#!/bin/sh
######################################################################
# Nombre: PutBacks
# Descripcion: CGI para detectar e insertar citas a las paginas web
# Author: Alejandro Rivero (rivero@sol.unizar.es) 
# Date: noviembre 1996 
##########################################################################
# Usage:
# With CERN httpd (3.0 or near) add to the config file some lines
# indicating the directories to monitorize for backlinks
#    Exec    /wwwlab/experiences/*.html      /home/http/cgi-bin/PutBacks
#    Exec    /alejo/*htm		     /home/http/cgi-bin/PutBacks
# Path comes from start of data tree, as always.  
# Warnings:
# - Provided as proof of concept only. A lot of work must we made to make
#   the script fool-proof.  
# - Use it at your OWN risk. 
##########################################################################
# variables for testing only.
#SCRIPT_NAME="wwwlab/links.html"
#HTTP_REFERER="http://some.site/nose.html"
#########################################################################
#
# We are sending out html files only.
#
echo 'Content-Type: text/html'
echo ''
#
# base directory: root of our data tree
#
B_DIR=/home/http/htdocs
#
# Exclude file: list of nodes to exclude. Must have at least one name
#
EXCLUDE_FILE=/home/http/conf/hosts.noindex
#
# We first test for "default" http path specification, then look
# for Welcome, welcome, or index files, in this order
#
if test -d ${B_DIR}/${SCRIPT_NAME}; then
 if test -f ${B_DIR}/${SCRIPT_NAME}/Welcome.html; then
  SCRIPT_NAME=${SCRIPT_NAME}/Welcome.html
 elif test -f ${B_DIR}/${SCRIPT_NAME}/welcome.html; then
  SCRIPT_NAME=${SCRIPT_NAME}/welcome.html
 elif test -f ${B_DIR}/${SCRIPT_NAME}/index.html; then
  SCRIPT_NAME=${SCRIPT_NAME}/index.html
 else
   echo "<h1>Error</h1> Can not process directory"
   exit 0
 fi
fi
# 
# And of course we check if file exists... if not, we have a special log
# for this kind of things
if !(test -f ${B_DIR}/${SCRIPT_NAME}); then
 echo "<h1>Error</h1> File does not exist."
 echo -n `date` >> /home/http/logs/lost_files.log
 echo -n " " ${B_DIR}/${SCRIPT_NAME} >>/home/http/logs/lost_files.log
 echo    " " ${HTTP_REFERER} >>/home/http/logs/lost_files.log
 exit 0
fi
# 
# Now we really begin the game
#
# First, we test for "filename.backs", the file containing detected backlinks  
if   (!(test -f ${B_DIR}/${SCRIPT_NAME}.backs )) then 
 cat ${B_DIR}/$SCRIPT_NAME
else
 #Ok, there are backlinks for this file. We are going to include them
 cat ${B_DIR}/${SCRIPT_NAME}| ( 
  while read linea;  do 
  # if the html has a well separated HEAD tag, we add LINK info there 
         #        if (`echo $linea | grep -i -q "^</HEAD>"`) then
         #        This "if" changued for speed...
   if test "$linea" = "</HEAD>" -o "$linea" = "</head>";  then 
   for bklink in `cat  ${B_DIR}/${SCRIPT_NAME}.backs`  
    do
     echo -n "<LINK HREF=\""
     echo -n $bklink 
     echo    "\"  REV=\"X-Default\" > "
     #
     # Note for developers:
     # If your browser can not cope with a REV flag without parameters,
     # please suggest me the adequate one 
     # 
    done
  fi
  # and if the html has well separated BODY tag, we put some
  # visible backlinks there, for compatibility with old browsers :-)
               #  if `echo $linea | grep -i -q "^</BODY>"`; then
               # again, this "if" changed to optimize output speed
  if test "$linea" = "</BODY>" -o "$linea" = "</body>";  then 
   echo "<p><hr><i>"
   echo "Note that we have"
   echo "detected some pages probably pointing to this one:<menu>"
                                 # would be better UL COMPACT?
   for bklink in `cat  ${B_DIR}/${SCRIPT_NAME}.backs`  
   do
    echo -n "<li><A HREF=\""
    echo -n  $bklink
    echo -n "\" REV=\"X-Default\">"
    echo -n  $bklink
    echo    "</A>"
   done
   echo "</menu>"
   echo "you could be interested on checking them."
   echo "</i>"
  fi
  echo $linea 
 done
 ) 
fi

# Now we check if the current access can qualify as backlink, then
# register it in the .backs file
if (!(test -z "${HTTP_REFERER}" )) then
  #mini-bug: EXCLUDE_FILE must have at least one line
 if (!(`echo $HTTP_REFERER | grep -F -q -i -f ${EXCLUDE_FILE}`)) then
   # Of course, we create the file when it is needed 
   if (!(test -f ${B_DIR}/${SCRIPT_NAME}.backs)) then  
    touch  ${B_DIR}/${SCRIPT_NAME}.backs
   fi
   # and we try to avoid reiteration...
   if (!(`grep -q -i $HTTP_REFERER ${B_DIR}/${SCRIPT_NAME}.backs`)) then 
    echo  $HTTP_REFERER  >>   ${B_DIR}/${SCRIPT_NAME}.backs
   fi 
 fi
fi
#
exit 0
#