feat: add record building with threshold and input validation

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/lib/record.js

@@ -0,0 +1,53 @@
+import { isVideoId } from './video-id.js';
+
+const PAGES = new Set(['home', 'watch', 'search', 'channel']);
+const MAX_TEXT = 300;
+
+export function shouldSave({ views, outlierScore }, { threshold, minViews }) {
+  return typeof outlierScore === 'number' && outlierScore >= threshold && views >= minViews;
+}
+
+const finiteOrNull = (value) => (typeof value === 'number' && Number.isFinite(value) ? value : null);
+const textOrNull = (value) => (typeof value === 'string' && value.trim() ? value.trim().slice(0, MAX_TEXT) : null);
+const urlOrNull = (value, prefix) => (typeof value === 'string' && value.startsWith(prefix) ? value : null);
+
+// Validates a message coming from the content script before anything is stored.
+export function sanitizeItem(raw) {
+  if (!raw || !isVideoId(raw.videoId)) return null;
+  const outlierScore = finiteOrNull(raw.outlierScore);
+  const views = finiteOrNull(raw.views);
+  if (outlierScore === null || outlierScore < 0 || views === null || views < 0) return null;
+  const subscribers = finiteOrNull(raw.subscribers);
+  return {
+    videoId: raw.videoId,
+    title: textOrNull(raw.title),
+    thumbnailUrl: urlOrNull(raw.thumbnailUrl, 'https://i.ytimg.com/'),
+    channelTitle: textOrNull(raw.channelTitle),
+    channelUrl: urlOrNull(raw.channelUrl, 'https://www.youtube.com/'),
+    subscribers: subscribers !== null && subscribers >= 0 ? subscribers : null,
+    views,
+    outlierScore: Math.round(outlierScore * 100) / 100,
+    isShort: raw.isShort === true,
+    page: PAGES.has(raw.page) ? raw.page : 'home',
+  };
+}
+
+export function buildRecord(item, previous, settings, now = new Date()) {
+  if (!previous && !shouldSave(item, settings)) return null;
+  const nowIso = now.toISOString();
+  return {
+    videoId: item.videoId,
+    title: item.title ?? previous?.title ?? item.videoId,
+    url: `https://www.youtube.com/watch?v=${item.videoId}`,
+    thumbnailUrl: item.thumbnailUrl ?? previous?.thumbnailUrl ?? null,
+    channelTitle: item.channelTitle ?? previous?.channelTitle ?? null,
+    channelUrl: item.channelUrl ?? previous?.channelUrl ?? null,
+    subscribers: item.subscribers ?? previous?.subscribers ?? null,
+    views: item.views,
+    outlierScore: item.outlierScore,
+    isShort: item.isShort || previous?.isShort || false,
+    foundOn: previous?.foundOn ?? item.page,
+    firstSeenAt: previous?.firstSeenAt ?? nowIso,
+    updatedAt: nowIso,
+  };
+}