export type FsErrorCode =
  | "EXDEV" // 跨设备,不会自动降级
  | "EEXIST" // 目标已存在(no-clobber)
  | "ENOENT"
  | "EACCES"
  | "ENOSPC"
  | "VERIFY_FAILED"
  | "SOURCE_CHANGED"
  | "ROOT_OFFLINE"
  | "ABORTED"
  /** 文件操作挂死(进度停滞/快操作超时),执行子进程已被回收;与 IO 同属可退避重试,不代表文件缺失 */
  | "TIMEOUT"
  /** 本地文件操作收到 Alist 虚拟路径(/@alist/…):调用方没按存储分派,拒绝而不是写错位置 */
  | "REMOTE_PATH_ON_LOCAL_FS"
  | "IO";

/**
 * 错误码 → 处置类别(对照 MP:所有 IO 故障归 OSError 复用重试;我们更细):
 * - retry:可退避重试(IO / TIMEOUT / ROOT_OFFLINE / SOURCE_CHANGED),超限后进待处理
 * - attention:直接进待处理、不重试(EACCES / ENOSPC / EXDEV)
 * - manual:需人工判断(EEXIST / VERIFY_FAILED / ENOENT)
 * - aborted:被取消
 */
export type FsErrorClass = "retry" | "attention" | "manual" | "aborted";

export function fsErrorClass(code: string): FsErrorClass {
  switch (code) {
    case "IO":
    case "TIMEOUT":
    case "ROOT_OFFLINE":
    case "SOURCE_CHANGED":
      return "retry";
    case "EACCES":
    case "ENOSPC":
    case "EXDEV":
      return "attention";
    case "ABORTED":
      return "aborted";
    default:
      return "manual";
  }
}

export class FsError extends Error {
  override readonly name = "FsError";
  constructor(
    readonly code: FsErrorCode,
    message: string,
    readonly detail: { path?: string; syscall?: string; cause?: unknown } = {},
  ) {
    super(message);
  }
}

export function errnoOf(e: unknown): string | undefined {
  return (e as NodeJS.ErrnoException | undefined)?.code;
}

export function toFsError(e: unknown, path?: string): FsError {
  if (e instanceof FsError) return e;
  const code = errnoOf(e);
  const mapped: FsErrorCode =
    code === "EXDEV" || code === "EEXIST" || code === "ENOENT" || code === "ENOSPC"
      ? code
      : code === "EACCES" || code === "EPERM"
        ? "EACCES"
        : code === "ETIMEDOUT"
          ? "TIMEOUT"
          : (e as Error)?.name === "AbortError"
            ? "ABORTED"
            : "IO";
  return new FsError(mapped, (e as Error)?.message ?? String(e), {
    ...(path !== undefined ? { path } : {}),
    ...((e as NodeJS.ErrnoException)?.syscall ? { syscall: (e as NodeJS.ErrnoException).syscall! } : {}),
    cause: e,
  });
}