require 'chunks/chunk'

# This wiki chunk matches arbitrary URIs, using patterns from the Ruby URI modules.
# It parses out a variety of fields that could be used by renderers to format
# the links in various ways (shortening domain names, hiding email addresses)
# It matches email addresses and host.com.au domains without schemes (http://)
# but adds these on as required.
#
# The heuristic used to match a URI is designed to err on the side of caution.
# That is, it is more likely to not autolink a URI than it is to accidently
# autolink something that is not a URI. The reason behind this is it is easier
# to force a URI link by prefixing 'http://' to it than it is to escape and
# incorrectly marked up non-URI.
#
# I'm using a part of the [ISO 3166-1 Standard][iso3166] for country name suffixes.
# The generic names are from www.bnoack.com/data/countrycode2.html)
#   [iso3166]: http://geotags.com/iso3166/
class URIChunk < Chunk::Abstract
  include URI::REGEXP::PATTERN

  GENERIC = '(?:aero|biz|com|coop|edu|gov|info|int|mil|museum|name|net|org)'
  COUNTRY = '(?:au|at|be|ca|ch|de|dk|fr|hk|in|ir|it|jp|nl|no|pt|ru|se|sw|tv|tw|uk|us)'

  # These are needed otherwise HOST will match almost anything
  TLDS = "\\.(?:#{GENERIC}|#{COUNTRY})\b" 

  # Redefine USERINFO so that it must have non-zero length
  USERINFO = "(?:[#{UNRESERVED};:&=+$,]|#{ESCAPED})+"

  # Pattern of legal URI endings to stop interference with some Textile
  # markup. (Images: !URI!) and other punctuation eg, (http://wiki.com/)
  URI_ENDING = '[)!]'

  # The basic URI expression as a string
  URI_PATTERN = 
	"(?:(#{SCHEME})://)?" +    # Optional scheme://              (\1|\8)
	"(?:(#{USERINFO})@)?" +    # Optional userinfo@              (\2|\9)
	"(#{HOSTNAME}#{TLDS})" +   # Mandatory host eg, HOST.com.au  (\3|\10)
	"(?::(#{PORT}))?" +        # Optional :port                  (\4|\11)
	"(#{ABS_PATH})?" +         # Optional absolute path          (\5|\12)
	"(?:\\?(#{QUERY}))?" +     # Optional ?query                 (\6|\13)
	"(?:\\#(#{FRAGMENT}))?"    # Optional #fragment              (\7|\14)

  def self.pattern()
    # This pattern first tries to match the URI_PATTERN that ends with 
    # punctuation that is a valid URI character (eg, ')', '!'). If
    # such a match occurs, there should be no backtracking (hence the ?> ). 
    # If the string cannot match a URI ending with URI_ENDING, then a second
    # attempt is tried.
    Regexp.new("(?>#{URI_PATTERN}(?=#{URI_ENDING}))|#{URI_PATTERN}", Regexp::EXTENDED, 'N')
  end

  attr_reader :uri, :scheme, :user, :host, :port, :path, :query, :fragment, :link_text
  
  def initialize(match_data, revision)
    super(match_data, revision)
    # Since the URI_PATTERN is tried twice, there are two sets of
    # groups, one from \1 to \7 and the second from \8 to \14.
    # The fields are set by which ever group matches.
    @scheme   	= match_data[1] || match_data[8]
    @user     	= match_data[2] || match_data[9]
    @host     	= match_data[3] || match_data[10]
    @port		    = match_data[4] || match_data[11]
    @path		    = match_data[5] || match_data[12]
    @query		  = match_data[6] || match_data[13]
    @fragment 	= match_data[7] || match_data[14]

    # If there is no scheme, add an appropriate one, otherwise
    # set the URI to the matched text.
    @text_scheme = scheme
    @uri = (scheme ? match_data[0] : nil )
    @scheme = scheme || ( user ? 'mailto' : 'http' )
    @delimiter = ( scheme == 'mailto' ? ':' : '://' ) 
    @uri ||= scheme + @delimiter + match_data[0]

    # Build up the link text. Schemes are omitted unless explicitly given.
    @link_text = ''
    @link_text << "#{@scheme}#{@delimiter}" if @text_scheme
    @link_text << "#{@user}@" if @user
    @link_text << "#{@host}" if @host
    @link_text << ":#{@port}" if @port
    @link_text << "#{@path}" if @path
    @link_text << "?#{@query}" if @query
  end

  # If the text should be escaped then don't keep this chunk.
  # Otherwise only keep this chunk if it was substituted back into the
  # content.
  def unmask(content) 
    return nil if escaped_text
    return self if content.sub!( Regexp.new(mask(content)), "<a href=\"#{uri}\">#{link_text}</a>" )
  end

  # If there is no hostname in the URI, do not render it
  # It's probably only contains the scheme, eg 'something:' 
  def escaped_text() ( host.nil? ? @uri : nil )  end
end