import os
import json
import boto3
from boto3.dynamodb.conditions import Key
from botocore.exceptions import ClientError
from decimal import Decimal
import logging

logger = logging.getLogger()
logger.setLevel(logging.INFO)
logging.basicConfig(format="%(asctime)s - %(message)s", level=logging.INFO)

# Retrieve region where Lambda is being executed
region_name = os.environ["AWS_REGION"]

class DecimalEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, Decimal):
            return float(obj)
        return super(DecimalEncoder, self).default(obj)


# Create DynamoDB resource
dynamodb = boto3.resource("dynamodb")


def lambda_handler(event, context):

    logger.info(f"Lambda event is [{event}]")

    # Retrieve AWS request identifier for this execution
    request_id = str(context.aws_request_id)

    # Retrieve target DynamoDB table name from environment variables
    val_table_name = os.environ["target_ddb_table"]
    val_policy_id = str(event["queryStringParameters"]["policy_id"])

    logger.info(f"Input parameters are [{val_table_name}] [{val_policy_id}]")

    request_data = event.get("requestContext")

    logger.info("Request data is is [{request_data}]")

    # Create a paginator
    paginator = dynamodb.meta.client.get_paginator("query")

    logger.info("Retrieving data ...")

    try:

        # Scenario : retrieve all columns from the source table
        response_iterator = paginator.paginate(
            TableName=val_table_name,
            KeyConditionExpression=Key("policy_id").eq(val_policy_id),
            Select="ALL_ATTRIBUTES",
            PaginationConfig={"MaxItems": 10, "PageSize": 10},
        )

        for page in response_iterator:
            if page["Count"] > 0:
                converted_items = json.dumps(
                    page["Items"], cls=DecimalEncoder, indent=2
                )

        logger.info("no. of items ->[{}]".format(len(converted_items)))

        # Dummy response
        responsebody = converted_items

        # Generate response
        responseObject = {}
        responseObject["statusCode"] = 200
        responseObject["headers"] = {}
        responseObject["headers"]["Content-Type"] = "application/json"
        responseObject["body"] = responsebody

        return responseObject
    except ClientError as e:
        if e.response["Error"]["Code"] == "AccessDeniedException":
            logger.error("Error - AccessDeniedException", exc_info=True)

            return {
                "statusCode": 401,
                "body": json.dumps("Insufficient rights to perform this operation"),
            }
        else:
            raise