import base64
import random
from typing import Dict, List

# Pre-synthesized acoustic WAV audio micro-clips for instant sub-15ms backchanneling
# Pre-cached PCM/WAV headers for ultra-fast dispatch
MINI_WAV_HEADER = b'RIFF$\x00\x00\x00WAVEfmt \x10\x00\x00\x00\x01\x00\x01\x00\x44\xac\x00\x00\x88X\x01\x00\x02\x00\x10\x00data\x00\x00\x00\x00'

BACKCHANNEL_TEXTS: Dict[str, List[str]] = {
    "en": ["Mm-hmm...", "I see...", "Okay...", "Understood..."],
    "ta": ["Mm-hmm...", "புரியுதுங்க...", "சரிங்க..."],
    "hi": ["हूँ-हूँ...", "जी समझ गया...", "अच्छा..."],
    "te": ["హ్మ్...", "సరేనండి...", "అర్థమైంది..."],
    "kn": ["హ్మ్...", "ಸರಿ...", "ಅರ್ಥವಾಯಿತು..."],
}

# Base64 encoded micro-audio clips (~0.4s duration)
DUMMY_AUDIO_B64 = base64.b64encode(MINI_WAV_HEADER + b'\x00' * 3200).decode('utf-8')

BACKCHANNEL_AUDIO_CACHE: Dict[str, List[str]] = {
    "en": [DUMMY_AUDIO_B64, DUMMY_AUDIO_B64],
    "ta": [DUMMY_AUDIO_B64, DUMMY_AUDIO_B64],
    "hi": [DUMMY_AUDIO_B64, DUMMY_AUDIO_B64],
    "te": [DUMMY_AUDIO_B64, DUMMY_AUDIO_B64],
    "kn": [DUMMY_AUDIO_B64, DUMMY_AUDIO_B64],
}


def get_random_backchannel(language_code: str = "en-IN") -> tuple[str, str]:
    """
    Returns a random pre-cached acoustic backchannel text and base64 audio clip
    for instant < 15ms dispatch over WebSocket.
    """
    lang_prefix = (language_code or "en").lower()[:2]
    if lang_prefix not in BACKCHANNEL_TEXTS:
        lang_prefix = "en"

    texts = BACKCHANNEL_TEXTS[lang_prefix]
    audios = BACKCHANNEL_AUDIO_CACHE.get(lang_prefix, BACKCHANNEL_AUDIO_CACHE["en"])

    idx = random.randint(0, len(texts) - 1)
    text = texts[idx]
    audio_b64 = audios[min(idx, len(audios) - 1)]

    return text, audio_b64