#!/usr/bin/env python3
"""Add page numbers to a PDF using reportlab overlay."""
import argparse, json, sys, io
from pathlib import Path

def add_numbers(input_path, output_path, position='bottom-center', start_number=1, font_size=12):
    from PyPDF2 import PdfReader, PdfWriter
    from reportlab.pdfgen import canvas
    from reportlab.lib.pagesizes import letter
    
    reader = PdfReader(input_path)
    writer = PdfWriter()
    
    for i, page in enumerate(reader.pages):
        page_num = start_number + i
        media = page.mediabox
        pw = float(media.width)
        ph = float(media.height)
        
        packet = io.BytesIO()
        c = canvas.Canvas(packet, pagesize=(pw, ph))
        c.setFont("Helvetica", font_size)
        
        text = str(page_num)
        text_width = c.stringWidth(text, "Helvetica", font_size)
        
        margin = 36
        positions = {
            'bottom-center': (pw / 2, margin),
            'bottom-left': (margin, margin),
            'bottom-right': (pw - margin, margin),
            'top-center': (pw / 2, ph - margin),
            'top-left': (margin, ph - margin),
            'top-right': (pw - margin, ph - margin),
        }
        
        x, y = positions.get(position, positions['bottom-center'])
        
        if 'center' in position:
            x -= text_width / 2
        elif 'right' in position:
            x -= text_width
        
        c.drawString(x, y, text)
        c.save()
        
        packet.seek(0)
        overlay = PdfReader(packet)
        page.merge_page(overlay.pages[0])
        writer.add_page(page)
    
    if not output_path:
        output_path = str(Path(input_path).with_stem(Path(input_path).stem + '_numbered'))
    
    with open(output_path, 'wb') as f:
        writer.write(f)
    return output_path

def main():
    parser = argparse.ArgumentParser(description='Add page numbers to PDF')
    parser.add_argument('--input', required=True)
    parser.add_argument('--output', required=True)
    parser.add_argument('--position', default='bottom-center')
    parser.add_argument('--start-number', type=int, default=1)
    parser.add_argument('--font-size', type=int, default=12)
    args = parser.parse_args()
    try:
        result = add_numbers(args.input, args.output, args.position, args.start_number, args.font_size)
        print(json.dumps({"success": True, "output": result, "message": "Page numbers added successfully"}))
    except Exception as e:
        print(json.dumps({"success": False, "output": "", "message": str(e)}))
        sys.exit(1)

if __name__ == '__main__':
    main()