"""Utility functions for FinFast data collection from DynamoDB to MongoDB"""

import os
import boto3
from boto3.dynamodb.types import TypeDeserializer
from pymongo.errors import PyMongoError
from botocore.exceptions import ClientError, BotoCoreError


def get_dynamodb_client():
    """
    Create and return a DynamoDB client using AWS credentials from environment variables.
    
    Returns:
        boto3.client: Configured DynamoDB client
    """
    aws_access_key_id = os.getenv('AWS_ACCESS_KEY_ID')
    aws_secret_access_key = os.getenv('AWS_SECRET_ACCESS_KEY')

    return boto3.client(
        service_name='dynamodb',
        region_name='us-east-1',
        aws_access_key_id=aws_access_key_id,
        aws_secret_access_key=aws_secret_access_key
    )


def scan_dynamodb_table(table_name, filter_date, item_processor):
    """
    Scan a DynamoDB table and process items using the provided processor function.
    
    Args:
        table_name (str): Name of the DynamoDB table to scan
        filter_date (str): Filter date in 'YYYY-MM-DD' format
        item_processor (callable): Function to process each item
        
    Raises:
        ClientError: If there is an error during DynamoDB scan operation
        BotoCoreError: If there is a boto3 core error
    """
    dynamodb = get_dynamodb_client()
    last_evaluated_key = None
    deserializer = TypeDeserializer()

    try:
        while True:
            # Prepare scan parameters
            scan_params = {
                'TableName': table_name,
                'FilterExpression': 'publishDate >= :date',
                'ExpressionAttributeValues': {
                    ':date': {'S': filter_date}
                }
            }

            # Add ExclusiveStartKey if it exists
            if last_evaluated_key:
                scan_params['ExclusiveStartKey'] = last_evaluated_key

            # Scan the table
            response = dynamodb.scan(**scan_params)
            items = [
                {k: deserializer.deserialize(v) for k, v in item.items()}
                for item in response.get('Items', [])
            ]

            # Process items using the provided processor
            for item in items:
                item_processor(item)

            last_evaluated_key = response.get('LastEvaluatedKey')
            if not last_evaluated_key:
                break

    except (ClientError, BotoCoreError) as e:
        print(f"Error in scan operation: {e}")
        raise


def delete_old_documents(collection, cutoff_date, use_logger=None):
    """
    Delete documents from MongoDB collection that are older than the specified cutoff date.
    
    Args:
        collection: MongoDB collection object
        cutoff_date (str): The cutoff date in 'YYYY-MM-DD' format
        use_logger: Optional logger object. If provided, will use logger, otherwise use print
        
    Raises:
        PyMongoError: If there is an error during the delete operation
    """
    try:
        result = collection.delete_many({
            'publishDate': {'$lt': cutoff_date}
        })
        message = f"Deleted {result.deleted_count} documents older than {cutoff_date}"
        if use_logger:
            use_logger.info("Deleted %d documents older than %s", result.deleted_count, cutoff_date)
        else:
            print(message)
    except PyMongoError as e:
        error_message = f"Error deleting old documents: {e}"
        if use_logger:
            use_logger.error("Error deleting old documents: %s", e)
        else:
            print(error_message)
        raise

def upsert_item(collection, item):
    """Helper function to upsert an item into a MongoDB collection."""
    collection.update_one(
        {'_id': item['_id']},
        {'$set': item},
        upsert=True
    )
    print(f"Successfully processed item: {item['_id']}")