"""
Tool_OCR - File Management Service
Handles file uploads, storage, validation, and cleanup
"""

import logging
import shutil
import uuid
from pathlib import Path
from typing import List, Tuple, Optional
from datetime import datetime, timedelta

from fastapi import UploadFile
from sqlalchemy.orm import Session

from app.core.config import settings
from app.models.ocr import OCRBatch, OCRFile, FileStatus
from app.services.preprocessor import DocumentPreprocessor


logger = logging.getLogger(__name__)


class FileManagementError(Exception):
    """Exception raised for file management errors"""
    pass


class FileManager:
    """
    File management service for upload, storage, and cleanup

    Directory structure:
    uploads/
    ├── batches/
    │   └── {batch_id}/
    │       ├── inputs/           # Original uploaded files
    │       ├── outputs/          # OCR results
    │       │   ├── markdown/     # Markdown files
    │       │   ├── json/         # JSON files
    │       │   └── images/       # Extracted images
    │       └── exports/          # Export files (PDF, Excel, etc.)
    """

    def __init__(self):
        """Initialize file manager"""
        self.preprocessor = DocumentPreprocessor()
        self.base_upload_dir = Path(settings.upload_dir)
        self.base_upload_dir.mkdir(parents=True, exist_ok=True)

    def create_batch_directory(self, batch_id: int) -> Path:
        """
        Create directory structure for a batch

        Args:
            batch_id: Batch ID

        Returns:
            Path: Batch directory path
        """
        batch_dir = self.base_upload_dir / "batches" / str(batch_id)

        # Create subdirectories
        (batch_dir / "inputs").mkdir(parents=True, exist_ok=True)
        (batch_dir / "outputs" / "markdown").mkdir(parents=True, exist_ok=True)
        (batch_dir / "outputs" / "json").mkdir(parents=True, exist_ok=True)
        (batch_dir / "outputs" / "images").mkdir(parents=True, exist_ok=True)
        (batch_dir / "exports").mkdir(parents=True, exist_ok=True)

        logger.info(f"Created batch directory: {batch_dir}")
        return batch_dir

    def get_batch_directory(self, batch_id: int) -> Path:
        """
        Get batch directory path

        Args:
            batch_id: Batch ID

        Returns:
            Path: Batch directory path
        """
        return self.base_upload_dir / "batches" / str(batch_id)

    def validate_upload(self, file: UploadFile) -> Tuple[bool, Optional[str]]:
        """
        Validate uploaded file before saving

        Args:
            file: Uploaded file

        Returns:
            Tuple of (is_valid, error_message)
        """
        # Check filename
        if not file.filename:
            return False, "文件名不能為空"

        # Check file size (read content size)
        file.file.seek(0, 2)  # Seek to end
        file_size = file.file.tell()
        file.file.seek(0)  # Reset to beginning

        if file_size == 0:
            return False, "文件為空"

        if file_size > settings.max_upload_size:
            max_mb = settings.max_upload_size / (1024 * 1024)
            return False, f"文件大小超過限制 ({max_mb}MB)"

        # Check file extension
        file_ext = Path(file.filename).suffix.lower()
        allowed_extensions = {'.png', '.jpg', '.jpeg', '.pdf', '.doc', '.docx', '.ppt', '.pptx'}
        if file_ext not in allowed_extensions:
            return False, f"不支持的文件格式 ({file_ext})，僅支持: {', '.join(allowed_extensions)}"

        return True, None

    def save_upload(
        self,
        file: UploadFile,
        batch_id: int,
        validate: bool = True
    ) -> Tuple[Path, str]:
        """
        Save uploaded file to batch directory

        Args:
            file: Uploaded file
            batch_id: Batch ID
            validate: Whether to validate file

        Returns:
            Tuple of (file_path, original_filename)

        Raises:
            FileManagementError: If file validation or saving fails
        """
        # Validate if requested
        if validate:
            is_valid, error_msg = self.validate_upload(file)
            if not is_valid:
                raise FileManagementError(error_msg)

        # Generate unique filename to avoid conflicts
        original_filename = file.filename
        file_ext = Path(original_filename).suffix
        unique_filename = f"{uuid.uuid4()}{file_ext}"

        # Get batch input directory
        batch_dir = self.get_batch_directory(batch_id)
        input_dir = batch_dir / "inputs"
        input_dir.mkdir(parents=True, exist_ok=True)

        # Save file
        file_path = input_dir / unique_filename
        try:
            with file_path.open("wb") as buffer:
                shutil.copyfileobj(file.file, buffer)

            logger.info(f"Saved upload: {file_path} (original: {original_filename})")
            return file_path, original_filename

        except Exception as e:
            # Clean up partial file if exists
            file_path.unlink(missing_ok=True)
            raise FileManagementError(f"保存文件失敗: {str(e)}")

    def validate_saved_file(self, file_path: Path) -> Tuple[bool, Optional[str], Optional[str]]:
        """
        Validate saved file using preprocessor

        Args:
            file_path: Path to saved file

        Returns:
            Tuple of (is_valid, error_message, detected_format)
        """
        return self.preprocessor.validate_file(file_path)

    def create_batch(
        self,
        db: Session,
        user_id: int,
        batch_name: Optional[str] = None
    ) -> OCRBatch:
        """
        Create new OCR batch

        Args:
            db: Database session
            user_id: User ID
            batch_name: Optional batch name

        Returns:
            OCRBatch: Created batch object
        """
        # Create batch record
        batch = OCRBatch(
            user_id=user_id,
            batch_name=batch_name or f"Batch_{datetime.now().strftime('%Y%m%d_%H%M%S')}"
        )
        db.add(batch)
        db.commit()
        db.refresh(batch)

