feat: Phase 1 - Enhanced feed discovery with validation

- Add validator.js: validateFeedUrl with comments feed detection
- Add discovery.js: discoverAndValidateFeeds with type labels
- Add opml.js: OPML 2.0 export of all subscriptions
- Update reader.js: searchFeeds uses validation, subscribe validates
- Update feeds.js: updateFeedStatus for health tracking
- Update search.njk: Show feed types, validation status, error messages
- Add CSS for badges, notices, and invalid feed styling
- Register OPML export route at /reader/opml

Phase 1 of blogroll implementation plan.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

assets/styles.css

@@ -763,3 +763,108 @@
     width: 100%;
   }
 }
+
+/* ==========================================================================
+   Badges (for feed types, validation status)
+   ========================================================================== */
+
+.badge {
+  border-radius: var(--border-radius);
+  display: inline-block;
+  font-size: var(--font-size-small);
+  font-weight: 500;
+  padding: 2px var(--space-xs);
+  vertical-align: middle;
+}
+
+.badge--info {
+  background: var(--color-primary);
+  color: var(--color-background);
+}
+
+.badge--warning {
+  background: var(--color-warning, #ffcc00);
+  color: #000;
+}
+
+.badge--error {
+  background: var(--color-error, #ff4444);
+  color: #fff;
+}
+
+.badge--success {
+  background: var(--color-success, #22c55e);
+  color: #fff;
+}
+
+/* ==========================================================================
+   Search Enhancements (feed validation)
+   ========================================================================== */
+
+.search__name {
+  display: block;
+  font-weight: 600;
+  margin-bottom: var(--space-xs);
+}
+
+.search__type {
+  margin-left: var(--space-xs);
+}
+
+.search__error {
+  color: var(--color-error, #ff4444);
+  display: block;
+  font-size: var(--font-size-small);
+  margin-top: var(--space-xs);
+}
+
+.search__item--invalid {
+  opacity: 0.7;
+}
+
+.search__item--comments {
+  border-left: 3px solid var(--color-warning, #ffcc00);
+}
+
+.search__invalid-badge {
+  background: var(--color-error, #ff4444);
+  border-radius: var(--border-radius);
+  color: #fff;
+  font-size: var(--font-size-small);
+  font-weight: 500;
+  padding: var(--space-xs) var(--space-s);
+}
+
+.search__subscribe {
+  align-items: center;
+  display: flex;
+  gap: var(--space-s);
+}
+
+/* ==========================================================================
+   Notices (errors, warnings)
+   ========================================================================== */
+
+.notice {
+  border-radius: var(--border-radius);
+  margin-bottom: var(--space-m);
+  padding: var(--space-m);
+}
+
+.notice--error {
+  background: rgba(var(--color-error-rgb, 255, 68, 68), 0.1);
+  border: 1px solid var(--color-error, #ff4444);
+  color: var(--color-error, #ff4444);
+}
+
+.notice--warning {
+  background: rgba(255, 204, 0, 0.1);
+  border: 1px solid var(--color-warning, #ffcc00);
+  color: #856404;
+}
+
+.notice--success {
+  background: rgba(34, 197, 94, 0.1);
+  border: 1px solid var(--color-success, #22c55e);
+  color: var(--color-success, #22c55e);
+}

index.js

@@ -3,6 +3,7 @@ import path from "node:path";
 import express from "express";
 
 import { microsubController } from "./lib/controllers/microsub.js";
+import { opmlController } from "./lib/controllers/opml.js";
 import { readerController } from "./lib/controllers/reader.js";
 import { handleMediaProxy } from "./lib/media/proxy.js";
 import { startScheduler, stopScheduler } from "./lib/polling/scheduler.js";
@@ -97,6 +98,7 @@ export default class MicrosubEndpoint {
     readerRouter.post("/search", readerController.searchFeeds);
     readerRouter.post("/subscribe", readerController.subscribe);
     readerRouter.post("/api/mark-read", readerController.markAllRead);
+    readerRouter.get("/opml", opmlController.exportOpml);
     router.use("/reader", readerRouter);
 
