#!/bin/sh
# Compatible with ranger 1.6.0 through 1.7.*
#
# This script searches image files in a directory, opens them all with sxiv and
# sets the first argument to the first image displayed by sxiv.
#
# This is supposed to be used in rifle.conf as a workaround for the fact that
# sxiv takes no file name arguments for the first image, just the number.  Copy
# this file somewhere into your $PATH and add this at the top of rifle.conf:
#
#   mime ^image, has sxiv, X, flag f = path/to/this/script -- "$@"
#
# Implementation notes: this script is quite slow because of POSIX limitations
# and portability concerns. First calling the shell function 'abspath' is
# quicker than calling 'realpath' because it would fork a whole process, which
# is slow. Second, we need to append a file list to sxiv, which can only be done
# properly in two ways: arrays (which are not POSIX) or \0 sperated
# strings. Unfortunately, assigning \0 to a variable is not POSIX either (will
# not work in dash and others), so we cannot store the result of listfiles to a
# variable.

if [ $# -eq 0 ]; then
    echo "Usage: ${0##*/} PICTURES"
    exit
fi

[ "$1" = '--' ] && shift

abspath () {
    case "$1" in
        /*) printf "%s\n" "$1";;
        *)  printf "%s\n" "$PWD/$1";;
    esac
}

listfiles () {
    find -L "$(dirname "$target")" -maxdepth 1 -type f -iregex \
      '.*\(jpe?g\|bmp\|png\|gif\)$' -print0 | sort -z
}

target="$(abspath "$1")"
count="$(listfiles | grep -m 1 -ZznF "$target" | cut -d: -f1)"

if [ -n "$count" ]; then
    listfiles | xargs -0 sxiv -n "$count" --
else
    sxiv -- "$@" # fallback
fi