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November 17, 2020 04:24
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Node API Gateway Middleware
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/** | |
* Convert a nodejs http request into an AWS API Gateway 'event' object. | |
* Or apply middleware to automatically convert requests/responses. | |
* Useful for testing your API Gateway lambda handler locally. | |
*/ | |
import { IncomingMessage, IncomingHttpHeaders, ServerResponse } from 'http' | |
import { URL, URLSearchParams } from 'url' | |
import { APIGatewayProxyHandler, APIGatewayProxyResult } from 'aws-lambda' | |
const noop = () => {} | |
const MockApiGatewayContext = { | |
callbackWaitsForEmptyEventLoop: false, | |
functionName: '', | |
functionVersion: '', | |
invokedFunctionArn: '', | |
awsRequestId: '', | |
logGroupName: '', | |
memoryLimitInMB: '', | |
logStreamName: '', | |
getRemainingTimeInMillis: () => 100, | |
done: noop, | |
fail: noop, | |
succeed: noop | |
} | |
function normalizeIncomingHeaders(inParams: IncomingHttpHeaders) { | |
return Object.keys(inParams).reduce((params: Record<string, string>, key) => { | |
const value = inParams[key] | |
params[key] = (Array.isArray(value) ? value[0] : value) || '' | |
return params | |
}, {}) | |
} | |
function normalizeOutgoingHeaders(outParams: APIGatewayProxyResult['headers']) { | |
return Object.keys(outParams || {}).reduce((params: Record<string, string>, key) => { | |
params[key] = '' + outParams?.[key] | |
return params | |
}, {}) | |
} | |
function normalizeIncomingQueryParams(params: URLSearchParams) { | |
return [...params].reduce((obj, [key, val]) => ({ ...obj, [key]: val }), {}) | |
} | |
export function nodeRequestToApiGatewayEvent(request: IncomingMessage) { | |
const parsedUrl = new URL(request.url || '', 'x://x.x') | |
const httpMethod = request.method || 'GET' | |
const path = parsedUrl.pathname || '/' | |
return { | |
httpMethod, | |
path, | |
headers: normalizeIncomingHeaders(request.headers), | |
queryStringParameters: normalizeIncomingQueryParams(parsedUrl.searchParams), | |
multiValueQueryStringParameters: null, | |
multiValueHeaders: {}, | |
resource: '$default', | |
body: null, | |
pathParameters: null, | |
stageVariables: null, | |
isBase64Encoded: false, | |
requestContext: { | |
path, | |
httpMethod, | |
protocol: request.httpVersion, | |
accountId: '', | |
apiId: '', | |
domainName: '', | |
domainPrefix: '', | |
extendedRequestId: '', | |
authorizer: null, | |
requestId: '', | |
requestTime: '', | |
requestTimeEpoch: Date.now(), | |
resourceId: '$default', | |
resourcePath: '$default', | |
stage: '$default', | |
identity: { | |
accessKey: null, | |
accountId: null, | |
apiKey: null, | |
apiKeyId: null, | |
apiId: null, | |
caller: null, | |
cognitoAmr: null, | |
cognitoAuthenticationProvider: null, | |
cognitoAuthenticationType: null, | |
cognitoIdentityId: null, | |
cognitoIdentityPoolId: null, | |
principalOrgId: null, | |
sourceIp: '', | |
user: null, | |
userAgent: 'Mozilla/5.0', | |
userArn: null | |
} | |
} | |
} | |
} | |
export function applyApiGatewayResultToNodeResponse(result: APIGatewayProxyResult, response: ServerResponse) { | |
const responseHeaders = normalizeOutgoingHeaders({ ...result.headers, 'content-type': 'application/json' }) | |
response.writeHead(result.statusCode, responseHeaders) | |
response.end(result.body) | |
} | |
export function apiGatewayMiddleware(handler: APIGatewayProxyHandler) { | |
return async function ( | |
request: IncomingMessage, | |
response: ServerResponse, | |
next?: (request: IncomingMessage, response: ServerResponse) => void | |
) { | |
const result = (await handler( | |
nodeRequestToApiGatewayEvent(request), | |
MockApiGatewayContext, | |
noop | |
)) as APIGatewayProxyResult | |
applyApiGatewayResultToNodeResponse(result, response) | |
next?.(request, response) | |
} | |
} |
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