import { DeeplineError } from './errors.js';

/**
 * Shared reconnect policy for the canonical run SSE stream.
 *
 * Server stream windows are finite: the platform ends them cleanly at the
 * function ceiling even while the run keeps executing. Consumers that wait for
 * a terminal status (`plays run --watch`, `runs tail`, `client.runs.tail`)
 * therefore reconnect with full-jitter exponential backoff instead of treating
 * a window end as a failure.
 */

/** Base delay for the full-jitter exponential backoff between reconnects. */
export const STREAM_RECONNECT_BASE_DELAY_MS = 500;
/** Upper bound for a single reconnect delay. */
export const STREAM_RECONNECT_MAX_DELAY_MS = 15_000;
/**
 * A connection that stayed open at least this long (or delivered any event)
 * counts as healthy and resets the backoff sequence.
 */
export const STREAM_HEALTHY_CONNECTION_MS = 30_000;

/** Full-jitter exponential backoff: uniform in [1, min(cap, base * 2^attempt)]. */
export function streamReconnectDelayMs(attempt: number): number {
  const cappedExponentialMs = Math.min(
    STREAM_RECONNECT_MAX_DELAY_MS,
    STREAM_RECONNECT_BASE_DELAY_MS * 2 ** Math.max(0, attempt),
  );
  return Math.max(1, Math.floor(Math.random() * (cappedExponentialMs + 1)));
}

export function isTransientPlayStreamError(error: unknown): boolean {
  if (
    error instanceof DeeplineError &&
    error.code === 'PLAY_STREAM_NETWORK_ABORTED'
  ) {
    return true;
  }
  if (error instanceof DeeplineError && typeof error.statusCode === 'number') {
    // Server-shaped errors with a definite status code are NOT transient by
    // pattern — only network-level failures are. 5xx counts as transient
    // since the server may recover, but 4xx (especially 404 = run gone) is
    // terminal and should not be hidden behind a silent retry loop.
    return error.statusCode >= 500 && error.statusCode < 600;
  }
  const text = error instanceof Error ? error.message : String(error);
  return /auth validation backend timed out|coordinator \/submit(?:\?[^ ]*)? 5\d\d|Worker threw exception|Internal Server Error|Service Unavailable|fetch failed|eaddrnotavail|econnreset|etimedout|eai_again|socket hang up/i.test(
    text,
  );
}