import { HttpRequest } from "@aws-sdk/protocol-http";
import {
  BodyLengthCalculator,
  BuildHandler,
  BuildHandlerArguments,
  BuildHandlerOptions,
  BuildHandlerOutput,
  BuildMiddleware,
  MetadataBearer,
  Pluggable,
} from "@aws-sdk/types";

const CONTENT_LENGTH_HEADER = "content-length";

export function contentLengthMiddleware(bodyLengthChecker: BodyLengthCalculator): BuildMiddleware<any, any> {
  return <Output extends MetadataBearer>(next: BuildHandler<any, Output>): BuildHandler<any, Output> =>
    async (args: BuildHandlerArguments<any>): Promise<BuildHandlerOutput<Output>> => {
      const request = args.request;
      if (HttpRequest.isInstance(request)) {
        const { body, headers } = request;
        if (
          body &&
          Object.keys(headers)
            .map((str) => str.toLowerCase())
            .indexOf(CONTENT_LENGTH_HEADER) === -1
        ) {
          const length = bodyLengthChecker(body);
          if (length !== undefined) {
            request.headers = {
              ...request.headers,
              [CONTENT_LENGTH_HEADER]: String(length),
            };
          }
        }
      }

      return next({
        ...args,
        request,
      });
    };
}

export const contentLengthMiddlewareOptions: BuildHandlerOptions = {
  step: "build",
  tags: ["SET_CONTENT_LENGTH", "CONTENT_LENGTH"],
  name: "contentLengthMiddleware",
  override: true,
};

export const getContentLengthPlugin = (options: { bodyLengthChecker: BodyLengthCalculator }): Pluggable<any, any> => ({
  applyToStack: (clientStack) => {
    clientStack.add(contentLengthMiddleware(options.bodyLengthChecker), contentLengthMiddlewareOptions);
  },
});