"""
Tool_OCR - Task Management Router
Handles OCR task operations with user isolation
"""

import logging
from typing import Optional
from pathlib import Path
import shutil
import hashlib

from fastapi import APIRouter, Depends, HTTPException, status, Query, UploadFile, File, BackgroundTasks
from fastapi.responses import FileResponse
from sqlalchemy.orm import Session
import json
from datetime import datetime

from app.core.deps import get_db, get_current_user
from app.core.config import settings
from app.models.user import User
from app.models.task import TaskStatus, TaskFile
from app.schemas.task import (
    TaskCreate,
    TaskUpdate,
    TaskResponse,
    TaskDetailResponse,
    TaskListResponse,
    TaskStatsResponse,
    TaskStatusEnum,
    UploadResponse,
)
from app.services.task_service import task_service
from app.services.file_access_service import file_access_service
from app.services.ocr_service import OCRService

logger = logging.getLogger(__name__)

router = APIRouter(prefix="/api/v2/tasks", tags=["Tasks"])


def process_task_ocr(task_id: str, task_db_id: int, file_path: str, filename: str):
    """
    Background task to process OCR for a task

    Args:
        task_id: Task UUID string
        task_db_id: Task database ID
        file_path: Path to uploaded file
        filename: Original filename
    """
    from app.core.database import SessionLocal
    from app.models.task import Task

    db = SessionLocal()
    start_time = datetime.now()

    try:
        logger.info(f"Starting OCR processing for task {task_id}, file: {filename}")

        # Get task directly by database ID (bypass user isolation for background task)
        task = db.query(Task).filter(Task.id == task_db_id).first()
        if not task:
            logger.error(f"Task {task_id} not found in database")
            return

        # Initialize OCR service
        ocr_service = OCRService()

        # Create result directory before OCR processing (needed for saving extracted images)
        result_dir = Path(settings.result_dir) / task_id
        result_dir.mkdir(parents=True, exist_ok=True)

        # Process the file with OCR
        ocr_result = ocr_service.process_image(
            image_path=Path(file_path),
            lang='ch',
            detect_layout=True,
            output_dir=result_dir
        )

        # Calculate processing time
        processing_time_ms = int((datetime.now() - start_time).total_seconds() * 1000)

        # Save results using OCR service (includes JSON, Markdown, and PDF generation)
        json_path, markdown_path, pdf_path = ocr_service.save_results(
            result=ocr_result,
            output_dir=result_dir,
            file_id=Path(filename).stem,
            source_file_path=Path(file_path)
        )

        # Update task with results (direct database update)
        task.result_json_path = str(json_path) if json_path else None
        task.result_markdown_path = str(markdown_path) if markdown_path else None
        task.result_pdf_path = str(pdf_path) if pdf_path else None
        task.processing_time_ms = processing_time_ms
        task.status = TaskStatus.COMPLETED
        task.completed_at = datetime.utcnow()
        task.updated_at = datetime.utcnow()

        db.commit()

        logger.info(f"OCR processing completed for task {task_id} in {processing_time_ms}ms")

    except Exception as e:
        logger.exception(f"OCR processing failed for task {task_id}")

        # Update task status to failed (direct database update)
        try:
            task = db.query(Task).filter(Task.id == task_db_id).first()
            if task:
                task.status = TaskStatus.FAILED
                task.error_message = str(e)
                task.updated_at = datetime.utcnow()
                db.commit()
        except Exception as update_error:
            logger.error(f"Failed to update task status: {update_error}")

    finally:
        db.close()


@router.post("/", response_model=TaskResponse, status_code=status.HTTP_201_CREATED)
async def create_task(
    task_data: TaskCreate,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """
    Create a new OCR task

    - **filename**: Original filename (optional)
    - **file_type**: File MIME type (optional)
    """
    try:
        task = task_service.create_task(
            db=db,
            user_id=current_user.id,
            filename=task_data.filename,
            file_type=task_data.file_type
        )

        logger.info(f"Created task {task.task_id} for user {current_user.email}")
        return task

    except Exception as e:
        logger.exception(f"Failed to create task for user {current_user.id}")
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to create task: {str(e)}"
        )


