Podcast player: calmer line-following scroll, and a voice you can pick

"The scrolling works kinda weirdly" + "maybe a less robotic voice, preferably
male".

Scroll: the transcript now follows by LINE, not by word - words on the same
line never move the page (that was the jitter), a line only scrolls once it
leaves a comfortable band, small corrections are instant rather than animated,
and a wheel/touch/drag on the transcript pauses the following for four seconds
instead of fighting the reader. Chapter jumps and word taps re-centre at once.

Voice: lib/podcast-voices ranks what the platform installed (natural / neural
/ online names up, espeak / SAM / compact down, a male name preferred) and the
player picks the best one automatically; a new picker in the chrome lists
everything in the episode's language, applies it live and remembers the choice
per language. A note points at the system settings when only robotic voices
exist. The engine takes the chosen voice instead of guessing.

podcast-test: 34 checks now (voice ranking, filtered picker, persisted pick,
same-line silence, line following, manual-scroll suspension). Version 0.7.4,
SW v96.

lib/podcast-voices.ts

@@ -0,0 +1,231 @@
+"use client";
+
+/**
+ * Choosing a voice for the podcast player.
+ *
+ * The Web Speech API ships no voices of its own: the list comes from the OS
+ * and the browser, and it swings wildly between platforms — from espeak's
+ * robot on a bare Linux box to Google's network voices, Microsoft's neural
+ * ones and macOS's Alex. This module ranks what is installed, prefers a male
+ * voice (a podcast host, per the listener's wish) among the good ones, and
+ * remembers the listener's own pick per language.
+ */
+
+const STORAGE_KEY = "freezmo.podcast-voice.v1";
+
+/** Names that usually mean "a human actually recorded this". */
+const QUALITY_HINTS = ["natural", "neural", "online", "premium", "enhanced", "siri", "google", "microsoft"];
+/** Engines that always sound like a 1980s answering machine. */
+const ROBOTIC_HINTS = ["espeak", "sam", "pico", "festival", "flite", "compact", "robot"];
+
+/**
+ * Male first names that appear in speech-voice catalogues. Not exhaustive —
+ * it only has to beat "pick the first voice for the language".
+ */
+const MALE_NAMES = [
+  "male", // "Google UK English Male"
+  "alex",
+  "daniel",
+  "fred",
+  "thomas",
+  "oliver",
+  "david",
+  "mark",
+  "james",
+  "ryan",
+  "guy",
+  "george",
+  "pavel",
+  "jakub",
+  "marek",
+  "ondrej",
+  "vojtech",
+  "jirka",
+  "petr",
+  "tomas",
+  "martin",
+  "lukas",
+  "jan",
+  "antonin",
+  "josef",
+  "jorge",
+  "diego",
+  "carlos",
+  "juan",
+  "pablo",
+  "luca",
+  "matteo",
+  "marco",
+  "pierre",
+  "henri",
+  "klaus",
+  "hans",
+  "stefan",
+  "felix",
+  "magnus",
+  "erik",
+  "yuri",
+  "dmitri",
+  "ivan",
+  "xander",
+  "zhihao",
+  "takumi",
+  "haruto",
+  "minho",
+  "ji-hoon",
+  "wei",
+  "liang",
+  "mikhail",
+];
+
+const FEMALE_NAMES = [
+  "female", // "Google UK English Female"
+  "samantha",
+  "karen",
+  "moira",
+  "tessa",
+  "victoria",
+  "allison",
+  "ava",
+  "susan",
+  "zira",
+  "siri",
+  "zuzana",
+  "iveta",
+  "eliska",
+  "tana",
+  "katerina",
+  "monika",
+  "lucie",
+  "pavla",
+  "anna",
+  "maria",
+  "laura",
+  "julia",
+  "carmen",
+  "paulina",
+  "zofia",
+  "elsa",
+  "katja",
+  "ingrid",
+  "freya",
+  "yelena",
+  "svetlana",
+  "olga",
+  "yuki",
+  "sakura",
+  "mei",
+  "ling",
+  "xiaoxiao",
+];
+
+type StoredVoices = Record<string, string>;
+
+let stored: StoredVoices | null = null;
+
+function loadStored(): StoredVoices {
+  if (stored) return stored;
+  stored = {};
+  try {
+    const raw = window.localStorage.getItem(STORAGE_KEY);
+    if (raw) {
+      const parsed: unknown = JSON.parse(raw);
