app.py

"""Lost Frequency Radio backend — gradio.Server + streaming /tune."""

import queue
import re
import threading
import time
import zlib
from pathlib import Path

from fastapi.responses import HTMLResponse
from fastapi.staticfiles import StaticFiles
from gradio import Server

from decrypt import (
    ENCRYPTED_FREQUENCY,
    OPERATOR_SYSTEM_PROMPTS,
    is_valid_code,
    numbers_broadcast,
    reveal_text,
    seq_for,
    validate_bypass,
)
from game import (
    FINALE_SEED,
    FINALE_SYSTEM_PROMPT,
    FINALE_USER_PROMPT,
    fragment_text,
    get_fragment,
    hidden_band_catalog,
)
from model import stream_broadcast
from stations import (
    CURSED_FREQUENCY,
    CURSED_SYSTEM_PROMPT,
    STATION_TOLERANCE,
    get_station,
    localized_system_prompt,
    localized_user_prompt,
    nearest_station_frequency,
    normalize_lang,
    signal_strength,
    station_catalog,
    station_seed,
    station_system_prompt,
)

ROOT = Path(__file__).parent


class _NoCacheStatic(StaticFiles):
    """Serve static assets with revalidation so updated CSS/JS reach listeners
    immediately after a deploy (and during local development)."""

    async def get_response(self, path, scope):
        response = await super().get_response(path, scope)
        response.headers["Cache-Control"] = "no-cache, must-revalidate"
        return response


app = Server(title="Lost Frequency Radio")
app.mount("/static", _NoCacheStatic(directory=ROOT / "static"), name="static")


@app.get("/", response_class=HTMLResponse)
async def homepage():
    return (ROOT / "index.html").read_text(encoding="utf-8")


@app.get("/api/stations")
async def stations_api(variant: float = 0):
    catalog = station_catalog()
    enc = catalog.get(str(ENCRYPTED_FREQUENCY))
    if enc is not None:
        # the per-listener Morse sequence (public: it is dictated on air)
        enc["sequence"] = seq_for(_norm_variant(variant))
    return catalog


@app.get("/api/band")
async def band_api(code: str = "", variant: float = 0):
    """Hidden band: only with the code obtained by breaking the cipher."""
    if not is_valid_code(code, _norm_variant(variant)):
        return {"ok": False}
    return {"ok": True, **hidden_band_catalog()}


def _stream_fixed(text: str, char_delay: float = 0.025, should_continue=None):
    """Streams a fixed text with teletype cadence (accumulated)."""
    accumulated = ""
    for char in text:
        if should_continue is not None and not should_continue():
            return
        accumulated += char
        yield accumulated
        time.sleep(char_delay)


# Broadcasts are deterministic per (frequency, language, listener variant) →
# in-memory cache: retuning the same station replays instantly (key on CPU).
_broadcast_cache: dict[str, str] = {}
_CACHE_MAX = 256

# Rapid retuning: each /tune bumps this epoch. An in-flight generation that is
# no longer the latest self-terminates at the next token, releasing the model
# lock so the newest tune can run. Without this, a superseded generation runs to
# completion holding the lock and every later tune stalls behind it (the
# "everything goes to static and never comes back" bug).
_tune_epoch = 0
_tune_epoch_lock = threading.Lock()


def _next_tune_epoch() -> int:
    global _tune_epoch
    with _tune_epoch_lock:
        _tune_epoch += 1
        return _tune_epoch


# The 1B model occasionally regurgitates its own system prompt on air. Three
# layers scrub it before any listener hears it, and none of them touch the
# canonical [JINGLE]/[INTERFERENCIA]/[CORTE COMERCIAL]/[FIN DE TRANSMISION]
# markers (those are control tokens the frontend localizes and acts on).

# 1) Chat/special tokens, whole <think> blocks, and bare role labels that may
#    bleed through (model.py already filters thinking; this is a backstop).
_TOKEN_RE = re.compile(
    r"(?is)<think>.*?</think>|</?think>|"
    r"<\|im_start\|>\s*(?:system|user|assistant)?|<\|im_end\|>|<\|endoftext\|>"
)
_ROLE_LINE_RE = re.compile(r"(?im)^\s*(?:system|user|assistant)\s*[:：]?\s*$")

