app.py

import os
import shutil
import time
import uuid
from pathlib import Path
import gradio as gr

PERSIST_ROOT = Path(os.getenv("PERSIST_ROOT", "./data"))
OUT_DIR = PERSIST_ROOT / "outputs"
OUT_DIR.mkdir(parents=True, exist_ok=True)

from commonforms import prepare_form  # API documented in the repo README

def run_commonforms(
    input_pdf_path: str,
    model_name: str,
    keep_existing_fields: bool,
    use_signature_fields: bool,
    image_size: int,
    confidence: float,
) -> tuple[str, str]:
    """
    Runs CommonForms and returns (download_path, status_message).
    """
    work_id = f"{int(time.time())}-{uuid.uuid4().hex[:8]}"
    work_dir = Path("/tmp") / f"cf-{work_id}"
    work_dir.mkdir(parents=True, exist_ok=True)

    src = Path(input_pdf_path)
    in_path = work_dir / f"input{src.suffix or '.pdf'}"
    shutil.copy2(src, in_path)

    out_name = f"fillable-{src.stem}-{work_id}.pdf"
    out_tmp = work_dir / out_name
    out_final = OUT_DIR / out_name

    try:
        import torch  # optional, only for device detect
        device = "cuda" if torch.cuda.is_available() else "cpu"
    except Exception:
        device = "cpu"

    # Call CommonForms (kwargs mirror the CLI flags in README)
    prepare_form(
        in_path,
        out_tmp,
        model_or_path=model_name,                       # "FFDNet-L" or "FFDNet-S" or path to .pt
        keep_existing_fields=keep_existing_fields,
        use_signature_fields=use_signature_fields,
        device=device,                           # "cpu" | "cuda" | "0"
        image_size=image_size,                   # e.g. 1600
        confidence=confidence,                   # e.g. 0.3
    )

    shutil.move(out_tmp, out_final)
    return str(out_final), f"✅ Generated {out_name} on {device}"

def _process(pdf, model_name, keep_existing_fields, use_signature_fields, image_size, confidence ):
    if pdf is None:
        return None, None, "Please upload a PDF."
    in_path = pdf if isinstance(pdf, str) else getattr(pdf, "name", None)
    if not in_path or not os.path.exists(in_path):
        return None, None, "Could not locate uploaded file."
    try:
        path, msg = run_commonforms(
            in_path,
            model_name,
            keep_existing_fields,
            use_signature_fields,
            image_size,
            confidence,
        )
        # DownloadButton expects a filepath; File can mirror the same path.
        return path, path, msg
    except Exception as e:
        return None, None, f"❌ Error: {e}"

with gr.Blocks(title="CommonForms — PDF → Fillable PDF") as demo:
    gr.Markdown(
        """
        # CommonForms — PDF → Fillable PDF
        Upload a PDF, select options, and generate a fillable PDF.

        [📄 CommonForms Paper](https://arxiv.org/abs/2509.16506) | [🤗 Dataset](https://huggingface.co/datasets/jbarrow/CommonForms) | [🤗 FFDNet-L](https://huggingface.co/jbarrow/FFDNet-L) | [🤗 FFDNet-S](https://huggingface.co/jbarrow/FFDNet-S) | [💾 Code](https://github.com/jbarrow/commonforms)
        """
    )

    with gr.Row():
        with gr.Column(scale=2):
            pdf_in = gr.File(label="Upload PDF", file_types=[".pdf"], type="filepath")

            with gr.Row():
                model_name = gr.Dropdown(
                    label="Detector model",
                    choices=["FFDNet-L", "FFDNet-S"],
                    value="FFDNet-L",
                )

            with gr.Row():
                keep_existing_fields = gr.Checkbox(label="Keep existing fields", value=False)
                use_signature_fields = gr.Checkbox(label="Use signature widgets for signatures", value=True)

            with gr.Row():
                image_size = gr.Slider(800, 2048, value=1600, step=32, label="Image size")
                confidence = gr.Slider(0.05, 0.9, value=0.30, step=0.05, label="Confidence threshold")

            run_btn = gr.Button("Run CommonForms", variant="primary")
            status = gr.Textbox(label="Status", interactive=False)

        with gr.Column(scale=1):
            download_btn = gr.DownloadButton(label="Download Fillable PDF", value=None)
            file_out = gr.File(label="Output (preview / alt download)")

    run_btn.click(
        _process,
        inputs=[pdf_in, model_name, keep_existing_fields, use_signature_fields, image_size, confidence ],
        outputs=[download_btn, file_out, status],
        queue=True,
        api_name="run",
    )

# Limit default concurrency to 1 (safe for ZeroGPU / GPU-bound ops)
demo.launch()