feat: add legacy webmention recovery from old URLs

- Add urlAliases.js to parse redirect maps and build old→new URL mappings
- Enhance webmentionsForUrl filter to check legacy URLs (micro.blog, Known/WP)
- Update webmentions.njk to pass urlAliases data
- Add webmention-debug.njk page at /debug/webmentions/

This recovers webmentions sent to old URL structures:
- micro.blog: /YYYY/MM/DD/slug.html
- Known/WordPress: /YYYY/slug

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

_data/urlAliases.js

@@ -0,0 +1,139 @@
+/**
+ * URL Aliases for Webmention Recovery
+ *
+ * Maps new URLs to their old URLs so webmentions from previous
+ * URL structures can be displayed on current pages.
+ *
+ * Sources:
+ * - redirects.map.rmendes (micro.blog: /YYYY/MM/DD/slug.html → /notes/...)
+ * - old-blog-redirects.map.rmendes (Known/WP: /YYYY/slug → /content/...)
+ */
+
+import { readFileSync, existsSync } from "fs";
+import { resolve, dirname } from "path";
+import { fileURLToPath } from "url";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const siteUrl = process.env.SITE_URL || "https://example.com";
+
+/**
+ * Parse a redirect map file into URL mappings
+ * Format: old_path new_path;
+ */
+function parseRedirectMap(filePath) {
+  const aliases = {};
+
+  if (!existsSync(filePath)) {
+    console.log(`[urlAliases] File not found: ${filePath}`);
+    return aliases;
+  }
+
+  try {
+    const content = readFileSync(filePath, "utf-8");
+    const lines = content.split("\n").filter((line) => {
+      const trimmed = line.trim();
+      return trimmed && !trimmed.startsWith("#");
+    });
+
+    for (const line of lines) {
+      // Format: /old/path /new/path;
+      const match = line.match(/^(\S+)\s+(\S+);?$/);
+      if (match) {
+        const [, oldPath, newPath] = match;
+        // Normalize paths (remove trailing slashes, ensure leading slash)
+        const normalizedNew = newPath.replace(/;$/, "").replace(/\/$/, "");
+        const normalizedOld = oldPath.replace(/\/$/, "");
+
+        // Map new URL → array of old URLs
+        if (!aliases[normalizedNew]) {
+          aliases[normalizedNew] = [];
+        }
+        aliases[normalizedNew].push(normalizedOld);
+      }
+    }
+  } catch (error) {
+    console.error(`[urlAliases] Error parsing ${filePath}:`, error.message);
+  }
+
+  return aliases;
+}
+
+/**
+ * Merge multiple alias maps
+ */
+function mergeAliases(...maps) {
+  const merged = {};
+  for (const map of maps) {
+    for (const [newUrl, oldUrls] of Object.entries(map)) {
+      if (!merged[newUrl]) {
+        merged[newUrl] = [];
+      }
+      merged[newUrl].push(...oldUrls);
+    }
+  }
+  return merged;
+}
+
+// Parse redirect maps from package root (one level up from _data)
+const pkgRoot = resolve(__dirname, "../..");
+
+// Try multiple possible locations
+const mapLocations = [
+  resolve(pkgRoot, "redirects.map.rmendes"),
+  resolve(pkgRoot, "old-blog-redirects.map.rmendes"),
+  // Fallback to template files if .rmendes versions don't exist
+  resolve(pkgRoot, "redirects.map"),
+  resolve(pkgRoot, "old-blog-redirects.map"),
+];
+
+const microblogAliases = parseRedirectMap(mapLocations[0]) || parseRedirectMap(mapLocations[2]);
+const knownAliases = parseRedirectMap(mapLocations[1]) || parseRedirectMap(mapLocations[3]);
+
+const allAliases = mergeAliases(microblogAliases, knownAliases);
+
+// Log summary
+const totalMappings = Object.keys(allAliases).length;
+const totalOldUrls = Object.values(allAliases).reduce((sum, urls) => sum + urls.length, 0);
+console.log(`[urlAliases] Loaded ${totalMappings} URL mappings with ${totalOldUrls} old URLs`);
+
+export default {
+  // The merged alias map: new URL → [old URLs]
+  aliases: allAliases,
+
+  // Site URL for building absolute URLs
+  siteUrl,
+
+  /**
+   * Get all URLs (old and new) that should be checked for webmentions
+   * @param {string} url - Current page URL (relative)
+   * @returns {string[]} - Array of absolute URLs to check
+   */
+  getAllUrls(url) {
+    const normalizedUrl = url.replace(/\/$/, "");
+    const urls = [
+      `${siteUrl}${url}`,
+      `${siteUrl}${normalizedUrl}`,
+    ];
+
+    // Add old URL variations
+    const oldUrls = allAliases[normalizedUrl] || [];
+    for (const oldUrl of oldUrls) {
+      urls.push(`${siteUrl}${oldUrl}`);
+      // Also try with trailing slash
+      urls.push(`${siteUrl}${oldUrl}/`);
+    }
+
+    // Deduplicate
+    return [...new Set(urls)];
+  },
+
+  /**
+   * Get just the old URLs for a given new URL
+   * @param {string} url - Current page URL (relative)
+   * @returns {string[]} - Array of old relative URLs
+   */
+  getOldUrls(url) {
+    const normalizedUrl = url.replace(/\/$/, "");
+    return allAliases[normalizedUrl] || [];
+  },
+};

