#!/bin/bash

sedcmd=${SEDCMD:-sed}
defaultprivoxydir="/usr/local/etc/privoxy"
defaulturls=("https://easylist-downloads.adblockplus.org/easylist.txt")

#===  FUNCTION  ================================================================
#          NAME:  cleanup
#   DESCRIPTION:  cleans up after script termination
#    PARAMETERS:  none
#       RETURNS:  none
#===============================================================================
function cleanup() {
  trap - INT TERM EXIT
  [[ -f "${pidfile}" ]] && rm "$pidfile"
  exit
}

#===  FUNCTION  ================================================================
#          NAME:  isrunning
#   DESCRIPTION:  is any previous instance of this script already running
#    PARAMETERS:  pid file path
#       RETURNS:  boolean
#===============================================================================
function isrunning() {
  pidfile="${1}"
  [[ ! -f "${pidfile}" ]] && return 1  #pid file is nonexistent
  procpid=$(<"${pidfile}")
  [[ -z "${procpid}" ]] && return 1  #pid file contains no pid
  # check process list for pid existence and is an instance of this script
  [[ ! $(ps -p ${procpid} | grep $(basename ${0})) == "" ]] && value=0 || value=1
  return ${value}
}

#===  FUNCTION  ================================================================
#          NAME:  createpidfile
#   DESCRIPTION:  atomic creation of pid file with no race condition
#    PARAMETERS:  the pid to put in the file, the filename to use as a lock
#       RETURNS:  none
#===============================================================================
function createpidfile() {
  mypid=${1}
  pidfile=${2}
  #Close stderr, don't overwrite existing file, shove my pid in the lock file.
  $(exec 2>&-; set -o noclobber; echo "$mypid" > "$pidfile")
  [[ ! -f "${pidfile}" ]] && exit #Lock file creation failed
  procpid=$(<"${pidfile}")
  [[ ${mypid} -ne ${procpid} ]] && {
    #I'm not the pid in the lock file
    # Is the process pid in the lockfile still running?
    isrunning "${pidfile}" || {
      # No.  Kill the pidfile and relaunch
      rm "${pidfile}"
      $0 $@
    }
    exit
  }
}

#===  FUNCTION  ================================================================
#          NAME:  pidfilename
#   DESCRIPTION:  create a predictable pid file name, put it in the right inode
#    PARAMETERS:  none
#       RETURNS:  path and filename
#===============================================================================
function pidfilename() {
  myfile=$(basename "$0" .sh)
  whoiam=$(whoami)
  mypidfile="/tmp/${myfile}.pid"
  [[ "$whoiam" == 'root' ]] && mypidfile="/var/run/$myfile.pid"
  echo $mypidfile
}

#===  FUNCTION  ================================================================
#          NAME:  doconvert
#   DESCRIPTION:  download requested scripts and perform the conversion
#    PARAMETERS:  privoxy conf dir, list of urls
#       RETURNS:  none
#===============================================================================
function doconvert() {
  privoxydir=$1
  urls=$2
  for url in ${urls[@]}
  do
    file=${tempdir}/$(basename ${url})
    actionfile=${file%\.*}.script.action
    filterfile=${file%\.*}.script.filter
    list=$(basename ${file%\.*})

    # clean up files
    [[ -f "${file}" ]] && rm "${file}"
    [[ -f "${actionfile}" ]] && rm "${actionfile}"
    [[ -f "${filterfile}" ]] && rm "${filterfile}"

    echo "downloading ${url} ..."
    wget -t 3 --no-check-certificate -O ${file} "${url}" >${tempdir}/wget-${url//\//#}.log 2>&1

    [ "$(grep -E '^.*\[Adblock.*\].*$' ${file})" == "" ] && echo "The list recieved from ${url} isn't an AdblockPlus list. Skipped" && continue

    echo "Creating actionfile for ${list} ..."
    echo -e "{ +block{${list}} }" > ${actionfile}
    $sedcmd '/^!.*/d;1,1 d;/^@@.*/d;/\$.*/d;/#/d;s/\./\\./g;s/\?/\\?/g;s/\*/.*/g;s/(/\\(/g;s/)/\\)/g;s/\[/\\[/g;s/\]/\\]/g;s/\^/[\/\&:\?=_]/g;s/^||/\./g;s/^|/^/g;s/|$/\$/g;/|/d' ${file} >> ${actionfile}

