lambda_function.py

import boto3
import json
from custom_encoder import CustomEncoder
import logging
logger = logging.getLogger()
logger.setLevel(logging.INFO)

dynamodbTableName = 'product-inventory'
dynamodb = boto3.resource('dynamodb')
table = dynamodb.Table(dynamodbTableName)

getMethod = 'GET'
postMethod = 'POST'
patchMethod = 'PATCH'
deleteMethod = 'DELETE'
healthPath = '/health'
productPath = '/product'
productsPath = '/products'

def lambda_handler(event, context):
    logger.info(event)
    httpMethod = event['httpMethod']
    path = event['path']
    if httpMethod == getMethod and path == healthPath:
        response = buildResponse(200)
    elif httpMethod == getMethod and path == productPath:
        #confirm here:
        response = getProduct(event['queryStringParameters']['productId'])
    elif httpMethod == getMethod and path == productsPath:
        response = getProducts()
    elif httpMethod == postMethod and path == productPath:
        response = saveProduct(json.loads(event['body']))
    elif httpMethod == patchMethod and path == productPath:
        requestBody = json.loads(event['body'])
        response = modifyProduct(requestBody['productId'], requestBody['updateKey'], requestBody['updateValue'])
    elif httpMethod == deleteMethod and path == productPath:
        requestBody = json.loads(event['body'])
        response = deleteProduct(requestBody['productId'])
    else:
        response = buildResponse(404, 'Not Found')

    return response

def getProduct(productId):
    try:
        response = table.get_item(
            Key={
                'productId': productId
            }
        )
        if 'Item' in response:
            return buildResponse(200, response['Item'])
        else:
            return buildResponse(404, {'Message': 'ProductId: %s not found' % productId})
    except:
        logger.exception('Do your custom error handling here!')

def getProducts():
    try:
        response = table.scan()
        result = response["Items"]

        while "LastEvaluateKey" in response:
            response = table.scan(ExclusiveStartKey=response["LastEvaluatedKey"])
            result.extend(response["Items"])

        body = {
            "products": result
        }
        return buildResponse(200, body)
    except:
        logger.exception("Do your custom error handling here!")

def saveProduct(requestBody):
    try: 
        table.put_item(Item=requestBody)
        body = {
            "Operation": "SAVE",
            "Message": "SUCCESS",
            "Item": requestBody
        }
        return buildResponse(200, body)
    except:
        logger.exception("Do your custom error handling here!")

def modifyProduct(productId, updateKey, updateValue):
    try:
        response = table.update_item(
            Key={
                "productId": productId
            },

            UpdateExpression="set {0} = :value".format(updateKey),
            ExpressionAttributeValues={
                ":value": updateValue
            },
            ReturnValues="UPDATED_NEW"
        )
        body = {
            "Operation": "UPDATE",
            "Message": "SUCCESS",
            "UpdatedAttributes": response
        }
        return buildResponse(200, body)
    except:
        logger.exception("Do your custom error handling here!")

def deleteProduct(productId):
    try:
        response = table.delete_item(
            Key={
                "productId": productId
            },
            ReturnValues="ALL_OLD"
        )
        body = {
            "Operation": "DELETE",
            "Message": "SUCCESS",
            "deltedItem": response
        }
        return buildResponse(200, body)
    except:
        logger.exception("Do your custom error handling here!")
    


def buildResponse(statusCode, body=None):
    response = {
        'statusCode': statusCode,
        'headers': {
            'Content-Type': 'application/json',
            'Access-Control-Allow-Origin': '*'
        }
    }
    if body is not None:
        response['body'] = json.dumps(body, cls=CustomEncoder)
    return response