import process from "node:process";
import {
  collectErrorGraphCandidates,
  extractErrorCode,
  formatUncaughtError,
  readErrorName,
} from "./errors.js";

type UnhandledRejectionHandler = (reason: unknown) => boolean;

const handlers = new Set<UnhandledRejectionHandler>();

const FATAL_ERROR_CODES = new Set([
  "ERR_OUT_OF_MEMORY",
  "ERR_SCRIPT_EXECUTION_TIMEOUT",
  "ERR_WORKER_OUT_OF_MEMORY",
  "ERR_WORKER_UNCAUGHT_EXCEPTION",
  "ERR_WORKER_INITIALIZATION_FAILED",
]);

const CONFIG_ERROR_CODES = new Set(["INVALID_CONFIG", "MISSING_API_KEY", "MISSING_CREDENTIALS"]);

// Network error codes that indicate transient failures (shouldn't crash the gateway)
const TRANSIENT_NETWORK_CODES = new Set([
  "ECONNRESET",
  "ECONNREFUSED",
  "ENOTFOUND",
  "ETIMEDOUT",
  "ESOCKETTIMEDOUT",
  "ECONNABORTED",
  "EPIPE",
  "EHOSTUNREACH",
  "ENETUNREACH",
  "EAI_AGAIN",
  "UND_ERR_CONNECT_TIMEOUT",
  "UND_ERR_DNS_RESOLVE_FAILED",
  "UND_ERR_CONNECT",
  "UND_ERR_SOCKET",
  "UND_ERR_HEADERS_TIMEOUT",
  "UND_ERR_BODY_TIMEOUT",
  "EPROTO",
  "ERR_SSL_WRONG_VERSION_NUMBER",
  "ERR_SSL_PROTOCOL_RETURNED_AN_ERROR",
]);

const TRANSIENT_NETWORK_ERROR_NAMES = new Set([
  "AbortError",
  "ConnectTimeoutError",
  "HeadersTimeoutError",
  "BodyTimeoutError",
  "TimeoutError",
]);

const TRANSIENT_NETWORK_MESSAGE_CODE_RE =
  /\b(ECONNRESET|ECONNREFUSED|ENOTFOUND|ETIMEDOUT|ESOCKETTIMEDOUT|ECONNABORTED|EPIPE|EHOSTUNREACH|ENETUNREACH|EAI_AGAIN|EPROTO|UND_ERR_CONNECT_TIMEOUT|UND_ERR_DNS_RESOLVE_FAILED|UND_ERR_CONNECT|UND_ERR_SOCKET|UND_ERR_HEADERS_TIMEOUT|UND_ERR_BODY_TIMEOUT)\b/i;

const TRANSIENT_NETWORK_MESSAGE_SNIPPETS = [
  "getaddrinfo",
  "socket hang up",
  "client network socket disconnected before secure tls connection was established",
  "network error",
  "network is unreachable",
  "temporary failure in name resolution",
  "tlsv1 alert",
  "ssl routines",
  "packet length too long",
  "write eproto",
];

function isWrappedFetchFailedMessage(message: string): boolean {
  if (message === "fetch failed") {
    return true;
  }

  // Keep wrapped variants (for example "...: fetch failed") while avoiding broad
  // matches like "Web fetch failed (404): ..." that are not transport failures.
  return /:\s*fetch failed$/.test(message);
}

function getErrorCause(err: unknown): unknown {
  if (!err || typeof err !== "object") {
    return undefined;
  }
  return (err as { cause?: unknown }).cause;
}

function extractErrorCodeOrErrno(err: unknown): string | undefined {
  const code = extractErrorCode(err);
  if (code) {
    return code.trim().toUpperCase();
  }
  if (!err || typeof err !== "object") {
    return undefined;
  }
  const errno = (err as { errno?: unknown }).errno;
  if (typeof errno === "string" && errno.trim()) {
    return errno.trim().toUpperCase();
  }
  if (typeof errno === "number" && Number.isFinite(errno)) {
    return String(errno);
  }
  return undefined;
}

function extractErrorCodeWithCause(err: unknown): string | undefined {
  const direct = extractErrorCode(err);
  if (direct) {
    return direct;
  }
  return extractErrorCode(getErrorCause(err));
}

