// frontend/js/api.js — Lightloom "La Sala" · backend transport (LL.api)
//
// The ONLY sanctioned way to reach the GPU pipeline is @gradio/client. Raw
// fetch() against /api/recital BREAKS ZeroGPU quota attribution (the client
// injects the session/quota auth headers fetch cannot), so we never do that
// here. We connect once, submit "/recital", and fan each streamed message out
// to onEvent. See app.py @app.api(name="recital", ...) for the validated shape.
//
// Public surface (per the shared contract):
//   LL.api.connect()                              -> Promise<Client>  (memoized)
//   LL.api.streamRecital(text, lang, onEvent)     -> Promise<{session,done}>
//   LL.api.cancel()                               -> void  (aborts the live job)
//
// No frameworks, no build step — vanilla ES module.

// PINNED to the exact version currently resolving (2.2.2) and the real dist/index.js entry. The old
// unpinned @latest import meant a future @gradio/client publish could 404/restructure and fail to
// parse at load time -> window.LL.api never assigned -> the world is dead-on-stage with NO error.
// Re-pin deliberately when the Space's gradio SDK is bumped (keep client major in step with gradio).
import { Client } from "https://cdn.jsdelivr.net/npm/@gradio/client@2.2.2/dist/index.js";

const LL = (window.LL = window.LL || {});

// msg.data may arrive as the event object itself OR a 1-element array [event]
// (Gradio wraps single outputs either way depending on version). Normalize so
// the controller always receives a plain event object.
const asEvent = (d) => (Array.isArray(d) ? d[0] : d);

const api = {
  _clientPromise: null, // memoized Client.connect() so we connect at most once
  _job: null, // the live submit() job handle (has .cancel())
  _cancelled: false, // guards against late events after an explicit cancel()

  /**
   * Connect (once) to the gr.Server that serves this page. Memoized: repeated
   * calls return the same in-flight/resolved promise. A failed connect clears
   * the memo so a later call can retry.
   * @returns {Promise<import("@gradio/client").Client>}
   */
  async connect() {
    if (!this._clientPromise) {
      // window.location.origin => same Space that served index.html. This is
      // what carries the ZeroGPU quota identity; do not hardcode a URL.
      this._clientPromise = Client.connect(window.location.origin).catch((err) => {
        this._clientPromise = null; // allow a retry on the next call
        throw err;
      });
    }
    return this._clientPromise;
  },

  // Removed obsolete one-shot endpoints (streamRecital / streamPanorama / streamWorld / streamScroll) —
  // all superseded by streamScrollLive (the continuous-panorama path). The typed path now feeds
  // /scroll_live per sentence, identical Director/painter/continuity to voice.

  /**
   * LIVE narration — the world builds AS YOU SPEAK. Submit ONE spoken phrase segment
   * (base64 WAV); the server transcribes it AND paints a few strips that CONTINUE this
   * `session`'s panorama, streaming transcript/section/depth events. Call it once per
   * VAD-cut phrase; continuity is keyed server-side by `session`. Short-lived per call
   * (it does NOT touch the long-stream _job handle), so phrases can pipeline in order.
   * Pass an empty `audioB64` once on mic-tap to WARM the models ahead of the first word.
   * @returns {Promise<{session:string, done:boolean}>}
   */
  async streamScrollLive(session, audioB64 = "", lang = "en", onEvent, text = "") {
    const emit = typeof onEvent === "function" ? onEvent : () => {};
    let client;
    try {
      client = await this.connect();
    } catch (err) {
      emit({ stage: "error", error: `connect_failed: ${shortErr(err)}` });
      return { session, done: false };
    }
    let timedOut = false;
    try {
      const job = client.submit("/scroll_live", {
        session: session || "",
        text: text || "",
        audio_b64: audioB64 || "",
        lang: lang || "en",
      });
      // IDLE WATCHDOG: a `for await` over the job NEVER resolves if the server closes the socket cleanly
      // mid-job without the iterator signalling done -> the live drain wedges forever on one scene. If no
      // message arrives for 25 s, cancel the job so the loop ends and the drain can continue.
      let watchdog = null;
      const arm = () => { if (watchdog) clearTimeout(watchdog); watchdog = setTimeout(() => { timedOut = true; try { job.cancel(); } catch (_) {} }, 25000); };
      arm();
      try {
        for await (const msg of job) {
          arm();
          if (!msg || msg.type !== "data") continue;
          const ev = asEvent(msg.data);
          if (!ev || typeof ev !== "object") continue;
          if (ev.session) session = ev.session;
          try { emit(ev); } catch (e) { console.error("[LL.api] live onEvent threw", e); }
        }
      } finally {
        if (watchdog) clearTimeout(watchdog);
      }
    } catch (err) {
      if (!timedOut) emit({ stage: "error", error: `stream_failed: ${shortErr(err)}` });
    }
    if (timedOut) emit({ stage: "section_error", error: "phrase_timeout" }); // surfaced as a transient status, not a silent stall
    return { session, done: true };
  },

