module MultiXml::Parsers::Rexml

def collapse(element)

The document element to be collapsed.
element::

Actually converts an XML document element into a data structure. 
def collapse(element)
  hash = get_attributes(element)
  if element.has_elements?
    element.each_element { |child| merge_element!(hash, child) }
    merge_texts!(hash, element) unless empty_content?(element)
    hash
  else
    merge_texts!(hash, element)
  end
end

def empty_content?(element)

XML element to be checked.
element::

Determines if a document element has text content 
def empty_content?(element)
  element.texts.join.strip.empty?
end

def get_attributes(element)

XML element to extract attributes from.
element::

Returns an empty Hash if node has no attributes.
Converts the attributes array of an XML element into a hash. 
def get_attributes(element)
  attributes = {}
  element.attributes.each { |n, v| attributes[n] = v }
  attributes
end

def merge!(hash, key, value)

Value to be associated with key.
value::
Key to be added.
key::
Hash to add key/value pair to.
hash::

appended to that Array.
an Array, it will be wrapped in an Array. Then the new value is
already exists and the existing value associated with key is not
Adds a new key/value pair to an existing Hash. If the key to be added 
def merge!(hash, key, value)
  if hash.key?(key)
    if hash[key].instance_of?(Array)
      hash[key] << value
    else
      hash[key] = [hash[key], value]
    end
  elsif value.instance_of?(Array)
    hash[key] = [value]
  else
    hash[key] = value
  end
  hash
end

def merge_element!(hash, element)

XML element to merge into hash
element::
Hash to merge the converted element into.
hash::

Convert an XML element and merge into the hash 
def merge_element!(hash, element)
  merge!(hash, element.name, collapse(element))
end

def merge_texts!(hash, element)

XML element whose texts are to me merged into the hash
element::
Hash to add the converted element to.
hash::

Merge all the texts of an element into the hash 
def merge_texts!(hash, element)
  if element.has_text?
    # must use value to prevent double-escaping
    texts = element.texts.map(&:value).join
    merge!(hash, MultiXml::CONTENT_ROOT, texts)
  else
    hash
  end
end

def parse(xml)

XML Document IO to parse
xml::

Parse an XML Document IO into a simple hash using REXML 
def parse(xml)
  doc = REXML::Document.new(xml)
  raise(REXML::ParseException, "The document #{doc.to_s.inspect} does not have a valid root") unless doc.root
  merge_element!({}, doc.root)
end

def parse_error 

def parse_error
  ::REXML::ParseException
end