/**
 * Checks if an error is an AbortError.
 * These are typically intentional cancellations (e.g., during shutdown) and shouldn't crash.
 */
export function isAbortError(err: unknown): boolean {
  if (!err || typeof err !== "object") {
    return false;
  }
  const name = "name" in err ? String(err.name) : "";
  if (name === "AbortError") {
    return true;
  }
  // Check for "This operation was aborted" message from Node's undici
  const message = "message" in err && typeof err.message === "string" ? err.message : "";
  if (message === "This operation was aborted") {
    return true;
  }
  return false;
}

function isFatalError(err: unknown): boolean {
  const code = extractErrorCodeWithCause(err);
  return code !== undefined && FATAL_ERROR_CODES.has(code);
}

function isConfigError(err: unknown): boolean {
  const code = extractErrorCodeWithCause(err);
  return code !== undefined && CONFIG_ERROR_CODES.has(code);
}

/**
 * Checks if an error is a transient network error that shouldn't crash the gateway.
 * These are typically temporary connectivity issues that will resolve on their own.
 */
export function isTransientNetworkError(err: unknown): boolean {
  if (!err) {
    return false;
  }
  for (const candidate of collectErrorGraphCandidates(err, (current) => {
    const nested: Array<unknown> = [
      current.cause,
      current.reason,
      current.original,
      current.error,
      current.data,
    ];
    if (Array.isArray(current.errors)) {
      nested.push(...current.errors);
    }
    return nested;
  })) {
    const code = extractErrorCodeOrErrno(candidate);
    if (code && TRANSIENT_NETWORK_CODES.has(code)) {
      return true;
    }

    const name = readErrorName(candidate);
    if (name && TRANSIENT_NETWORK_ERROR_NAMES.has(name)) {
      return true;
    }

    if (!candidate || typeof candidate !== "object") {
      continue;
    }
    const rawMessage = (candidate as { message?: unknown }).message;
    const message = typeof rawMessage === "string" ? rawMessage.toLowerCase().trim() : "";
    if (!message) {
      continue;
    }
    if (TRANSIENT_NETWORK_MESSAGE_CODE_RE.test(message)) {
      return true;
    }
    if (isWrappedFetchFailedMessage(message)) {
      return true;
    }
    if (TRANSIENT_NETWORK_MESSAGE_SNIPPETS.some((snippet) => message.includes(snippet))) {
      return true;
    }
  }

  return false;
}

export function registerUnhandledRejectionHandler(handler: UnhandledRejectionHandler): () => void {
  handlers.add(handler);
  return () => {
    handlers.delete(handler);
  };
}

export function isUnhandledRejectionHandled(reason: unknown): boolean {
  for (const handler of handlers) {
    try {
      if (handler(reason)) {
        return true;
      }
    } catch (err) {
      console.error(
        "[openclaw] Unhandled rejection handler failed:",
        err instanceof Error ? (err.stack ?? err.message) : err,
      );
    }
  }
  return false;
}

export function installUnhandledRejectionHandler(): void {
  process.on("unhandledRejection", (reason, _promise) => {
    if (isUnhandledRejectionHandled(reason)) {
      return;
    }

    // AbortError is typically an intentional cancellation (e.g., during shutdown)
    // Log it but don't crash - these are expected during graceful shutdown
    if (isAbortError(reason)) {
      console.warn("[openclaw] Suppressed AbortError:", formatUncaughtError(reason));
      return;
    }

    if (isFatalError(reason)) {
      console.error("[openclaw] FATAL unhandled rejection:", formatUncaughtError(reason));
      process.exit(1);
      return;
    }

    if (isConfigError(reason)) {
      console.error("[openclaw] CONFIGURATION ERROR - requires fix:", formatUncaughtError(reason));
      process.exit(1);
      return;
    }

    if (isTransientNetworkError(reason)) {
      console.warn(
        "[openclaw] Non-fatal unhandled rejection (continuing):",
        formatUncaughtError(reason),
      );
      return;
    }

    console.error("[openclaw] Unhandled promise rejection:", formatUncaughtError(reason));
    process.exit(1);
  });
}