# 2) Whole sentences that are instruction-shaped (the dangerous parrots).
_LEAK_KEYWORDS = (
    # Spanish
    r"escrib\w*\s+s[oó]lo\s+el\s+gui[oó]n", r"gui[oó]n\s+al\s+aire",
    r"sin\s+explicaciones", r"entre\s+\d+\s+y\s+\d+\s+palabras",
    r"escribes?\s+(?:el\s+)?gui[oó]n", r"traduce\s+tu\s+frase",
    r"ni\s+una\s+palabra\s+en\s+(?:ingl[eé]s|espa[nñ]ol)",
    r"ejemplo\s+del\s+tono", r"responde\s+en\s+una\s+o\s+dos",
    r"cierra\s+(?:siempre\s+)?con\s+\[", r"transmites\s+[ií]ntegramente",
    # English
    r"write\s+only\s+the\s+on-?air", r"on-?air\s+script\s+only",
    r"no\s+explanations", r"between\s+\d+\s+and\s+\d+\s+words",
    r"you\s+write\s+(?:the\s+)?(?:on-?air\s+|radio\s+)?scripts?",
    r"translate\s+your\s+opening", r"not\s+a\s+single\s+word\s+of",
    r"example\s+of\s+the\s+(?:expected\s+)?tone",
    r"reply\s+in\s+one\s+or\s+two", r"always\s+close\s+with\s+\[",
    r"you\s+(?:broadcast|speak)\s+(?:and\s+write\s+)?(?:only|entirely)\s+in",
    r"never\s+in\s+spanish", r"translate\s+every\s+line",
    # French
    r"uniquement\s+le\s+script", r"sans\s+explications",
    r"entre\s+\d+\s+et\s+\d+\s+mots", r"tu\s+[ée]cris\s+le\s+script",
    r"traduis\s+(?:ta\s+phrase|chaque\s+ligne)", r"pas\s+un\s+mot\s+d",
    r"exemple\s+du\s+ton", r"r[ée]ponds\s+en\s+une\s+ou\s+deux",
    r"termine\s+(?:toujours\s+)?par\s+\[", r"tu\s+[ée]mets\s+enti[èe]rement",
    r"tu\s+parles\s+et\s+[ée]cris", r"jamais\s+en\s+espagnol",
    r"hablas\s+y\s+escribes\s+solo", r"nunca\s+en\s+(?:ingl[eé]s|espa[nñ]ol)",
)
_LEAK_RE = re.compile(
    r"(?i)[^.\n!?]*(?:" + "|".join(_LEAK_KEYWORDS) + r")[^.\n!?]*[.\n!?]*"
)

# 3) Bare "you begin with:" lead-ins — strip only the prefix, keep the opening
#    line that legitimately follows it.
_LEAD_RE = re.compile(
    r"(?i)\b(?:you\s+begin\s+with|empiezas\s+con|tu\s+commences\s+par)\s*[:：]?\s*"
)


def _strip_leaks(text: str) -> str:
    text = _TOKEN_RE.sub(" ", text)
    text = _ROLE_LINE_RE.sub(" ", text)
    text = _LEAK_RE.sub(" ", text)
    text = _LEAD_RE.sub("", text)
    # collapse the blanks the substitutions leave behind, keep newlines
    text = re.sub(r"[ \t]{2,}", " ", text)
    return text.lstrip()


_GEN_ERR = object()


def _threaded_broadcast(system_prompt: str, should_continue, **kwargs):
    """Generate in a worker thread and hand tokens over via a queue.

    The model lock lives inside `stream_broadcast`, held for the whole
    generation. If we iterated it directly from the HTTP response generator and
    the client disconnected, this generator would be suspended at a `yield`
    forever — still holding the lock — and every later generation would block
    (the "everything turns to static and never recovers" bug).

    Running it in a worker thread decouples the lock from the HTTP consumer: the
    worker keeps pulling tokens and checks `should_continue` itself, so it always
    finishes (and releases the lock) — when superseded, on disconnect, or at
    max_tokens — regardless of whether anyone is still listening.
    """
    q: queue.Queue = queue.Queue()
    DONE = object()

    def worker():
        try:
            for token in stream_broadcast(system_prompt, **kwargs):
                if should_continue is not None and not should_continue():
                    break
                q.put(token)
        except Exception as exc:  # noqa: BLE001 - surface, don't crash the worker
            q.put((_GEN_ERR, exc))
        finally:
            q.put(DONE)

    threading.Thread(target=worker, daemon=True).start()

    while True:
        item = q.get()
        if item is DONE:
            return
        if isinstance(item, tuple) and item and item[0] is _GEN_ERR:
            print(f"[model] generation error: {item[1]}")
            return
        yield item


def _stream_model_cached(cache_key: str, system_prompt: str, should_continue=None, **kwargs):
    def superseded():
        return should_continue is not None and not should_continue()

    cached = _broadcast_cache.get(cache_key)
    if cached:
        yield from _stream_fixed(cached, char_delay=0.018, should_continue=should_continue)
        return

