"""Render QR-ish message payloads as unicode half-block QR codes."""

import qrcode

QR_SCHEMES = ("https://wa.me/", "gmessages://")


def looks_like_qr_payload(body: str, sender_is_bridge_bot: bool) -> bool:
    """Deliberately simple heuristic:

    - message starts with a known pairing scheme (whatsapp / gmessages), or
    - a bridge-bot message that is a single URL/token: 20-199 chars, no
      whitespace, and either contains '://' or is alnum-ish (pairing code).
    """
    body = body.strip()
    if body.startswith(QR_SCHEMES):
        return True
    if sender_is_bridge_bot and 20 <= len(body) < 200 and not any(c.isspace() for c in body):
        return "://" in body or body.replace("-", "").replace("_", "").isalnum()
    return False


def render_qr(text: str) -> str:
    """QR code as text, two matrix rows per output line via half blocks."""
    qr = qrcode.QRCode(border=1)
    qr.add_data(text)
    qr.make(fit=True)
    matrix = qr.get_matrix()
    if len(matrix) % 2:
        matrix.append([False] * len(matrix[0]))
    chars = {(True, True): "█", (True, False): "▀", (False, True): "▄", (False, False): " "}
    return "\n".join(
        "".join(chars[(top[x], bottom[x])] for x in range(len(top)))
        for top, bottom in zip(matrix[::2], matrix[1::2])
    )