#!/usr/bin/env zsh
  #
  # This is a implementation of per directory history for zsh, some
  # implementations of which exist in bash[1,2].  It also implements
  # a per-directory-history-toggle-history function to change from using the
  # directory history to using the global history.  In both cases the history is
  # always saved to both the global history and the directory history, so the
  # toggle state will not effect the saved histories.  Being able to switch
  # between global and directory histories on the fly is a novel feature as far
  # as I am aware.
  #
  #-------------------------------------------------------------------------------
  # Configuration
  #-------------------------------------------------------------------------------
  #
  # HISTORY_BASE a global variable that defines the base directory in which the
  # directory histories are stored
  #
  #-------------------------------------------------------------------------------
  # History
  #-------------------------------------------------------------------------------
  #
  # The idea/inspiration for a per directory history is from Stewart MacArthur[1]
  # and Dieter[2], the implementation idea is from Bart Schaefer on the the zsh
  # mailing list[3].  The implementation is by Jim Hester in September 2012.
  #
  # [1]: http://www.compbiome.com/2010/07/bash-per-directory-bash-history.html
  # [2]: http://dieter.plaetinck.be/per_directory_bash
  # [3]: http://www.zsh.org/mla/users/1997/msg00226.html
  #
  ################################################################################
  #
  # Copyright (c) 2012 Jim Hester
  #
  # This software is provided 'as-is', without any express or implied warranty. 
  # In no event will the authors be held liable for any damages arising from the
  # use of this software.
  #
  # Permission is granted to anyone to use this software for any purpose,
  # including commercial applications, and to alter it and redistribute it
  # freely, subject to the following restrictions:
  #
  # 1. The origin of this software must not be misrepresented; you must not claim
  # that you wrote the original software. If you use this software in a product,
  # an acknowledgment in the product documentation would be appreciated but is
  # not required.
  #
  # 2. Altered source versions must be plainly marked as such, and must not be
  # misrepresented as being the original software.
  #
  # 3. This notice may not be removed or altered from any source distribution..
  #
  ################################################################################
  
  #-------------------------------------------------------------------------------
  # configuration, the base under which the directory histories are stored
  #-------------------------------------------------------------------------------
  
  [[ -z $HISTORY_BASE ]] && HISTORY_BASE="$HOME/.directory_history"
  
  #-------------------------------------------------------------------------------
  # toggle global/directory history used for searching - ctrl-G by default
  #-------------------------------------------------------------------------------
  
  function per-directory-history-toggle-history() {
    if [[ $_per_directory_history_is_global == true ]]; then
      _per-directory-history-set-directory-history
      print -n "
  using local history"
    else
      _per-directory-history-set-global-history
      print -n "
  using global history"
    fi
    zle .push-line
    zle .accept-line
  }
  
  autoload per-directory-history-toggle-history
  zle -N per-directory-history-toggle-history
  bindkey '^G' per-directory-history-toggle-history
  
  #-------------------------------------------------------------------------------
  # implementation details
  #-------------------------------------------------------------------------------
  
  _per_directory_history_directory="$HISTORY_BASE${PWD:A}/history"
  
  function _per-directory-history-change-directory() {
    _per_directory_history_directory="$HISTORY_BASE${PWD:A}/history"
    mkdir -p ${_per_directory_history_directory:h}
    if [[ $_per_directory_history_is_global == false ]]; then
      #save to the global history
      fc -AI $HISTFILE
      #save history to previous file
      local prev="$HISTORY_BASE${OLDPWD:A}/history"
      mkdir -p ${prev:h}
      fc -AI $prev
  
      #discard previous directory's history
      local original_histsize=$HISTSIZE
      HISTSIZE=0
      HISTSIZE=$original_histsize
  
      #read history in new file
      if [[ -e $_per_directory_history_directory ]]; then
        fc -R $_per_directory_history_directory
      fi
    fi
  }
  
  function _per-directory-history-addhistory() {
    print -Sr -- ${1%%$'
  '}
    fc -p $_per_directory_history_directory
  }
  
  
  function _per-directory-history-set-directory-history() {
    if [[ $_per_directory_history_is_global == true ]]; then
      fc -AI $HISTFILE
      local original_histsize=$HISTSIZE
      HISTSIZE=0
      HISTSIZE=$original_histsize
      if [[ -e "$_per_directory_history_directory" ]]; then
        fc -R "$_per_directory_history_directory"
      fi
    fi
    _per_directory_history_is_global=false
  }
  function _per-directory-history-set-global-history() {
    if [[ $_per_directory_history_is_global == false ]]; then
      fc -AI $_per_directory_history_directory
      local original_histsize=$HISTSIZE
      HISTSIZE=0
      HISTSIZE=$original_histsize
      if [[ -e "$HISTFILE" ]]; then
        fc -R "$HISTFILE"
      fi
    fi
    _per_directory_history_is_global=true
  }
  
  
  #add functions to the exec list for chpwd and zshaddhistory
  chpwd_functions=(${chpwd_functions[@]} "_per-directory-history-change-directory")
  zshaddhistory_functions=(${zshaddhistory_functions[@]} "_per-directory-history-addhistory")
  
  #start in directory mode
  mkdir -p ${_per_directory_history_directory:h}
  _per_directory_history_is_global=true
  _per-directory-history-set-directory-history