#!/usr/bin/env zsh
#
# Usage: -z4h-find-prev-zword
#
# Sets reply=(START END) such that BUFFER[START,END] contains the shell word
# that the cursor is on, or the previous shell word if the cursor is on
# whitespace. If there are no shell words in $PREBUFFER$BUFFER, return 1
# without setting reply. START and END can be non-positive, which means that
# a part of the shell word is in PREBUFFER.

emulate -L zsh -o extended_glob
local word buf=$PREBUFFER$BUFFER
for word in '' ${(Z:n:)buf}; do
  tail=${${buf:$#word}##[[:space:]]#}
  (( ! $#tail || $#tail < $#RBUFFER )) && break
  buf=$tail
done
[[ -n $word ]] || return
local -i start=$(($#BUFFER - $#buf + 1))
local -i end=$((start + $#word - 1))
typeset -g reply=($start $end)