import json
import boto3
from boto3.dynamodb.conditions import Key

dynamodb = boto3.resource('dynamodb')
table = dynamodb.Table('Users')

def lambda_handler(event, context):
    http_method = event['httpMethod']
    if http_method == 'POST':
        return create_user(event)
    elif http_method == 'GET':
        return get_user(event)
    elif http_method == 'PUT':
        return update_user(event)
    elif http_method == 'DELETE':
        return delete_user(event)
    else:
        return {
            'statusCode': 405,
            'body': json.dumps('Method Not Allowed')
        }

def create_user(event):
    body = json.loads(event['body'])
    user_id = body['userId']
    name = body['name']
    age = body['age']

    table.put_item(
        Item={
            'userId': user_id,
            'name': name,
            'age': age
        }
    )
    return {
        'statusCode': 201,
        'body': json.dumps(f'User {user_id} created successfully')
    }

def get_user(event):
    user_id = event['queryStringParameters']['userId']

    response = table.get_item(
        Key={
            'userId': user_id
        }
    )

    if 'Item' in response:
        return {
            'statusCode': 200,
            'body': json.dumps(response['Item'])
        }
    else:
        return {
            'statusCode': 404,
            'body': json.dumps(f'User {user_id} not found')
        }

def update_user(event):
    body = json.loads(event['body'])
    user_id = body['userId']
    name = body.get('name')
    age = body.get('age')

    update_expression = 'set '
    expression_attribute_values = {}

    if name:
        update_expression += 'name = :name, '
        expression_attribute_values[':name'] = name
    if age:
        update_expression += 'age = :age, '
        expression_attribute_values[':age'] = age

    update_expression = update_expression.rstrip(', ')

    table.update_item(
        Key={'userId': user_id},
        UpdateExpression=update_expression,
        ExpressionAttributeValues=expression_attribute_values
    )

    return {
        'statusCode': 200,
        'body': json.dumps(f'User {user_id} updated successfully')
    }

def delete_user(event):
    user_id = event['queryStringParameters']['userId']

    table.delete_item(
        Key={
            'userId': user_id
        }
    )

    return {
        'statusCode': 200,
        'body': json.dumps(f'User {user_id} deleted successfully')
    }