##
# Subclass of the RDoc::Markup::ToHtml class that supports looking up method
# names, classes, etc to create links.  RDoc::CrossReference is used to
# generate those links based on the current context.

class RDoc::Markup::ToHtmlCrossref < RDoc::Markup::ToHtml

  # :stopdoc:
  ALL_CROSSREF_REGEXP = RDoc::CrossReference::ALL_CROSSREF_REGEXP
  CLASS_REGEXP_STR    = RDoc::CrossReference::CLASS_REGEXP_STR
  CROSSREF_REGEXP     = RDoc::CrossReference::CROSSREF_REGEXP
  METHOD_REGEXP_STR   = RDoc::CrossReference::METHOD_REGEXP_STR
  # :startdoc:

  ##
  # RDoc::CodeObject for generating references

  attr_accessor :context

  ##
  # Should we show '#' characters on method references?

  attr_accessor :show_hash

  ##
  # Creates a new crossref resolver that generates links relative to +context+
  # which lives at +from_path+ in the generated files.  '#' characters on
  # references are removed unless +show_hash+ is true.  Only method names
  # preceded by '#' or '::' are linked, unless +hyperlink_all+ is true.

  def initialize(options, from_path, context, markup = nil)
    raise ArgumentError, 'from_path cannot be nil' if from_path.nil?

    super options, markup

    @context       = context
    @from_path     = from_path
    @hyperlink_all = @options.hyperlink_all
    @show_hash     = @options.show_hash

    crossref_re = @hyperlink_all ? ALL_CROSSREF_REGEXP : CROSSREF_REGEXP
    @markup.add_special crossref_re, :CROSSREF

    @cross_reference = RDoc::CrossReference.new @context
  end

  ##
  # Creates a link to the reference +name+ if the name exists.  If +text+ is
  # given it is used as the link text, otherwise +name+ is used.

  def cross_reference name, text = nil
    lookup = name

    name = name[1..-1] unless @show_hash if name[0, 1] == '#'

    name = "#{CGI.unescape $'} at #{$1}" if name =~ /(.*[^#:])@/

    text = name unless text

    link lookup, text
  end

  ##
  # We're invoked when any text matches the CROSSREF pattern.  If we find the
  # corresponding reference, generate a link.  If the name we're looking for
  # contains no punctuation, we look for it up the module/class chain.  For
  # example, ToHtml is found, even without the <tt>RDoc::Markup::</tt> prefix,
  # because we look for it in module Markup first.

  def handle_special_CROSSREF(special)
    name = special.text

    return name if name =~ /@[\w-]+\.[\w-]/ # labels that look like emails

    unless @hyperlink_all then
      # This ensures that words entirely consisting of lowercase letters will
      # not have cross-references generated (to suppress lots of erroneous
      # cross-references to "new" in text, for instance)
      return name if name =~ /\A[a-z]*\z/
    end

    cross_reference name
  end

  ##
  # Handles <tt>rdoc-ref:</tt> scheme links and allows RDoc::Markup::ToHtml to
  # handle other schemes.

  def handle_special_HYPERLINK special
    return cross_reference $' if special.text =~ /\Ardoc-ref:/

    super
  end

  ##
  # +special+ is an rdoc-schemed link that will be converted into a hyperlink.
  # For the rdoc-ref scheme the cross-reference will be looked up and the
  # given name will be used.
  #
  # All other contents are handled by
  # {the superclass}[rdoc-ref:RDoc::Markup::ToHtml#handle_special_RDOCLINK]

  def handle_special_RDOCLINK special
    url = special.text

    case url
    when /\Ardoc-ref:/ then
      cross_reference $'
    else
      super
    end
  end

  ##
  # Generates links for <tt>rdoc-ref:</tt> scheme URLs and allows
  # RDoc::Markup::ToHtml to handle other schemes.

  def gen_url url, text
    return super unless url =~ /\Ardoc-ref:/

    cross_reference $', text
  end

  ##
  # Creates an HTML link to +name+ with the given +text+.

  def link name, text
    original_name = name

    if name =~ /(.*[^#:])@/ then
      name = $1
      label = $'
    end

    ref = @cross_reference.resolve name, text

    text = ref.output_name @context if
      RDoc::MethodAttr === ref and text == original_name

    case ref
    when String then
      ref
    else
      path = ref.as_href @from_path

      if path =~ /#/ then
        path << "-label-#{label}"
      else
        path << "#label-#{label}"
      end if label

      "<a href=\"#{path}\">#{text}</a>"
    end
  end

end