action_to_http_request.ts

import { AxiosRequestConfig } from "axios";
import contentType from "content-type";
import URI from "urijs";
import { Action, Field } from "./siren";

export type FieldValueResolverFn = (
  field: Field
) => Promise<string | undefined>;

export default async function actionToHttpRequest(
  action: Action,
  resolver?: FieldValueResolverFn
): Promise<AxiosRequestConfig> {
  const fields = action.fields || [];
  const fieldValues = await resolveAllFieldValues(fields, resolver);

  const requestMethod = action.method ? action.method : "GET";

  if (requestMethod === "GET") {
    return Promise.resolve({
      url: action.href,
      method: action.method,
      params: fieldValues,
      paramsSerializer: (params: any) => {
        return URI.buildQuery(params);
      },
      data: {} // Need to set this because of https://github.com/axios/axios/issues/86
    });
  } else {
    return Promise.resolve({
      url: action.href,
      method: action.method,
      data: fieldValues,
      transformRequest: [jsonRequestTransformer, failIfNotBuffer],
      headers: {
        "Content-Type": action.type
      }
    });
  }
}

function jsonRequestTransformer(data: any, headers: any): any {
  const rawContentType = headers["Content-Type"];

  if (!rawContentType) {
    return data;
  }

  const parsedContentType = contentType.parse(rawContentType).type;

  if (parsedContentType !== "application/json") {
    return data; // pass on data to the next transformer
  }

  return Buffer.from(JSON.stringify(data), "utf-8");
}

function failIfNotBuffer(data: any, headers: any): any {
  if (data && !Buffer.isBuffer(data)) {
    throw new Error(
      `Failed to serialize data for content-type ${headers["Content-Type"]}`
    );
  }

  return data;
}

async function resolveAllFieldValues(
  fields: Field[],
  resolver?: FieldValueResolverFn
): Promise<any> {
  const data: any = {};

  if (!resolver) {
    return Promise.resolve(data);
  }

  for (const field of fields) {
    const value = await resolver(field);

    if (value) {
      data[field.name] = value;
    }
  }

  return Promise.resolve(data);
}