line, pos
end
# Return a textual representation of the node.
def to_s
s = ""
@children.each { |child| s << child.to_s }
s
end
# Return false (subclasses must override this to provide specific matching
# behavior.) +conditions+ may be of any type.
def match(conditions)
false
end
# Search the children of this node for the first node for which #find
# returns non +nil+. Returns the result of the #find call that succeeded.
def find(conditions)
@children.each do |child|
node = child.find(conditions)
return node if node
end
nil
end
# Search for all nodes that match the given conditions, and return them
# as an array.
def find_all(conditions)
matches = []
matches << self if match(conditions)
@children.each do |child|
matches.concat child.find_all(conditions)
end
matches
end
# Returns +false+. Subclasses may override this if they define a kind of
# tag.
def tag?
false
end
def validate_conditions(conditions)
Conditions === conditions ? conditions : Conditions.new(conditions)
end
class <<self
def parse(parent, line, pos, content)
if content !~ /^<\S/
Text.new(parent, line, pos, content)
else
scanner = StringScanner.new(content)
scanner.skip(/</) or raise "expected <"
closing = ( scanner.scan(/\//) ? :close : nil )
return Text.new(parent, line, pos, content) unless name = scanner.scan(/[\w:]+/)
name.downcase!
unless closing
scanner.skip(/\s*/)
attributes = {}
while attr = scanner.scan(/[-\w:]+/)
value = true
if scanner.scan(/\s*=\s*/)
if delim = scanner.scan(/['"]/)
value = ""
while text = scanner.scan(/[^#{delim}\\]+|./)
case text
when "\\" then
value << text
value << scanner.getch
when delim
break
else value << text
end
end
else
value = scanner.scan(/[^\s>\/]+/)
end
end
attributes[attr.downcase] = value
scanner.skip(/\s*/)
end
closing = ( scanner.scan(/\//) ? :self : nil )
end
scanner.scan(/\s*>/) or raise "expected > (got #{scanner.rest.inspect} for #{content}, #{attributes.inspect})"
Tag.new(parent, line, pos, name, attributes, closing)
end
end
end
end
# A node that represents text, rather than markup.
class Text < Node
attr_reader :content
# Creates a new text node as a child of the given parent, with the given
# content.
def initialize(parent, line, pos, content)
super(parent, line, pos)
@content = content
end
# Returns the content of this node.
def to_s
@content
end
# Returns +self+ if this node meets the given conditions. Text nodes support
# conditions of the following kinds:
#
# * if +conditions+ is a string, it must be a substring of the node's
# content
# * if +conditions+ is a regular expression, it must match the node's
# content
# * if +conditions+ is a hash, it must contain a <tt>:content</tt> key that
# is either a string or a regexp, and which is interpreted as described
# above.
def find(conditions)
match(conditions) && self
end
# Returns non-+nil+ if this node meets the given conditions, or +nil+
# otherwise. See the discussion of #find for the valid conditions.
def match(conditions)
case conditions
when String
@content.index(conditions)
when Regexp
@content =~ conditions
when Hash
conditions = validate_conditions(conditions)
# Text nodes only have :content, :parent, :ancestor
unless (conditions.keys - [:content, :parent, :ancestor]).empty?
return false
end
match(conditions[:content])
else
nil
end
end
end
# A Tag is any node that represents markup. It may be an opening tag, a
# closing tag, or a self-closing tag. It has a name, and may have a hash of
# attributes.
class Tag < Node
# Either +nil+, <tt>:close</tt>, or <tt>:self</tt>
attr_reader :closing
# Either +nil+, or a hash of attributes for this node.
attr_reader :attributes
# The name of this tag.
attr_reader :name
# Create a new node as a child of the given parent, using the given content
# to describe the node. It will be parsed and the node name, attributes and
# closing status extracted.
def initialize(parent, line, pos, name, attributes, closing)
super(parent, line, pos)
@name = name
@attributes = attributes
@closing = closing
end
# A convenience for obtaining an attribute of the node. Returns +nil+ if
# the node has no attributes.
def [](attr)
@attributes ? @attributes[attr] : nil
end
# Returns non-+nil+ if this tag can contain child nodes.
def childless?
