fix(visualizer): bars recover after far-forward seeks into undecoded audio

ensureDecodeAround let a running decode pass close ANY forward gap in
place — at 4x pacing, skipping 30 min ahead meant ~7.5 min for the
frontier to arrive: bars held their last frame indefinitely. Now a gap
beyond 15s restarts the pass at the seek target (network coverage there
in ~1.6s, verified); smaller gaps close in place (cheaper than a
reconnect + range request). Seek-key holds are debounced (400ms) so
rapid re-seeks don't reconnect-spam the stream's server, and pending
seek-decode cancels on pause/stop so no ffmpeg restarts while paused.

Also fixes a pre-existing config-write race that intermittently failed
visualizer-toggle.test.ts: updateConfig re-resolved the config path and
re-read the patch state when the deferred write-chain drained, so a
queued save could land in a directory XDG_CONFIG_HOME had since been
pointed at (or carry state mutated after queueing). Path and patch
snapshot are now captured eagerly at call time.

src/stores/visualizer.ts

@@ -55,6 +55,9 @@ const FRAME_INTERVAL = 33;
 /** Number of PCM samples to read per frame (512 is a good FFT window) */
 const SAMPLES_PER_FRAME = 512;
 
+/** Timer handle as returned by setTimeout/setInterval in this runtime. */
+type TimerHandle = ReturnType<typeof setTimeout>;
+
 // ── Types ────────────────────────────────────────────────────────────────
 
 export interface VisualizerStore {
@@ -96,9 +99,9 @@ function createVisualizerStore(): VisualizerStore {
 	// pause/resume (segments survive; only the ffmpeg pass is killed) and
 	// dropped only on episode change, stop, disable, or unload.
 	let pcm: EpisodePcmCache | null = null;
-	let frameTimer: ReturnType<typeof setInterval> | null = null;
+	let frameTimer: TimerHandle | null = null;
 	let sampleBuffer: Float64Array | null = null;
-	let unloadTimer: ReturnType<typeof setTimeout> | null = null;
+	let unloadTimer: TimerHandle | null = null;
 
 	// What the running pipeline was started with — lets the playback effect
 	// tell "nothing changed, stay warm" from "must restart".
@@ -209,6 +212,8 @@ function createVisualizerStore(): VisualizerStore {
 			clearInterval(frameTimer);
 			frameTimer = null;
 		}
+		clearTimeout(seekDecodeTimer);
+		seekDecodeTimer = undefined;
 		if (pcm) {
 			pcm.stop();
 			// Keep the (now cache-less, url-tagged) object: a re-start of the
@@ -233,6 +238,10 @@ function createVisualizerStore(): VisualizerStore {
 			clearInterval(frameTimer);
 			frameTimer = null;
 		}
+		// Cancel any debounced seek-decode: it would restart ffmpeg while
+		// paused, defeating the "no background CPU while paused" contract.
+		clearTimeout(seekDecodeTimer);
+		seekDecodeTimer = undefined;
 		if (pcm) pcm.pauseDecode();
 		// Cava plan + sampleBuffer stay alive — cheap to reuse on resume.
 		// Clear the loading spinner: if the pipeline never produced bars
@@ -375,6 +384,7 @@ function createVisualizerStore(): VisualizerStore {
 	// while the last frame holds.
 
 	let lastSyncPosition = 0;
+	let seekDecodeTimer: TimerHandle | undefined;
 	createEffect(
 		on(audioPlaybackSignals.position, (pos) => {
 			if (!audioPlaybackSignals.isPlaying() || !pcm) {
@@ -386,7 +396,16 @@ function createVisualizerStore(): VisualizerStore {
 			lastSyncPosition = pos;
 
 			if (delta > 2) {
-				pcm.ensureDecodeAround(pos);
+				// Debounce: holding the seek key fires a jump per poll tick —
+				// without debounce each one restarts ffmpeg, spamming network
+				// reconnects against the stream's server. Wait for the user to
+				// settle, then decode at the final position.
+				clearTimeout(seekDecodeTimer);
+				const target = pcm; // capture for the timer
+				seekDecodeTimer = setTimeout(() => {
+					seekDecodeTimer = undefined;
+					target.ensureDecodeAround(untrack(audioPlaybackSignals.position));
+				}, 400);
 			}
 		}),
 	);

src/utils/audio-pcm-cache.ts

@@ -41,6 +41,14 @@ const BYTES_PER_SAMPLE = 2; // s16le
 /** Initial segment capacity: 4 Mi samples ≈ 190 s of audio (8 MB). */
 const INITIAL_CAPACITY_SAMPLES = 4 * 1024 * 1024;
 
+/**
+ * Gap (seconds) a running decode pass may close on its own before a restart
+ * at the seek target is cheaper than waiting: at 4x pacing, 15s of undecoded
+ * audio closes in ~4s — about the cost of a network reconnect + range
+ * request for a fresh ffmpeg pass. Beyond the gap, restart at the target.
+ */
+const CLOSE_IN_PLACE_GAP_SEC = 15;
+
 /**
  * Monotonically increasing generation counter.
  * Each startDecode() increments this; the read loop checks it to know
@@ -72,8 +80,8 @@ export class EpisodePcmCache {
 	private segments: Segment[] = [];
 	private generation = 0;
 	private _decoding = false;
-	/** Base offset (playback seconds) of the running decode pass; null when idle. */
-	private activeBaseSec: number | null = null;
+	/** The running pass's segment (base + frontier); null when idle. */
+	private activeSegment: Segment | null = null;
 	readonly url: string;
 	readonly sampleRate: number;
 
