#!/usr/bin/env bash
# Guarantee EXACTLY ZERO xenia instances, then clear the lock. Source or run.
#
# `run-canary` holds /tmp/xenia-canary.lock to enforce the "one emulator at a
# time" rule. A `kill -9` orphans it, and the obvious unblock -- `rm -f` the lock
# -- ALSO DISABLES THE GUARD FOR EVERY LATER LAUNCH. On 2026-08-30 that left
# three instances live at once, all reading /tmp/xenia_pad.txt and sharing
# display :98, which silently confounded an input experiment: a scripted press
# reaches every instance while `screenshot` grabs whichever window is topmost.
# The finding built on it had to be withdrawn.
#
# So: the lock is only ever removed AFTER the condition it guards against is
# verified absent. Never `rm -f` it directly.
#
#   . ensure_single_emulator.sh     (or)     ensure_single_emulator.sh
emu_count(){ ps -C xenia_canary --no-headers 2>/dev/null | wc -l; }

ensure_single_emulator() {
  local n; n=$(emu_count)
  if [ "$n" -gt 0 ]; then
    echo "ensure_single_emulator: $n instance(s) live — stopping them"
    # kill by NAME. `pkill -f xenia_canary` matches the shell running it and
    # kills the caller instead; that has happened three times in this corpus.
    ps -o pid= -C xenia_canary | xargs -r kill
    for _ in 1 2 3 4 5 6 7 8 9 10; do [ "$(emu_count)" -eq 0 ] && break; sleep 1; done
    if [ "$(emu_count)" -gt 0 ]; then
      ps -o pid= -C xenia_canary | xargs -r kill -9
      for _ in 1 2 3 4 5 6 7 8 9 10; do [ "$(emu_count)" -eq 0 ] && break; sleep 1; done
    fi
  fi
  n=$(emu_count)
  if [ "$n" -ne 0 ]; then
    echo "ensure_single_emulator: REFUSING — $n instance(s) still live." >&2
    echo "  Do NOT rm the lock: it is the only thing stopping a second one." >&2
    return 3
  fi
  rm -f /tmp/xenia-canary.lock          # safe now, and only now
  echo "ensure_single_emulator: 0 instances, lock cleared"
  return 0
}
# run directly (not sourced) -> do it
(return 0 2>/dev/null) || ensure_single_emulator