# Automatically update the environment when the current working directory
# changes, this is a reimplementation of the ideas found in the repository
# https://github.com/Tarrasch/zsh-autoenv stripped down to suit my specific
# needs.

# Global entered directories array.
_autoenv_entered=()

# Check if the given file is authorized, if not prompt the user to authorize,
# ignore, or view the file. Authorized files and their modified times are
# stored in the ~/.cache/autoenv/authorized file to make authorization
# persistant.
_autoenv_authorized() {
  local file=$1
  # If autoenv cache directory does not exist, create it.
  local cache_dir=~/.config/autoenv
  ! [ -d $cache_dir ] && mkdir -p $cache_dir
  local authorized_file=$cache_dir/authorized
  # Define the associative array to hold authorized key value pairs.
  # If the authorized file exists, load it into an associative array.
  typeset -A authorized=()
  [ -f $authorized_file ] && typeset -A authorized=(`cat $authorized_file`)
  # If the given file has been authorized, return.
  local modified_time=`zstat +mtime $file`
  [ "$authorized[$file]" = "$modified_time" ] && return
  # Prompt to authorize file.
  while true; do
    read "answer?Authorize $file [Y/n/v]? "
    case "$answer" in
      y|Y|yes|'')             # Authorize the file.
        authorized[$file]=$modified_time; break ;;
      n|N|no) return 1 ;;     # Do not authorize the file.
      v|V|view) cat $file ;;  # View the file.
    esac
  done
  # Store authorized associative array in authorized file.
  echo ${(kv)authorized) > $authorized_file
}

# Source an enter script and add its directory to the global entered
# directories array.
_autoenv_enter() {
  local entered=$1
  # If entered exists in the entered directories array, return.
  (( ${+_autoenv_entered[${_autoenv_entered[(i)$entered]}]} )) && return
  # If the enter script is not authorized, return.
  _autoenv_authorized $entered/.enter || return
  # Source the enter script.
  source $entered/.enter
  # Add the entered directory to the global entered array.
  _autoenv_entered+=$entered
}

# Source an exit script and remove its directory from the global entered
# directories array.
_autoenv_exit() {
  local entered=$1
  # If the exit script is not authorized, return.
  _autoenv_authorized $entered/.exit || return
  # Source the exit script.
  source $entered/.exit
  # Remove the entered directory from the global entered array.
  _autoenv_entered[${_autoenv_entered[(i)$entered]}]=()
}

# Find a directory containing a .enter file by searching up the directory tree
# starting in the current directory.
_autoenv_find_enter() {
  local current=$PWD
  # If an enter script is found in the current directory, return it.
  [ -f "$current/.enter" ] && echo $current
  # Loop until an enter script or the root directory is found.
  while true; do
    # Go up one directory and make the path absolute.
    local next=$current/..; local next=${next:A}
    # If the current directory equals the next directory, return.
    [[ $current == $next ]] && return || local current=$next
    # If an enter script is found in the current directory, return it.
    [ -f $current/.enter ] && echo $current
  done
}

# A chpwd hook function which automatically sources enter and exit scripts to
# setup local environments for directory and its subdirectories.
_autoenv_chpwd() {
  local entered
  # Loop over the entered directory stack.
  for entered in $_autoenv_entered; do
    # If the the current directory was previously entered then exit.
    # TODO: Verify what this condition expression actually does.
    ! [[ $PWD/ == $entered/* ]] && _autoenv_exit $entered
  done
  # Find the nearest enter script directory.
  local enter=`_autoenv_find_enter`
  # If the enter directory exists, enter it.
  [ -d "$enter" ] && _autoenv_enter $enter
}

# Register the autoenv chpwd hook.
autoload -U add-zsh-hook
add-zsh-hook chpwd _autoenv_chpwd

# Ensure autoenv is activated in the current directory on first load.
_autoenv_chpwd