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apps/miniprogram/utils/ttsSettings.js

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+/* global module */
+
+/**
+ * 终端播报长度配置拆成“总量”和“单段”两层：
+ * 1. 总量决定一轮回答最多取多少正文；
+ * 2. 单段决定每次送给 TTS 的请求大小，用来压低首段等待时延；
+ * 3. 单段限制必须保守落在 gateway 当前长度校验之内；
+ * 4. “分片长度”只控制单段字符窗口，实际仍会再受 UTF-8 byte 上限兜底。
+ */
+const DEFAULT_TTS_SPEAKABLE_MAX_CHARS = 500;
+const MIN_TTS_SPEAKABLE_MAX_CHARS = 120;
+const MAX_TTS_SPEAKABLE_MAX_CHARS = 1200;
+const DEFAULT_TTS_SEGMENT_MAX_CHARS = 80;
+const MIN_TTS_SEGMENT_MAX_CHARS = 40;
+const MAX_TTS_SEGMENT_MAX_CHARS = 200;
+const TTS_SEGMENT_MAX_CHARS = DEFAULT_TTS_SEGMENT_MAX_CHARS;
+const TTS_SEGMENT_MAX_UTF8_BYTES = DEFAULT_TTS_SEGMENT_MAX_CHARS * 3;
+
+function normalizeTtsSpeakableMaxChars(value) {
+  const parsed = Number(value);
+  if (!Number.isFinite(parsed)) {
+    return DEFAULT_TTS_SPEAKABLE_MAX_CHARS;
+  }
+  const normalized = Math.round(parsed);
+  if (normalized < MIN_TTS_SPEAKABLE_MAX_CHARS) {
+    return MIN_TTS_SPEAKABLE_MAX_CHARS;
+  }
+  if (normalized > MAX_TTS_SPEAKABLE_MAX_CHARS) {
+    return MAX_TTS_SPEAKABLE_MAX_CHARS;
+  }
+  return normalized;
+}
+
+function normalizeTtsSegmentMaxChars(value) {
+  const parsed = Number(value);
+  if (!Number.isFinite(parsed)) {
+    return DEFAULT_TTS_SEGMENT_MAX_CHARS;
+  }
+  const normalized = Math.round(parsed);
+  if (normalized < MIN_TTS_SEGMENT_MAX_CHARS) {
+    return MIN_TTS_SEGMENT_MAX_CHARS;
+  }
+  if (normalized > MAX_TTS_SEGMENT_MAX_CHARS) {
+    return MAX_TTS_SEGMENT_MAX_CHARS;
+  }
+  return normalized;
+}
+
+/**
+ * 总量截断只负责控制“这一轮最多保留多少正文”，并不直接对应单次网关请求。
+ * 对中文按 3 bytes/字估算，可让 500 字正文完整进入后续分段流程。
+ */
+function resolveTtsSpeakableUtf8ByteLimit(maxChars) {
+  const normalized = normalizeTtsSpeakableMaxChars(maxChars);
+  return Math.max(TTS_SEGMENT_MAX_UTF8_BYTES, Math.min(normalized * 3, MAX_TTS_SPEAKABLE_MAX_CHARS * 3));
+}
+
+/**
+ * 单段 byte 限制始终卡在安全阈值内：
+ * 1. 默认 80 字对应 240 bytes；
+ * 2. 即使用户把分片长度调大，最终也不会超过 360 bytes；
+ * 3. 这样可避免单段再次撞到网关 450 bytes 的校验。
+ */
+function resolveTtsSegmentUtf8ByteLimit(maxChars) {
+  const normalized = normalizeTtsSegmentMaxChars(maxChars);
+  return Math.max(TTS_SEGMENT_MAX_UTF8_BYTES, Math.min(normalized * 3, 360));
+}
+
+module.exports = {
+  DEFAULT_TTS_SPEAKABLE_MAX_CHARS,
+  MIN_TTS_SPEAKABLE_MAX_CHARS,
+  MAX_TTS_SPEAKABLE_MAX_CHARS,
+  DEFAULT_TTS_SEGMENT_MAX_CHARS,
+  MIN_TTS_SEGMENT_MAX_CHARS,
+  MAX_TTS_SEGMENT_MAX_CHARS,
+  TTS_SEGMENT_MAX_CHARS,
+  TTS_SEGMENT_MAX_UTF8_BYTES,
+  normalizeTtsSpeakableMaxChars,
+  normalizeTtsSegmentMaxChars,
+  resolveTtsSpeakableUtf8ByteLimit,
+  resolveTtsSegmentUtf8ByteLimit
+};