Add feed discovery plugin

plugins/feed-discovery/src/providers/opml-directory.ts

@@ -0,0 +1,92 @@
+import { readFile } from "node:fs/promises";
+import { XMLParser } from "fast-xml-parser";
+import type { DiscoveredFeed, FeedDiscoveryProvider, FeedDiscoveryQuery } from "../types.js";
+
+const parser = new XMLParser({
+  ignoreAttributes: false,
+  attributeNamePrefix: "",
+  textNodeName: "text"
+});
+
+export class OpmlDirectoryProvider implements FeedDiscoveryProvider {
+  id = "opml-directory";
+  name = "OPML Directory";
+  enabledByDefault = true;
+  requiresApiKey = false;
+
+  constructor(private readonly paths: string[] = []) {}
+
+  async search(query: FeedDiscoveryQuery) {
+    const feeds: DiscoveredFeed[] = [];
+    for (const path of this.paths) {
+      const content = await readFile(path, "utf8");
+      const parsed = parser.parse(content) as unknown;
+      for (const outline of collectOutlines(parsed)) {
+        const feedUrl = stringValue(outline.xmlUrl);
+        if (!feedUrl) {
+          continue;
+        }
+        const title = stringValue(outline.title) || stringValue(outline.text) || feedUrl;
+        const tags = [stringValue(outline.category)].filter((tag): tag is string => Boolean(tag));
+        const feed: DiscoveredFeed = {
+          title,
+          description: stringValue(outline.description),
+          homepageUrl: stringValue(outline.htmlUrl),
+          feedUrl,
+          kind: inferKind(tags.join(" "), query.type),
+          provider: this.id,
+          score: 0,
+          confidence: 0.7,
+          tags
+        };
+        if (matches(feed, query)) {
+          feeds.push(feed);
+        }
+      }
+    }
+    return feeds;
+  }
+}
+
+function collectOutlines(value: unknown): Array<Record<string, unknown>> {
+  if (!isRecord(value)) {
+    return [];
+  }
+  const current = "xmlUrl" in value ? [value] : [];
+  return [
+    ...current,
+    ...Object.values(value).flatMap((entry) => {
+      if (Array.isArray(entry)) {
+        return entry.flatMap(collectOutlines);
+      }
+      return collectOutlines(entry);
+    })
+  ];
+}
+
+function matches(feed: DiscoveredFeed, query: FeedDiscoveryQuery) {
+  if (query.type && query.type !== "all" && feed.kind !== query.type) {
+    return false;
+  }
+  const terms = query.q.toLowerCase().split(/[^a-z0-9]+/).filter(Boolean);
+  const haystack = [feed.title, feed.description, feed.homepageUrl, feed.feedUrl, feed.tags.join(" ")].join(" ").toLowerCase();
+  return terms.length === 0 || terms.some((term) => haystack.includes(term));
+}
+
+function inferKind(tags: string, requested?: FeedDiscoveryQuery["type"]) {
+  if (requested && requested !== "all") {
+    return requested;
+  }
+  if (tags.includes("podcast")) {
+    return "podcast";
+  }
+  return "opml";
+}
+
+function stringValue(value: unknown) {
+  return typeof value === "string" && value.trim() ? value.trim() : undefined;
+}
+
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null && !Array.isArray(value);
+}