/**
 * Cooperative advisory **`fcntl`** lock slot + **`F_SETLKW`** waiter drain (**FIFO** per path).
 * Used by **`packages/bare-os-booter/index.js`** **`bareOsSyscall('fcntl')`**.
 */

/**
 * @param {{ readers: Set<string>; writer: string | null }} slot
 * @param {string} owner
 * @param {boolean} wantWrite
 */
export function bareOsTryAcquireCooperativeLock(slot, owner, wantWrite) {
  if (wantWrite) {
    if (slot.writer && slot.writer !== owner) return false
    if (
      slot.readers.size > 0 &&
      [...slot.readers].some((sid) => sid !== owner)
    ) {
      return false
    }
    slot.readers.clear()
    slot.writer = owner
    return true
  }
  if (slot.writer && slot.writer !== owner) return false
  slot.readers.add(owner)
  return true
}

/**
 * @param {Record<string, unknown>} c
 * @param {string} lockPath
 * @param {{ resolve: (v: unknown) => void, timer: ReturnType<typeof setTimeout> | null, owner: string, wantWrite: boolean }} entry
 */
export function bareOsRemoveFcntlWaiter(c, lockPath, entry) {
  const m = /** @type {Record<string, unknown>} */ (c)
  const qm = m.bareOsFcntlLockWaitQueues
  if (!qm || typeof qm !== 'object') return
  const q = /** @type {unknown[]} */ (qm[lockPath])
  if (!Array.isArray(q)) return
  const i = q.indexOf(entry)
  if (i >= 0) q.splice(i, 1)
  if (q.length === 0) delete qm[lockPath]
}

/**
 * @param {Record<string, unknown>} c
 * @param {string} lockPath
 */
export function bareOsDrainFcntlLockWaiters(c, lockPath) {
  const locks = /** @type {Record<string, { readers: Set<string>; writer: string | null }>} */ (
    c.bareOsCooperativeLocks
  )
  const slot = locks?.[lockPath]
  if (!slot) return
  const m = /** @type {Record<string, unknown>} */ (c)
  const qm = m.bareOsFcntlLockWaitQueues
  const q = qm?.[lockPath]
  if (!Array.isArray(q) || q.length === 0) return
  while (q.length > 0) {
    const w = /** @type {{ resolve: (v: unknown) => void, timer: ReturnType<typeof setTimeout> | null, owner: string, wantWrite: boolean }} */ (
      q[0]
    )
    if (!bareOsTryAcquireCooperativeLock(slot, w.owner, w.wantWrite)) break
    q.shift()
    if (w.timer) clearTimeout(w.timer)
    w.resolve({
      ok: true,
      op: 'fcntl',
      cmd: 'F_SETLKW',
      path: lockPath,
      cooperative: true,
      locked: w.wantWrite ? 'write' : 'read',
      blockedWait: true
    })
  }
  if (q.length === 0 && qm && typeof qm === 'object') delete qm[lockPath]
}