import boto3
from botocore.exceptions import ClientError
import datetime
from typing import Optional, List
from .models import User, FileUpload

dynamodb = boto3.resource('dynamodb')
users_table = dynamodb.Table('Users')
files_table = dynamodb.Table('Files')

async def get_user_by_username(username: str) -> Optional[User]:
    try:
        response = users_table.get_item(Key={'username': username})
        if 'Item' in response:
            return User(**response['Item'])
        return None
    except ClientError:
        return None

async def create_user(user: User) -> bool:
    try:
        users_table.put_item(
            Item={
                'username': user.username,
                'email': user.email,
                'password': user.password,
            },
            ConditionExpression='attribute_not_exists(username)'
        )
        return True
    except ClientError:
        return False

async def save_file(username: str, file_upload: FileUpload) -> bool:
    try:
        files_table.put_item(
            Item={
                'username': username,
                'filename': file_upload.filename,
                'content': file_upload.content,
                'created_at': datetime.datetime.now(datetime.UTC).isoformat(),
                'updated_at': datetime.datetime.now(datetime.UTC).isoformat()
            }
        )
        return True
    except ClientError:
        return False

async def get_user_files(username: str) -> List[FileUpload]:
    try:
        response = files_table.query(
            KeyConditionExpression='username = :username',
            ExpressionAttributeValues={':username': username}
        )
        return [FileUpload(**item) for item in response.get('Items', [])]
    except ClientError:
        return []