_includes/components/webmentions.njk

@@ -1,7 +1,8 @@
 {# Webmentions Component #}
 {# Displays likes, reposts, and replies for a post #}
+{# Also checks legacy URLs from micro.blog and old blog for historical webmentions #}
 
-{% set mentions = webmentions | webmentionsForUrl(page.url) %}
+{% set mentions = webmentions | webmentionsForUrl(page.url, urlAliases) %}
 
 {% if mentions.length %}
 <section class="webmentions mt-8 pt-8 border-t border-surface-200 dark:border-surface-700" id="webmentions">

eleventy.config.js

@@ -235,17 +235,33 @@ export default function (eleventyConfig) {
     return date.toLocaleDateString("en-US", options);
   });
 
-  // Webmention filters
-  eleventyConfig.addFilter("webmentionsForUrl", function (webmentions, url) {
+  // Webmention filters - with legacy URL support
+  // This filter checks both current URL and any legacy URLs from redirects
+  eleventyConfig.addFilter("webmentionsForUrl", function (webmentions, url, urlAliases) {
     if (!webmentions || !url) return [];
-    const absoluteUrl = url.startsWith("http")
-      ? url
-      : `${siteUrl}${url}`;
-    return webmentions.filter(
-      (wm) =>
-        wm["wm-target"] === absoluteUrl ||
-        wm["wm-target"] === absoluteUrl.replace(/\/$/, "")
-    );
+
+    // Build list of all URLs to check (current + legacy)
+    const urlsToCheck = new Set();
+
+    // Add current URL variations
+    const absoluteUrl = url.startsWith("http") ? url : `${siteUrl}${url}`;
+    urlsToCheck.add(absoluteUrl);
+    urlsToCheck.add(absoluteUrl.replace(/\/$/, ""));
+    urlsToCheck.add(absoluteUrl.endsWith("/") ? absoluteUrl : `${absoluteUrl}/`);
+
+    // Add legacy URLs from aliases (if provided)
+    if (urlAliases?.aliases) {
+      const normalizedUrl = url.replace(/\/$/, "");
+      const oldUrls = urlAliases.aliases[normalizedUrl] || [];
+      for (const oldUrl of oldUrls) {
+        urlsToCheck.add(`${siteUrl}${oldUrl}`);
+        urlsToCheck.add(`${siteUrl}${oldUrl}/`);
+        urlsToCheck.add(`${siteUrl}${oldUrl}`.replace(/\/$/, ""));
+      }
+    }
+
+    // Filter webmentions matching any of our URLs
+    return webmentions.filter((wm) => urlsToCheck.has(wm["wm-target"]));
   });
 