    echo "... creating filterfile for ${list} ..."
    echo "FILTER: ${list} Tag filter of ${list}" > ${filterfile}
    $sedcmd '/^#/!d;s/^##//g;s/^#\(.*\)\[.*\]\[.*\]*/s@<([a-zA-Z0-9]+)\\s+.*id=.?\1.*>.*<\/\\1>@@g/g;s/^#\(.*\)/s@<([a-zA-Z0-9]+)\\s+.*id=.?\1.*>.*<\/\\1>@@g/g;s/^\.\(.*\)/s@<([a-zA-Z0-9]+)\\s+.*class=.?\1.*>.*<\/\\1>@@g/g;s/^a\[\(.*\)\]/s@<a.*\1.*>.*<\/a>@@g/g;s/^\([a-zA-Z0-9]*\)\.\(.*\)\[.*\]\[.*\]*/s@<\1.*class=.?\2.*>.*<\/\1>@@g/g;s/^\([a-zA-Z0-9]*\)#\(.*\):.*[:[^:]]*[^:]*/s@<\1.*id=.?\2.*>.*<\/\1>@@g/g;s/^\([a-zA-Z0-9]*\)#\(.*\)/s@<\1.*id=.?\2.*>.*<\/\1>@@g/g;s/^\[\([a-zA-Z]*\).=\(.*\)\]/s@\1^=\2>@@g/g;s/\^/[\/\&:\?=_]/g;s/\.\([a-zA-Z0-9]\)/\\.\1/g' ${file} >> ${filterfile}
    echo "... filterfile created - adding filterfile to actionfile ..."
    echo "{ +filter{${list}} }" >> ${actionfile}
    echo "*" >> ${actionfile}
    echo "... filterfile added ..."

    echo "... creating and adding whitlist for urls ..."
    echo "{ -block }" >> ${actionfile}
    $sedcmd '/^@@.*/!d;s/^@@//g;/\$.*/d;/#/d;s/\./\\./g;s/\?/\\?/g;s/\*/.*/g;s/(/\\(/g;s/)/\\)/g;s/\[/\\[/g;s/\]/\\]/g;s/\^/[\/\&:\?=_]/g;s/^||/\./g;s/^|/^/g;s/|$/\$/g;/|/d' ${file} >> ${actionfile}
    echo "... created and added whitelist - creating and adding image handler ..."

    echo "{ -block +handle-as-image }" >> ${actionfile}
    $sedcmd '/^@@.*/!d;s/^@@//g;/\$.*image.*/!d;s/\$.*image.*//g;/#/d;s/\./\\./g;s/\?/\\?/g;s/\*/.*/g;s/(/\\(/g;s/)/\\)/g;s/\[/\\[/g;s/\]/\\]/g;s/\^/[\/\&:\?=_]/g;s/^||/\./g;s/^|/^/g;s/|$/\$/g;/|/d' ${file} >> ${actionfile}
    echo "... created and added image handler ..."
    echo "... created actionfile for ${list}."

    actionfiledest="${privoxydir}/$(basename ${actionfile})"
    echo "... copying ${actionfile} to ${actionfiledest}"
    cp "${actionfile}" "${actionfiledest}"
    filterfiledest="${privoxydir}/$(basename ${filterfile})"
    echo "... copying ${filterfile} to ${filterfiledest}"
    cp "${filterfile}" "${filterfiledest}"
  done
}

#===  FUNCTION  ================================================================
#          NAME:  usage
#   DESCRIPTION:  prints command usage
#    PARAMETERS:  none
#       RETURNS:  none
#===============================================================================
function usage() {
  echo "Usage: ${0} [-d] [-p <privoxy config dir>] [-u <url1>] [-u <url2>]..."
  exit 1
}

#===  FUNCTION  ================================================================
#          NAME:  main
#   DESCRIPTION:  main script entry point
#    PARAMETERS:  none
#       RETURNS:  none
#===============================================================================
function main() {
  pidfile="$(pidfilename)"

  tempfile="$(mktemp -t j.XXX)"
  tempdir="$(dirname $tempfile)"
  rm ${tempfile}

  isrunning "${pidfile}" && {
    echo "$(basename ${0}) is already running"
    exit 1
  }

  createpidfile $$ "${pidfile}"
  trap 'cleanup' INT TERM EXIT
  debug="false"
  trap 'logger -t $0 -i -- $USER : $BASH_COMMAND' ERR  #log errors regardless

  privoxydir=$defaultprivoxydir
  urls=( "${defaulturls[@]}" )
  while getopts "dp:u:" opt; do
    case "${opt}" in
      p)
        privoxydir=${OPTARG}
        ;;
      u)
        urls+=("${OPTARG}")
        ;;
      d)
        debug="true"
        ;;
      *)
        usage
        ;;
      :)
        echo "Option -"$OPTARG" requires an arguemnt." >&2
        usage
        ;;
    esac
  done

  [[ "$debug" == "true" ]] && trap 'logger -t $0 -i -- $USER : $BASH_COMMAND' DEBUG #syslog everything if we're debugging
  [[ ! -d "$privoxydir" ]] && usage
  [[ "${#urls[@]}" -eq "0" ]] && usage

  # perform the operation
  doconvert $privoxydir $urls
}

main $@

exit 0