+      if (parsed && typeof parsed === "object") {
+        for (const [locale, uri] of Object.entries(parsed as Record<string, unknown>)) {
+          if (typeof uri === "string") stored[locale] = uri;
+        }
+      }
+    }
+  } catch {
+    /* private mode */
+  }
+  return stored;
+}
+
+const languageOf = (voice: SpeechSynthesisVoice) => voice.lang.toLowerCase().replace("_", "-");
+
+/** Voices usable for `locale` (exact region first, then the language). */
+export function voicesFor(locale: string, voices?: SpeechSynthesisVoice[]): SpeechSynthesisVoice[] {
+  const all = voices ?? platformVoices();
+  if (all.length === 0) return [];
+  const wanted = locale.toLowerCase().replace("_", "-");
+  const prefix = wanted.split("-")[0];
+  const matching = all.filter((voice) => {
+    const lang = languageOf(voice);
+    return lang === wanted || lang.startsWith(`${prefix}-`) || lang === prefix;
+  });
+  /* Some platforms tag voices oddly (e.g. "en-GB" for a US voice): never show
+   * an empty list when voices exist at all. */
+  return matching.length > 0 ? matching : all;
+}
+
+/** The platform's voice list (empty offline/unsupported). */
+export function platformVoices(): SpeechSynthesisVoice[] {
+  try {
+    if (typeof window === "undefined" || !("speechSynthesis" in window)) return [];
+    return window.speechSynthesis.getVoices();
+  } catch {
+    return [];
+  }
+}
+
+/** A larger score wins. `male` tilts the ranking towards male names. */
+export function scoreVoice(voice: SpeechSynthesisVoice, locale: string, male: boolean): number {
+  const name = voice.name.toLowerCase();
+  const lang = languageOf(voice);
+  const wanted = locale.toLowerCase().replace("_", "-");
+  let score = 0;
+
+  if (lang === wanted) score += 6;
+  else if (lang.split("-")[0] === wanted.split("-")[0]) score += 3;
+
+  if (QUALITY_HINTS.some((hint) => name.includes(hint))) score += 10;
+  if (ROBOTIC_HINTS.some((hint) => name.includes(hint))) score -= 12;
+
+  if (MALE_NAMES.some((entry) => name.includes(entry))) score += male ? 8 : 1;
+  if (FEMALE_NAMES.some((entry) => name.includes(entry))) score += male ? 1 : 4;
+
+  /* Network voices are usually the neural ones; local ones are the fallback. */
+  if (!voice.localService) score += 3;
+  if (voice.default) score += 1;
+
+  return score;
+}
+
+/** The best voice for the episode: the listener's stored pick, else the best
+ *  male, else the best of whatever there is. */
+export function bestVoice(locale: string, voices?: SpeechSynthesisVoice[]): SpeechSynthesisVoice | null {
+  const list = voicesFor(locale, voices);
+  if (list.length === 0) return null;
+  const chosen = getStoredVoice(locale);
+  if (chosen) {
+    const match = list.find((voice) => voice.voiceURI === chosen);
+    if (match) return match;
+  }
+  const ranked = [...list].sort((a, b) => scoreVoice(b, locale, true) - scoreVoice(a, locale, true));
+  return ranked[0] ?? null;
+}
+
+export function getStoredVoice(locale: string): string | null {
+  return loadStored()[locale.toLowerCase().replace("_", "-")] ?? null;
+}
+
+export function setStoredVoice(locale: string, voiceURI: string): void {
+  const key = locale.toLowerCase().replace("_", "-");
+  const next = { ...loadStored(), [key]: voiceURI };
+  stored = next;
+  try {
+    window.localStorage.setItem(STORAGE_KEY, JSON.stringify(next));
+  } catch {
+    /* private mode */
+  }
+}
+
+/** True when nothing but the platform's robotic voices exist for `locale`. */
+export function onlyRoboticVoices(locale: string, voices?: SpeechSynthesisVoice[]): boolean {
+  const list = voicesFor(locale, voices);
+  if (list.length === 0) return false;
+  return list.every((voice) => ROBOTIC_HINTS.some((hint) => voice.name.toLowerCase().includes(hint)));
+}
+
+export const MALE_VOICE_HINTS = MALE_NAMES;