@router.get("/", response_model=TaskListResponse)
async def list_tasks(
    status_filter: Optional[TaskStatusEnum] = Query(None, alias="status"),
    filename_search: Optional[str] = Query(None, alias="filename"),
    date_from: Optional[str] = Query(None, alias="date_from"),
    date_to: Optional[str] = Query(None, alias="date_to"),
    page: int = Query(1, ge=1),
    page_size: int = Query(50, ge=1, le=100),
    order_by: str = Query("created_at"),
    order_desc: bool = Query(True),
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """
    List user's tasks with pagination and filtering

    - **status**: Filter by task status (optional)
    - **filename**: Search by filename (partial match, optional)
    - **date_from**: Filter tasks from this date (YYYY-MM-DD, optional)
    - **date_to**: Filter tasks until this date (YYYY-MM-DD, optional)
    - **page**: Page number (starts from 1)
    - **page_size**: Number of tasks per page (max 100)
    - **order_by**: Sort field (created_at, updated_at, completed_at)
    - **order_desc**: Sort descending (default: true)
    """
    try:
        # Convert enum to model enum if provided
        status_enum = TaskStatus[status_filter.value.upper()] if status_filter else None

        # Parse date strings
        from datetime import datetime
        date_from_dt = datetime.fromisoformat(date_from) if date_from else None
        date_to_dt = datetime.fromisoformat(date_to) if date_to else None

        # Calculate offset
        skip = (page - 1) * page_size

        # Get tasks
        tasks, total = task_service.get_user_tasks(
            db=db,
            user_id=current_user.id,
            status=status_enum,
            filename_search=filename_search,
            date_from=date_from_dt,
            date_to=date_to_dt,
            skip=skip,
            limit=page_size,
            order_by=order_by,
            order_desc=order_desc
        )

        # Calculate pagination
        has_more = (skip + len(tasks)) < total

        return {
            "tasks": tasks,
            "total": total,
            "page": page,
            "page_size": page_size,
            "has_more": has_more
        }

    except Exception as e:
        logger.exception(f"Failed to list tasks for user {current_user.id}")
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to list tasks: {str(e)}"
        )


@router.get("/stats", response_model=TaskStatsResponse)
async def get_task_stats(
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """
    Get task statistics for current user

    Returns counts by status
    """
    try:
        stats = task_service.get_user_stats(db=db, user_id=current_user.id)
        return stats

    except Exception as e:
        logger.exception(f"Failed to get stats for user {current_user.id}")
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to get statistics: {str(e)}"
        )


@router.get("/{task_id}", response_model=TaskDetailResponse)
async def get_task(
    task_id: str,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """
    Get task details by ID

    - **task_id**: Task UUID
    """
    task = task_service.get_task_by_id(
        db=db,
        task_id=task_id,
        user_id=current_user.id
    )

    if not task:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Task not found"
        )

    return task


@router.patch("/{task_id}", response_model=TaskResponse)
async def update_task(
    task_id: str,
    task_update: TaskUpdate,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """
    Update task status and results

    - **task_id**: Task UUID
    - **status**: New task status (optional)
    - **error_message**: Error message if failed (optional)
    - **processing_time_ms**: Processing time in milliseconds (optional)
    - **result_json_path**: Path to JSON result (optional)
    - **result_markdown_path**: Path to Markdown result (optional)
    - **result_pdf_path**: Path to searchable PDF (optional)
    """
    try:
        # Update status if provided
        if task_update.status:
            status_enum = TaskStatus[task_update.status.value.upper()]
            task = task_service.update_task_status(
                db=db,
                task_id=task_id,
                user_id=current_user.id,
                status=status_enum,
                error_message=task_update.error_message,
                processing_time_ms=task_update.processing_time_ms
            )

            if not task:
                raise HTTPException(
                    status_code=status.HTTP_404_NOT_FOUND,
                    detail="Task not found"
                )

        # Update result paths if provided
        if any([
            task_update.result_json_path,
            task_update.result_markdown_path,
            task_update.result_pdf_path
        ]):
            task = task_service.update_task_results(
                db=db,
                task_id=task_id,
                user_id=current_user.id,
                result_json_path=task_update.result_json_path,
                result_markdown_path=task_update.result_markdown_path,
                result_pdf_path=task_update.result_pdf_path
            )

            if not task:
                raise HTTPException(
                    status_code=status.HTTP_404_NOT_FOUND,
                    detail="Task not found"
                )

        return task

    except HTTPException:
        raise
    except Exception as e:
        logger.exception(f"Failed to update task {task_id}")
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to update task: {str(e)}"
        )


