from sqlalchemy.orm import Session
from typing import Optional, List, Dict, Any
from uuid import uuid4
import csv
import logging
import os
from io import StringIO

from db.utils import db_transaction
from db.models import File, StagedFileProduct
from schemas.file import CreateFileRequest

logger = logging.getLogger(__name__)

class FileConfig:
    """Configuration constants for file processing"""
    TEMP_DIR = os.path.join(os.getcwd(), 'app/' + 'temp')
    
    MANABOX_HEADERS = [
        'Name', 'Set code', 'Set name', 'Collector number', 'Foil', 
        'Rarity', 'Quantity', 'ManaBox ID', 'Scryfall ID', 'Purchase price',
        'Misprint', 'Altered', 'Condition', 'Language', 'Purchase price currency'
    ]
    
    SOURCES = {
        "manabox": {
            "required_headers": MANABOX_HEADERS,
            "allowed_extensions": ['.csv'],
            "allowed_types": ['scan_export_common', 'scan_export_rare']
        }
    }

class FileValidationError(Exception):
    """Custom exception for file validation errors"""
    pass

class FileService:
    def __init__(self, db: Session):
        self.db = db

    def get_config(self, source: str) -> Dict[str, Any]:
        """Get configuration for a specific source"""
        config = FileConfig.SOURCES.get(source)
        if not config:
            raise FileValidationError(f"Unsupported source: {source}")
        return config

    def validate_file_extension(self, filename: str, config: Dict[str, Any]) -> bool:
        """Validate file extension against allowed extensions"""
        return any(filename.endswith(ext) for ext in config["allowed_extensions"])

    def validate_file_type(self, metadata: CreateFileRequest, config: Dict[str, Any]) -> bool:
        """Validate file type against allowed types"""
        return metadata.type in config["allowed_types"]

    def validate_csv(self, content: bytes, required_headers: Optional[List[str]] = None) -> bool:
        """Validate CSV content and headers"""
        try:
            csv_text = content.decode('utf-8')
            csv_file = StringIO(csv_text)
            csv_reader = csv.reader(csv_file)
            
            if required_headers:
                headers = next(csv_reader, None)
                if not headers or not all(header in headers for header in required_headers):
                    return False
            return True
            
        except (UnicodeDecodeError, csv.Error) as e:
            logger.error(f"CSV validation error: {str(e)}")
            return False

    def validate_file_content(self, content: bytes, metadata: CreateFileRequest, config: Dict[str, Any]) -> bool:
        """Validate file content based on file type"""
        extension = os.path.splitext(metadata.filename)[1].lower()
        if extension == '.csv':
            return self.validate_csv(content, config.get("required_headers"))
        return False

    def validate_file(self, content: bytes, metadata: CreateFileRequest) -> bool:
        """Validate file against all criteria"""
        config = self.get_config(metadata.source)
        
        if not self.validate_file_extension(metadata.filename, config):
            raise FileValidationError("Invalid file extension")
        
        if not self.validate_file_type(metadata, config):
            raise FileValidationError("Invalid file type")
        
        if not self.validate_file_content(content, metadata, config):
            raise FileValidationError("Invalid file content or headers")
            
        return True

    def create_file(self, content: bytes, metadata: CreateFileRequest) -> File:
        """Create a new file record and save the file"""
        with db_transaction(self.db):
            file = File(
                id=str(uuid4()),
                filename=metadata.filename,
                filepath=os.path.join(FileConfig.TEMP_DIR, metadata.filename),
                type=metadata.type,
                source=metadata.source,
                filesize_kb=round(len(content) / 1024, 2),
                status='pending',
                service=metadata.service
            )
            self.db.add(file)
            
        os.makedirs(FileConfig.TEMP_DIR, exist_ok=True)
        with open(file.filepath, 'wb') as f:
            f.write(content)
            
        return file

    def get_file(self, file_id: str) -> File:
        """Get a file by ID"""
        file = self.db.query(File).filter(File.id == file_id).first()
        if not file:
            raise FileValidationError(f"File with id {file_id} not found")
        return file

    def get_files(self, status: Optional[str] = None) -> List[File]:
        """Get all files, optionally filtered by status"""
        query = self.db.query(File)
        if status:
            query = query.filter(File.status == status)
        return query.all()

    def get_staged_products(self, file_id: str) -> List[StagedFileProduct]:
        """Get staged products for a file"""
        return self.db.query(StagedFileProduct).filter(
            StagedFileProduct.file_id == file_id
        ).all()

    def delete_file(self, file_id: str) -> File:
        """Mark a file as deleted and remove associated staged products"""
        file = self.get_file(file_id)
        staged_products = self.get_staged_products(file_id)
        
        with db_transaction(self.db):
            file.status = 'deleted'
            for staged_product in staged_products:
                self.db.delete(staged_product)
                
        return file

    def get_file_content(self, file_id: str) -> bytes:
        """Get the content of a file"""
        file = self.get_file(file_id)
        try:
            with open(file.filepath, 'rb') as f:
                return f.read()
        except IOError as e:
            logger.error(f"Error reading file {file_id}: {str(e)}")
            raise FileValidationError(f"Could not read file content for {file_id}")