# License at bottom.

# Update after FIFO change.
cdlog.update()
{
  # Update the one-letter nicknames for most recent four dirs.
  x=$c1
  y=$c2
  z=$c3
  w=$c4

  # Persist to disk.
  cat > "$cdlog_dirs" <<!
$PWD
$c1
$c2
$c3
$c4
$c5
$c6
$c7
$c8
$c9
!
}

# Set state from args
cdlog.args()
{
  c1=$1; c2=$2; c3=$3
  c4=$4; c5=$5; c6=$6
  c7=$7; c8=$8; c9=$9

  cdlog.update
}

# Utility for nth positional param
cdlog.get_param()
{
  if shift $1 ; then
    echo "$1"
  fi
}

# Initialize state, allocating new ~/.cdlog.N.dirs storage,
# with LRU replacement.
cdlog.init()
{
  local i
  local oldest
  local context

  c9=; c8=; c7=
  c6=; c5=; c4=
  c3=; c2=

  cdlog_dirs=
  context=

  for i in {1..10}; do
    if ! [ -f ~/.cdlog.$i.dirs ] ; then
      context=$i
      break
    fi
  done

  if ! [ $context ] ; then
    oldest=1
    for i in {2..10}; do
      if [ ~/.cdlog.$i.dirs -ot ~/.cdlog.$oldest.dirs ] ; then
        oldest=$i
      fi
    done
    context=$oldest
  fi

  cdlog_dirs=~/.cdlog.$context.dirs
  rm -f $cdlog_dirs

  set -- ~/.cdlog.*.dirs
  if [ $# -gt 0 -a $1 != ~/.cdlog.'*'.dirs ] ; then
    printf "Use 'cdr' or 'cdlog.recover' to switch to prior cdlog context.\n"
  fi
}

cdlog.recover()
{
  local -a d
  local dir
  local i
  local sel

  set -- ~/.cdlog.*.dirs

  if [ $# -gt 0 -a $1 != ~/.cdlog.'*'.dirs ] ; then
    printf "These cdlog contexts exist:\n"
    i=0
    for dir in "$@"; do
      printf "[%d]: %s\n" $((++i)) "$(date -r "$dir")"
      sed -e '/^$/d' "$dir"
    done

    while true; do
      if [ $i -eq 1 ] ; then
        printf "Use 1 to select context, c1 to clone,\n"
      else
        printf "Use 1-%s to select context, c1-c%s to clone,\n" $i $i
      fi
      printf "or Enter to keep current context: "
      read sel
      case $sel in
      ( [1-9] )
        sel=$(cdlog.get_param $sel "$@")
        if [ -n "$sel" ] ; then
          cdlog_dirs=$sel
          break
        fi
        ;;
      ( c[1-9] )
        sel=$(cdlog.get_param ${sel#c} "$@")
        if [ -n "$sel" ] ; then
          cp "$sel" "$cdlog_dirs"
          break
        fi
        ;;
      ( "" )
        break
        ;;
      esac
    done
  fi

  if [ -f "$cdlog_dirs" ] ; then
    mapfile -t d < "$cdlog_dirs"
    command cd "${d[0]}"
    unset d[0]
    cdlog.args "${d[@]}"
  fi
}

# Change to directory: this is aliased to cd command.
cdlog.chdir()
{
  local cur=$PWD

  if command cd "$@" && [ "$PWD" != "$cur" ]; then
    # only if we successfully change to a different
    # directory do the following

    c9=$c8; c8=$c7; c7=$c6
    c6=$c5; c5=$c4; c4=$c3
    c3=$c2; c2=$c1

    c1=$cur

    cdlog.update
  fi
}

# Rotate through specified directories.
cdlog.rot()
{
  local cur=$PWD
  local p=$cur
  local n=$cur
  local d=("" "$c1" "$c2" "$c3" "$c4" "$c5" "$c6" "$c7" "$c8" "$c9")
  local first=y

  unset d[0]

  [ $# -gt 0 ] || set 1

  while [ $# -gt 0 ] ; do
    n=$1; shift
    case $n in
    ( [1-9] )
      if [ $first ] ; then
        command cd "${d[$n]}" || return
        printf "%s\n" "$PWD"
      else
        d[$p]=${d[$n]}
      fi
      first=
      p=$n
      ;;
    ( * )
      printf "cdlog.rot: bad argument: %s\n" "$n"
      return 1
      ;;
    esac
  done

  d[$p]=$cur

  cdlog.args "${d[@]}"
}


# Change to most recent diretory in cdlog and remove it
# from the log.
cdlog.pop()
{
  local d=("" "$c1" "$c2" "$c3" "$c4" "$c5" "$c6" "$c7" "$c8" "$c9")
  local n=1
  local i

  unset d[0]

  if [ $# -gt 0 ] ; then
    n=$1; shift
  fi

  case $n in
  ( [1-9] )
    if command cd "${d[$n]}" ; then
      for ((i = n; i <= 8; i++)); do
        d[$i]=${d[$((i + 1))]}
      done
      d[9]=
      cdlog.args "${d[@]}"
      printf "%s\n" "$PWD"
    fi
    ;;
  ( * )
    printf "cdlog.pop: bad argument: %s\n" "$n"
    return 1
    ;;
  esac
}

# Print four recent cdlog entries.
cdlog()
{
  printf "1: %s\n" "$c1"
  printf "2: %s\n" "$c2"
  printf "3: %s\n" "$c3"
  printf "4: %s\n" "$c4"

  if [ "${1-}" = "-l" ] ; then
    printf "5: %s\n" "$c5"
    printf "6: %s\n" "$c6"
    printf "7: %s\n" "$c7"
    printf "8: %s\n" "$c8"
    printf "9: %s\n" "$c9"
  fi
}

# Menu-based cd/cs.
cdlog.mcd()
{
  local sel=
  local swap=
  local res=1
  local i
  local d=("" "$c1" "$c2" "$c3" "$c4" "$c5" "$c6" "$c7" "$c8" "$c9")

  if [ $# -gt 0 ] && [ "$1" = -s ] ; then
    swap=y
  fi

  for i in {1..9}; do
    printf "%s: %s\n" $i "${d[$i]}"
  done

  read -p "? " sel

  for i in {1..10}; do
    printf "\e[A\e[K"
  done

  case "$sel" in
  ( [1-9] )
    if [ $swap ] ; then
      cdlog.rot $sel
    else
      if cdlog.chdir -P "${d[$sel]}" ; then
        printf "%s\n" "$PWD"
      fi
    fi
    res=$?
    ;;
  esac

  return $res
}

# Aliases.
alias cd='cdlog.chdir -P'
alias pd='cdlog.pop'
alias cs='cdlog.rot'
alias cl='cdlog'
alias cll='cdlog -l'
alias mcd='cdlog.mcd'
alias mcs='cdlog.mcd -s'
alias cdr='cdlog.recover'

# Better completion for $x[Tab]
shopt -s direxpand

# Initialize cdlog the first time.

c1=${c1-}

if [ -z "$c1" -o -z "$cdlog_dirs" ] ; then
  cdlog.init
fi


# Copyright 2024
# Kaz Kylheku <kaz@kylheku.com>
# Vancouver, Canada
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following condition is met:
#
# 1. Redistributions of source code must retain the above copyright notice, this
#    list of conditions and the following disclaimer.
#
# 2. Redistributions in binary form need not reproduce any copyright notice.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.