@router.delete("/{task_id}", status_code=status.HTTP_204_NO_CONTENT)
async def delete_task(
    task_id: str,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """
    Delete a task

    - **task_id**: Task UUID
    """
    success = task_service.delete_task(
        db=db,
        task_id=task_id,
        user_id=current_user.id
    )

    if not success:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Task not found"
        )

    logger.info(f"Deleted task {task_id} for user {current_user.email}")
    return None


@router.get("/{task_id}/download/json", summary="Download JSON result")
async def download_json(
    task_id: str,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """
    Download task result as JSON file

    - **task_id**: Task UUID
    """
    # Get task
    task = task_service.get_task_by_id(
        db=db,
        task_id=task_id,
        user_id=current_user.id
    )

    if not task:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Task not found"
        )

    # Validate file access
    is_valid, error_msg = file_access_service.validate_file_access(
        db=db,
        user_id=current_user.id,
        task_id=task_id,
        file_path=task.result_json_path
    )

    if not is_valid:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail=error_msg
        )

    # Return file
    filename = f"{task.filename or task_id}_result.json"
    return FileResponse(
        path=task.result_json_path,
        filename=filename,
        media_type="application/json"
    )


@router.get("/{task_id}/download/markdown", summary="Download Markdown result")
async def download_markdown(
    task_id: str,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """
    Download task result as Markdown file

    - **task_id**: Task UUID
    """
    # Get task
    task = task_service.get_task_by_id(
        db=db,
        task_id=task_id,
        user_id=current_user.id
    )

    if not task:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Task not found"
        )

    # Validate file access
    is_valid, error_msg = file_access_service.validate_file_access(
        db=db,
        user_id=current_user.id,
        task_id=task_id,
        file_path=task.result_markdown_path
    )

    if not is_valid:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail=error_msg
        )

    # Return file
    filename = f"{task.filename or task_id}_result.md"
    return FileResponse(
        path=task.result_markdown_path,
        filename=filename,
        media_type="text/markdown"
    )


@router.get("/{task_id}/download/pdf", summary="Download PDF result")
async def download_pdf(
    task_id: str,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """
    Download task result as layout-preserving PDF file

    - **task_id**: Task UUID

    Returns a PDF that preserves the original document layout using OCR results.
    The PDF is generated from OCR JSON data and cached for subsequent requests.
    """
    from pathlib import Path
    from app.services.pdf_generator_service import pdf_generator_service

    # Get task
    task = task_service.get_task_by_id(
        db=db,
        task_id=task_id,
        user_id=current_user.id
    )

    if not task:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Task not found"
        )

    # Check if task is completed
    if task.status.value != "completed":
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Task is not completed yet. Please wait for OCR processing to finish."
        )

    # Check if PDF path is stored in database
    if task.result_pdf_path and Path(task.result_pdf_path).exists():
        pdf_path = Path(task.result_pdf_path)
        logger.info(f"Using pre-generated PDF from database: {pdf_path.name}")
    else:
        # Fallback: Try to generate PDF on-demand
        result_dir = Path(settings.result_dir) / task_id

        # Use stored JSON path or construct it
        if task.result_json_path and Path(task.result_json_path).exists():
            json_path = Path(task.result_json_path)
        else:
            # Try to find JSON file in result directory
            json_files = list(result_dir.glob("*_result.json"))
            if not json_files:
                raise HTTPException(
                    status_code=status.HTTP_404_NOT_FOUND,
                    detail="OCR result JSON not found"
                )
            json_path = json_files[0]

        # Construct PDF path based on JSON filename
        pdf_filename = json_path.stem.replace("_result", "_layout") + ".pdf"
        pdf_path = result_dir / pdf_filename

        # Generate PDF if it doesn't exist
        if not pdf_path.exists():
            logger.info(f"Generating layout-preserving PDF for task {task_id}")

            # Get source file path if available
            source_file = None
            task_file = db.query(TaskFile).filter(TaskFile.task_id == task.id).first()
            if task_file and task_file.stored_path and Path(task_file.stored_path).exists():
                source_file = Path(task_file.stored_path)