     return router;

lib/controllers/opml.js

@@ -0,0 +1,151 @@
+/**
+ * OPML export controller
+ * @module controllers/opml
+ */
+
+import { getChannels } from "../storage/channels.js";
+import { getFeedsForChannel } from "../storage/feeds.js";
+import { getUserId } from "../utils/auth.js";
+
+/**
+ * Generate OPML export of all subscriptions
+ * GET /opml
+ * @param {object} request - Express request
+ * @param {object} response - Express response
+ * @returns {Promise<void>}
+ */
+async function exportOpml(request, response) {
+  const { application } = request.app.locals;
+  const userId = getUserId(request);
+
+  const channels = await getChannels(application, userId);
+
+  // Build OPML structure
+  const outlines = [];
+
+  for (const channel of channels) {
+    const feeds = await getFeedsForChannel(application, channel._id);
+
+    if (feeds.length === 0) continue;
+
+    const channelOutlines = feeds.map((feed) => ({
+      text: feed.title || extractDomain(feed.url),
+      title: feed.title || "",
+      type: "rss",
+      xmlUrl: feed.url,
+      htmlUrl: deriveSiteUrl(feed.url),
+    }));
+
+    outlines.push({
+      text: channel.name,
+      title: channel.name,
+      children: channelOutlines,
+    });
+  }
+
+  const siteUrl = application.publication?.me || "https://example.com";
+  const siteName = extractDomain(siteUrl);
+
+  const opml = generateOpmlXml({
+    title: `${siteName} - Microsub Subscriptions`,
+    dateCreated: new Date().toUTCString(),
+    ownerName: userId,
+    outlines,
+  });
+
+  response.set("Content-Type", "text/x-opml");
+  response.set(
+    "Content-Disposition",
+    'attachment; filename="subscriptions.opml"',
+  );
+  response.send(opml);
+}
+
+/**
+ * Generate OPML XML from data
+ * @param {object} data - OPML data
+ * @param {string} data.title - Document title
+ * @param {string} data.dateCreated - Creation date
+ * @param {string} data.ownerName - Owner name
+ * @param {Array} data.outlines - Outline items
+ * @returns {string} OPML XML string
+ */
+function generateOpmlXml({ title, dateCreated, ownerName, outlines }) {
+  const renderOutline = (outline, indent = "    ") => {
+    if (outline.children) {
+      const childrenXml = outline.children
+        .map((child) => renderOutline(child, indent + "  "))
+        .join("\n");
+      return `${indent}<outline text="${escapeXml(outline.text)}" title="${escapeXml(outline.title)}">\n${childrenXml}\n${indent}</outline>`;
+    }
+    return `${indent}<outline text="${escapeXml(outline.text)}" title="${escapeXml(outline.title)}" type="${outline.type}" xmlUrl="${escapeXml(outline.xmlUrl)}" htmlUrl="${escapeXml(outline.htmlUrl)}"/>`;
+  };
+
+  const outlinesXml = outlines.map((o) => renderOutline(o)).join("\n");
+
+  return `<?xml version="1.0" encoding="UTF-8"?>
+<opml version="2.0">
+  <head>
+    <title>${escapeXml(title)}</title>
+    <dateCreated>${dateCreated}</dateCreated>
+    <ownerName>${escapeXml(ownerName)}</ownerName>
+  </head>
+  <body>
+${outlinesXml}
+  </body>
+</opml>`;
+}
+
+/**
+ * Escape XML special characters
+ * @param {string} str - String to escape
+ * @returns {string} Escaped string
+ */
+function escapeXml(str) {
+  if (!str) return "";
+  return String(str)
+    .replace(/&/g, "&amp;")
+    .replace(/</g, "&lt;")
+    .replace(/>/g, "&gt;")
+    .replace(/"/g, "&quot;")
+    .replace(/'/g, "&apos;");
+}
+
+/**
+ * Extract domain from URL
+ * @param {string} url - URL to extract domain from
+ * @returns {string} Domain
+ */
+function extractDomain(url) {
+  try {
+    return new URL(url).hostname;
+  } catch {
+    return url;
+  }
+}
+
+/**
+ * Derive site URL from feed URL
+ * @param {string} feedUrl - Feed URL
+ * @returns {string} Site URL
+ */
+function deriveSiteUrl(feedUrl) {
+  try {
+    const url = new URL(feedUrl);
+    // Remove common feed paths
+    const path = url.pathname
+      .replace(/\/feed\/?$/, "")
+      .replace(/\/rss\/?$/, "")
+      .replace(/\/atom\.xml$/, "")
+      .replace(/\/rss\.xml$/, "")
+      .replace(/\/feed\.xml$/, "")
+      .replace(/\/index\.xml$/, "")
+      .replace(/\.rss$/, "")
+      .replace(/\.atom$/, "");
+    return `${url.origin}${path || "/"}`;
+  } catch {
+    return feedUrl;
+  }
+}
+
+export const opmlController = { exportOpml };

