We're creating a web application for a unicorn ride-sharing service called Wild Riders. The app uses IAM, Amplify, Cognito, Lambda, API Gateway and DynamoDB, with code stored in GitHub and incorporated into a CI/CD pipeline with Amplify.
The app will let you create an account and log in, then request a ride by clicking on a map (powered by ArcGIS). The code can also be extended to build out more functionality.
All services used are eligible for the AWS Free Tier. Outside of the Free Tier, there may be small charges associated with building the app (less than ₹100), but charges will continue to incur if you leave the app running.
Here is the code for the Lambda function, originally taken from the AWS workshop, and updated for Node 20.x:
import { randomBytes } from 'crypto';
import { DynamoDBClient } from '@aws-sdk/client-dynamodb';
import { DynamoDBDocumentClient, PutCommand } from '@aws-sdk/lib-dynamodb';
const client = new DynamoDBClient({});
const ddb = DynamoDBDocumentClient.from(client);
const fleet = [
{ Name: 'Angel', Color: 'White', Gender: 'Female' },
{ Name: 'Gil', Color: 'White', Gender: 'Male' },
{ Name: 'Rocinante', Color: 'Yellow', Gender: 'Female' },
];
export const handler = async (event, context) => {
if (!event.requestContext.authorizer) {
return errorResponse('Authorization not configured', context.awsRequestId);
}
const rideId = toUrlString(randomBytes(16));
console.log('Received event (', rideId, '): ', event);
const username = event.requestContext.authorizer.claims['cognito:username'];
const requestBody = JSON.parse(event.body);
const pickupLocation = requestBody.PickupLocation;
const unicorn = findUnicorn(pickupLocation);
try {
await recordRide(rideId, username, unicorn);
return {
statusCode: 201,
body: JSON.stringify({
RideId: rideId,
Unicorn: unicorn,
Eta: '30 seconds',
Rider: username,
}),
headers: {
'Access-Control-Allow-Origin': '*',
},
};
} catch (err) {
console.error(err);
return errorResponse(err.message, context.awsRequestId);
}
};
function findUnicorn(pickupLocation) {
console.log('Finding unicorn for ', pickupLocation.Latitude, ', ', pickupLocation.Longitude);
return fleet[Math.floor(Math.random() * fleet.length)];
}
async function recordRide(rideId, username, unicorn) {
const params = {
TableName: 'Rides',
Item: {
RideId: rideId,
User: username,
Unicorn: unicorn,
RequestTime: new Date().toISOString(),
},
};
await ddb.send(new PutCommand(params));
}
function toUrlString(buffer) {
return buffer.toString('base64')
.replace(/\+/g, '-')
.replace(/\//g, '_')
.replace(/=/g, '');
}
function errorResponse(errorMessage, awsRequestId) {
return {
statusCode: 500,
body: JSON.stringify({
Error: errorMessage,
Reference: awsRequestId,
}),
headers: {
'Access-Control-Allow-Origin': '*',
},
};
}Here is the code used to test the Lambda function:
{
"path": "/ride",
"httpMethod": "POST",
"headers": {
"Accept": "*/*",
"Authorization": "eyJraWQiOiJLTzRVMWZs",
"content-type": "application/json; charset=UTF-8"
},
"queryStringParameters": null,
"pathParameters": null,
"requestContext": {
"authorizer": {
"claims": {
"cognito:username": "the_username"
}
}
},
"body": "{\"PickupLocation\":{\"Latitude\":47.6174755835663,\"Longitude\":-122.28837066650185}}"
}