export type RetryConfig = {
  attempts?: number;
  minDelayMs?: number;
  maxDelayMs?: number;
  jitter?: number;
};

export type RetryInfo = {
  attempt: number;
  maxAttempts: number;
  delayMs: number;
  err: unknown;
  label?: string;
};

export type RetryOptions = RetryConfig & {
  label?: string;
  shouldRetry?: (err: unknown, attempt: number) => boolean;
  retryAfterMs?: (err: unknown) => number | undefined;
  onRetry?: (info: RetryInfo) => void;
};

const DEFAULT_RETRY_CONFIG = {
  attempts: 3,
  minDelayMs: 300,
  maxDelayMs: 30_000,
  jitter: 0,
};

const sleep = (ms: number) => new Promise((r) => setTimeout(r, ms));

const asFiniteNumber = (value: unknown): number | undefined =>
  typeof value === "number" && Number.isFinite(value) ? value : undefined;

const clampNumber = (
  value: unknown,
  fallback: number,
  min?: number,
  max?: number,
) => {
  const next = asFiniteNumber(value);
  if (next === undefined) return fallback;
  const floor = typeof min === "number" ? min : Number.NEGATIVE_INFINITY;
  const ceiling = typeof max === "number" ? max : Number.POSITIVE_INFINITY;
  return Math.min(Math.max(next, floor), ceiling);
};

export function resolveRetryConfig(
  defaults: Required<RetryConfig> = DEFAULT_RETRY_CONFIG,
  overrides?: RetryConfig,
): Required<RetryConfig> {
  const attempts = Math.max(
    1,
    Math.round(clampNumber(overrides?.attempts, defaults.attempts, 1)),
  );
  const minDelayMs = Math.max(
    0,
    Math.round(clampNumber(overrides?.minDelayMs, defaults.minDelayMs, 0)),
  );
  const maxDelayMs = Math.max(
    minDelayMs,
    Math.round(clampNumber(overrides?.maxDelayMs, defaults.maxDelayMs, 0)),
  );
  const jitter = clampNumber(overrides?.jitter, defaults.jitter, 0, 1);
  return { attempts, minDelayMs, maxDelayMs, jitter };
}

function applyJitter(delayMs: number, jitter: number): number {
  if (jitter <= 0) return delayMs;
  const offset = (Math.random() * 2 - 1) * jitter;
  return Math.max(0, Math.round(delayMs * (1 + offset)));
}

export async function retryAsync<T>(
  fn: () => Promise<T>,
  attemptsOrOptions: number | RetryOptions = 3,
  initialDelayMs = 300,
): Promise<T> {
  if (typeof attemptsOrOptions === "number") {
    const attempts = Math.max(1, Math.round(attemptsOrOptions));
    let lastErr: unknown;
    for (let i = 0; i < attempts; i += 1) {
      try {
        return await fn();
      } catch (err) {
        lastErr = err;
        if (i === attempts - 1) break;
        const delay = initialDelayMs * 2 ** i;
        await sleep(delay);
      }
    }
    throw lastErr ?? new Error("Retry failed");
  }

  const options = attemptsOrOptions;

  const resolved = resolveRetryConfig(DEFAULT_RETRY_CONFIG, options);
  const maxAttempts = resolved.attempts;
  const minDelayMs = resolved.minDelayMs;
  const maxDelayMs =
    Number.isFinite(resolved.maxDelayMs) && resolved.maxDelayMs > 0
      ? resolved.maxDelayMs
      : Number.POSITIVE_INFINITY;
  const jitter = resolved.jitter;
  const shouldRetry = options.shouldRetry ?? (() => true);
  let lastErr: unknown;

  for (let attempt = 1; attempt <= maxAttempts; attempt += 1) {
    try {
      return await fn();
    } catch (err) {
      lastErr = err;
      if (attempt >= maxAttempts || !shouldRetry(err, attempt)) break;

      const retryAfterMs = options.retryAfterMs?.(err);
      const hasRetryAfter =
        typeof retryAfterMs === "number" && Number.isFinite(retryAfterMs);
      const baseDelay = hasRetryAfter
        ? Math.max(retryAfterMs, minDelayMs)
        : minDelayMs * 2 ** (attempt - 1);
      let delay = Math.min(baseDelay, maxDelayMs);
      delay = applyJitter(delay, jitter);
      delay = Math.min(Math.max(delay, minDelayMs), maxDelayMs);

      options.onRetry?.({
        attempt,
        maxAttempts,
        delayMs: delay,
        err,
        label: options.label,
      });
      await sleep(delay);
    }
  }

  throw lastErr ?? new Error("Retry failed");
}