            # Generate PDF
            success = pdf_generator_service.generate_layout_pdf(
                json_path=json_path,
                output_path=pdf_path,
                source_file_path=source_file
            )

            if not success:
                raise HTTPException(
                    status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
                    detail="Failed to generate PDF. Please check server logs."
                )

            logger.info(f"PDF generated successfully: {pdf_path.name}")

    # Validate file access
    is_valid, error_msg = file_access_service.validate_file_access(
        db=db,
        user_id=current_user.id,
        task_id=task_id,
        file_path=str(pdf_path)
    )

    if not is_valid:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail=error_msg
        )

    # Return file
    filename = f"{task.filename or task_id}_result.pdf"
    return FileResponse(
        path=str(pdf_path),
        filename=filename,
        media_type="application/pdf"
    )


@router.post("/{task_id}/start", response_model=TaskResponse, summary="Start task processing")
async def start_task(
    task_id: str,
    background_tasks: BackgroundTasks,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """
    Start processing a pending task

    - **task_id**: Task UUID
    """
    try:
        # Get task details
        task = task_service.get_task_by_id(
            db=db,
            task_id=task_id,
            user_id=current_user.id
        )

        if not task:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Task not found"
            )

        # Check if task is in pending status
        if task.status != TaskStatus.PENDING:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail=f"Cannot start task in '{task.status.value}' status"
            )

        # Get task file
        task_file = db.query(TaskFile).filter(TaskFile.task_id == task.id).first()
        if not task_file:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Task file not found"
            )

        # Update task status to processing
        task = task_service.update_task_status(
            db=db,
            task_id=task_id,
            user_id=current_user.id,
            status=TaskStatus.PROCESSING
        )

        # Start OCR processing in background
        background_tasks.add_task(
            process_task_ocr,
            task_id=task_id,
            task_db_id=task.id,
            file_path=task_file.stored_path,
            filename=task_file.original_name
        )

        logger.info(f"Started OCR processing task {task_id} for user {current_user.email}")
        return task

    except HTTPException:
        raise
    except Exception as e:
        logger.exception(f"Failed to start task {task_id}")
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to start task: {str(e)}"
        )


@router.post("/{task_id}/cancel", response_model=TaskResponse, summary="Cancel task")
async def cancel_task(
    task_id: str,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """
    Cancel a pending or processing task

    - **task_id**: Task UUID
    """
    try:
        # Get current task
        task = task_service.get_task_by_id(
            db=db,
            task_id=task_id,
            user_id=current_user.id
        )

        if not task:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Task not found"
            )

        # Only allow canceling pending or processing tasks
        if task.status not in [TaskStatus.PENDING, TaskStatus.PROCESSING]:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail=f"Cannot cancel task in '{task.status.value}' status"
            )

        # Update to failed status with cancellation message
        task = task_service.update_task_status(
            db=db,
            task_id=task_id,
            user_id=current_user.id,
            status=TaskStatus.FAILED,
            error_message="Task cancelled by user"
        )

        logger.info(f"Cancelled task {task_id} for user {current_user.email}")
        return task

    except HTTPException:
        raise
    except Exception as e:
        logger.exception(f"Failed to cancel task {task_id}")
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to cancel task: {str(e)}"
        )


@router.post("/{task_id}/retry", response_model=TaskResponse, summary="Retry failed task")
async def retry_task(
    task_id: str,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """
    Retry a failed task

    - **task_id**: Task UUID
    """
    try:
        # Get current task
        task = task_service.get_task_by_id(
            db=db,
            task_id=task_id,
            user_id=current_user.id
        )

        if not task:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Task not found"
            )

        # Only allow retrying failed tasks
        if task.status != TaskStatus.FAILED:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail=f"Cannot retry task in '{task.status.value}' status"
            )

        # Reset task to pending status
        task = task_service.update_task_status(
            db=db,
            task_id=task_id,
            user_id=current_user.id,
            status=TaskStatus.PENDING,
            error_message=None
        )

        logger.info(f"Retrying task {task_id} for user {current_user.email}")
        return task

    except HTTPException:
        raise
    except Exception as e:
        logger.exception(f"Failed to retry task {task_id}")
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to retry task: {str(e)}"
        )
