"""tutor/lang_detect.py — lightweight keyword-based language detection."""
from __future__ import annotations
import re

_MARKERS = {
    "kin": ["mbiri","gatatu","kane","gatanu","ikibazo","igisubizo","komeza",
             "byiza","wabitsinze","ntangaza","umwe","babiri","batatu","bane","batanu"],
    "sw":  ["moja","mbili","tatu","nne","tano","sita","saba","nane","tisa","kumi",
             "jibu","swali","hesabu","vizuri","hongera","endelea","jaribu"],
    "fr":  ["un","deux","trois","quatre","cinq","six","sept","huit","neuf","dix",
             "bonjour","merci","oui","non","la","le","les","est","une","je","tu",
             "combien","réponse","bravo","essaie","encore"],
    "en":  ["one","two","three","four","five","six","seven","eight","nine","ten",
             "hello","yes","no","the","answer","how","many","count","add","minus",
             "great","amazing","correct","wrong","next"],
}


def detect(text: str) -> str:
    tokens = re.findall(r"[a-zA-ZÀ-öø-ÿ']+", text.lower())
    if not tokens:
        return "en"
    scores = {lang: sum(1 for t in tokens if t in markers)
              for lang, markers in _MARKERS.items()}
    best = max(scores.values())
    if best == 0:
        return "en"
    winners = [l for l, s in scores.items() if s == best]
    if len(winners) == 1:
        return winners[0]
    return "en" if "en" in winners else "mix"


def reply_lang(detected: str, fallback: str = "en") -> str:
    return detected if detected in ("en","fr","kin","sw") else fallback