#!/usr/bin/env python3
"""
fill_flat_pdf.py — overlay text onto a flat (non-fillable) PDF.

For forms that look like forms but have no AcroForm fields. You supply the
placements (page index, x, y in PDF points from the bottom-left, and the text);
this stamps them onto a copy of the PDF.

Usage:
    python fill_flat_pdf.py INPUT.pdf OUTPUT.pdf PLACEMENTS.json
    # or pass placements inline:
    python fill_flat_pdf.py INPUT.pdf OUTPUT.pdf '[{"page":0,"x":150,"y":690,"text":"Message Point Media of Alabama Inc."}]'

PLACEMENTS.json format:
    [
      {"page": 0, "x": 150, "y": 690, "text": "Message Point Media of Alabama Inc.", "size": 10},
      {"page": 0, "x": 150, "y": 668, "text": "4628 Montevallo Rd, Suite 204"}
    ]

Coordinates: PDF origin is bottom-left; y increases upward; 72 points = 1 inch.
If your source coordinates are top-left, convert with y_pdf = page_height - y_top.
Use --list-sizes to print each page's width/height in points to help you place text.

Requires: pypdf and reportlab  (pip install pypdf reportlab --break-system-packages)
"""
import sys
import json
import io


def page_sizes(input_pdf):
    from pypdf import PdfReader
    reader = PdfReader(input_pdf)
    for i, page in enumerate(reader.pages):
        box = page.mediabox
        print(f"page {i}: width={float(box.width):.1f} height={float(box.height):.1f} (points)")


def fill(input_pdf, output_pdf, placements):
    from pypdf import PdfReader, PdfWriter
    from reportlab.pdfgen import canvas

    reader = PdfReader(input_pdf)
    writer = PdfWriter()

    # group placements by page
    by_page = {}
    for p in placements:
        by_page.setdefault(int(p.get("page", 0)), []).append(p)

    for i, page in enumerate(reader.pages):
        if i in by_page:
            box = page.mediabox
            w, h = float(box.width), float(box.height)
            buf = io.BytesIO()
            c = canvas.Canvas(buf, pagesize=(w, h))
            for p in by_page[i]:
                size = float(p.get("size", 10))
                c.setFont(p.get("font", "Helvetica"), size)
                c.drawString(float(p["x"]), float(p["y"]), str(p["text"]))
            c.save()
            buf.seek(0)
            overlay = PdfReader(buf).pages[0]
            page.merge_page(overlay)
        writer.add_page(page)

    with open(output_pdf, "wb") as f:
        writer.write(f)
    print(f"Wrote {output_pdf} with {sum(len(v) for v in by_page.values())} text placements.")


def main():
    args = sys.argv[1:]
    if args and args[0] == "--list-sizes":
        if len(args) != 2:
            print("Usage: python fill_flat_pdf.py --list-sizes INPUT.pdf")
            sys.exit(1)
        page_sizes(args[1])
        return

    if len(args) != 3:
        print(__doc__)
        sys.exit(1)

    input_pdf, output_pdf, placements_arg = args
    try:
        placements = json.loads(placements_arg)
    except json.JSONDecodeError:
        with open(placements_arg) as f:
            placements = json.load(f)

    if not isinstance(placements, list):
        print("Placements must be a JSON array of {page,x,y,text} objects.")
        sys.exit(1)

    fill(input_pdf, output_pdf, placements)


if __name__ == "__main__":
    main()