"""Utilis Functions"""
import os
import glob
import boto3
import pandas as pd

AWS_ACCESS_KEY_ID = os.getenv("AWS_ACCESS_KEY_ID")
AWS_SECRET_ACCESS_KEY = os.getenv("AWS_SECRET_ACCESS_KEY")

#Downloads .parquet files from an S3 bucket and concatenates them into a single pandas DataFrame.
def download_files_from_s3(folder):
    """Download Data Files"""
    if not os.path.exists(folder):
        os.makedirs(folder)
    client = boto3.client(
        's3',
        aws_access_key_id=AWS_ACCESS_KEY_ID,
        aws_secret_access_key=AWS_SECRET_ACCESS_KEY,
    )
    response = client.list_objects_v2(Bucket='finfast-china', Prefix=f"{folder}/")
    for obj in response['Contents']:
        key = obj['Key']
        if key.endswith('.parquet'):
            client.download_file('finfast-china', key, key)
    file_paths = glob.glob(os.path.join(folder, '*.parquet'))
    return pd.concat([pd.read_parquet(file_path) for file_path in file_paths], ignore_index=True)

# Returns a DynamoDB client connection.
def get_client_connection():
    """Get dynamoDB connection"""
    dynamodb = 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
    )
    return dynamodb

# Updates an entity in the specified DynamoDB table.
def update_entity(table_name, row):
    """update entity data to db"""
    dynamodb = get_client_connection()
    response = dynamodb.update_item(
                TableName=table_name,
                Key={
                    'entity': {'S': row['entity']},
                    'entityType': {'S': row['entitytype']}
                },
                UpdateExpression='SET total_occurrence = :total_occurrence',
                ExpressionAttributeValues={
                    ':total_occurrence': {'N': str(row['total_occurrence'])}
                }
            )
    print(response)

# Updates a category in the specified DynamoDB table.
def update_category(table_name, row):
    """update category data to db"""
    dynamodb = get_client_connection()
    response = dynamodb.update_item(
                TableName=table_name,
                Key={
                    'site': {'S': row['site']},
                    'category': {'S': row['category']}
                },
                UpdateExpression='SET cnt = :cnt',
                ExpressionAttributeValues={
                    ':cnt': {'N': str(row['count'])},
                }
            )
    print(response)

# Deletes an entity from the specified DynamoDB table.
def delete_entity(table_name, row):
    """delete entity from db"""
    dynamodb = get_client_connection()
    dynamodb.delete_item(
        TableName=table_name,
        Key={
            'entity': {'S': row['entity']},
            'entityType': {'S': row['entityType']}
        }
    )

# Scans the specified DynamoDB table and deletes all items.
def scan(table_name):
    """scan record from db"""
    dynamodb = get_client_connection()
    response = dynamodb.scan(TableName=table_name)
    while 'LastEvaluatedKey' in response:
        for item in response['Items']:
            dynamodb.delete_item(
                TableName=table_name,
                Key=dict(item)
            )
        response = dynamodb.scan(TableName=table_name,
        ExclusiveStartKey=response['LastEvaluatedKey'])
    return response