app.py

# app.py
# FastAPI service that converts HTML to PDF using Playwright (Chromium).
# Auth: Bearer token via RENDERER_TOKEN env var.

import os
import base64
from fastapi import FastAPI, Header, HTTPException
from pydantic import BaseModel
from playwright.sync_api import sync_playwright

APP = FastAPI(title="PDF Renderer", version="1.0.0")

RENDERER_TOKEN = os.getenv("RENDERER_TOKEN")  # set in Heroku Config Vars

class Payload(BaseModel):
    html: str
    header: str | None = None  # optional HTML for header template
    footer: str | None = None  # optional HTML for footer template
    format: str = "A4"         # e.g., "A4" or "Letter"

def _require_bearer(authorization: str | None):
    if not RENDERER_TOKEN:
        # If you forget to set the token, refuse to start/publicize
        raise RuntimeError("RENDERER_TOKEN is not set")
    if not authorization or not authorization.startswith("Bearer "):
        raise HTTPException(401, "Missing or invalid Authorization")
    token = authorization.split(" ", 1)[1]
    if token != RENDERER_TOKEN:
        raise HTTPException(403, "Forbidden")

@APP.post("/render")
def render(payload: Payload, authorization: str | None = Header(default=None)):
    _require_bearer(authorization)

    with sync_playwright() as p:
        browser = p.chromium.launch(args=["--no-sandbox"])
        page = browser.new_page()
        page.set_content(payload.html, wait_until="networkidle")
        pdf = page.pdf(
            format=payload.format,
            print_background=True,
            display_header_footer=bool(payload.header or payload.footer),
            header_template=payload.header or "<div></div>",
            footer_template=payload.footer or "<div></div>",
            margin={"top": "18mm", "bottom": "18mm", "left": "15mm", "right": "15mm"},
        )
        browser.close()

    # Return base64 to avoid content-type proxying issues and keep it simple
    return {"pdf_base64": base64.b64encode(pdf).decode("ascii")}