Smart truncating of directory names

rtab.zsh

#!/bin/zsh
### vss:ft=zsh
## reverse tabbing, useful in the prompt
## Copyright (C) 2008 by Daniel Friesel <derf@xxxxxxxxxxxxxxxxxx>
## License: WTFPL <http://sam.zoy.org/wtfpl>

## CAVEAT: directory-names containing two or more consecutive spaces
## are not yet supported

setopt localoptions
setopt rc_quotes null_glob

typeset -i lastfull=0
typeset -i short=0
typeset -i tilde=0
typeset -i named=0

if zstyle -t ':prompt:rtab' fish; then
  lastfull=1
  short=1
  tilde=1
fi
if zstyle -t ':prompt:rtab' nameddirs; then
  tilde=1
  named=1
fi
zstyle -t ':prompt:rtab' last && lastfull=1
zstyle -t ':prompt:rtab' short && short=1
zstyle -t ':prompt:rtab' tilde && tilde=1

while [[ $1 == -* ]]; do
  case $1 in
    -f|--fish)
      lastfull=1
      short=1
      tilde=1
    ;;
    -h|--help)
      print 'Usage: rtab [-f -l -s -t] [directory]'
      print ' -f, --fish      fish-simulation, like -l -s -t'
      print ' -l, --last      Print the last directory''s full name'
      print ' -s, --short     Truncate directory names to the first character'
      print ' -t, --tilde     Substitute ~ for the home directory'
      print ' -T, --nameddirs Substitute named directories as well'
      print 'The long options can also be set via zstyle, like'
      print '  zstyle :prompt:rtab fish yes'
      return 0
    ;;
    -l|--last) lastfull=1 ;;
    -s|--short) short=1 ;;
    -t|--tilde) tilde=1 ;;
    -T|--nameddirs)
      tilde=1
      named=1
    ;;
  esac
  shift
done

typeset -a tree expn
typeset result part dir=${1-$PWD}
typeset -i i

[[ -d $dir ]] || return 0

if (( named )) {
  for part in ${(k)nameddirs}; {
    [[ $dir == ${nameddirs[$part]}(/*|) ]] && dir=${dir/${nameddirs[$part]}/\~$part}
  }
}
(( tilde )) && dir=${dir/$HOME/\~}
tree=(${(s:/:)dir})
(
  unfunction chpwd 2> /dev/null
  if [[ $tree[1] == \~* ]] {
    cd ${~tree[1]}
    result=$tree[1]
    shift tree
  } else {
    cd /
  }
  for dir in $tree; {
    if (( lastfull && $#tree == 1 )) {
      result+="/$tree"
      break
    }
    expn=(a b)
    part=''
    i=0
    until [[ (( ${#expn} == 1 )) || $dir = $expn || $i -gt 99 ]]  do
      (( i++ ))
      part+=$dir[$i]
      #expn=($(echo ${part}*(/)))
      expn=($(echo ${part}*(-/)))
      (( short )) && break
    done
    result+="/$part"
    cd $dir
    shift tree
  }
  echo ${result:-/}
  )