"""Token-free detection of user *reactions* to the agent.

The only reaction today is ``vibe`` — affection/gratitude aimed at the agent
(``ily``, ``<3``, ``good bot``, a heart emoji). Detection is a curated regex:
no model call. Single source of truth for the CLI pet, TUI heart and desktop
hearts via ``AIAgent.reaction_callback``. :func:`detect_reaction` returns a
*kind* string so new kinds can be added without touching callers. Matches
affection specifically, not general positive sentiment ("this is great" does
NOT fire).
"""

from __future__ import annotations

import re

#: The affection/gratitude reaction — the only kind today.
VIBE = "vibe"

# Narrow lexicon: gratitude + love aimed at the agent, hearts, ``<3`` (not ``</3``).
_VIBE_RE = re.compile(
    "|".join(
        (
            r"\bgood\s*bot\b",
            r"\bi\s*(?:love|luv)\s*(?:you|u|ya)\b",
            r"\b(?:love|luv)\s*(?:you|u|ya)\b",
            r"\bily(?:sm)?\b",
            r"\bthank\s*(?:you|u)\b",
            r"\b(?:thanks|thx|tysm|ty)\b",
            r"<3+",  # <3, <33 … but not </3
            # Hearts + affection faces (❤ ♥ 🥰 😍 😘 💕 💖 💗 💞 💛 💜 💚 💙 💓 💘 💝 🩷).
            r"[\u2764\u2665"
            r"\U0001F970\U0001F60D\U0001F618"
            r"\U0001F495\U0001F496\U0001F497\U0001F49E"
            r"\U0001F49B\U0001F49C\U0001F49A\U0001F499"
            r"\U0001F493\U0001F498\U0001F49D\U0001FA77]",
        )
    ),
    re.IGNORECASE,
)


def detect_reaction(text: str | None) -> str | None:
    """Return the reaction kind for *text* (currently :data:`VIBE`), or ``None``."""
    if not text:
        return None
    return VIBE if _VIBE_RE.search(text) else None