import { encode } from 'js-base64';

// Flatten a nested object to params object { field: { text: 'foo' } } => { field.text ='foo' }
function flattenParams(data: object, path = ''): object {
  const params: any = {};

  Object.entries(data).forEach(([key, value]) => {
    const isObject =
      value !== null && typeof value === 'object' && !Array.isArray(value);
    const fieldPath = resolvePath(path, key);

    if (isObject) {
      const serializedObject = flattenParams(value, fieldPath);
      Object.assign(params, serializedObject);
    } else {
      params[fieldPath] = value;
    }
  });

  return params;
}

function resolvePath(path: string, key: string) {
  return `${path}${path ? '.' : ''}${key}`;
}

/**
 * serializes the params object to URLSearchParams,
 * if isComplexRequest is true and the payload is not serializable as regular URLSearchParams (because of nested fields),
 * it will serialize the payload into the .r query param exclusively
 * @param params
 * @param isComplexRequest
 * @returns
 */
export function toURLSearchParams(params: object, isComplexRequest?: boolean) {
  const flatten = flattenParams(params);

  // payloads with deep arrays or complex arrays are not serializable as URLSearchParams
  const isPayloadNonSerializableAsUrlSearchParams = Object.entries(
    flatten,
  ).some(
    ([key, value]) =>
      key.includes('.') ||
      (Array.isArray(value) && value.some((v) => typeof v === 'object')),
  );
  const shouldSerializeToRParam =
    isComplexRequest && isPayloadNonSerializableAsUrlSearchParams;

  if (shouldSerializeToRParam) {
    return new URLSearchParams({ '.r': encode(JSON.stringify(params), true) });
  } else {
    return Object.entries(flatten).reduce((urlSearchParams, [key, value]) => {
      // inorder to make `foo: [1,2]` turn into `foo=1&foo=2` and not `foo[]=1&foo[]=2`
      const keyParams = Array.isArray(value) ? value : [value];

      keyParams.forEach((param: any) => {
        if (
          param === undefined ||
          param === null ||
          (Array.isArray(value) && typeof param === 'object')
        ) {
          return;
        }

        urlSearchParams.append(key, param);
      });

      return urlSearchParams;
    }, new URLSearchParams());
  }
}