lambda_function.py

import json
import boto3
import os

# LocalStack requires us to explicitly point to its internal endpoint
LOCALSTACK_HOSTNAME = os.environ.get("LOCALSTACK_HOSTNAME", "localhost")
ENDPOINT_URL = f"http://{LOCALSTACK_HOSTNAME}:4566"

ec2_client = boto3.client("ec2", endpoint_url=ENDPOINT_URL, region_name="us-east-1")

def lambda_handler(event, context):
    print("Received event:", json.dumps(event))
    
    # Handle both direct JSON payloads and stringified API Gateway proxy payloads
    body = event.get("body", "{}")
    if isinstance(body, str):
        try:
            body = json.loads(body)
        except Exception:
            return {
                "statusCode": 400,
                "body": json.dumps({"error": "Invalid JSON format in request body"})
            }
            
    action = body.get("action")       # 'start' or 'stop'
    instance_id = body.get("instance_id")
    
    if not action or not instance_id:
        return {
            "statusCode": 400,
            "body": json.dumps({"error": "Missing 'action' or 'instance_id' in payload"})
        }
        
    try:
        if action.lower() == "start":
            response = ec2_client.start_instances(InstanceIds=[instance_id])
            current_state = response['StartingInstances'][0]['CurrentState']['Name']
            message = f"Instance {instance_id} is turning on. Current state: {current_state}"
            
        elif action.lower() == "stop":
            response = ec2_client.stop_instances(InstanceIds=[instance_id])
            current_state = response['StoppingInstances'][0]['CurrentState']['Name']
            message = f"Instance {instance_id} is shutting down. Current state: {current_state}"
            
        else:
            return {
                "statusCode": 400,
                "body": json.dumps({"error": f"Unsupported action: {action}. Use 'start' or 'stop'"})
            }
            
        return {
            "statusCode": 200,
            "headers": {"Content-Type": "application/json"},
            "body": json.dumps({"status": "success", "message": message})
        }
        
    except Exception as e:
        return {
            "statusCode": 500,
            "body": json.dumps({"error": str(e)})
        }