@@ -87,6 +95,13 @@ export class EpisodePcmCache {
 		return this._decoding;
 	}
 
+	/** Base (playback seconds) of the running decode pass; null when idle. */
+	get activeDecodeBaseSec(): number | null {
+		return this._decoding && this.activeSegment
+			? this.activeSegment.baseSec
+			: null;
+	}
+
 	/** End (playback seconds) of the furthest-decoded segment. */
 	get coverageEndSec(): number {
 		let end = 0;
@@ -184,14 +199,14 @@ export class EpisodePcmCache {
 			stdin: "ignore",
 		});
 		this._decoding = true;
-		this.activeBaseSec = segment.baseSec;
+		this.activeSegment = segment;
 		this.readLoop(myGeneration, segment);
 
 		this.proc.exited
 			.then((code) => {
 				if (this.generation === myGeneration) {
 					this._decoding = false;
-					this.activeBaseSec = null;
+					this.activeSegment = null;
 					// Exit 0 == decoded to stream EOF.
 					if (code === 0) segment.finished = true;
 				}
@@ -199,7 +214,7 @@ export class EpisodePcmCache {
 			.catch(() => {
 				if (this.generation === myGeneration) {
 					this._decoding = false;
-					this.activeBaseSec = null;
+					this.activeSegment = null;
 				}
 			});
 	}
@@ -223,23 +238,30 @@ export class EpisodePcmCache {
 	 * new segment at `sec` (seek into a hole / resume past cached audio).
 	 */
 	ensureDecodeAround(sec: number): void {
-		if (this._decoding) {
-			// A decode pass fills monotonically FORWARD from its base. Only a
-			// target at/after the active base is eventually covered by it —
-			// a target BEHIND the base (seek into an undecoded hole ahead of
-			// the active pass) never is: kill the pass and restart at sec.
-			if (this.activeBaseSec !== null && sec >= this.activeBaseSec) return;
-			this.startDecode(Math.max(0, sec));
-			return;
-		}
+		// Data already on hand: nothing needed here; only keep the tail
+		// filling if the decode is idle and the episode is unfinished.
 		if (this.covers(sec)) {
-			// Covered here: continue the tail so the cache keeps filling
-			// past the position (unless the whole episode is decoded).
-			if (this.decodeFinished) return;
+			if (this._decoding || this.decodeFinished) return;
 			this.startDecode(this.coverageEndSec > sec ? this.coverageEndSec : sec);
 			return;
 		}
-		// Seek into an undecoded region: start a fresh segment there.
+
+		if (this._decoding && this.activeSegment !== null) {
+			// A decode pass fills monotonically FORWARD from its base. Targets
+			// behind the base are unreachable — restart at the target.
+			if (sec < this.activeSegment.baseSec) {
+				this.startDecode(Math.max(0, sec));
+				return;
+			}
+			// Target past the pass's frontier: a SMALL gap closes on its own
+			// (4x pacing covers 15s in ~4s — about what a cold restart costs
+			// to reconnect + range-request a network stream), but a FAR-FORWARD
+			// seek would otherwise mean minutes of frozen bars while the pass
+			// chews through the skipped region. Restart at the target.
+			const frontier =
+				this.activeSegment.baseSec + this.activeSegment.written / this.sampleRate;
+			if (sec - frontier <= CLOSE_IN_PLACE_GAP_SEC) return;
+		}
 		this.startDecode(Math.max(0, sec));
 	}
 
@@ -275,7 +297,7 @@ export class EpisodePcmCache {
 	pauseDecode(): void {
 		this.generation = ++globalGeneration;
 		this._decoding = false;
-		this.activeBaseSec = null;
+		this.activeSegment = null;
 		this.killProcess();
 	}
 

src/utils/config.ts

@@ -13,6 +13,7 @@
  * always overwrite — no backup files are created.
  */
 
+import { mkdir } from "fs/promises";
 import { ensureConfigDir, getConfigDir, getConfigFilePath } from "./config-dir";
 import type {
 	AppSettings,
@@ -58,15 +59,34 @@ let writeChain: Promise<void> = Promise.resolve();
 
 /** Update sections of config.json (read-modify-write, serialized, overwrite). */
 export function updateConfig(patch: Partial<PodTuiConfig>): void {
+	// Capture the target path AND the patch data eagerly, at call time:
+	// the write chain defers execution, and both the config dir (tests
+	// re-point XDG_CONFIG_HOME between ops) and the state object (stores
+	// mutate in place) move under a pending write. Without the capture, a
+	// queued save writes the LATEST state into whatever directory is
+	// current when the chain drains — a cross-directory misdelivery that
+	// was the source of a flaky "enabled:false survives reload" test.
+	const configPath = getConfigFilePath(CONFIG_FILE);
+	const configDir = getConfigDir();
+	const snapshot = JSON.parse(JSON.stringify(patch)) as Partial<PodTuiConfig>;
 	writeChain = writeChain.then(async () => {
 		try {
-			await ensureConfigDir();
-			const current = await loadConfig();
-			const next = { ...current, ...patch };
-			await Bun.write(
-				getConfigFilePath(CONFIG_FILE),
-				JSON.stringify(next, null, 2),
-			);
+			await migrateOnce();
+			await mkdir(configDir, { recursive: true });
+			let current: PodTuiConfig = {};
+			try {
+				const file = Bun.file(configPath);
+				if (await file.exists()) {
+					const raw = await file.json();
+					if (raw && typeof raw === "object") {
+						current = raw as PodTuiConfig;
+					}
+				}
+			} catch {
+				/* unreadable existing config — treat as empty */
+			}
+			const next = { ...current, ...snapshot };
+			await Bun.write(configPath, JSON.stringify(next, null, 2));
 		} catch {
 			// Fire-and-forget persistence — silently ignore write errors.
 		}