// Copyright 2019 @polkadot/extension-ui authors & contributors
// This software may be modified and distributed under the terms
// of the Apache-2.0 license. See the LICENSE file for details.

interface InputError {
  errorDescription: string;
}

export type Result<T> = { error: InputError } | { ok: T }
export const Result = {
  error: <T>(errorDescription: string): Result<T> => ({ error: { errorDescription } }),
  isError<T> (value: Result<T>): value is ({ error: InputError }) {
    return Object.hasOwnProperty.call(value, 'error');
  },
  isOk<T> (value: Result<T>): value is ({ ok: T }) {
    return Object.hasOwnProperty.call(value, 'ok');
  },
  ok: <T>(ok: T): Result<T> => ({ ok })
};

export declare type Validator<T> = (value: T) => Result<T> | Promise<Result<T>>;

export const allOf = <T>(...validators: Validator<T>[]): Validator<T> => async (value: T): Promise<Result<T>> => {
  for (const validator of validators) {
    const validationResult = await validator(value);

    if (Result.isError(validationResult)) {
      return validationResult;
    }
  }

  return Result.ok(value);
};

export const isNotShorterThan = (minLength: number, errorText: string): Validator<string> =>
  (value: string): Result<string> => {
    if (value.length < minLength) {
      return Result.error(errorText);
    }

    return Result.ok(value);
  };

export const isSameAs = <T>(expectedValue: T, errorText: string): Validator<T> => (value: T): Result<T> => {
  if (value !== expectedValue) {
    return Result.error(errorText);
  }

  return Result.ok(value);
};