#!/bin/sh
# The one-Gradle-build-at-a-time lock (CLAUDE.md › Build and verify). Sourced, not run, by tools/gradle-serial.sh,
# tools/clean-builds.sh, infra/dev/build.sh and infra/build-images.sh; plain POSIX sh, so sh and bash scripts share it.
# The lock is a directory holding the pid of its owner; a lock whose owner has died is taken over.
# shellcheck disable=SC2034  # KVITT_GRADLE_LOCK is used by the scripts that source this file
KVITT_GRADLE_LOCK=/tmp/kvitt-gradle.lock

# Prints the pid of the live process holding the lock and succeeds; fails when nobody holds it.
gradle_lock_holder() {
  _pid=$(cat "$KVITT_GRADLE_LOCK/pid" 2>/dev/null) || return 1
  [ -n "$_pid" ] && kill -0 "$_pid" 2>/dev/null || return 1
  printf '%s\n' "$_pid"
}

# Waits until the lock is free, then takes it for this shell ($$). The caller removes it on exit:
#   trap 'rm -rf "$KVITT_GRADLE_LOCK"' EXIT INT TERM HUP
gradle_lock_acquire() {
  while ! mkdir "$KVITT_GRADLE_LOCK" 2>/dev/null; do
    _pid=$(cat "$KVITT_GRADLE_LOCK/pid" 2>/dev/null)
    if [ -n "$_pid" ] && ! kill -0 "$_pid" 2>/dev/null; then rm -rf "$KVITT_GRADLE_LOCK"; continue; fi
    sleep 5
  done
  echo $$ > "$KVITT_GRADLE_LOCK/pid"
}