model.py

from typing import Literal

Lang = Literal["vi", "en", "mix", "unknown"]

VI_CHARS = set("ăâđêôơưáàảãạấầẩẫậắằẳẵặéèẻẽẹếềểễệíìỉĩịóòỏõọốồổỗộớờởỡợúùủũụứừửữựýỳỷỹỵ")
EN_CHARS = set("abcdefghijklmnopqrstuvwxyz")

def detect_language(text: str) -> Lang:
    """Very small heuristic detector for Vietnamese vs English vs mixed."""
    t = text.lower()

    has_vi = any(ch in VI_CHARS for ch in t)
    has_en = any(ch in EN_CHARS for ch in t)

    if has_vi and has_en:
        return "mix"
    if has_vi:
        return "vi"
    if has_en:
        return "en"
    return "unknown"

if __name__ == "__main__":
    tests = [
        "Đi tới phòng khách",
        "Turn on the lights",
        "Đi tới living room",
        "12345 !!!",
    ]
    for t in tests:
        print(t, "->", detect_language(t))