SoulStream/src/lib/preview/previewSession.svelte.js

// Svelte-side preview session: one store, one service instance, and the
// production wiring (resolver → Tauri, transport → native player, focus →
// main player). state.svelte.js hands us its player accessors at init
// (dependency injection, deliberately: this module must not import the
// 4000-line state module, and the state module needs to import US for
// gateway bumps — injection breaks what would otherwise be a cycle).

import { createPreviewService } from "./service.js";
import { createProductionResolver } from "./productionResolver.js";
import { createNativeTransport } from "./nativeTransport.js";
import { createProductionFocus } from "./focusBridge.js";
import { createFixtureResolver } from "./resolver.js";
import { createFixtureTransport } from "./transport.js";
import { buildFixtureManifest } from "./manifest.js";
import { AVAILABILITY } from "./contracts.js";

/** Reactive mirror of the session for components. `snapshot` is the frozen
 * reducer state; everything else is presentation-level. */
export const previewUi = $state({
    open: false,
    snapshot: null,
    focusWaiting: false,
    /** element to restore focus to when the modal closes */
    returnFocusTo: null,
    /** page-supplied "play this item as a full track" starter */
    playFull: null,
    /** page-supplied "take me to this item's album" navigator */
    openAlbum: null,
});

let service = null;
let unsubscribe = null;
let focusParts = null; // { coordinator, gateway }
let demoTicker = null;
let readPlayerRef = null; // injected with the bridge; app volume source

// ------------------------------------------------------------- gateway ----

/** Bump the main-player revision gateway from state.svelte.js. A no-op
 * until the bridge is initialised, and a no-op for unknown kinds — the
 * caller sites stay one-liners. */
export function bumpMainRevision(kind, opts) {
    const g = focusParts?.gateway;
    if (g && typeof g[kind] === "function") g[kind](opts);
}

let playbackGeneration = 0;
/** Called by state.svelte.js on every main "buffering" — each new decode is
 * a new renderer-side playback generation (the focusBridge invariant). */
export function notePlaybackGeneration() {
    playbackGeneration += 1;
}

/** One-time wiring from state.svelte.js. */
export function initPreviewBridge({ readPlayer, resumeMain }) {
    readPlayerRef = readPlayer;
    focusParts = createProductionFocus({
        readPlayer,
        readPlaybackGeneration: () => playbackGeneration,
        resumeMain,
    });
}

// -------------------------------------------------------------- session ---

function attach(svc) {
    service = svc;
    unsubscribe = svc.subscribe((snapshot, extras) => {
        previewUi.snapshot = snapshot;
        previewUi.focusWaiting = extras.focusWaiting;
    });
}

/** Open a preview session over the production stack. `manifest` comes from
 * a page adapter (artist page in Phase 3). */
export async function openPreview(manifest, { playFull, openAlbum } = {}) {
    if (!focusParts) throw new Error("preview bridge not initialised");
    await closePreview(); // one session at a time, always torn down first
    previewUi.returnFocusTo = document.activeElement;
    previewUi.playFull = playFull ?? null;
    previewUi.openAlbum = openAlbum ?? null;
    attach(
        createPreviewService({
            resolver: createProductionResolver(),
            transportFactory: (dispatch) => createNativeTransport(dispatch),
            focus: focusParts,
        })
    );
    // Preview volume follows the APP volume (mute = 0) — set it BEFORE the
    // first load so the opening clip can't blast at the backend default.
    // The overlay keeps it mirrored live while the modal is open.
    const p = readPlayerRef?.();
    if (p) service.setVolume(p.muted ? 0 : (p.volume ?? 0.7));
    previewUi.open = true;
    await service.open({ sessionId: crypto.randomUUID(), manifest });
}

/**
 * Dev/browser fixture session: deterministic resolver + a fixture transport
 * driven by a wall-clock ticker, no Tauri and no audio. This is what the
 * Phase 2 exit gate's 500-item responsiveness check runs against, and what
 * a plain `vite` browser shows.
 */
export async function openPreviewFixture(count = 12) {
    await closePreview();
    previewUi.returnFocusTo = document.activeElement;
    const rows = Array.from({ length: count }, (_, i) => ({
        providerTrackId: String(i + 1),
        title: `Fixture track ${i + 1}`,
        artists: ["Fixture Artist"],
        album: `Fixture Album ${1 + (i % 7)}`,
        fullDurationMs: 180_000 + (i % 9) * 21_000,
        initialAvailability: i % 11 === 5 ? AVAILABILITY.NOT_PROVIDED : AVAILABILITY.AVAILABLE,
    }));
    const manifest = buildFixtureManifest({
        kind: "collection",
        contextKey: `fixture:${count}`,
        title: `Fixture · ${count} tracks`,
        rows,
        createdAtMs: Date.now(),
    });
    const plan = {};
    for (let i = 1; i <= count; i++) plan[i] = { opaqueLeaseId: `fx-${i}` };

    let transport = null;
    const focus = {
        coordinator: {
            async acquirePreview() {
                return { granted: true, token: { id: "fixture", pausedByPreview: false } };
            },
            release: () => ({ restored: false, reason: "fixture" }),
            handoffToMain: () => ({ restored: false, reason: "fixture" }),
        },
    };
    attach(
        createPreviewService({
            resolver: createFixtureResolver(plan),
            transportFactory: (dispatch) => {
                transport = createFixtureTransport(dispatch);
                return transport;
            },
            focus,
        })
    );
    // Drive the fixture transport at ~10 fps so progress/auto-advance behave
    // like real playback in the browser.
    demoTicker = setInterval(() => transport?.tick(100), 100);
    previewUi.open = true;
    await service.open({ sessionId: crypto.randomUUID(), manifest });
}

export async function closePreview() {
    if (demoTicker) {
        clearInterval(demoTicker);
        demoTicker = null;
    }
    if (!service) return { restored: false };
    // Detach first (re-entrancy: a second Escape lands on the early return),
    // and hide the modal BEFORE awaiting the close — service.close() now
    // holds the line for the close-crossfade tail (~CROSSFADE_MS), and the
    // visual out-transition must not wait on audio. The snapshot stays until
    // the close resolves so the dialog has content through its exit.
    const svc = service;
    service = null;
    previewUi.open = false;
    const back = previewUi.returnFocusTo;
    previewUi.returnFocusTo = null;
    if (back && typeof back.focus === "function" && back.isConnected) {
        back.focus();
    }
    const out = await svc.close();
    unsubscribe?.();
    unsubscribe = null;
    previewUi.snapshot = null;
    previewUi.focusWaiting = false;
    previewUi.playFull = null;
    previewUi.openAlbum = null;
    return out;
}

// Thin command pass-throughs for the overlay component.
export const previewCommands = {
    step: (dir) => service?.step(dir),
    activateKey: (k) => service?.activateKey(k),
    togglePlay: () => service?.togglePlay(),
    replay: () => service?.replay(),
    seek: (ms) => service?.seek(ms),
    setMuted: (v) => service?.setMuted(v),
    playFullTrack: (starter) => service?.playFullTrack(starter),
    setVolume: (v) => service?.setVolume(v),
};