#!/bin/sh
# sigabrt-run -- run a command and report how it went.
#
#     sigabrt-run <token> <command> [args...]
#     sigabrt-run <pulse-url> <command> [args...]
#
# Pulses the start, runs the command, and then sends a heartbeat if it
# succeeded or a failure if it did not. What the command printed and the
# status it exited with pass through untouched.
#
# Install it once, rather than fetching it on every run:
#
#     sudo curl -fsS https://sigabrt.dev/run.sh -o /usr/local/bin/sigabrt-run
#     sudo chmod +x /usr/local/bin/sigabrt-run
#
# Cron brings a PATH of its own, commonly /sbin:/bin:/usr/sbin:/usr/bin,
# which has no /usr/local/bin in it. Put
#
#     PATH=/usr/local/bin:/usr/bin:/bin
#
# at the top of the crontab, or name this by its full path on the job.
#
# The endpoint can come from the environment instead of the command line,
# which is what a crontab of jobs on one endpoint wants:
#
#     SIGABRT_TOKEN=<token> sigabrt-run ./backup.sh
#
# SIGABRT_URL takes a whole pulse URL in its place, and SIGABRT_BASE points
# the token form at a different instance than the one this came from.
#
# Nothing here is required. It sends the same three pulses you would send
# with curl by hand; see https://sigabrt.dev/docs.

set -u

DEFAULT_BASE="https://sigabrt.dev"

usage() {
    echo "usage: sigabrt-run <token|pulse-url> <command> [args...]" >&2
    exit "${1:-64}"
}

case ${1:-} in
    -h | --help) usage 0 ;;
esac

# Named in the environment, the first argument is the command rather than
# the endpoint.
target=${SIGABRT_URL:-${SIGABRT_TOKEN:-}}
if [ -z "$target" ]; then
    target=${1:-}
    [ $# -gt 0 ] && shift
fi

[ -n "$target" ] || usage
[ $# -gt 0 ] || usage

base=${SIGABRT_BASE:-$DEFAULT_BASE}
case $target in
    http://* | https://*) pulse_url=$target ;;
    *) pulse_url="${base%/}/pulse/$target" ;;
esac

# What the dashboard shows is the heartbeat URL, so take it with any of the
# three verbs on the end -- or none -- and speak to all three.
pulse_url=${pulse_url%/}
pulse_url=${pulse_url%/beat}
pulse_url=${pulse_url%/start}
pulse_url=${pulse_url%/fail}

if command -v curl > /dev/null 2>&1; then
    send() { curl -fsS -m 10 --retry 3 -o /dev/null "$pulse_url/$1"; }
elif command -v wget > /dev/null 2>&1; then
    send() { wget -q -T 10 -t 3 -O /dev/null "$pulse_url/$1"; }
else
    echo "sigabrt-run: no curl or wget; running the job without pulses" >&2
    send() { :; }
fi

# Monitoring must not be able to change what the job did. Every failure to
# reach sigabrt is swallowed, and the status this exits with is the
# command's own.
pulse() { send "$1" || true; }

pulse start
"$@"
status=$?

if [ "$status" -eq 0 ]; then
    pulse beat
else
    pulse fail
fi

exit "$status"