import type { AxiosError } from 'axios';

import { appConfig } from '../../config/appConfig';
import type { ApiError } from '../../types/api';
import { sleep } from '../../utils/async';
import { isCbsApiError } from './cbsErrors';

const isApiError = (value: unknown): value is ApiError =>
  typeof value === 'object' &&
  value !== null &&
  'status' in value &&
  'message' in value;

export const toApiError = (error: unknown): ApiError => {
  // A named backend failure. Keep the code and the field map — they are what
  // the screens branch on and paint onto forms.
  if (isCbsApiError(error)) {
    return {
      status: error.status,
      message: error.message,
      code: error.code,
      fieldErrors: error.fieldErrors,
    };
  }

  if (isApiError(error)) {
    return error;
  }

  const axiosError = error as AxiosError;

  return {
    status: Number(axiosError.response?.status ?? 500),
    message: axiosError.message || 'Unexpected service error',
    code: 'UNKNOWN_ERROR',
    data: axiosError.response?.data,
  };
};

/**
 * Fixture-backed resolution for the modules that have no backend behind them
 * yet. Endpoints the CBS API actually implements must not go through here —
 * they call `apiClient` directly so a failure surfaces instead of being
 * papered over with demo data.
 */
export const resolveWithMock = async <T>({
  mockData,
  request,
  delayMs = 320,
}: {
  mockData: T | (() => T);
  request: () => Promise<T>;
  delayMs?: number;
}): Promise<{ data: T } | { error: ApiError }> => {
  if (appConfig.features.useMockServer) {
    await sleep(delayMs);
    return {
      data: typeof mockData === 'function' ? (mockData as () => T)() : mockData,
    };
  }

  try {
    return {
      data: await request(),
    };
  } catch (error) {
    return {
      error: toApiError(error),
    };
  }
};

/** Same contract as `resolveWithMock`, but always live. */
export const resolveLive = async <T>(
  request: () => Promise<T>,
): Promise<{ data: T } | { error: ApiError }> => {
  try {
    return { data: await request() };
  } catch (error) {
    return { error: toApiError(error) };
  }
};