# Description
# ===========
#
# Change to a recently used directory recorded in a file so that the
# recent file list persists across sessions.
#
# To use this system,
#
#   autoload -Uz chpwd_recent_dirs cdr add-zsh-hook
#   add-zsh-hook chpwd chpwd_recent_dirs
#
# (add-zsh-hook appeared in zsh version 4.3.4.)  This ensures that all
# directories you change to interactively are registered.  The
# chpwd_recent_dirs function does some guesswork to see if you are "really"
# changing directory permanently, see below.
#
# The argument to cdr is a number corresponding to the Nth most recently
# changed-to directory starting at 1 for the immediately preceding
# directory (the current directory is remembered but is not offered as a
# destination).  You can use directory arguments if you set the
# recent-dirs-default style, see below; however, it should be noted
# that if you do you gain nothing over using cd directly (the recent
# directory list is updated in either case).
#
# If the argument is omitted, 1 is assumed.
#
# Completion is available if compinit has been run; menu selection is
# recommended, using
#
#   zstyle ':completion:*:*:cdr:*:*' menu selection
#
# and also the verbose style to ensure the directory is shown (this
# is on by default).
#
# Options
# =======
#
# "cdr -l" lists the numbers and the corresponding directories in
# abbreviated form (i.e. with "~" substitution reapplied), one per line.
# The directories here are not quoted (this would only be an issue if a
# directory name contained a newline).  This is used by the completion
# system.
#
# "cdr -r" sets the parameter "reply" to the current set of directories.
#
# "cdr -e" allows you to edit the list of directories, one per line.  The
# list can be edited to any extent you like; no sanity checking is
# performed.  Completion is available.  No quoting is necessary (except for
# newlines, where I have in any case no sympathy); directories are in
# unabbreviated from and contain an absolute path, i.e. they start with /
# (and only /).  Usually the first entry should be left as the current
# directory.
#
# "cdr -p 'pattern'" prunes anything matching the given extended glob
# pattern from the directory list.  The match is against the fully
# expanded directory path and the full string must match (use wildcards
# at the ends if needed).  If output is going to a terminal, the
# function will print the new list for the user to confrim; this can be
# skipped by giving -P instead of -p.
#
# Details of directory handling
# =============================
#
# Recent directories are saved to a file immediately and hence are
# preserved across sessions.  Note currently no file locking is applied:
# the list is updated immediately on interactive commands and nowhere else
# (unlike history), and it is assumed you are only going to change
# directory in one window at once.  This is not safe on shared accounts,
# but in any case the system has limited utility when someone else is
# changing to a different set of directories behind your back.
#
# To make this a little safer, only directory changes instituted from the
# command line, either directly or indirectly through shell function calls
# (but not through subshells, evals, traps, completion functions and the
# like) are saved.  This works best in versions of the shell from 4.3.11
# which has facilities to check the evaluation context.  Shell functions
# should use cd -q or pushd -q to avoid side effects if the change to the
# directory is to be invisible at the command line.  See the function
# chpwd_recent_dirs for more details.
#
# Styles
# ======
#
# Various styles are available.  The context for setting styles should be
# ':chpwd:*' in case the meaning of the context is extended in future, for
# example:
#
#   zstyle ':chpwd:*' recent-dirs-max 0
#
# although the style name is specific enough that a context of '*' should
# be fine in practice.  The only exception is recent-dirs-insert, which is
# used exclusively by the completion system and so has the usual completion
# system context (':completion:*' if nothing more specific is needed,
# though again '*' should be fine in practice).
#
#   recent-dirs-default
#     If true, and the command is expecting a recent directory index, and
#     either there is more than one argument or the argument is not an
#     integer, then fall through to "cd".  This allows the lazy to use only
#     one command for directory changing.  Completion recognises this, too;
#     see recent-dirs-insert for how to control completion when this option
#     is in use.
#
#   recent-dirs-file
#     The file where the list of directories is saved.  The default
#     is ${ZDOTDIR:-$HOME}/.chpwd-recent-dirs, i.e. this is in your
#     home directory unless you have set ZDOTDIR to point somewhere else.
#     Directory names are saved in $'...' quoted form, so each line
#     in the file can be supplied directly to the shell as an argument.
#
#     The value of this style may be an array.  In this case, the first
#     file in the list will always be used for saving directories while any
#     other files are left untouched.  When reading the recent directory
#     list, if there are fewer than the maximum number of entries in the
#     first file, the contents of later files in the array will be appended
#     with duplicates removed from the list shown.  The contents of the two
#     files are not sorted together, i.e. all the entries in the first file
#     are shown first.  The special value "+" can appear in the list to
#     indicate the default file should be read at that point.  This allows
#     effects like the following:
#
#       zstyle recent-dirs-file ':chpwd:*' ~/.chpwd-recent-dirs-${TTY##*/} +
#
#     Recent directories are read from a file numbered according to
#     the terminal.  If there are insufficient entries the list
#     is supplemented from the default file.
#
#   recent-dirs-insert
#     Used by completion.  If recent-dirs-default is true, then setting
#     this to true causes the actual directory, rather than its index, to
#     be inserted on the command line; this has the same effect as using
#     the corresponding index, but makes the history clearer and the line
#     easier to edit.  With this setting, if part of an argument was
#     already typed, normal directory completion rather than recent
#     directory completion is done; this is because recent directory
#     completion is expected to be done by cycling through entries menu
#     fashion.  However, if the value of the style is "always", then only
#     recent directories will be completed; in that case, use the cd
#     command when you want to complete other directories.  If the value is
#     "fallback", recent directories will be tried first, then normal
#     directory completion is performed if recent directory completion
#     failed to find a match.  Finally, if the value is "both" then both
#     sets of completions are presented; the usual tag mechanism can be
#     used to distinguish results, with recent directories tagged as
#     "recent-dirs".  Note that the recent directories inserted are
#     abbreviated with directory names where appropriate.
#
#   recent-dirs-max
#     The maximum number of directories to save to the file.  If
#     this is zero or negative there is no maximum.  The default is 20.
#     Note this includes the current directory, which isn't offered,
#     so the highest number of directories you will be offered
#     is one less than the maximum.
#
#   recent-dirs-prune
#     This style is an array determining what directories should (or should
#     not) be added to the recent list.  Elements of the array can include:
#       parent
#         Prune parents (more accurately, ancestors) from the recent list.
#         If present, changing directly down by any number of directories
#         causes the current directory to be overwritten.  For example,
#         changing from ~pws to ~pws/some/other/dir causes ~pws not to be
#         left on the recent directory stack.  This only applies to direct
#         changes to descendant directories; earlier directories on the
#         list are not pruned.  For example, changing from ~pws/yet/another
#         to ~pws/some/other/dir does not cause ~pws to be pruned.
#       pattern:<pattern>
#         Gives a zsh pattern for directories that should not be
#         added to the recent list (if not already there).  This element
#         can be repeated to add different patterns.  For example,
#         'pattern:/tmp(|/*)' stops /tmp or its descendants from being
#         added.  The EXTENDED_GLOB option is always turned on for
#         these patterns.
#
#   recent-dirs-pushd
#     If set to true, cdr will use pushd instead of cd to change the
#     directory, so the directory is saved on the directory stack.  As the
#     directory stack is completely separate from the list of files saved
#     by the mechanism used in this file there is no obvious reason to do
#     this.
#
# Use with dynamic directory naming
# =================================
#
# It is possible to refer to recent directories using the dynamic directory
# name syntax that appeared in zsh version 4.3.7.  If you create and
# autoload a function zsh_directory_name containing the following code,
# ~[1] will refer to the most recent directory other than $PWD, and so on.
# This also includes completion (version 4.3.11 is required for this to
# work; previous versions needed the file _dynamic_directory_name to
# be overloaded).
#
#   if [[ $1 = n ]]; then
#     if [[ $2 = <-> ]]; then
#       # Recent directory
#       typeset -ga reply
#       autoload -Uz cdr
#       cdr -r
#       if [[ -n ${reply[$2]} ]]; then
#         reply=(${reply[$2]})
#         return 0
#       else
#         reply=()
#         return 1
#       fi
#     fi
#   elif [[ $1 = c ]]; then
#     if [[ $PREFIX = <-> || -z $PREFIX ]]; then
#       typeset -a keys values
#   
#       values=(${${(f)"$(cdr -l)"}/ ##/:})
#       keys=(${values%%:*})
#   
#       _describe -t dir-index 'recent directory index' \
#         values keys -V unsorted -S']'
#       return
#     fi
#   fi
#   return 1


