import { HeaderMap } from '@apollo/server';
import type { APIGatewayProxyEvent, APIGatewayProxyResult } from 'aws-lambda';
import { createRequestHandler } from './_create';

export const createAPIGatewayProxyEventRequestHandler = <
  Event extends APIGatewayProxyEvent = APIGatewayProxyEvent,
>() => {
  return createRequestHandler<Event, APIGatewayProxyResult>(
    {
      parseHttpMethod(event) {
        return event.httpMethod;
      },
      parseHeaders(event) {
        const headerMap = new HeaderMap();
        for (const [key, value] of Object.entries(event.headers ?? {})) {
          headerMap.set(key, value ?? '');
        }
        return headerMap;
      },
      parseBody(event, headers) {
        if (event.body) {
          const contentType = headers.get('content-type');
          const parsedBody = event.isBase64Encoded
            ? Buffer.from(event.body, 'base64').toString('utf8')
            : event.body;
          if (contentType?.startsWith('application/json')) {
            return JSON.parse(parsedBody);
          }
          if (contentType?.startsWith('text/plain')) {
            return parsedBody;
          }
        }
        return '';
      },
      parseQueryParams(event) {
        const params = new URLSearchParams();
        for (const [key, value] of Object.entries(
          event.multiValueQueryStringParameters ?? {},
        )) {
          for (const v of value ?? []) {
            params.append(key, decodeURIComponent(v));
          }
        }
        return params.toString();
      },
    },
    {
      success({ body, headers, status }) {
        if (body.kind !== 'complete') {
          throw new Error('Only complete body type supported');
        }

        return {
          statusCode: status ?? 200,
          headers: {
            ...Object.fromEntries(headers),
            'content-length': Buffer.byteLength(body.string).toString(),
          },
          body: body.string,
        };
      },
      error(error) {
        return {
          statusCode: 400,
          body: (error as Error).message,
        };
      },
    },
  );
};