lib/controllers/reader.js

@@ -3,7 +3,8 @@
  * @module controllers/reader
  */
 
-import { discoverFeedsFromUrl } from "../feeds/fetcher.js";
+import { discoverAndValidateFeeds } from "../feeds/discovery.js";
+import { validateFeedUrl } from "../feeds/validator.js";
 import { refreshFeedNow } from "../polling/scheduler.js";
 import {
   getChannels,
@@ -585,7 +586,7 @@ export async function searchPage(request, response) {
 }
 
 /**
- * Search for feeds from URL
+ * Search for feeds from URL - enhanced with validation
  * @param {object} request - Express request
  * @param {object} response - Express response
  * @returns {Promise<void>}
@@ -598,11 +599,14 @@ export async function searchFeeds(request, response) {
   const channelList = await getChannels(application, userId);
 
   let results = [];
+  let discoveryError = null;
+
   if (query) {
     try {
-      results = await discoverFeedsFromUrl(query);
+      // Use enhanced discovery with validation
-    } catch {
+      results = await discoverAndValidateFeeds(query);
-      // Ignore discovery errors
+    } catch (error) {
+      discoveryError = error.message;
     }
   }
 
@@ -611,13 +615,14 @@ export async function searchFeeds(request, response) {
     channels: channelList,
     query,
     results,
+    discoveryError,
     searched: true,
     baseUrl: request.baseUrl,
   });
 }
 
 /**
- * Subscribe to a feed from search results
+ * Subscribe to a feed from search results - with validation
  * @param {object} request - Express request
  * @param {object} response - Express response
  * @returns {Promise<void>}
@@ -625,13 +630,34 @@ export async function searchFeeds(request, response) {
 export async function subscribe(request, response) {
   const { application } = request.app.locals;
   const userId = getUserId(request);
-  const { url, channel: channelUid } = request.body;
+  const { url, channel: channelUid, skipValidation } = request.body;
 
   const channelDocument = await getChannel(application, channelUid, userId);
   if (!channelDocument) {
     return response.status(404).render("404");
   }
 
+  // Validate feed unless explicitly skipped (for power users)
+  if (!skipValidation) {
+    const validation = await validateFeedUrl(url);
+
+    if (!validation.valid) {
+      const channelList = await getChannels(application, userId);
+      return response.render("search", {
+        title: request.__("microsub.search.title"),
+        channels: channelList,
+        query: url,
+        validationError: validation.error,
+        baseUrl: request.baseUrl,
+      });
+    }
+
+    // Warn about comments feeds but allow subscription
+    if (validation.isCommentsFeed) {
+      console.warn(`[Microsub] Subscribing to comments feed: ${url}`);
+    }
+  }
+
   // Create feed subscription
   const feed = await createFeed(application, {
     channelId: channelDocument._id,

