# Directory stack begins
DIR_STACK_POINTER=0
DIR_STACK_SIZE=0
pushd()
{
  if [ $# -eq 0 ]; then
    DIR="${HOME}"
  else
    DIR="$1"
  fi

  builtin pushd "${DIR}" > /dev/null
  DIR_STACK_POINTER=0
  DIR_STACK_SIZE=$(dirs -v | tail -n 1 | awk '{print $1}')
}

pushd_builtin()
{
  builtin pushd > /dev/null
}

popd()
{
  builtin popd > /dev/null
}

stack_list()
{
  dirs -v | awk -v stackp=$DIR_STACK_POINTER '{
    if ($1 == stackp)
      if ($1 == 0)
        printf "%-25s%s\n","Current dir",$2
      else
        printf "%-15s%-10s%s\n","->",$1,$2
    else
      if ($1 == 0)
        printf "%-25s%s\n","Current dir",$2
      else
        printf "%-15s%-10s%s\n","  ",$1,$2
  }'
}

list_stack_reverse()
{
  stack_list | awk '{a[i++]=$0} END {for (j=i-1; j>=0;) print a[j--] }'
}

back_stack()
{
  if [ $(($DIR_STACK_POINTER)) -lt $(($DIR_STACK_SIZE)) ]
  then
    if [ $(($DIR_STACK_POINTER)) -eq 0 ]
    then
      builtin pushd $PWD > /dev/null
      ((DIR_STACK_POINTER++))
      DIR_STACK_SIZE=$(dirs -v | tail -n 1 | awk '{print $1}')
    fi
    ((DIR_STACK_POINTER++))
    NEXT_DIR_POINTER=$( dirs -v | grep -w "$DIR_STACK_POINTER\s\s" | awk ' {print $2}' )
    if [ "$NEXT_DIR_POINTER" = "~" ]
    then
      \cd $HOME
    else
      \cd $NEXT_DIR_POINTER
    fi
  fi
  list_stack_reverse
}

forward_stack()
{
  if [ $(($DIR_STACK_POINTER)) -gt 0 ]
  then
    ((DIR_STACK_POINTER--))
    if [ $(($DIR_STACK_POINTER)) -gt 1 ]
    then 
      NEXT_DIR_POINTER=$( dirs -v | grep -w "$DIR_STACK_POINTER\s\s" | awk ' {print $2}' )
      if [ "$NEXT_DIR_POINTER" = "~" ]
      then
        \cd $HOME
      else
        \cd $NEXT_DIR_POINTER
      fi
    else
      builtin popd > /dev/null
      DIR_STACK_SIZE=$(dirs -v | tail -n 1 | awk '{print $1}')
      DIR_STACK_POINTER=0
    fi
  fi
  list_stack_reverse
}


goto_stack()
{
  DIR_STACK_SIZE=$(dirs -v | tail -n 1 | awk '{print $1}')
  if [ $(($DIR_STACK_SIZE)) -lt $(($1)) ]
  then
    echo "The stack is smaller than argument"
  else
    GOTO_POINTER=$1
    if [ $(($DIR_STACK_POINTER)) -eq 0 ]
    then
      builtin pushd $PWD > /dev/null
      DIR_STACK_SIZE=$(dirs -v | tail -n 1 | awk '{print $1}')
      ((GOTO_POINTER++))
    fi
    if [ $(($GOTO_POINTER)) -gt 1 ]
    then 
      NEXT_DIR_POINTER=$( dirs -v | grep -w "$GOTO_POINTER\s\s" | awk ' {print $2}' )
      if [ "$NEXT_DIR_POINTER" = "~" ]
      then
        \cd $HOME
      else
        \cd $NEXT_DIR_POINTER
      fi
      DIR_STACK_POINTER=$GOTO_POINTER
    else
      builtin popd > /dev/null
      DIR_STACK_SIZE=$(dirs -v | tail -n 1 | awk '{print $1}')
      DIR_STACK_POINTER=0
    fi
  fi
  list_stack_reverse
}

clear_directory_stack()
{
  dirs -c
  DIR_STACK_SIZE=0
  DIR_STACK_POINTER=0
  list_stack_reverse
}

alias cd='pushd'
alias bb='back_stack'
alias ff='forward_stack'
alias ll='list_stack_reverse'
alias gg='goto_stack'
alias dcl='clear_directory_stack'
# Directory stack ends