  /**
   * DIRECTOR'S CUT keepsake. Over the FINISHED session panorama (already on disk under `session`), run the
   * post-process: the MiniCPM-V-4.6 Art Director names it from the pixels, then a depth-parallax fly-through
   * is rendered to world.mp4. Streams {stitched,titled,rendering,encoding,ready} (ready carries .video + the
   * .title). Short-lived per call; does NOT touch the live _job handle. Independent of the live painter.
   * @returns {Promise<{session:string, done:boolean}>}
   */
  async streamPostprocess(session, lang = "en", onEvent) {
    const emit = typeof onEvent === "function" ? onEvent : () => {};
    let client;
    try {
      client = await this.connect();
    } catch (err) {
      emit({ stage: "postprocess_error", error: `connect_failed: ${shortErr(err)}` });
      return { session, done: false };
    }
    let timedOut = false;
    let sawTerminal = false;
    const isTerminal = (s) => s === "ready" || s === "postprocess_error" || s === "quota_exceeded" || s === "render_timeout" || s === "error";
    try {
      const job = client.submit("/postprocess", { session: session || "", lang: lang || "en" });
      // IDLE WATCHDOG (mirrors streamScrollLive): a clean mid-stream socket close would otherwise leave the
      // keepsake stuck forever on the sticky "Crafting…" status. 45s — renders have longer legitimate gaps
      // (cold model load, a long encode) than a live phrase, so the live 25s budget would false-cancel.
      let watchdog = null;
      const arm = () => { if (watchdog) clearTimeout(watchdog); watchdog = setTimeout(() => { timedOut = true; try { job.cancel(); } catch (_) {} }, 45000); };
      arm();
      try {
        for await (const msg of job) {
          arm();
          if (!msg || msg.type !== "data") continue;
          const ev = asEvent(msg.data);
          if (!ev || typeof ev !== "object") continue;
          if (ev.session) session = ev.session;
          if (isTerminal(ev.stage)) sawTerminal = true;
          try { emit(ev); } catch (e) { console.error("[LL.api] postprocess onEvent threw", e); }
        }
      } finally {
        if (watchdog) clearTimeout(watchdog);
      }
    } catch (err) {
      if (!timedOut) { emit({ stage: "postprocess_error", error: `stream_failed: ${shortErr(err)}` }); sawTerminal = true; }
    }
    // Never strand the UI on the sticky "Crafting…" status: if the stream ended (clean close or a watchdog
    // cancel) without a terminal event, synthesize one so the controller clears the status and toasts.
    if (!sawTerminal) emit({ stage: "postprocess_error", error: timedOut ? "postprocess_timeout" : "stream_ended" });
    return { session, done: true };
  },

  /**
   * "Ask Your World" — MiniCPM-V-4.6 answers a free-form question about the FINISHED world from its pixels.
   * Short (one VLM call); resolves with { answer, error? }. Independent of live image creation.
   */
  async ask(session, question, lang = "en") {
    let client;
    try { client = await this.connect(); } catch (err) { return { answer: "", error: `connect_failed: ${shortErr(err)}` }; }
    try {
      const job = client.submit("/ask", { session: session || "", question: question || "", lang: lang || "en" });
      let res = { answer: "" };
      for await (const msg of job) {
        if (!msg || msg.type !== "data") continue;
        const ev = asEvent(msg.data);
        if (ev && typeof ev === "object") res = ev;
      }
      return res;
    } catch (err) { return { answer: "", error: `stream_failed: ${shortErr(err)}` }; }
  },