emulate -L zsh
setopt extendedglob

autoload -Uz chpwd_recent_filehandler chpwd_recent_add

integer list set_reply i bad edit force_prune
local opt dir prune
local -aU dirs

while getopts "elp:P:r" opt; do
  case $opt in
    (e)
    edit=1
    ;;

    (l)
    list=1
    ;;

    ([pP])
    prune=$OPTARG
    edit=1
    [[ $opt = P ]] && force_prune=1
    ;;

    (r)
    set_reply=1
    ;;

    (*)
    return 1
    ;;
  esac
done
shift $(( OPTIND - 1 ))

if (( set_reply )); then
  typeset -ga reply
else
  local -a reply
fi

if (( list || set_reply || edit )); then
  (( $# )) && bad=1
else
  if [[ $#1 -eq 0 ]]; then
    1=1
  elif [[ $# -ne 1 || $1 != <-> ]]; then
    if zstyle -t ':chpwd:' recent-dirs-default; then
      cd "$@"
      return
    else
      bad=1
    fi
  fi
fi

if (( bad )); then
  print "Usage: $0 [-l | -r | <dir-num> ]
Use $0 -l or completion to see possible directories."
  return 1
fi

chpwd_recent_filehandler

if [[ $PWD != $reply[1] ]]; then
  # When we first start we don't have the current directory.
  # Add it now for consistency.
  chpwd_recent_add $PWD && chpwd_recent_filehandler $reply
fi

if (( edit )); then
  if [[ -n $prune ]]; then
    reply=(${reply:#$~prune})
    if [[ force_prune -eq 0 && -t 1 ]]; then
      print -nrl "New list:" $reply 'Accept? '
      if ! read -q; then
	print
	return 1
      fi
      print
    fi
  else
    local compcontext='directories:directory:_path_files -/'
    IFS='
' vared reply || return 1
  fi
  chpwd_recent_filehandler $reply
fi

# Skip current directory if present (may have been pruned).
[[ $reply[1] = $PWD ]] && reply=($reply[2,-1])

if (( list )); then
  dirs=($reply)
  for (( i = 1; i <= ${#dirs}; i++ )); do
    print -n ${(r.5.)i}
    print -r ${(D)dirs[i]}
  done
  return
fi

(( set_reply || edit )) && return

if (( $1 > ${#reply} )); then
  print "Not enough directories ($(( ${#dirs} - 1)) possibilities)" >&2
  return 1
fi
dir=${reply[$1]}

if zstyle -t ':chpwd:' recent-dirs-pushd; then
  pushd -- $dir
else
  cd -- $dir
fi