#!/bin/sh
# cause plain rm wasn't good enough
# auto selects what trash directory to put files in if rmtrash is available
# otherwise, uses rm

set -eu

rm='rm'

err_differing_filesystems() {
   echo 'Error: some files are apart of different filesystems.' >&2
   # shellcheck disable=SC2016
   echo 'Either set RM=rm to force not using `trash`, or remove the files individually' >&2
}

fs(){
   df "$1" | sed '1d' | cut -d ' ' -f 1
}

dbg() {
   echo "$@" >&2
}

rm_warning() {
   echo 'WARNING: using rm - NOT trash. Files will be PERMINANTLY DELETED!' >&2
   printf '%s'  "Type Y to continue: " >&2
   read -r confirm
   if [ "$confirm" != 'Y' ]; then
      printf '\n'
      exit 1
   fi
   echo 'Waiting 3 seconds before continuing.' >&2
   sleep 3
}

rm_custom_warning() {
   echo 'WARNING: using custom rm command: '"$rm" >&2
   echo 'This might NOT use the trash'
   echo ''
   echo 'Waiting 5 seconds before continuing.' >&2
   sleep 5
}

err_no_trashdirs() {
   echo 'Error: No trash directorys with matching filesystems are available.' >&2
   echo 'Please set TRASH_DIRS to a colon-separated list of your preferred trash directories.' >&2
}

usage() {
   echo "Wrapper for rm and rm-trash commands"
   echo ""
   echo "Environment:"
   echo " RM          Force using a particular rm command."
   # shellcheck disable=SC2016
   echo ' TRASH_DIRS  What directories to use as trash locations for `trash`.'
   echo ' DRY         Dry run: print the rm command instead of executing it.'
   echo ""
   echo "Usage:"
   echo " ${0##*/} [ARGS]"
   echo ""
   echo "Where ARGS is the argument list corresponding to the rm command to be used."
   echo ""
   echo "Current selection for rm command: $which_rm"
}

do_rm() {
   if [ "${DRY:-false}" = true ]; then
      echo "$rm" "$@"
   else
      "$rm" "$@"
   fi
}

do_rmnormal() {
   # shellcheck disable=SC2209
   rm=rm
   rm_warning
   do_rm "$@"
}

do_rmcustom() {
   # check if we have been given an rm command
   rm="$RM"
   rm_custom_warning
   do_rm "$@"
}

do_rmtrash() {
   # get trash directories
   trash_default_fallback="$HOME"/.local/share
   trash_default="${XDG_DATA_HOME:-"$trash_default_fallback"}/Trash"
   trashdirs="${TRASH_DIRS:-"$trash_default"}"

   # if trash is available, use it
   rm='trash'
   fs1=''
   # validate that all files are on the same filesystem
   for a; do
      if [ -e "$a" ]; then
         fs="$(fs "$a")"
         if [ -z "$fs1" ]; then
            fs1="$fs"
            # this will only run the first time through the loop
            continue
         fi
         # ensure all files are on the same filesystem
         if [ "$fs1" != "$fs" ]; then
            err_differing_filesystems
            exit 1
         fi
      fi
   done
   if [ "$fs1" != '' ]; then
      # if we get here, we have validated that all the files are on the same filesystem
      trashdir=''
      found_trash=false
      while [ "$trashdirs" != "$trashdir" ]; do
         trashdir="${trashdirs%%:*}"
         trashdirs="${trashdirs#"$trashdir":}"
         fs="$(fs "$trashdir")"
         if [ "$fs" = "$fs1" ]; then
            found_trash=true
            break
         fi
      done
      if [ "$found_trash" = true ]; then
         set -- --trash-dir "$trashdir" "$@"
      else
         err_no_trashdirs
         exit 1
      fi
   fi
   echo "trash dir:" "$trashdir"
   do_rm "$@"
}

main() {
   # which rm command to use
   rm=''

   # calculate which rm command to use
   which_rm=''
   if [ -n "${RM:-}" ]; then
      which_rm='custom: '"$RM"
   elif command -v trash > /dev/null; then
      which_rm='trash'
   else
      which_rm='rm'
   fi

   # print usage information (including which rm command we'll use)
   if [ $# = 0 ]; then
      usage
      exit
   fi

   # execute rm
   case "$which_rm" in
      rm)
         do_rmnormal "$@";;
      trash)
         do_rmtrash "$@";;
      custom*)
         do_rmcustom "$@";;
      *)
         usage; exit;;
   esac
}

main "$@"