"""
Storage service for handling file storage with S3-compatible backend and multi-tenant support.
"""

import asyncio
import logging
import hashlib
import mimetypes
from typing import Optional, Dict, Any, List
from pathlib import Path
import uuid
from datetime import datetime, timedelta

import boto3
from botocore.exceptions import ClientError, NoCredentialsError
import aiofiles
from fastapi import UploadFile

from app.core.config import settings
from app.models.tenant import Tenant

logger = logging.getLogger(__name__)


class StorageService:
    """Storage service with S3-compatible backend and multi-tenant support."""
    
    def __init__(self, tenant: Tenant):
        self.tenant = tenant
        self.s3_client = None
        self.bucket_name = f"vbm-documents-{tenant.id}"
        
        # Initialize S3 client if credentials are available
        if settings.AWS_ACCESS_KEY_ID and settings.AWS_SECRET_ACCESS_KEY:
            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 or 'us-east-1',
                endpoint_url=settings.S3_ENDPOINT_URL  # For MinIO or other S3-compatible services
            )
        else:
            logger.warning("AWS credentials not configured, using local storage")
    
    async def upload_file(self, file: UploadFile, document_id: str) -> Dict[str, Any]:
        """
        Upload a file to storage with security validation.
        """
        try:
            # Security validation
            await self._validate_file_security(file)
            
            # Generate file path
            file_path = self._generate_file_path(document_id, file.filename)
            
            # Read file content
            content = await file.read()
            
            # Calculate checksum
            checksum = hashlib.sha256(content).hexdigest()
            
            # Upload to storage
            if self.s3_client:
                await self._upload_to_s3(content, file_path, file.content_type)
                storage_url = f"s3://{self.bucket_name}/{file_path}"
            else:
                await self._upload_to_local(content, file_path)
                storage_url = str(file_path)
            
            return {
                "file_path": file_path,
                "storage_url": storage_url,
                "file_size": len(content),
                "checksum": checksum,
                "mime_type": file.content_type,
                "uploaded_at": datetime.utcnow().isoformat()
            }
            
        except Exception as e:
            logger.error(f"Error uploading file {file.filename}: {str(e)}")
            raise
    
    async def download_file(self, file_path: str) -> bytes:
        """
        Download a file from storage.
        """
        try:
            if self.s3_client:
                return await self._download_from_s3(file_path)
            else:
                return await self._download_from_local(file_path)
                
        except Exception as e:
            logger.error(f"Error downloading file {file_path}: {str(e)}")
            raise
    
    async def delete_file(self, file_path: str) -> bool:
        """
        Delete a file from storage.
        """
        try:
            if self.s3_client:
                return await self._delete_from_s3(file_path)
            else:
                return await self._delete_from_local(file_path)
                
        except Exception as e:
            logger.error(f"Error deleting file {file_path}: {str(e)}")
            return False
    
    async def get_file_info(self, file_path: str) -> Optional[Dict[str, Any]]:
        """
        Get file information from storage.
        """
        try:
            if self.s3_client:
                return await self._get_s3_file_info(file_path)
            else:
                return await self._get_local_file_info(file_path)
                
        except Exception as e:
            logger.error(f"Error getting file info for {file_path}: {str(e)}")
            return None
    
    async def list_files(self, prefix: str = "", max_keys: int = 1000) -> List[Dict[str, Any]]:
        """
        List files in storage with optional prefix filtering.
        """
        try:
            if self.s3_client:
                return await self._list_s3_files(prefix, max_keys)
            else:
                return await self._list_local_files(prefix, max_keys)
                
        except Exception as e:
            logger.error(f"Error listing files with prefix {prefix}: {str(e)}")
            return []
    
    async def _validate_file_security(self, file: UploadFile) -> None:
        """
        Validate file for security threats.
        """
        # Check file size
        if not file.filename:
            raise ValueError("No filename provided")
        
        # Check file extension
        allowed_extensions = {
            '.pdf', '.docx', '.xlsx', '.pptx', '.txt', '.csv',
            '.jpg', '.jpeg', '.png', '.gif', '.bmp', '.tiff'
        }
        
        file_extension = Path(file.filename).suffix.lower()
        if file_extension not in allowed_extensions:
            raise ValueError(f"File type {file_extension} not allowed")
        
        # Check MIME type
        if file.content_type:
            allowed_mime_types = {
                'application/pdf',
                'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
                'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
                'application/vnd.openxmlformats-officedocument.presentationml.presentation',
                'text/plain',
                'text/csv',
                'image/jpeg',
                'image/png',
                'image/gif',
                'image/bmp',
                'image/tiff'
            }
            
            if file.content_type not in allowed_mime_types:
                raise ValueError(f"MIME type {file.content_type} not allowed")
    
    def _generate_file_path(self, document_id: str, filename: str) -> str:
        """
        Generate a secure file path for storage.
        """
        # Create tenant-specific path
        tenant_path = f"tenants/{self.tenant.id}/documents"
        
