refactor(bgnotify): clean up and reorganize code

plugins/bgnotify/bgnotify.plugin.zsh

 #!/usr/bin/env zsh
 
-## setup ##
+## Setup
 
-[[ -o interactive ]] || return #interactive only!
-zmodload zsh/datetime || { print "can't load zsh/datetime"; return } # faster than date()
-autoload -Uz add-zsh-hook || { print "can't add zsh hook!"; return }
+[[ -o interactive ]] || return # don't load on non-interactive shells
+[[ -z "$SSH_CLIENT" && -z "$SSH_TTY" ]] || return # don't load on a SSH connection
 
-(( ${+bgnotify_threshold} )) || bgnotify_threshold=5 #default 10 seconds
+zmodload zsh/datetime # faster than `date`
 
 
-## definitions ##
+## Zsh Hooks
 
-if ! (type bgnotify_formatted | grep -q 'function'); then ## allow custom function override
-  function bgnotify_formatted { ## args: (exit_status, command, elapsed_seconds)
-    elapsed="$(( $3 % 60 ))s"
-    (( $3 >= 60 )) && elapsed="$((( $3 % 3600) / 60 ))m $elapsed"
-    (( $3 >= 3600 )) && elapsed="$(( $3 / 3600 ))h $elapsed"
-    [ $1 -eq 0 ] && bgnotify "#win (took $elapsed)" "$2" || bgnotify "#fail (took $elapsed)" "$2"
+function bgnotify_begin {
+  bgnotify_timestamp=$EPOCHSECONDS
+  bgnotify_lastcmd="${1:-$2}"
+}
+
+function bgnotify_end {
+  {
+    local exit_status=$?
+    local elapsed=$(( EPOCHSECONDS - bgnotify_timestamp ))
+
+    # check time elapsed
+    [[ $bgnotify_timestamp -gt 0 ]] || return
+    [[ $elapsed -ge $bgnotify_threshold ]] || return
+
+    # check if Terminal app is not active
+    [[ $(bgnotify_appid) != "$bgnotify_termid" ]] || return
+
+    printf '\a' # beep sound
+    bgnotify_formatted "$exit_status" "$bgnotify_lastcmd" "$elapsed"
+  } always {
+    bgnotify_timestamp=0
   }
-fi
+}
+
+autoload -Uz add-zsh-hook
+add-zsh-hook preexec bgnotify_begin
+add-zsh-hook precmd bgnotify_end
+
+
+## Functions
+
+# allow custom function override
+(( ${+functions[bgnotify_formatted]} )) || \
+function bgnotify_formatted {
+  local exit_status=$1
+  local cmd="$2"
 
+  # humanly readable elapsed time
+  local elapsed="$(( $3 % 60 ))s"
+  (( $3 < 60 )) || elapsed="$((( $3 % 3600) / 60 ))m $elapsed"
+  (( $3 < 3600 )) || elapsed="$(( $3 / 3600 ))h $elapsed"
+
+  if [[ $1 -eq 0 ]]; then
+    bgnotify "#win (took $elapsed)" "$2"
+  else
+    bgnotify "#fail (took $elapsed)" "$2"
+  fi
 }
 
-function currentAppId {
+# for macOS, output is "app ID, window ID" (com.googlecode.iterm2, 116)
+function bgnotify_appid {
   if (( ${+commands[osascript]} )); then
-    # output: com.googlecode.iterm2, 116
     osascript -e 'tell application (path to frontmost application as text) to get the {id, id of front window}' 2>/dev/null
-  elif (( ${+commands[notify-send]} || ${+commands[kdialog]} )); then
-    xprop -root 2> /dev/null | awk '/NET_ACTIVE_WINDOW/{print $5;exit} END{exit !$5}' || echo "0"
+  elif (( ${+commands[xprop]} )); then
+    xprop -root _NET_ACTIVE_WINDOW 2>/dev/null | cut -d' ' -f5
   else
     echo $EPOCHSECONDS
   fi
 }
 
-# currentAppId is expensive (more on macOS!) and it will remain the same until the shell is close
-bgnotify_termid=$(currentAppId)
-
-bgnotify () { ## args: (title, subtitle)
-  if hash terminal-notifier 2>/dev/null; then #osx
+function bgnotify {
+  # $1: title, $2: message
+  if (( ${+commands[terminal-notifier]} )); then # macOS
     local term_id="${bgnotify_termid%%,*}" # remove window id
     if [[ -z "$term_id" ]]; then
       case "$TERM_PROGRAM" in
@@ -46,46 +81,26 @@ bgnotify () { ## args: (title, subtitle)
       esac
     fi
 
-    ## now call terminal-notifier, (hopefully with $term_id!)
     if [[ -z "$term_id" ]]; then
-      terminal-notifier -message "$2" -title "$1" >/dev/null
+      terminal-notifier -message "$2" -title "$1" &>/dev/null
     else
-      terminal-notifier -message "$2" -title "$1" -activate "$term_id" -sender "$term_id" >/dev/null
+      terminal-notifier -message "$2" -title "$1" -activate "$term_id" -sender "$term_id" &>/dev/null
     fi
-  elif hash growlnotify 2>/dev/null; then #osx growl
+  elif (( ${+commands[growlnotify]} )); then # macOS growl
     growlnotify -m "$1" "$2"
-  elif hash notify-send 2>/dev/null; then #ubuntu gnome!
+  elif (( ${+commands[notify-send]} )); then # GNOME
     notify-send "$1" "$2"
-  elif hash kdialog 2>/dev/null; then #ubuntu kde!
+  elif (( ${+commands[kdialog]} )); then # KDE
     kdialog --title "$1" --passivepopup  "$2" 5
-  elif hash notifu 2>/dev/null; then #cygwyn support!
+  elif (( ${+commands[notifu]} )); then # cygwin
     notifu /m "$2" /p "$1"
   fi
 }
 
+## Defaults
 
-## Zsh hooks ##
-
-bgnotify_begin() {
-  bgnotify_timestamp=$EPOCHSECONDS
-  bgnotify_lastcmd="${1:-$2}"
-}
-
-bgnotify_end() {
-  didexit=$?
-  elapsed=$(( EPOCHSECONDS - bgnotify_timestamp ))
-  past_threshold=$(( elapsed >= bgnotify_threshold ))
-  if (( bgnotify_timestamp > 0 )) && (( past_threshold )); then
-    if [[ $(currentAppId) != "$bgnotify_termid" ]]; then
-      print -n "\a"
-      bgnotify_formatted "$didexit" "$bgnotify_lastcmd" "$elapsed"
-    fi
-  fi
-  bgnotify_timestamp=0 #reset it to 0!
-}
+# notify if command took longer than 5s by default
+bgnotify_threshold=${bgnotify_threshold:-5}
 
-## only enable if a local (non-ssh) connection
-if [ -z "$SSH_CLIENT" ] && [ -z "$SSH_TTY" ]; then
-  add-zsh-hook preexec bgnotify_begin
-  add-zsh-hook precmd bgnotify_end
-fi
+# bgnotify_appid is slow in macOS and the terminal ID won't change, so cache it at startup
+bgnotify_termid="$(bgnotify_appid)"