#!/usr/bin/ruby -w

# This is a Pavatar plugin written in ruby by Jeena Paradies
# I hereby place this script into the public domain.
#
# This is version 0.1 and it could include some bugs I haven't found yet.
# Because the program is licensed free of charge, there is no warranty
# for the program, but it works for me, try it if you want.
#
# If you have some questions contact me: pavatar@jeenaparadies.net
#
# To use it add it in the src attribute of you image:
# <img src="http://example.com/cgi-bin/pavatar.rb?url=http://example.org" alt="" />

# include some libraries to handle HTTP requests
require 'cgi'
require 'uri'
require 'net/http'
require 'image_size' # see http://www.rubycgi.org/archive/

class Pavatar
    # content types defined by the spec http://pavatar.com/spec#technical-definition
    @@content_types = ['image/png', 'image/jpeg', 'image/gif']

    # fetch the pavatar url on initialize
    def initialize url
        
        @url = url
        @purl = URI.parse(@url)

        # check for the first real pavatar url and save it into a class variable
        if (@pavatar = xHeader).nil? and (@pavatar = link).nil? and (@pavatar = path).nil?
            @pavatar = favicon
        end
    end

    # Autodiscovery methods

    # get url from header if there is one
    def xHeader
        begin
            res = FetchHelper.head(@url)
            res['X-Pavatar'] unless res['X-Pavatar'].nil?
        rescue
        end
    end

    # get url from <link> if there is one
    def link
        begin
            res = FetchHelper.get(@url)
            pavatar = /<link rel="pavatar" href="([^"]+)" ?\/?>/.match(res.body)
            pavatar[1] unless pavatar.nil?
        rescue
        end
    end

    # look in users path if there is a pavatar
    def path
        begin
            # to discover the given directory is a little bit tricky in ruby
            path = @purl.path.to_s
            unless path[-1..-1] == '/'
                path = File.dirname(path)
                unless path == '.' or path == '/'
                    path << '/'
                end
            end

            if path == '.'
                path = '/'
            end

            url = 'http://' + @purl.host.to_s + path + 'pavatar.png'

            # if would be ok to look on the header here but Apache has a problem with
            # head requests so we use a get request to workaround it
            res = FetchHelper.get(url)

            # some people redirect to a 404 page and send status 200 so we need to check the content type
            url unless res['content-type'].nil? or not @@content_types.include?(res['content-type']) 
        rescue
        end
    end

    # look in users home directory if there is a pavatar
    def favicon
        begin
            url = 'http://' + @purl.host.to_s + '/pavatar.png'

            # same problem with apache here
            res = FetchHelper.get(url)
            url unless res['content-type'].nil? or not @@content_types.include?(res['content-type']) 
        rescue
        end
    end

    # url getter
    def get_url
        @pavatar
    end

    # get a whole html string to show a pavatar
    def get_html (attr = '')
        attr = ' ' + attr unless attr.length > 0
        '<img src="' + get_url + '"' + attr + ' />'
    end

end


# helps us handle redirections
module FetchHelper

    def FetchHelper.head(url_str, limit = 10)

      # stop if there is a loop
      raise ArgumentError, 'HTTP redirect too deep' if limit == 0

      url = URI.parse(url_str)
      path = File.dirname(url.path.to_s)

      response = nil

      Net::HTTP.start(url.host, url.port) { |http|
        response = http.head(  path == '.' ? '/' : url.path.to_s )
      }

      case response
      when Net::HTTPSuccess     then response
      when Net::HTTPRedirection then FetchHelper.head(response['location'], limit - 1)
      else
        response.error!
      end
    end

    def FetchHelper.get(url_str, limit = 10)
      raise ArgumentError, 'HTTP redirect too deep.' if limit == 0

      response = Net::HTTP.get_response(URI.parse(url_str))
      case response
      when Net::HTTPSuccess     then response
      when Net::HTTPRedirection then FetchHelper.get(response['location'], limit - 1)
      else
        response.error!
      end
    end

    def FetchHelper.validate(url, what)
      begin
        uri = URI.parse(url)
        if uri.class != URI::HTTP
          raise ArgumentError, "Only HTTP protocol addresses can be used in the #{what} URL."
        end
        rescue URI::InvalidURIError
          raise ArgumentError, "The format of the #{what} URL is not valid."
        end
      end

end

if __FILE__ == $0
    # cach the GET variable
    cgi = CGI.new
    
    types = {
      'PNG' => 'image/png',
      'GIF' => 'image/gif',
      'JPEG' => 'image/jpeg'
    }

    begin
      FetchHelper.validate(cgi['url'], 'homepage')
      pavatar_url = Pavatar.new(cgi['url'])
      raise ArgumentError, "No pavatar here." if pavatar_url.get_url.nil? or pavatar_url.get_url == "none"
      FetchHelper.validate(pavatar_url.get_url, 'Pavatar')
      pavatar = FetchHelper.get(pavatar_url.get_url)
      raise ArgumentError, "File size too big (#{(pavatar.body.to_s.size * 8)}) max: 409600." if (pavatar.body.to_s.size * 8) > 409600
      img = ImageSize.new(pavatar.body)
      raise ArgumentError, "Width is not 80px but #{img.get_width}px." unless img.get_width == 80
      raise ArgumentError, "Height is not 80px but #{img.get_height}px." unless img.get_height == 80
      raise ArgumentError, "False image type: #{img.get_type} #{pavatar_url.get_url}." unless types.has_key? img.get_type
    rescue Exception => e
      pavatar = FetchHelper.get("http://example/img/default-pavatar.png")
      print "X-Pavatar-Error: #{e}\r\n"
      print "Content-type: #{pavatar['content-type']}\r\n\r\n"
      print pavatar.body
      exit  
    end

    # print our HTML header
    print "Content-type: #{types[img.get_type]}\r\n\r\n"
    print pavatar.body

end
# end of file