import { pipe } from "./composition.ts";

/**
 * Get a function to check that inputs are instances of a given type
 */
export function isinstance<T, S extends T>(
  ref: { new (...args: any[]): T },
): (input: S) => input is Extract<T, S> {
  return (x): x is Extract<T, S> => x instanceof ref;
}

/**
 * Check that a value is not null, throwing an error if it is
 */
export function nn<T>(value: T | null): T {
  if (value === null) {
    throw new Error("null value");
  } else {
    return value;
  }
}

/**
 * Check that a value is not undefined, throwing an error if it is
 */
export function nu<T>(value: T | undefined): T {
  if (typeof value === "undefined") {
    throw new Error("undefined value");
  } else {
    return value;
  }
}

/**
 * Check that a value is not null nor undefined, throwing an error if it is
 */
export const nnu: <T>(value: T | null | undefined) => T = pipe(nn, nu);