import NativeMyidSdk from './NativeMyidSdk';
import type {
  MyIdAppearanceInput,
  MyIdConfigInput,
  MyIdOrganizationDetailsInput,
} from './NativeMyidSdk';
import { MyIdError, MyIdErrorCode } from './myid-error';
import type { MyIdResult, StartMyIdOptions } from './myid-types';

/**
 * Drops undefined keys. Native only applies a setting when its key is present,
 * so an absent key preserves the SDK default.
 */
function stripUndefined<T extends object>(value: T): T {
  const entries = Object.entries(value).filter(
    ([, fieldValue]) => fieldValue !== undefined
  );

  return Object.fromEntries(entries) as T;
}

/** Arrives as a string on one platform and a number on the other. */
function readErrorCode(error: unknown): string {
  if (typeof error === 'object' && error !== null && 'code' in error) {
    const { code } = error as { code: unknown };

    if (typeof code === 'string' && code.length > 0) {
      return code;
    }

    if (typeof code === 'number') {
      return String(code);
    }
  }

  return MyIdErrorCode.FAILURE;
}

function readErrorMessage(error: unknown): string {
  if (error instanceof Error && error.message) {
    return error.message;
  }

  return 'MyID verification failed';
}

/**
 * Launches the MyID verification flow.
 *
 * Rejects with a {@link MyIdError} on every failure path, including the user
 * dismissing the flow (code `101`).
 *
 * @example
 * ```ts
 * const result = await start({
 *   config: { sessionId, clientHash, clientHashId },
 * });
 * ```
 */
export async function start(options: StartMyIdOptions): Promise<MyIdResult> {
  const { config, iosAppearance } = options;

  // An empty details object would replace the SDK default, which carries MyID's
  // call-centre number. The ternary also blocks an explicit null: the generated
  // iOS accessor checks for nil but not NSNull, and would crash on first access.
  const organizationDetails = config.organizationDetails
    ? stripUndefined<MyIdOrganizationDetailsInput>(config.organizationDetails)
    : undefined;

  const payload = stripUndefined<MyIdConfigInput>({
    ...config,
    organizationDetails:
      organizationDetails && Object.keys(organizationDetails).length > 0
        ? organizationDetails
        : undefined,
  });

  const appearance: MyIdAppearanceInput = iosAppearance
    ? stripUndefined<MyIdAppearanceInput>(iosAppearance)
    : {};

  try {
    const result = await NativeMyidSdk.start(payload, appearance);

    return { code: result.code, base64: result.base64 };
  } catch (error) {
    throw new MyIdError(readErrorCode(error), readErrorMessage(error));
  }
}