    accumulated = ""
    completed = False
    try:
        for token in _threaded_broadcast(system_prompt, should_continue, **kwargs):
            if superseded():
                return  # a newer tune arrived: stop streaming to this listener
            accumulated += token
            yield _strip_leaks(accumulated)
        completed = True
    finally:
        # Only cache full broadcasts: a cancelled stream (listener retuned)
        # must never freeze a truncated script for everyone after.
        clean = _strip_leaks(accumulated)
        if completed and clean.strip():
            if len(_broadcast_cache) >= _CACHE_MAX:
                _broadcast_cache.pop(next(iter(_broadcast_cache)))
            _broadcast_cache[cache_key] = clean


def _mix_seed(base: int, variant: int) -> int:
    """Blends the station seed with the listener's session variant."""
    if not variant:
        return base
    return (base ^ (variant * 2654435761)) % (2**31 - 1)


def _norm_variant(variant) -> int:
    try:
        return abs(int(float(variant))) % (2**31 - 1)
    except (TypeError, ValueError):
        return 0


# concurrency 2: a cancelled-but-unfinished stream must not head-block the
# queue (that froze "the other stations" when retuning fast). Real generation
# stays serialized by model._gen_lock.
@app.api(name="tune", concurrency_limit=2, stream_every=0.02)
def tune(frequency: float, language: str = "es", variant: float = 0) -> str:
    """Tunes a frequency and streams the broadcast (SSE).

    `variant` is a per-listener session nonce: every visitor hears their own
    edition of each station (the world re-broadcasts for every new listener).
    """
    frequency = float(frequency)
    lang = normalize_lang(language)
    var = _norm_variant(variant)
    my_epoch = _next_tune_epoch()

    def still_current():
        return my_epoch == _tune_epoch

    # Encrypted number station: fixed text, the frontend adds the Morse.
    if abs(frequency - ENCRYPTED_FREQUENCY) <= STATION_TOLERANCE:
        yield from _stream_fixed(numbers_broadcast(lang, var), should_continue=still_current)
        return

    # The unsolvable station: the model broadcasts, the frontend never cleans it.
    if abs(frequency - CURSED_FREQUENCY) <= STATION_TOLERANCE:
        yield from _stream_model_cached(
            f"cursed:{CURSED_FREQUENCY}:{lang}:{var}",
            localized_system_prompt(CURSED_SYSTEM_PROMPT, "es", lang),
            should_continue=still_current,
            user_prompt=localized_user_prompt(None, lang),
            seed=_mix_seed(station_seed(CURSED_FREQUENCY), var),
            max_tokens=160,
        )
        return

    # Hidden band fragments (minigame): deterministic text.
    fragment = get_fragment(frequency)
    if fragment is not None:
        yield from _stream_fixed(fragment_text(fragment, lang), should_continue=still_current)
        return

    canonical = nearest_station_frequency(frequency)
    station = get_station(frequency)

    if station is None or canonical is None or signal_strength(frequency) <= 0:
        yield ""
        return

    yield from _stream_model_cached(
        f"station:{canonical}:{lang}:{var}",
        station_system_prompt(canonical, lang),
        should_continue=still_current,
        user_prompt=localized_user_prompt(station, lang),
        seed=_mix_seed(station_seed(canonical), var),
    )


@app.api(name="transmit", concurrency_limit=1, stream_every=0.02)
def transmit(message: str, language: str = "es", variant: float = 0) -> str:
    """Console of the encrypted frequency.

    Victory is decided by decrypt.validate_bypass (deterministic);
    the model only role-plays the operator's resistance.
    """
    message = str(message).strip()[:500]
    lang = normalize_lang(language)
    var = _norm_variant(variant)
    if not message:
        yield ""
        return

    if validate_bypass(message, var):
        yield from _stream_fixed(reveal_text(lang, var), char_delay=0.02)
        return

    accumulated = ""
    for token in _threaded_broadcast(
        OPERATOR_SYSTEM_PROMPTS[lang],
        None,
        user_prompt=message,
        seed=zlib.crc32(message.encode("utf-8")) % (2**31 - 1),
        max_tokens=90,
    ):
        accumulated += token
        yield _strip_leaks(accumulated)


@app.api(name="finale", concurrency_limit=1, stream_every=0.02)
def finale(code: str, language: str = "es", variant: float = 0) -> str:
    """The complete final transmission (after collecting every fragment)."""
    lang = normalize_lang(language)
    if not is_valid_code(str(code), _norm_variant(variant)):
        yield "[ACCESO DENEGADO]"
        return

    yield from _stream_model_cached(
        f"finale:{lang}",
        localized_system_prompt(FINALE_SYSTEM_PROMPT, "es", lang),
        user_prompt=FINALE_USER_PROMPT,
        seed=FINALE_SEED,
        max_tokens=300,
    )


if __name__ == "__main__":
    app.launch(server_name="0.0.0.0", server_port=7860, show_error=True)