#! /usr/bin/ruby

# Copyright 2002 Neil Spring <nspring@cs.washington.edu> 
# GPL
# report bugs to wmbiff-devel@lists.sourceforge.net
# or (preferred) use the debian BTS via 'reportbug'

# Based on security-update-check.py by Rob Bradford

require 'net/http'

#require 'profile'

# re-fetch interval - only bug the server once every hour.
# allows wmbiff to ask us often how many packages have been
# updated so that the number goes back to cyan (old) from
# yellow (new) quickly on upgrade.

# this still doesn't mean we grab the whole file.  we get
# if-modified-since.  it just means we don't connect to the
# server more often than this.
# 6 hours * 60 min/hour * 60 sec/min
Refetch_Interval_Sec = 6 * 60 * 60

# as an ordinary user, we store Packages in the home directory.
Cachedir = ENV['HOME'] + '/.wmbiff-sdr'

# look for updates from this server.  This script is designed around
# (and simplified greatly by) using just a single server. 
Server = 'security.debian.org'

# extend the Array class with a max method.
class Array
  def inject(n)
    each { |value| n = yield(n, value) }
    n
  end
  def max
    inject(0) { |n, value| ((n > value) ? n : value) }
  end
end

def debugmsg(str)
  $stderr.puts str if($VERBOSE)
end

# to be reimplemented without execing touch.
def touch(filename)
  debugmsg "touching #{filename}"
  Kernel.system('/usr/bin/touch ' + filename)
end

# to be reimplemented without execing dpkg, though running
# dpkg excessively doesn't seem to be a bottleneck.
def version_a_gt_b(a, b)
  cmd = "/usr/bin/dpkg --compare-versions %s le %s" % [ a, b ]
  # $stderr.puts cmd
  return (!Kernel.system(cmd)) 
end

# figure out which lists to check
# there can be many implementations of
# this behavior, this seemed simplest.


# we're going to make an array of arrays, for each package
# file, the url, the system's cache of the file, and a
# per-user cache of the file.
packagelists = Dir.glob("/var/lib/apt/lists/#{Server}*Packages").map { |pkgfile|
  [ pkgfile.gsub(/.*#{Server}/, '').tr('_','/'), # the url path 
    pkgfile,  # the system cache of the packages file.  probably up-to-date.
    # and finally, a user's cache of the page, if needed.
    "%s/%s" % [ Cachedir, pkgfile.gsub(/.*#{Server}_/,'') ] 
  ]
}

# we'll open a persistent session, but only if we need it.
session = nil

# update the user's cache if necessary.
packagelists.each { |urlpath, sc, uc|
  sctime = File.stat(sc).mtime
  cached_time = 
    if(test(?e, uc)) then
      uctime = File.stat(uc).mtime 
      if ( uctime < sctime ) then
        # we have a user cache, but it is older than the system cache
        File.unlink(uc)  # delete the obsolete user cache.
        sctime 
      else
        uctime
      end
    else 
      # the user cache doesn't exist, but we might have
      # talked to the server recently.
      if(test(?e, uc + '.stamp')) then
        File.stat(uc + '.stamp').mtime 
      else
        sctime
      end
    end 
  if(Time.now > cached_time + Refetch_Interval_Sec) then
    debugmsg "fetching #{urlpath} %s > %s + %d" % [Time.now, cached_time, Refetch_Interval_Sec] 
    begin
      if(session == nil) then
        session = Net::HTTP.new(Server)
        # session.set_pipe($stderr); 
      end
      begin 
        # the warning with ruby1.8 on the following line 
        # has to do with the resp, data bit, which should
        # eventually be replaced with (copied from the 
        # docs with the 1.8 net/http.rb)
        #         response = http.get('/index.html')
        #         puts response.body
        resp, data = session.get(urlpath, 
                                 { 'If-Modified-Since' => 
                                   cached_time.strftime( "%a, %d %b %Y %H:%M:%S GMT" ) })
      rescue SocketError => e
        # if the net is down, we'll get this error; avoid printing a stack trace.
        puts "XX old"
        puts e
        exit 1;
      rescue Timeout::Error => e
        # if the net is down, we might get this error instead.
        # but there is no good reason to print the specific exception. (execution expired)
        puts "XX old"
        exit 1;
      end
      test(?e, Cachedir) or Dir.mkdir(Cachedir)
      File.open(uc, 'w') { |o| o.puts data }
      test(?e, uc + '.stamp') and File.unlink(uc + '.stamp')  # we have a copy, don't need the stamp.
      debugmsg "urlpath updated"
    rescue Net::ProtoRetriableError => detail
      head = detail.data
      if head.code != "304"
        raise "unexpected error occurred: " + detail
      end
      test(?e, Cachedir) or Dir.mkdir(Cachedir)
      if(test(?e, uc)) then
        touch(uc)
      else
        # we didn't get an update, but we don't have a cached
        # copy in the user directory.
        touch(uc + '.stamp')
      end
    end
  else
    debugmsg "skipping #{urlpath}"
  end
}

available = Hash.new
package = nil
packagelists.each { |url, sc, uc|
  File.open( (test(?e, uc)) ? uc : sc, 'r').each { |ln|
    if(m = /^Package: (.*)/.match(ln)) then
      package = m[1]
    elsif(m = /^Version: (.*)/.match(ln)) then
      available[package] = m[1]
    end
  }
}

installed = Hash.new
package = nil
isinstalled = false
File.open('/var/lib/dpkg/status').each { |ln|
  if(m = /^Package: (.*)$/.match(ln)) then
    package = m[1]
    isinstalled = false # reset
  elsif(m = /^Status: install ok installed/.match(ln)) then
    isinstalled = true
  elsif(m = /^Version: (.*)$/.match(ln)) then
    isinstalled && installed[package] = m[1]
  end
}

debugmsg "%d installed, %d available" % [ installed.length, available.length ]

updatedcount = 0
updated = Array.new
( installed.keys & available.keys ).each { |pkg|
  if(version_a_gt_b(available[pkg], installed[pkg])) then
    updatedcount += 1
    updated.push(pkg + ": #{available[pkg]} > #{installed[pkg]}")
  end
}

# we're done.  output a count in the format expected by wmbiff.
if(updatedcount > 0) then
  puts "%d new" % [ updatedcount ] 
else
  puts "%d old" % [ installed.length ] 
end

puts updated.join("\n")