#!/bin/bash 
#	@(#)	newdirstack.bsh

# Date: Tue, 31 Jan 2012 16:28:52 +0100
# Subject: A Bash source code example
# From: Eric Sanchis <eric.sanchis@iut-rodez.fr>
# To: chet.ramey@case.edu
#
# Using Bash everyday, I developped an enhanced implementation of the
# cd/dir functions described in the Bolsky & Korn book, which
# illustrates several specific Bash syntax elements.
#
# It works fine with a non empty CDPATH and cdable variables. In
# addition, a directory name is indexed only once into the stack.
#
# If you find this code snippet useful, would it be possible to include
# it into the bash-doc section of future bash packages ?
#
# Sincerely yours,
#
# Eric
# IUT Rodez
# University of Toulouse (France)

###
# Another implementation of the directory manipulation functions
# published in the Bolsky & Korn book : "The new Korn shell" :
# 	cd, to change current directory
#	d,  to display the stack content
# Eric Sanchis (eric.sanchis@iut-rodez.fr), 2012
###


shopt -s expand_aliases
shopt -s extglob
shopt -s cdable_vars

alias integer='declare -i'

	integer	MAX=32
	integer INDMAX=MAX-1
	integer	INDTOP=0

unalias cd 2>/dev/null
alias cd=cdir

unset tab
tab[INDTOP]="$(pwd)"


function cdir      
{
	local -i ind 

dir="${1:-$HOME}"
case "$dir" in
 - )			# cd -  => equivalent to : cd -1
		ind=INDTOP-1
 		cd_by_number  $ind
		  ;;
 -+([[:digit:]]) )	# cd -n
		ind=$INDTOP-${dir#-}
		cd_by_number  $ind 
		  ;;
 *)			# cd ~   or    cd dir_name
		cd_by_name  "$dir"
esac
}


function  cd_by_number
{
	local -i  k=$1
	local -i  j 
	local     dirtmp

if (( k < 0 ))
 then 		
   echo Impossible to change directory >&2
   return 1
 else
   dirtmp="${tab[k]}"
   j=k+1 
   while (( j <= INDTOP ))
    do
      tab[j-1]="${tab[j]}"
      j=j+1
    done
   tab[INDTOP]="$dirtmp"
   \cd "${tab[INDTOP]}"
fi
}


function cd_by_name
{
 	local -i  i
	local  rep

rep=$( \cd "$1" &>/dev/null && pwd)
if [[ -z "$rep" ]]
  then 
    echo cd : "$1" unknown >&2
    return 1
fi

	i=$INDTOP 
	while (( i >= 0 ))
  	 do
	   if [[ "${tab[i]}" == "$rep" ]]
	     then  break
	   fi
	   i=i-1
	 done

if (( i == INDTOP ))
  then	#  cd -0	=> we do nothing !
     return 0	
  elif (( i == -1 ))
     then	# the directory isn't in the stack
       if (( INDTOP == INDMAX ))
         then 	# the stack is FULL
		# the oldest directory is removed
            local -i  m
       
          m=1
	  while (( m <= INDMAX ))
	   do
	     tab[m-1]="${tab[m]}"
	     m=m+1
           done
        else 	# the new directory is added to the top of the stack
	  INDTOP=INDTOP+1
      fi
      tab[INDTOP]="$rep"
      \cd "${tab[INDTOP]}"
      return 0
  
     else # the directory is already in the stack 
	# $i gives its index
       cd_by_number $i
fi
}


function d	# display the directory stack
{
	local -i  i 
	local rep

i=0
while (( $i <= $INDTOP ))
 do
   rep="${tab[INDTOP-i]#$HOME/}"
   case "$rep" in
    $HOME)  rep="~" ;;
    /*   )   :  ;;
    *    )  rep="~/$rep"
   esac
   
   echo "$i )		$rep"
   i=i+1
 done
}