lib/feeds/discovery.js

@@ -0,0 +1,95 @@
+/**
+ * Enhanced feed discovery with type labels and validation
+ * @module feeds/discovery
+ */
+
+import { discoverFeedsFromUrl } from "./fetcher.js";
+import { validateFeedUrl } from "./validator.js";
+
+/**
+ * Feed type display labels
+ */
+const FEED_TYPE_LABELS = {
+  rss: "RSS Feed",
+  atom: "Atom Feed",
+  jsonfeed: "JSON Feed",
+  hfeed: "h-feed (Microformats)",
+  activitypub: "ActivityPub",
+  unknown: "Unknown",
+};
+
+/**
+ * Discover and validate all feeds from a URL
+ * @param {string} url - Page or feed URL
+ * @returns {Promise<Array>} Array of discovered feeds with validation status
+ */
+export async function discoverAndValidateFeeds(url) {
+  // First discover feeds from the URL
+  const feeds = await discoverFeedsFromUrl(url);
+
+  // If no feeds found, return empty with error info
+  if (feeds.length === 0) {
+    return [
+      {
+        url,
+        type: "unknown",
+        typeLabel: "No feed found",
+        valid: false,
+        error: "No feeds were discovered at this URL",
+        isCommentsFeed: false,
+      },
+    ];
+  }
+
+  // Validate each discovered feed in parallel
+  const validatedFeeds = await Promise.all(
+    feeds.map(async (feed) => {
+      const validation = await validateFeedUrl(feed.url);
+
+      return {
+        url: feed.url,
+        type: validation.feedType || feed.type,
+        typeLabel:
+          FEED_TYPE_LABELS[validation.feedType] ||
+          FEED_TYPE_LABELS[feed.type] ||
+          "Feed",
+        valid: validation.valid,
+        error: validation.error,
+        isCommentsFeed: validation.isCommentsFeed || false,
+        title: validation.title || feed.title,
+        rel: feed.rel,
+      };
+    }),
+  );
+
+  // Sort: valid feeds first, non-comments before comments, then alphabetically
+  return validatedFeeds.sort((a, b) => {
+    // Valid feeds first
+    if (a.valid !== b.valid) return a.valid ? -1 : 1;
+    // Non-comments before comments
+    if (a.isCommentsFeed !== b.isCommentsFeed) return a.isCommentsFeed ? 1 : -1;
+    // Then by URL
+    return a.url.localeCompare(b.url);
+  });
+}
+
+/**
+ * Filter to only main content feeds (exclude comments)
+ * @param {Array} feeds - Array of feed objects
+ * @returns {Array} Filtered array of main content feeds
+ */
+export function filterMainFeeds(feeds) {
+  return feeds.filter((feed) => feed.valid && !feed.isCommentsFeed);
+}
+
+/**
+ * Get the best feed from a list (first valid, non-comments feed)
+ * @param {Array} feeds - Array of feed objects
+ * @returns {object|undefined} Best feed or undefined
+ */
+export function getBestFeed(feeds) {
+  const mainFeeds = filterMainFeeds(feeds);
+  return mainFeeds.length > 0 ? mainFeeds[0] : undefined;
+}
+
+export { FEED_TYPE_LABELS };

