#!/usr/bin/sh -e
# Fortune implementation in POSIX sh/awk

usage() {
  echo 'Usage: fortune [OPTIONS]
a simple POSIX sh/awk implementation of fortune

  -h, --help                    show this help message
  -l, --list                    list installed cookie files
  -c FILE, --cookie FILE        specify cookie file
  -n LENGTH, --min LENGTH       specify min fortune length
  -N LENGTH, --max LENGTH       specify max fortune length

  fortune looks for fortunes in $FORTUNEDIR, which defaults to
  /usr/share/fortune.

Exit codes:
  0    success
  1    argument error
  2    parse error'
}

DIR=${FORTUNEDIR:-"/usr/share/fortune/"}
FILE="$(find $DIR -type f -not -name '*.dat')"
MAXLENGTH=1000000000000
MINLENGTH=0

while [ "$1" != "" ]; do
  case $1 in
    -h | --help)
      usage
      exit
      ;;
    -c | --cookie)
      FILE=$DIR/$2
      ;;
    -n | --min)
      MINLENGTH=$2
      ;;
    -N | --max)
      MAXLENGTH=$2
      ;;
    -l | --list)
      ls -1 $DIR
      exit
      ;;
    *)
      echo "ERROR: unknown option \"$1\""
      usage
      exit 1
      ;;
  esac
  shift 2
done

[ "$MAXLENGTH" -lt "$MINLENGTH" ] && {
  echo "ERROR: maximum length is less than minimum length"
  exit 2
}

[ -d "$FILE" ] && {
  echo "ERROR: directory given, please provide a file or glob of files"
  exit 2
}

awk -v maxlen=$MAXLENGTH -v minlen=$MINLENGTH \
'BEGIN {
  f++
}

$1 == "%" {
  len = length(fortunes[f])
  if ( len>maxlen || len<minlen ) {
    fortunes[f] = ""
  } else {
    f++
  }
}

{
  sub("%", "")
  fortunes[f] = fortunes[f] (length(fortunes[f])?"\n":"") $0
}

END {
  "date +%N" | getline time
  srand(time)
  print fortunes[int(rand() * (f - 2)) + 1]
}' $FILE