#!/bin/bash
# 05-caffeinate-guard.sh — keep the Mac awake while a HearthGate session is open.
#
# Why you might want this:
#   You SSH in to your Mac mini from your laptop, start a long-running task,
#   close the laptop, and an hour later the connection dies because the Mac
#   went to sleep. This hook starts `caffeinate` the moment a remote session
#   begins, and stops it the moment the session ends — your Mac stays awake
#   while someone is using it remotely and goes back to its normal sleep
#   schedule when they leave.
#
# How it stays clean:
#   We write the caffeinate PID to a tiny pidfile when the session starts;
#   when the session ends we kill exactly that PID. No orphan caffeinate
#   processes if the Mac reboots between events — caffeinate dies with the
#   shell that spawned it, and a stale pidfile is harmless because kill on
#   a missing PID just fails silently.
#
# Scope note:
#   This is a simple one-guard example. If you regularly allow multiple
#   simultaneous remote sessions, adapt the PIDFILE to include a session
#   identifier from your own wrapper so one disconnect does not release the
#   guard for another active session.
#
# Setup:
#   Make the script executable, then add it from HearthGate's Hooks tab.
#   Full guide: https://codnamacs.com/hearthgate/help/features/hooks
#
# Variants you can flip:
#   The flags below default to keeping the *display* awake too (-d). If you
#   only want the CPU awake but the screen allowed to sleep (so you can
#   close the laptop lid and let it run remotely), remove the `d` from
#   CAFFEINATE_FLAGS.
#
# Environment HearthGate provides:
#   HEARTHGATE_EVENT
#
# Test it:
#   HEARTHGATE_EVENT=on-connect ./05-caffeinate-guard.sh
#   ps -p $(cat /tmp/hearthgate-caffeinate.pid)    # should show caffeinate
#   HEARTHGATE_EVENT=after-disconnect ./05-caffeinate-guard.sh
#   ps -p $(cat /tmp/hearthgate-caffeinate.pid)    # should be gone

set -euo pipefail

EVENT="${HEARTHGATE_EVENT:-${1:-unknown}}"
PIDFILE="/tmp/hearthgate-caffeinate.pid"
# -d keeps display awake, -i prevents idle sleep, -m disk sleep, -s system sleep.
# Drop the d to allow the screen to sleep while the SSH tunnel stays alive.
CAFFEINATE_FLAGS="-disu"

start_caffeinate() {
    # If a previous run left a live caffeinate, do not stack a second one.
    if [ -f "$PIDFILE" ]; then
        local old
        old="$(cat "$PIDFILE" 2>/dev/null || true)"
        if [ -n "$old" ] && kill -0 "$old" 2>/dev/null; then
            return 0
        fi
    fi
    # `disown` so caffeinate keeps living after this script exits.
    caffeinate $CAFFEINATE_FLAGS &
    local pid=$!
    disown "$pid" 2>/dev/null || true
    echo "$pid" > "$PIDFILE"
}

stop_caffeinate() {
    if [ ! -f "$PIDFILE" ]; then
        return 0
    fi
    local pid
    pid="$(cat "$PIDFILE" 2>/dev/null || true)"
    if [ -n "$pid" ]; then
        kill "$pid" 2>/dev/null || true
    fi
    rm -f "$PIDFILE"
}

case "$EVENT" in
    on-connect|after-connect)
        start_caffeinate
        ;;
    on-disconnect|after-disconnect)
        stop_caffeinate
        ;;
    *)
        echo "caffeinate-guard: unrecognised event '$EVENT'" >&2
        ;;
esac