"""Document storage service."""

import shutil
import uuid
import pymupdf
from pathlib import Path
from fastapi import UploadFile, HTTPException

from app.config import settings

def validate_pdf(filepath: Path) -> None:
    """Validate PDF magic bytes and PyMuPDF openability."""
    with open(filepath, "rb") as f:
        header = f.read(5)
        if header != b"%PDF-":
            raise ValueError("Not a valid PDF file (missing magic bytes)")

    try:
        doc = pymupdf.open(filepath)
        doc.close()
    except Exception as e:
        raise ValueError(f"Failed to open PDF with PyMuPDF: {e}")

async def save_upload_file(upload_file: UploadFile) -> tuple[str, int, int]:
    """Save an uploaded file to disk and validate it."""
    file_id = str(uuid.uuid4())
    filepath = settings.PDF_STORAGE_PATH / f"{file_id}.pdf"

    try:
        with open(filepath, "wb") as f:
            shutil.copyfileobj(upload_file.file, f)
    except Exception as e:
        if filepath.exists():
            filepath.unlink()
        raise HTTPException(status_code=500, detail="Failed to save file")

    page_count = 0
    try:
        doc = pymupdf.open(filepath)
        page_count = len(doc)
        doc.close()
    except Exception as e:
        filepath.unlink()
        raise HTTPException(status_code=400, detail=f"Failed to open PDF with PyMuPDF: {e}")
    
    size = filepath.stat().st_size
    return file_id, size, page_count

def delete_pdf_file(file_id: str) -> None:
    """Delete a PDF file from storage."""
    filepath = settings.PDF_STORAGE_PATH / f"{file_id}.pdf"
    if filepath.exists():
        filepath.unlink()