Add feed discovery plugin

plugins/feed-discovery/src/scoring.ts

@@ -0,0 +1,95 @@
+import type { DiscoveredFeed, FeedDiscoveryQuery } from "./types.js";
+
+const PROVIDER_SCORES: Record<string, number> = {
+  "manual-curated": 1,
+  podcastindex: 0.9,
+  "itunes-podcast": 0.85,
+  "opml-directory": 0.75,
+  "web-feed-probe": 0.7,
+  rsshub: 0.7,
+  reddit: 0.65,
+  github: 0.65,
+  youtube: 0.65,
+  unknown: 0.3
+};
+
+export function scoreFeed(feed: DiscoveredFeed, query: FeedDiscoveryQuery): DiscoveredFeed {
+  const keywordScore = feed.keywordScore ?? calculateKeywordScore(feed, query.q);
+  const freshnessScore = feed.freshnessScore ?? calculateFreshnessScore(feed.lastPublishedAt);
+  const providerScore = feed.providerScore ?? PROVIDER_SCORES[feed.provider] ?? PROVIDER_SCORES.unknown;
+  const validationScore = feed.validationScore ?? (feed.isValid === false ? 0.2 : 1);
+  const score = keywordScore * 0.4 + freshnessScore * 0.25 + providerScore * 0.2 + validationScore * 0.15;
+
+  return {
+    ...feed,
+    score: round(score),
+    confidence: round(Math.max(feed.confidence, score * validationScore)),
+    freshnessScore: round(freshnessScore),
+    keywordScore: round(keywordScore),
+    providerScore: round(providerScore),
+    validationScore: round(validationScore)
+  };
+}
+
+export function calculateKeywordScore(feed: DiscoveredFeed, query: string) {
+  const terms = normalizeTerms(query);
+  if (terms.length === 0) {
+    return 0.1;
+  }
+
+  const weightedText = [
+    [feed.title, 0.35],
+    [feed.description, 0.2],
+    [feed.homepageUrl, 0.1],
+    [feed.feedUrl, 0.05],
+    [feed.tags.join(" "), 0.15],
+    [feed.sampleItems?.map((item) => item.title).join(" "), 0.15]
+  ] as const;
+
+  let score = 0;
+  for (const [value, weight] of weightedText) {
+    const text = String(value ?? "").toLowerCase();
+    if (!text) {
+      continue;
+    }
+    const matches = terms.filter((term) => text.includes(term)).length;
+    score += weight * (matches / terms.length);
+  }
+
+  return Math.min(1, Math.max(0.05, score));
+}
+
+export function calculateFreshnessScore(lastPublishedAt?: string) {
+  if (!lastPublishedAt) {
+    return 0.1;
+  }
+  const ageDays = (Date.now() - Date.parse(lastPublishedAt)) / 86_400_000;
+  if (!Number.isFinite(ageDays) || ageDays < 0) {
+    return 0.1;
+  }
+  if (ageDays <= 7) {
+    return 1;
+  }
+  if (ageDays <= 30) {
+    return 0.8;
+  }
+  if (ageDays <= 90) {
+    return 0.6;
+  }
+  if (ageDays <= 365) {
+    return 0.3;
+  }
+  return 0.1;
+}
+
+function normalizeTerms(query: string) {
+  return query
+    .toLowerCase()
+    .split(/[^a-z0-9]+/)
+    .map((term) => term.trim())
+    .filter(Boolean);
+}
+
+function round(value: number) {
+  return Math.round(value * 1000) / 1000;
+}