// Node-flavoured error mapping, shared by the runtime (guest-facing fs/loader
// errors) and the host (fs facade rejections). Lives in shared/ so both sides
// map one kernel FsError identically — one source of truth for code/errno/
// syscall/path, per the FS slice brief.
import type { FsError } from "./protocol";

const ERRNO_TEXT: Record<string, string> = {
  ENOENT: "no such file or directory",
  EEXIST: "file already exists",
  ENOTDIR: "not a directory",
  EISDIR: "illegal operation on a directory",
  EBADF: "bad file descriptor",
  EINVAL: "invalid argument",
  ENOTEMPTY: "directory not empty",
  EIO: "i/o error",
  EMFILE: "too many open files",
  EAGAIN: "resource temporarily unavailable",
  EADDRINUSE: "address already in use",
  ELOOP: "too many symbolic links encountered",
};

const FS_ERRNO_NUMBER: Record<string, number> = {
  EPERM: 1, ENOENT: 2, ESRCH: 3, EINTR: 4, EIO: 5, EEXIST: 17,
  EBADF: 9, EAGAIN: 11, ENOMEM: 12, EACCES: 13, EFAULT: 14, EBUSY: 16,
  ENOTDIR: 20, EISDIR: 21, EINVAL: 22, EMFILE: 24, ENOSPC: 28,
  ENOTEMPTY: 39, ELOOP: 40, EADDRINUSE: 98,
};

/** A guest-facing fs error exactly as Node's uvException builds it: message
 *  `CODE: text, syscall 'path' -> 'dest'`, a negative errno, and own keys in Node's
 *  order (errno, code, syscall, path, dest). */
export function uvError(e: FsError): Error {
  const text = ERRNO_TEXT[e.code] ?? "unknown error";
  let message = `${e.code}: ${text}, ${e.syscall}`;
  if (e.path !== undefined) message += ` '${e.path}'`;
  if (e.dest !== undefined) message += ` -> '${e.dest}'`;
  const fields: Record<string, unknown> = { errno: -(FS_ERRNO_NUMBER[e.code] ?? 0), code: e.code, syscall: e.syscall };
  if (e.path !== undefined) fields.path = e.path;
  if (e.dest !== undefined) fields.dest = e.dest;
  return Object.assign(new Error(message), fields);
}

/** Map a kernel FsError into a Node-flavoured Error with a numeric errno. */
export function toNodeError(e: FsError): Error {
  const text = ERRNO_TEXT[e.code] ?? "unknown error";
  const errno = FS_ERRNO_NUMBER[e.code] ?? 0;
  const error = new Error(`${e.code}: ${text}${e.path ? `, ${e.syscall ?? "syscall"} '${e.path}'` : ""}`);
  (error as Error & { code?: string; errno?: number; syscall?: string; path?: string }).code = e.code;
  (error as Error & { errno?: number }).errno = errno;
  (error as Error & { syscall?: string }).syscall = e.syscall;
  if (e.path) (error as Error & { path?: string }).path = e.path;
  return error;
}