ifne

#!/usr/bin/env bash
set -euo pipefail

YP_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." >/dev/null && pwd)"
source ${YP_DIR}/sh/common.inc.sh

#- ifne 1.0
## Usage: ifne -- COMMAND
## Poor man's version of moreutils ifne.
##
##   -n, --not            Reverse operation. Run the command if the standard input is empty.
##   -f, --fail           Return non-zero exist status if command isn't ran.
##   -p, --print-on-fail  Print stdin if command isn't ran.
##
##   -h, --help     Display this help and exit
##   -v, --version  Output version information and exit

TMP_IFNE=$(mktemp -t yplatform.XXXXXXXXXX)
function on_exit() {
    rm -rf ${TMP_IFNE}
}
trap on_exit EXIT

if { getopt --test >/dev/null 2>&1 && false; } || [[ "$?" = "4" ]] || false; then
    ARGS=$(getopt -o hvnfp -l help,version,not,fail,print-on-fail -n $(basename ${BASH_SOURCE[0]}) -- "$@") || sh_script_usage
    eval set -- "${ARGS}"
fi

SHOULD_BE_EMPTY=false
FAIL_COMMAND=true
PRINT_ON_FAIL=false

while [[ $# -gt 0 ]]; do
    case "$1" in
        -n|--not)
            SHOULD_BE_EMPTY=true
            shift
            ;;
        -f|--fail)
            FAIL_COMMAND=false
            shift
            ;;
        -p|--print-on-fail)
            PRINT_ON_FAIL=true
            shift
            ;;
        -h|--help)
            sh_script_usage
            ;;
        -v|--version)
            sh_script_version
            ;;
        --)
            shift
            break
            ;;
        -*)
            sh_script_usage
            ;;
        *)
            break
            ;;
    esac
done
# [[ $# -eq 0 ]] || sh_script_usage

cat - > ${TMP_IFNE}

EMPTY=false
cat ${TMP_IFNE} | grep -q . || EMPTY=true

case ${EMPTY}-${SHOULD_BE_EMPTY} in
    true-true|false-false)
        # we need eval
        # shellcheck disable=SC2294
        [[ $# -eq 0 ]] || eval "$@"
        ;;
    *)
        [[ "${PRINT_ON_FAIL}" = "false" ]] || cat ${TMP_IFNE}
        trap - ERR # disable on_error trap
        eval "${FAIL_COMMAND}"
        ;;
esac