/**
 * Lease timing policy for runtime receipts and Runtime Sheet attempts.
 *
 * Expiry is a liveness signal, not a logical ordering token. B2 moves write
 * ordering to coordinator run-attempt epochs; these values only decide how
 * long an owner may hold a lease without renewal.
 */

const DEFAULT_PLAY_RUNTIME_WORK_RECEIPT_LEASE_TTL_MS = 10 * 60_000;
const DEFAULT_PLAY_RUNTIME_SHEET_ATTEMPT_LEASE_TTL_MS = 10 * 60_000;

function readRuntimeLeaseEnv(name: string): string | undefined {
  if (typeof process === 'undefined') return undefined;
  return process.env?.[name];
}

function resolveRuntimeLeaseTtlMs(
  envName: string,
  defaultValueMs: number,
): number {
  const raw = readRuntimeLeaseEnv(envName);
  if (raw === undefined || raw.trim() === '') return defaultValueMs;
  if (!/^\d+$/.test(raw.trim())) {
    throw new Error(
      `${envName} must be a positive integer number of milliseconds.`,
    );
  }
  const value = Number(raw.trim());
  if (!Number.isSafeInteger(value) || value <= 0) {
    throw new Error(
      `${envName} must be a positive integer number of milliseconds.`,
    );
  }
  return value;
}

export const PLAY_RUNTIME_WORK_RECEIPT_LEASE_TTL_MS = resolveRuntimeLeaseTtlMs(
  'DEEPLINE_WORK_RECEIPT_LEASE_TTL_MS',
  DEFAULT_PLAY_RUNTIME_WORK_RECEIPT_LEASE_TTL_MS,
);
export const PLAY_RUNTIME_SHEET_ATTEMPT_LEASE_TTL_MS = resolveRuntimeLeaseTtlMs(
  'DEEPLINE_SHEET_ATTEMPT_LEASE_TTL_MS',
  DEFAULT_PLAY_RUNTIME_SHEET_ATTEMPT_LEASE_TTL_MS,
);
export const PLAY_RUNTIME_LEASE_HEARTBEAT_DIVISOR = 3;

export function runtimeLeaseHeartbeatIntervalMs(ttlMs: number): number {
  if (!Number.isFinite(ttlMs) || ttlMs <= 0) {
    throw new Error('Runtime lease heartbeat interval needs a positive TTL.');
  }
  return Math.max(1, Math.floor(ttlMs / PLAY_RUNTIME_LEASE_HEARTBEAT_DIVISOR));
}

/**
 * The receipt store is authoritative for lease duration. Executors may not
 * inherit the coordinator's environment, so derive renewal cadence from the
 * expiry returned with the actual claim instead of assuming a local TTL.
 */
export function runtimeLeaseHeartbeatIntervalFromExpiry(input: {
  leaseExpiresAt?: string | null;
  fallbackTtlMs: number;
  nowMs?: number;
}): number {
  const expiresAtMs = input.leaseExpiresAt
    ? Date.parse(input.leaseExpiresAt)
    : Number.NaN;
  const nowMs = input.nowMs ?? Date.now();
  const remainingMs = expiresAtMs - nowMs;
  return runtimeLeaseHeartbeatIntervalMs(
    Number.isFinite(remainingMs) && remainingMs > 0
      ? remainingMs
      : input.fallbackTtlMs,
  );
}