   eleventyConfig.addFilter("webmentionsByType", function (mentions, type) {

webmention-debug.njk

@@ -0,0 +1,123 @@
+---
+layout: layouts/base.njk
+title: Webmention Debug
+permalink: /debug/webmentions/
+eleventyExcludeFromCollections: true
+---
+<div class="page-header mb-8">
+  <h1 class="text-3xl font-bold text-surface-900 dark:text-surface-100 mb-2">Webmention Debug</h1>
+  <p class="text-surface-600 dark:text-surface-400">
+    Debug page for webmention recovery from legacy URLs.
+    This page is excluded from collections and won't appear in feeds.
+  </p>
+</div>
+
+<div class="space-y-8">
+  {# Summary #}
+  <section class="p-4 bg-surface-100 dark:bg-surface-800 rounded-lg">
+    <h2 class="text-xl font-bold mb-4">Summary</h2>
+    <dl class="grid grid-cols-2 gap-4 text-sm">
+      <div>
+        <dt class="font-semibold text-surface-600 dark:text-surface-400">Total URL Mappings</dt>
+        <dd class="text-2xl font-bold">{{ urlAliases.aliases | length }}</dd>
+      </div>
+      <div>
+        <dt class="font-semibold text-surface-600 dark:text-surface-400">Total Webmentions</dt>
+        <dd class="text-2xl font-bold">{{ webmentions | length }}</dd>
+      </div>
+    </dl>
+  </section>
+
+  {# Recent Posts with Webmentions #}
+  <section>
+    <h2 class="text-xl font-bold mb-4">Posts with Webmentions</h2>
+    <div class="overflow-x-auto">
+      <table class="w-full text-sm">
+        <thead class="bg-surface-100 dark:bg-surface-800">
+          <tr>
+            <th class="p-2 text-left">Current URL</th>
+            <th class="p-2 text-left">Legacy URLs</th>
+            <th class="p-2 text-right">Webmentions</th>
+          </tr>
+        </thead>
+        <tbody class="divide-y divide-surface-200 dark:divide-surface-700">
+          {% for post in collections.posts | head(50) %}
+            {% set allMentions = webmentions | webmentionsForUrl(post.url, urlAliases) %}
+            {% set legacyUrls = urlAliases.getOldUrls(post.url) %}
+            {% if allMentions.length > 0 or legacyUrls.length > 0 %}
+            <tr class="hover:bg-surface-50 dark:hover:bg-surface-800/50">
+              <td class="p-2">
+                <a href="{{ post.url }}" class="text-primary-600 dark:text-primary-400 hover:underline">
+                  {{ post.url }}
+                </a>
+              </td>
+              <td class="p-2 text-xs text-surface-500 font-mono">
+                {% if legacyUrls.length %}
+                  {% for legacyUrl in legacyUrls %}
+                    <div>{{ legacyUrl }}</div>
+                  {% endfor %}
+                {% else %}
+                  <span class="text-surface-400">-</span>
+                {% endif %}
+              </td>
+              <td class="p-2 text-right">
+                {% if allMentions.length %}
+                  <span class="inline-flex items-center px-2 py-1 rounded-full text-xs font-medium bg-green-100 text-green-800 dark:bg-green-900 dark:text-green-100">
+                    {{ allMentions.length }}
+                  </span>
+                {% else %}
+                  <span class="text-surface-400">0</span>
+                {% endif %}
+              </td>
+            </tr>
+            {% endif %}
+          {% endfor %}
+        </tbody>
+      </table>
+    </div>
+  </section>
+
+  {# URL Alias Sample #}
+  <section>
+    <h2 class="text-xl font-bold mb-4">URL Alias Sample (first 20)</h2>
+    <div class="overflow-x-auto">
+      <table class="w-full text-sm font-mono">
+        <thead class="bg-surface-100 dark:bg-surface-800">
+          <tr>
+            <th class="p-2 text-left">New URL</th>
+            <th class="p-2 text-left">Old URL(s)</th>
+          </tr>
+        </thead>
+        <tbody class="divide-y divide-surface-200 dark:divide-surface-700">
+          {% set aliasEntries = urlAliases.aliases | dictsort %}
+          {% for newUrl, oldUrls in aliasEntries | head(20) %}
+          <tr>
+            <td class="p-2 text-xs break-all">{{ newUrl }}</td>
+            <td class="p-2 text-xs break-all text-surface-500">
+              {% for oldUrl in oldUrls %}
+                <div>{{ oldUrl }}</div>
+              {% endfor %}
+            </td>
+          </tr>
+          {% endfor %}
+        </tbody>
+      </table>
+    </div>
+  </section>
+
+  {# Raw Webmention Targets (for debugging) #}
+  <section>
+    <h2 class="text-xl font-bold mb-4">Recent Webmention Targets</h2>
+    <p class="text-sm text-surface-600 dark:text-surface-400 mb-4">
+      Shows which URLs webmentions were sent to (useful for verifying legacy URL matches).
+    </p>
+    <ul class="space-y-1 font-mono text-xs">
+      {% for wm in webmentions | head(30) %}
+      <li class="p-2 bg-surface-50 dark:bg-surface-800/50 rounded">
+        <span class="text-surface-500">{{ wm["wm-property"] }}:</span>
+        <span class="break-all">{{ wm["wm-target"] }}</span>
+      </li>
+      {% endfor %}
+    </ul>
+  </section>
+</div>