Path parser middleware for lambda-middleware

path-parser.ts

// path-parser.ts

import { APIGatewayProxyEvent, APIGatewayProxyResult, Context } from "aws-lambda";
import { Path } from 'path-parser';

type PromiseHandler<TEvent = any, TResult = any> = (
  event: TEvent,
  context: Context
) => Promise<TResult>;

export const pathParser = (pathExpression: string) =>
  <E extends APIGatewayProxyEvent>(handler: PromiseHandler<E, APIGatewayProxyResult>): PromiseHandler<E, APIGatewayProxyResult> =>
  async (event: E, context: Context) => {
    const path = new Path(pathExpression);
    const params = path.test(event.path);

    if (params === null) {
      throw new Error("path didn't match expectation")
    }

    event.pathParameters = params;
    return handler({ ...event }, context)
}
    
// handler.ts
    
import { compose } from "@lambda-middleware/compose";
import { errorHandler } from "@lambda-middleware/http-error-handler";
import { cors } from '@lambda-middleware/cors';
import { pathParser } from './path-parser';
    
const handlerW = compose(
  cors(),
  errorHandler(),
  pathParser('/path/:pathparam/'),
  jsonSerializer(),
// @ts-ignore https://github.com/dbartholomae/lambda-middleware/issues/45
)(handler)