@name =~ /^(img|br|hr|link|meta|area|base|basefont|col|frame|input|isindex|param)$/o
end
# Returns a textual representation of the node
def to_s
if @closing == :close
"</#{@name}>"
else
s = "<#{@name}"
@attributes.each { |k,v| s << " #{k}='#{v.gsub(/'/,"\\\\'")}'" }
s << " /" if @closing == :self
s << ">"
@children.each { |child| s << child.to_s }
s
end
end
# If either the node or any of its children meet the given conditions, the
# matching node is returned. Otherwise, +nil+ is returned. (See the
# description of the valid conditions in the +match+ method.)
def find(conditions)
match(conditions) && self || super
end
# Returns +true+, indicating that this node represents an HTML tag.
def tag?
true
end
# Returns +true+ if the node meets any of the given conditions. The
# +conditions+ parameter must be a hash of any of the following keys
# (all are optional):
#
# * <tt>:tag</tt>: the node name must match the corresponding value
# * <tt>:attributes</tt>: a hash. The node's values must match the
# corresponding values in the hash.
# * <tt>:parent</tt>: a hash. The node's parent must match the
# corresponding hash.
# * <tt>:child</tt>: a hash. At least one of the node's immediate children
# must meet the criteria described by the hash.
# * <tt>:ancestor</tt>: a hash. At least one of the node's ancestors must
# meet the criteria described by the hash.
# * <tt>:descendant</tt>: a hash. At least one of the node's descendants
# must meet the criteria described by the hash.
# * <tt>:children</tt>: a hash, for counting children of a node. Accepts the
# keys:
# ** <tt>:count</tt>: either a number or a range which must equal (or
# include) the number of children that match.
# ** <tt>:less_than</tt>: the number of matching children must be less than
# this number.
# ** <tt>:greater_than</tt>: the number of matching children must be
# greater than this number.
# ** <tt>:only</tt>: another hash consisting of the keys to use
# to match on the children, and only matching children will be
# counted.
#
# Conditions are matched using the following algorithm:
#
# * if the condition is a string, it must be a substring of the value.
# * if the condition is a regexp, it must match the value.
# * if the condition is a number, the value must match number.to_s.
# * if the condition is +true+, the value must not be +nil+.
# * if the condition is +false+ or +nil+, the value must be +nil+.
#
# Usage:
#
# # test if the node is a "span" tag
# node.match :tag => "span"
#
# # test if the node's parent is a "div"
# node.match :parent => { :tag => "div" }
#
# # test if any of the node's ancestors are "table" tags
# node.match :ancestor => { :tag => "table" }
#
# # test if any of the node's immediate children are "em" tags
# node.match :child => { :tag => "em" }
#
# # test if any of the node's descendants are "strong" tags
# node.match :descendant => { :tag => "strong" }
#
# # test if the node has between 2 and 4 span tags as immediate children
# node.match :children => { :count => 2..4, :only => { :tag => "span" } }
#
# # get funky: test to see if the node is a "div", has a "ul" ancestor
# # and an "li" parent (with "class" = "enum"), and whether or not it has
# # a "span" descendant that contains # text matching /hello world/:
# node.match :tag => "div",
# :ancestor => { :tag => "ul" },
# :parent => { :tag => "li",
# :attributes => { :class => "enum" } },
# :descendant => { :tag => "span",
# :child => /hello world/ }
def match(conditions)
conditions = validate_conditions(conditions)
# only Text nodes have content
return false if conditions[:content]
# test the name
return false unless match_condition(@name, conditions[:tag]) if conditions[:tag]
# test attributes
(conditions[:attributes] || {}).each do |key, value|
return false unless match_condition(self[key], value)
end
# test parent
return false unless parent.match(conditions[:parent]) if conditions[:parent]
# test children
return false unless children.find { |child| child.match(conditions[:child]) } if conditions[:child]
# test ancestors
if conditions[:ancestor]
return false unless catch :found do
p = self
throw :found, true if p.match(conditions[:ancestor]) while p = p.parent
end
end
# test descendants
if conditions[:descendant]
return false unless children.find do |child|
# test the child
child.match(conditions[:descendant]) ||
# test the child's descendants
child.match(:descendant => conditions[:descendant])
end
end
# count children
if opts = conditions[:children]
matches = children
matches = matches.select { |c| c.match(opts[:only]) } if opts[:only]
opts.each do |key, value|
next if key == :only
case key
when :count
if Integer === value
return false if matches.length != value
else
return false unless value.include?(matches.length)
end
when :less_than
return false unless matches.length < value
when :greater_than
return false unless matches.length > value
else raise "unknown count condition #{key}"
end
end
end
true
end
private
# Match the given value to the given condition.
def match_condition(value, condition)
case condition
when String
value && value.index(condition)
when Regexp
value && value.match(condition)
when Numeric
value == condition.to_s
when true
!value.nil?
when false, nil
value.nil?
else
false
end
end
end
end
