itty-lambda - AWS Lambda support for [itty-router]

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AWS Lambda functions can respond to HTTP requests via one of the following invocation types:
- [Function urls][lambda-function-urls]
- [API gateways][api-gateways]
- [Application load balancers][albs].

This library aims to maintain support for running [itty-router] in any such environment.

Example

``js
// supports CJS -or- ESM
// const { url, ag, alb } = require('itty-lambda');
// import { url, ag, alb } from 'itty-lambda';

// for just API Gateway support, use 'itty-lambda/ag'
// for just Application Load Balancer support, use 'itty-lambda/alb'
// for just Lambda function url support, use 'itty-lambda/url'

import { AutoRouter } from 'itty-router';

// using an app load balancer...
import { eventToRequest, responseToResult } from 'itty-lambda/alb';

export async function handler (event) {
const router = AutoRouter();
router.get('/foo', () => ({ success: true }));

const request = await eventToRequest(event);
// { path: string, httpMethod: string, headers: object, ... }
// ->
// { url: string, method: string, headers: Headers, ... }

const response = await router.fetch(request);

const result = await responseToResult(response);
// { status: number, headers: Headers, body: ReadableStream, ... }
// ->
// { statusCode: number, body: string, headers: object, ... }

return result;
}
`

Each implementation provides these two named exports, for you to plug in before and after routing...

For more information, see the documentation.

eventToRequest

Accepts an AWS Lambda event for the invocation type, and resolves to a well formed RequestLike.

`ts
eventToRequest(
event: APIGatewayProxyEvent | ALBEvent | LambdaFunctionURLEvent,
options: EventOptions | undefined
) : Promise
`

$3

| Name | Type(s) | Default Value | Description |
| -- | -- | -- | -- |
| defaultMethod | string | GET | HTTP method if none provided from event |

responseToResult

Accepts a router Response, and resolves to a result for the invocation type.

`ts
responseToResult(
response: Response | undefined,
options : ResponseOptions | undefined
) : Promise
`

$3

| Name | Type(s) | Default Value | Description |
| -- | -- | -- | -- |
| base64Encode | boolean | false | Encode response body |
| fallbackStatus | number | 404 | Status if no response provided from router |
| multiValueHeaders | boolean | false` | Split response headers with multiple values |

[itty-router]: https://itty.dev/itty-router/
[lambda-function-urls]: https://docs.aws.amazon.com/lambda/latest/dg/urls-invocation.html
[api-gateways]: https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-lambda-integrations.html
[albs]: https://docs.aws.amazon.com/elasticloadbalancing/latest/application/lambda-functions.html