lib/feeds/validator.js

@@ -0,0 +1,128 @@
+/**
+ * Feed validation utilities
+ * @module feeds/validator
+ */
+
+import { fetchFeed } from "./fetcher.js";
+import { detectFeedType } from "./parser.js";
+
+/**
+ * Feed types that are valid subscriptions
+ */
+const VALID_FEED_TYPES = ["rss", "atom", "jsonfeed", "hfeed"];
+
+/**
+ * Patterns that indicate a comments feed (not a main feed)
+ */
+const COMMENTS_PATTERNS = [
+  /\/comments\/?$/i,
+  /\/feed\/comments/i,
+  /commentsfeed/i,
+  /comment-feed/i,
+  /-comments\.xml$/i,
+  /\/replies\/?$/i,
+  /comments\.rss$/i,
+  /comments\.atom$/i,
+];
+
+/**
+ * Validate a URL is actually a feed
+ * @param {string} url - URL to validate
+ * @returns {Promise<object>} Validation result
+ */
+export async function validateFeedUrl(url) {
+  try {
+    const result = await fetchFeed(url, { timeout: 15000 });
+
+    if (result.notModified || !result.content) {
+      return {
+        valid: false,
+        error: "Unable to fetch content from URL",
+      };
+    }
+
+    const feedType = detectFeedType(result.content, result.contentType);
+
+    if (feedType === "activitypub") {
+      return {
+        valid: false,
+        error:
+          "URL returns ActivityPub JSON instead of a feed. Try the direct feed URL.",
+        feedType,
+      };
+    }
+
+    if (!VALID_FEED_TYPES.includes(feedType)) {
+      return {
+        valid: false,
+        error: `URL does not contain a valid feed (detected: ${feedType})`,
+        feedType,
+      };
+    }
+
+    // Check if it's a comments feed
+    const isCommentsFeed = COMMENTS_PATTERNS.some((pattern) =>
+      pattern.test(url),
+    );
+
+    return {
+      valid: true,
+      feedType,
+      isCommentsFeed,
+      title: extractFeedTitle(result.content, feedType),
+      contentType: result.contentType,
+    };
+  } catch (error) {
+    return {
+      valid: false,
+      error: error.message,
+    };
+  }
+}
+
+/**
+ * Extract feed title from content
+ * @param {string} content - Feed content
+ * @param {string} feedType - Type of feed
+ * @returns {string|undefined} Feed title
+ */
+function extractFeedTitle(content, feedType) {
+  if (feedType === "jsonfeed") {
+    try {
+      const json = JSON.parse(content);
+      return json.title;
+    } catch {
+      return undefined;
+    }
+  }
+
+  // Extract title from XML (RSS or Atom)
+  // Try channel/title first (RSS), then just title (Atom)
+  const channelTitleMatch = content.match(
+    /<channel[^>]*>[\s\S]*?<title[^>]*>([^<]+)<\/title>/i,
+  );
+  if (channelTitleMatch) {
+    return decodeXmlEntities(channelTitleMatch[1].trim());
+  }
+
+  const titleMatch = content.match(/<title[^>]*>([^<]+)<\/title>/i);
+  return titleMatch ? decodeXmlEntities(titleMatch[1].trim()) : undefined;
+}
+
+/**
+ * Decode XML entities
+ * @param {string} str - String with XML entities
+ * @returns {string} Decoded string
+ */
+function decodeXmlEntities(str) {
+  return str
+    .replace(/&amp;/g, "&")
+    .replace(/&lt;/g, "<")
+    .replace(/&gt;/g, ">")
+    .replace(/&quot;/g, '"')
+    .replace(/&apos;/g, "'")
+    .replace(/&#(\d+);/g, (_, code) => String.fromCharCode(parseInt(code, 10)))
+    .replace(/&#x([0-9a-fA-F]+);/g, (_, code) =>
+      String.fromCharCode(parseInt(code, 16)),
+    );
+}