        # Use document ID and sanitized filename
        sanitized_filename = Path(filename).name.replace(" ", "_")
        file_path = f"{tenant_path}/{document_id}_{sanitized_filename}"
        
        return file_path
    
    async def _upload_to_s3(self, content: bytes, file_path: str, content_type: str) -> None:
        """
        Upload file to S3-compatible storage.
        """
        try:
            self.s3_client.put_object(
                Bucket=self.bucket_name,
                Key=file_path,
                Body=content,
                ContentType=content_type,
                Metadata={
                    'tenant_id': str(self.tenant.id),
                    'uploaded_at': datetime.utcnow().isoformat()
                }
            )
        except ClientError as e:
            logger.error(f"S3 upload error: {str(e)}")
            raise
        except NoCredentialsError:
            logger.error("AWS credentials not found")
            raise
    
    async def _upload_to_local(self, content: bytes, file_path: str) -> None:
        """
        Upload file to local storage.
        """
        try:
            # Create directory structure
            local_path = Path(f"storage/{file_path}")
            local_path.parent.mkdir(parents=True, exist_ok=True)
            
            # Write file
            async with aiofiles.open(local_path, 'wb') as f:
                await f.write(content)
                
        except Exception as e:
            logger.error(f"Local upload error: {str(e)}")
            raise
    
    async def _download_from_s3(self, file_path: str) -> bytes:
        """
        Download file from S3-compatible storage.
        """
        try:
            response = self.s3_client.get_object(
                Bucket=self.bucket_name,
                Key=file_path
            )
            return response['Body'].read()
        except ClientError as e:
            logger.error(f"S3 download error: {str(e)}")
            raise
    
    async def _download_from_local(self, file_path: str) -> bytes:
        """
        Download file from local storage.
        """
        try:
            local_path = Path(f"storage/{file_path}")
            async with aiofiles.open(local_path, 'rb') as f:
                return await f.read()
        except Exception as e:
            logger.error(f"Local download error: {str(e)}")
            raise
    
    async def _delete_from_s3(self, file_path: str) -> bool:
        """
        Delete file from S3-compatible storage.
        """
        try:
            self.s3_client.delete_object(
                Bucket=self.bucket_name,
                Key=file_path
            )
            return True
        except ClientError as e:
            logger.error(f"S3 delete error: {str(e)}")
            return False
    
    async def _delete_from_local(self, file_path: str) -> bool:
        """
        Delete file from local storage.
        """
        try:
            local_path = Path(f"storage/{file_path}")
            if local_path.exists():
                local_path.unlink()
                return True
            return False
        except Exception as e:
            logger.error(f"Local delete error: {str(e)}")
            return False
    
    async def _get_s3_file_info(self, file_path: str) -> Optional[Dict[str, Any]]:
        """
        Get file information from S3-compatible storage.
        """
        try:
            response = self.s3_client.head_object(
                Bucket=self.bucket_name,
                Key=file_path
            )
            
            return {
                "file_size": response['ContentLength'],
                "last_modified": response['LastModified'].isoformat(),
                "content_type": response.get('ContentType'),
                "metadata": response.get('Metadata', {})
            }
        except ClientError:
            return None
    
    async def _get_local_file_info(self, file_path: str) -> Optional[Dict[str, Any]]:
        """
        Get file information from local storage.
        """
        try:
            local_path = Path(f"storage/{file_path}")
            if not local_path.exists():
                return None
            
            stat = local_path.stat()
            return {
                "file_size": stat.st_size,
                "last_modified": datetime.fromtimestamp(stat.st_mtime).isoformat(),
                "content_type": mimetypes.guess_type(local_path)[0]
            }
        except Exception:
            return None
    
    async def _list_s3_files(self, prefix: str, max_keys: int) -> List[Dict[str, Any]]:
        """
        List files in S3-compatible storage.
        """
        try:
            tenant_prefix = f"tenants/{self.tenant.id}/documents/{prefix}"
            
            response = self.s3_client.list_objects_v2(
                Bucket=self.bucket_name,
                Prefix=tenant_prefix,
                MaxKeys=max_keys
            )
            
            files = []
            for obj in response.get('Contents', []):
                files.append({
                    "key": obj['Key'],
                    "size": obj['Size'],
                    "last_modified": obj['LastModified'].isoformat()
                })
            
            return files
        except ClientError as e:
            logger.error(f"S3 list error: {str(e)}")
            return []
    
    async def _list_local_files(self, prefix: str, max_keys: int) -> List[Dict[str, Any]]:
        """
        List files in local storage.
        """
        try:
            tenant_path = Path(f"storage/tenants/{self.tenant.id}/documents/{prefix}")
            if not tenant_path.exists():
                return []
            
            files = []
            for file_path in tenant_path.rglob("*"):
                if file_path.is_file():
                    stat = file_path.stat()
                    files.append({
                        "key": str(file_path.relative_to(Path("storage"))),
                        "size": stat.st_size,
                        "last_modified": datetime.fromtimestamp(stat.st_mtime).isoformat()
                    })
                    
                    if len(files) >= max_keys:
                        break
            
            return files
        except Exception as e:
            logger.error(f"Local list error: {str(e)}")
            return []
    
    async def cleanup_old_files(self, days_old: int = 30) -> int:
        """
        Clean up old files from storage.
        """
        try:
            cutoff_date = datetime.utcnow() - timedelta(days=days_old)
            deleted_count = 0
            
            files = await self.list_files()
            
            for file_info in files:
                last_modified = datetime.fromisoformat(file_info['last_modified'])
                if last_modified < cutoff_date:
                    if await self.delete_file(file_info['key']):
                        deleted_count += 1
            
            return deleted_count
            
        except Exception as e:
            logger.error(f"Cleanup error: {str(e)}")
            return 0