class UrlEncodedPairParser < StringScanner #:nodoc: attr_reader :top, :parent, :result def initialize(pairs = []) super('') @result = {} pairs.each { |key, value| parse(key, value) } end KEY_REGEXP = %r{([^\[\]=&]+)} BRACKETED_KEY_REGEXP = %r{\[([^\[\]=&]+)\]} # Parse the query string def parse(key, value) self.string = key @top, @parent = result, nil # First scan the bare key key = scan(KEY_REGEXP) or return key = post_key_check(key) # Then scan as many nestings as present until eos? r = scan(BRACKETED_KEY_REGEXP) or return key = self[1] key = post_key_check(key) end bind(key, value) end private # After we see a key, we must look ahead to determine our next action. Cases: # # [] follows the key. Then the value must be an array. # = follows the key. (A value comes next) # & or the end of string follows the key. Then the key is a flag. # otherwise, a hash follows the key. def post_key_check(key) if scan(/\[\]/) # a[b][] indicates that b is an array container(key, Array) nil elsif check(/\[[^\]]/) # a[b] indicates that a is a hash container(key, Hash) nil else # End of key? We do nothing. key end end # Add a container to the stack. def container(key, klass) type_conflict! klass, top[key] if top.is_a?(Hash) && top.key?(key) && ! top[key].is_a?(klass) value = bind(key, klass.new) type_conflict! klass, value unless value.is_a?(klass) push(value) end # Push a value onto the 'stack', which is actually only the top 2 items. def push(value) @parent, @top = @top, value end # Bind a key (which may be nil for items in an array) to the provided value. def bind(key, value) if top.is_a? Array if key if top[-1].is_a?(Hash) && ! top[-1].key?(key) top[-1][key] = value else top << {key => value}.with_indifferent_access push top.last value = top[key] end else top << value end elsif top.is_a? Hash key = CGI.unescape(key) parent << (@top = {}) if top.key?(key) && parent.is_a?(Array) top[key] ||= value return top[key] else raise ArgumentError, "Don't know what to do: top is #{top.inspect}" end return value end def type_conflict!(klass, value) raise TypeError, "Conflicting types for parameter containers. Expected an instance of #{klass} but found an instance of #{value.class}. This can be caused by colliding Array and Hash parameters like qs[]=value&qs[key]=value. (The parameters received were #{value.inspect}.)" end end