import boto3
from botocore.exceptions import ClientError
from core.config import settings
import logging

logger = logging.getLogger(__name__)

class S3Service:
    def __init__(self):
        self.s3_client = boto3.client(
            's3',
            aws_access_key_id=settings.AWS_ACCESS_KEY_ID,
            aws_secret_access_key=settings.AWS_SECRET_ACCESS_KEY,
            region_name=settings.AWS_REGION
        )
        self.bucket_name = settings.AWS_S3_BUCKET

    def get_public_url(self, key: str):
        """
        Generates the standard S3 public URL for a given key.
        """
        return f"https://{self.bucket_name}.s3.{settings.AWS_REGION}.amazonaws.com/{key}"

    def get_presigned_url(self, key: str, expires_in: int = 3600):
        """
        Generates a pre-signed URL for secure access. Default: 1 hour.
        """
        try:
            url = self.s3_client.generate_presigned_url(
                'get_object',
                Params={'Bucket': self.bucket_name, 'Key': key},
                ExpiresIn=expires_in
            )
            return url
        except ClientError as e:
            logger.error(f"Failed to generate presigned URL: {e}")
            return None

    async def upload_file(self, file_content: bytes, filename: str, user_id: str):
        """
        Uploads a file to S3 under a user-specific folder.
        """
        key = f"users/{user_id}/sources/{filename}"
        try:
            self.s3_client.put_object(
                Bucket=self.bucket_name,
                Key=key,
                Body=file_content
            )
            return {
                "key": key,
                "public_url": self.get_public_url(key),
                "private_url": self.get_presigned_url(key)
            }
        except ClientError as e:
            logger.error(f"Failed to upload to S3: {e}")
            raise Exception("S3 Upload Failed")

    async def list_user_files(self, user_id: str):
        """
        Lists files for a specific user.
        """
        prefix = f"users/{user_id}/sources/"
        try:
            response = self.s3_client.list_objects_v2(
                Bucket=self.bucket_name,
                Prefix=prefix
            )
            files = []
            if 'Contents' in response:
                for obj in response['Contents']:
                    # Remove the prefix from the filename for display
                    filename = obj['Key'].replace(prefix, "")
                    if filename: # Avoid empty strings if the prefix itself is returned
                        files.append({
                            "filename": filename,
                            "key": obj['Key'],
                            "public_url": self.get_public_url(obj['Key']),
                            "private_url": self.get_presigned_url(obj['Key']),
                            "size": obj['Size'],
                            "last_modified": obj['LastModified']
                        })
            return files
        except ClientError as e:
            logger.error(f"Failed to list S3 files: {e}")
            raise Exception("S3 List Failed")

    async def delete_file(self, key: str):
        """
        Deletes a file from S3.
        """
        try:
            self.s3_client.delete_object(
                Bucket=self.bucket_name,
                Key=key
            )
            logger.info(f"Deleted S3 object: {key}")
            return True
        except ClientError as e:
            logger.error(f"Failed to delete S3 object: {e}")
            return False

s3_service = S3Service()