app/routers/pdf/pdf_tools.py

from fastapi import APIRouter, UploadFile, File, HTTPException, Security
from fastapi.responses import FileResponse
from pypdf import PdfReader, PdfWriter
import os
import shutil
import tempfile

# Define the APIRouter object
router = APIRouter(
    prefix="/pdf",
    tags=["PDF Manipulation"],
)

@router.post("/merge")
async def merge_pdfs(files: list[UploadFile] = File(description="List of PDFs to merge")):
    """
    Merges multiple uploaded PDF files into a single PDF.
    """
    if len(files) < 2:
        raise HTTPException(status_code=400, detail="Please upload at least two PDF files to merge.")

    pdf_writer = PdfWriter()
    
    # Create a temporary directory to store files
    with tempfile.TemporaryDirectory() as temp_dir:
        output_path = os.path.join(temp_dir, "merged_output.pdf")
        
        for file in files:
            # Save the uploaded file temporarily
            temp_file_path = os.path.join(temp_dir, file.filename)
            with open(temp_file_path, "wb") as buffer:
                shutil.copyfileobj(file.file, buffer)
            
            # Read and append pages
            try:
                reader = PdfReader(temp_file_path)
                for page in reader.pages:
                    pdf_writer.add_page(page)
            except Exception as e:
                 raise HTTPException(status_code=500, detail=f"Error reading PDF file {file.filename}: {e}")
        
        # Write the merged PDF to the output path
        with open(output_path, "wb") as output_file:
            pdf_writer.write(output_file)
            
        # Return the merged file as a response
        return FileResponse(output_path, media_type="application/pdf", filename="merged_document.pdf")

@router.post("/rotate")
async def rotate_pdf(
    file: UploadFile = File(description="PDF file to rotate"),
    degrees: int = 90  # Default rotation is 90 degrees clockwise
):
    """
    Rotates all pages of a single PDF by a specified degree (90, 180, or 270).
    """
    if degrees not in [90, 180, 270]:
        raise HTTPException(status_code=400, detail="Rotation must be 90, 180, or 270 degrees.")
        
    pdf_writer = PdfWriter()

    with tempfile.TemporaryDirectory() as temp_dir:
        input_path = os.path.join(temp_dir, file.filename)
        output_path = os.path.join(temp_dir, "rotated_output.pdf")
        
        # Save the uploaded file temporarily
        with open(input_path, "wb") as buffer:
            shutil.copyfileobj(file.file, buffer)

        # Read, rotate, and write
        try:
            reader = PdfReader(input_path)
            for page in reader.pages:
                page.rotate(degrees)
                pdf_writer.add_page(page)
        except Exception as e:
             raise HTTPException(status_code=500, detail=f"Error processing PDF: {e}")

        # Write the rotated PDF
        with open(output_path, "wb") as output_file:
            pdf_writer.write(output_file)

        return FileResponse(output_path, media_type="application/pdf", filename=f"rotated_{degrees}.pdf")