  /**
   * Transcribe a base64 WAV (the narrator's mic audio) via Cohere Transcribe.
   * Resolves with {text, error}. Used by LL.recorder; the transcript then drives
   * streamPanorama just like a typed recital.
   *
   * @param {string} audioB64  data:audio/wav;base64,... (or bare base64)
   * @param {string} lang      ISO code ("en"/"es"/...); default "en"
   * @param {(event:object)=>void} [onEvent]  optional per-stage callback
   * @returns {Promise<{text:string, error:?string}>}
   */
  async transcribe(audioB64, lang = "en", onEvent) {
    const emit = typeof onEvent === "function" ? onEvent : () => {};
    let client;
    try {
      client = await this.connect();
    } catch (err) {
      return { text: "", error: `connect_failed: ${shortErr(err)}` };
    }
    let text = "";
    let error = null;
    try {
      const job = client.submit("/transcribe", { audio_b64: audioB64, lang: lang || "en" });
      for await (const msg of job) {
        if (!msg || msg.type !== "data") continue;
        const ev = asEvent(msg.data);
        if (!ev || typeof ev !== "object") continue;
        emit(ev);
        if (ev.stage === "transcript") text = ev.text || "";
        if (ev.stage === "error" || ev.stage === "quota_exceeded") error = ev.error || ev.stage;
      }
    } catch (err) {
      error = `stream_failed: ${shortErr(err)}`;
    }
    return { text, error };
  },

  /** Shared streaming core for the @app.api endpoints (recital + panorama). */
  async _streamEndpoint(endpoint, text, lang = "en", onEvent) {
    const emit = typeof onEvent === "function" ? onEvent : () => {};

    // Guard empty input before spending a GPU connect: surface a soft error
    // event the controller can render as a toast, then resolve cleanly.
    const poem = (text || "").trim();
    if (!poem) {
      emit({ stage: "error", error: "empty_text" });
      return { session: null, done: false, cancelled: false };
    }

    // A fresh stream supersedes any previous one.
    this.cancel();
    this._cancelled = false;

    let client;
    try {
      client = await this.connect();
    } catch (err) {
      // Connection failure is terminal for this attempt — report and stop.
      emit({ stage: "error", error: `connect_failed: ${shortErr(err)}` });
      return { session: null, done: false, cancelled: false };
    }

    let session = null;
    let done = false;
    let job = null;

    try {
      // Payload keys MUST be text+lang (the @app.api signatures take text, lang).
      job = client.submit(endpoint, { text: poem, lang: lang || "en" });
      this._job = job;

      // The job is an async iterable of status/data messages. We only act on
      // "data" messages; "status" carries queue/progress info we ignore here.
      for await (const msg of job) {
        if (this._cancelled) break;
        if (!msg || msg.type !== "data") continue;

        const event = asEvent(msg.data);
        if (!event || typeof event !== "object") continue;

        if (event.session) session = event.session;
        if (event.stage === "done") done = true;

        try {
          emit(event);
        } catch (handlerErr) {
          // A throwing handler must not tear down the whole stream — one bad
          // beat render shouldn't end the film. Log and keep streaming.
          console.error("[LL.api] onEvent handler threw", handlerErr);
        }
      }
    } catch (err) {
      if (!this._cancelled) {
        emit({ stage: "error", error: `stream_failed: ${shortErr(err)}` });
      }
    } finally {
      // Only clear the handle if a newer submit() hasn't already replaced it.
      if (this._job === job) this._job = null;
    }

    return { session, done, cancelled: this._cancelled };
  },

  /**
   * Abort the in-flight recital job (if any). Idempotent and safe to call when
   * nothing is running. Marks the stream cancelled so any already-queued events
   * are dropped by the loop guard above.
   */
  cancel() {
    this._cancelled = true;
    const job = this._job;
    this._job = null;
    if (job && typeof job.cancel === "function") {
      try {
        job.cancel();
      } catch (err) {
        console.warn("[LL.api] job.cancel() failed", err);
      }
    }
  },
};

// Tiny helper kept local (no extra globals).
function shortErr(err) {
  const m = err && (err.message || err.toString());
  return String(m || "unknown").slice(0, 160);
}

LL.api = api;

export default api;