        # Create directory structure
        self.create_batch_directory(batch.id)

        logger.info(f"Created batch: {batch.id} for user {user_id}")
        return batch

    def add_file_to_batch(
        self,
        db: Session,
        batch_id: int,
        file: UploadFile
    ) -> OCRFile:
        """
        Add file to batch and save to disk

        Args:
            db: Database session
            batch_id: Batch ID
            file: Uploaded file

        Returns:
            OCRFile: Created file record

        Raises:
            FileManagementError: If file operations fail
        """
        # Save file to disk
        file_path, original_filename = self.save_upload(file, batch_id)

        # Validate saved file
        is_valid, detected_format, error_msg = self.validate_saved_file(file_path)

        # Create file record
        ocr_file = OCRFile(
            batch_id=batch_id,
            filename=file_path.name,
            original_filename=original_filename,
            file_path=str(file_path),
            file_size=file_path.stat().st_size,
            file_format=detected_format or Path(original_filename).suffix.lower().lstrip('.'),
            status=FileStatus.PENDING if is_valid else FileStatus.FAILED,
            error_message=error_msg if not is_valid else None
        )

        db.add(ocr_file)

        # Update batch total_files count
        batch = db.query(OCRBatch).filter(OCRBatch.id == batch_id).first()
        if batch:
            batch.total_files += 1
            if not is_valid:
                batch.failed_files += 1

        db.commit()
        db.refresh(ocr_file)

        logger.info(f"Added file to batch {batch_id}: {ocr_file.id} (status: {ocr_file.status})")
        return ocr_file

    def add_files_to_batch(
        self,
        db: Session,
        batch_id: int,
        files: List[UploadFile]
    ) -> List[OCRFile]:
        """
        Add multiple files to batch

        Args:
            db: Database session
            batch_id: Batch ID
            files: List of uploaded files

        Returns:
            List[OCRFile]: List of created file records
        """
        ocr_files = []
        for file in files:
            try:
                ocr_file = self.add_file_to_batch(db, batch_id, file)
                ocr_files.append(ocr_file)
            except FileManagementError as e:
                logger.error(f"Failed to add file {file.filename} to batch {batch_id}: {e}")
                # Continue with other files
                continue

        return ocr_files

    def get_file_paths(self, batch_id: int, file_id: int) -> dict:
        """
        Get all paths for a file in a batch

        Args:
            batch_id: Batch ID
            file_id: File ID

        Returns:
            Dict containing all relevant paths
        """
        batch_dir = self.get_batch_directory(batch_id)

        return {
            "input_dir": batch_dir / "inputs",
            "output_dir": batch_dir / "outputs",
            "markdown_dir": batch_dir / "outputs" / "markdown",
            "json_dir": batch_dir / "outputs" / "json",
            "images_dir": batch_dir / "outputs" / "images" / str(file_id),
            "export_dir": batch_dir / "exports",
        }

    def cleanup_expired_batches(self, db: Session, retention_hours: int = 24) -> int:
        """
        Clean up expired batch files

        Args:
            db: Database session
            retention_hours: Number of hours to retain files

        Returns:
            int: Number of batches cleaned up
        """
        cutoff_time = datetime.utcnow() - timedelta(hours=retention_hours)

        # Find expired batches
        expired_batches = db.query(OCRBatch).filter(
            OCRBatch.created_at < cutoff_time
        ).all()

        cleaned_count = 0
        for batch in expired_batches:
            try:
                # Delete batch directory
                batch_dir = self.get_batch_directory(batch.id)
                if batch_dir.exists():
                    shutil.rmtree(batch_dir)
                    logger.info(f"Deleted batch directory: {batch_dir}")

                # Delete database records (cascade will handle related records)
                db.delete(batch)
                cleaned_count += 1

            except Exception as e:
                logger.error(f"Failed to cleanup batch {batch.id}: {e}")
                continue

        if cleaned_count > 0:
            db.commit()
            logger.info(f"Cleaned up {cleaned_count} expired batches")

        return cleaned_count

    def verify_file_ownership(
        self,
        db: Session,
        user_id: int,
        batch_id: int
    ) -> bool:
        """
        Verify user owns the batch

        Args:
            db: Database session
            user_id: User ID
            batch_id: Batch ID

        Returns:
            bool: True if user owns batch, False otherwise
        """
        batch = db.query(OCRBatch).filter(
            OCRBatch.id == batch_id,
            OCRBatch.user_id == user_id
        ).first()

        return batch is not None

    def get_batch_statistics(self, db: Session, batch_id: int) -> dict:
        """
        Get statistics for a batch

        Args:
            db: Database session
            batch_id: Batch ID

        Returns:
            Dict containing batch statistics
        """
        batch = db.query(OCRBatch).filter(OCRBatch.id == batch_id).first()
        if not batch:
            return {}

        # Calculate total file size
        total_size = sum(f.file_size for f in batch.files)

        # Calculate processing time
        processing_time = None
        if batch.completed_at and batch.started_at:
            processing_time = (batch.completed_at - batch.started_at).total_seconds()

        return {
            "batch_id": batch.id,
            "batch_name": batch.batch_name,
            "status": batch.status,
            "total_files": batch.total_files,
            "completed_files": batch.completed_files,
            "failed_files": batch.failed_files,
            "pending_files": batch.total_files - batch.completed_files - batch.failed_files,
            "progress_percentage": batch.progress_percentage,
            "total_file_size": total_size,
            "total_file_size_mb": round(total_size / (1024 * 1024), 2),
            "created_at": batch.created_at.isoformat(),
            "started_at": batch.started_at.isoformat() if batch.started_at else None,
            "completed_at": batch.completed_at.isoformat() if batch.completed_at else None,
            "processing_time": processing_time,
        }