lib/storage/feeds.js

@@ -297,3 +297,68 @@ export async function updateFeedWebsub(application, id, websub) {
 export async function getFeedBySubscriptionId(application, subscriptionId) {
   return getFeedById(application, subscriptionId);
 }
+
+/**
+ * Update feed status after processing
+ * Tracks health status, errors, and success metrics
+ * @param {object} application - Indiekit application
+ * @param {ObjectId|string} id - Feed ObjectId
+ * @param {object} status - Status update
+ * @param {boolean} status.success - Whether fetch was successful
+ * @param {string} [status.error] - Error message if failed
+ * @param {number} [status.itemCount] - Number of items in feed
+ * @returns {Promise<object|null>} Updated feed
+ */
+export async function updateFeedStatus(application, id, status) {
+  const collection = getCollection(application);
+  const objectId = typeof id === "string" ? new ObjectId(id) : id;
+
+  const updateFields = {
+    updatedAt: new Date(),
+  };
+
+  if (status.success) {
+    updateFields.status = "active";
+    updateFields.lastSuccessAt = new Date();
+    updateFields.consecutiveErrors = 0;
+    updateFields.lastError = undefined;
+    updateFields.lastErrorAt = undefined;
+
+    if (status.itemCount !== undefined) {
+      updateFields.itemCount = status.itemCount;
+    }
+  } else {
+    updateFields.status = "error";
+    updateFields.lastError = status.error;
+    updateFields.lastErrorAt = new Date();
+  }
+
+  // Use $set for most fields, $inc for consecutiveErrors on failure
+  const updateOp = { $set: updateFields };
+
+  if (!status.success) {
+    // Increment consecutive errors
+    updateOp.$inc = { consecutiveErrors: 1 };
+  }
+
+  return collection.findOneAndUpdate({ _id: objectId }, updateOp, {
+    returnDocument: "after",
+  });
+}
+
+/**
+ * Get feeds with errors
+ * @param {object} application - Indiekit application
+ * @param {number} [minErrors=3] - Minimum consecutive errors
+ * @returns {Promise<Array>} Array of feeds with errors
+ */
+export async function getFeedsWithErrors(application, minErrors = 3) {
+  const collection = getCollection(application);
+
+  return collection
+    .find({
+      status: "error",
+      consecutiveErrors: { $gte: minErrors },
+    })
+    .toArray();
+}

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@rmdes/indiekit-endpoint-microsub",
-  "version": "1.0.22",
+  "version": "1.0.23",
   "description": "Microsub endpoint for Indiekit. Enables subscribing to feeds and reading content using the Microsub protocol.",
   "keywords": [
     "indiekit",

views/search.njk

@@ -25,16 +25,40 @@
       </div>
     </form>
 
+    {% if validationError %}
+    <div class="notice notice--error">
+      <p>{{ validationError }}</p>
+    </div>
+    {% endif %}
+
+    {% if discoveryError %}
+    <div class="notice notice--error">
+      <p>{{ discoveryError }}</p>
+    </div>
+    {% endif %}
+
     {% if results and results.length > 0 %}
     <div class="search__results">
       <h3>{{ __("microsub.search.title") }}</h3>
       <div class="search__list">
         {% for result in results %}
-        <div class="search__item">
+        <div class="search__item{% if not result.valid %} search__item--invalid{% endif %}{% if result.isCommentsFeed %} search__item--comments{% endif %}">
           <div class="search__feed">
-            <span class="search__name">{{ result.title or "Feed" }}</span>
+            <span class="search__name">
+              {{ result.title or "Feed" }}
+              <span class="search__type badge badge--{% if result.valid %}info{% else %}warning{% endif %}">
+                {{ result.typeLabel }}
+              </span>
+              {% if result.isCommentsFeed %}
+              <span class="search__type badge badge--warning">Comments</span>
+              {% endif %}
+            </span>
             <span class="search__url">{{ result.url | replace("https://", "") | replace("http://", "") }}</span>
+            {% if not result.valid %}
+            <span class="search__error">{{ result.error }}</span>
+            {% endif %}
           </div>
+          {% if result.valid %}
           <form method="post" action="{{ baseUrl }}/subscribe" class="search__subscribe">
             <input type="hidden" name="url" value="{{ result.url }}">
             <label for="channel-{{ loop.index }}" class="visually-hidden">{{ __("microsub.channels.title") }}</label>
@@ -48,6 +72,9 @@
               classes: "button--small"
             }) }}
           </form>
+          {% else %}
+          <span class="search__invalid-badge">Invalid</span>
+          {% endif %}
         </div>
         {% endfor %}
       </div>