Add Chez Mon Libraire, ISBN-first search with title fallback, and result caching

Anna's Archive and Waterstones now search by ISBN first and only fall
back to title/author when that comes back with an explicit no-results,
since a specific edition's ISBN can be unindexed even though the book
exists under another edition. Chez Mon Libraire is added as a third
source (isbn-based search, French no-results/found text patterns).
Results are cached per site+isbn via GM_getValue/GM_setValue for 14
days to cut down on repeat requests.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

book-links.user.js

@@ -12,9 +12,12 @@
 // @match        https://www.amazon.com/*/dp/*
 // @connect      annas-archive.gl
 // @connect      www.waterstones.com
+// @connect      www.chez-mon-libraire.fr
 // @updateURL    https://raw.githubusercontent.com/alexture/book-links/main/book-links.user.js
 // @downloadURL  https://raw.githubusercontent.com/alexture/book-links/main/book-links.user.js
 // @grant        GM_xmlhttpRequest
+// @grant        GM_getValue
+// @grant        GM_setValue
 // ==/UserScript==
 
 (function () {
@@ -136,8 +139,20 @@
     });
   }
 
-  async function checkAnna(isbn, title, author) {
-    const query = (title && author) ? `${title} ${author}` : isbn;
+  const CACHE_TTL_MS = 14 * 24 * 60 * 60 * 1000; // 14 days
+
+  async function withCache(key, fn) {
+    const entry = GM_getValue(key);
+    if (entry && Date.now() - entry.ts < CACHE_TTL_MS) return entry.value;
+
+    const value = await fn();
+    // Only cache confident answers — retry uncertain ones (network error,
+    // timeout, JS-rendered page) next visit instead of freezing them in.
+    if (value.found !== null) GM_setValue(key, { value, ts: Date.now() });
+    return value;
+  }
+
+  async function checkAnnaQuery(query) {
     const url = `https://annas-archive.gl/search?q=${encodeURIComponent(query)}`;
     const res = await gmFetch(url);
     if (!res.ok) return { found: null, url };
@@ -152,8 +167,21 @@
     return { found: null, url };
   }
 
-  async function checkWaterstones(isbn) {
-    const searchUrl = `https://www.waterstones.com/books/search/term/${isbn}`;
+  async function checkAnna(isbn, title, author) {
+    if (isbn) {
+      const byIsbn = await checkAnnaQuery(isbn);
+      // A specific edition's ISBN may be unindexed even though the book exists
+      // under another edition — retry by title/author before calling it not found.
+      if (byIsbn.found === false && title && author) {
+        return checkAnnaQuery(`${title} ${author}`);
+      }
+      return byIsbn;
+    }
+    return checkAnnaQuery(`${title} ${author}`);
+  }
+
+  async function checkWaterstonesQuery(query) {
+    const searchUrl = `https://www.waterstones.com/books/search/term/${encodeURIComponent(query)}`;
     const res = await gmFetch(searchUrl);
     if (!res.ok) return { found: null, url: searchUrl };
 
@@ -172,6 +200,36 @@
     return { found: null, url: searchUrl };
   }
 
+  async function checkWaterstones(isbn, title, author) {
+    const byIsbn = await checkWaterstonesQuery(isbn);
+    if (byIsbn.found === false && title && author) {
+      return checkWaterstonesQuery(`${title} ${author}`);
+    }
+    return byIsbn;
+  }
+
+  async function checkChezMonLibraireQuery(query) {
+    const searchUrl = `https://www.chez-mon-libraire.fr/listeliv.php?base=allbooks&mots_recherche=${encodeURIComponent(query)}`;
+    const res = await gmFetch(searchUrl);
+    if (!res.ok) return { found: null, url: searchUrl };
+
+    const noResults = /n.avons pas trouv/i.test(res.text);
+    if (noResults) return { found: false, url: searchUrl };
+
+    const hasResults = /\/livre\/\d/.test(res.text) || /produit[s]?\s+trouv/i.test(res.text);
+    if (hasResults) return { found: true, url: searchUrl };
+
+    return { found: null, url: searchUrl };
+  }
+
+  async function checkChezMonLibraire(isbn, title, author) {
+    const byIsbn = await checkChezMonLibraireQuery(isbn);
+    if (byIsbn.found === false && title && author) {
+      return checkChezMonLibraireQuery(`${title} ${author}`);
+    }
+    return byIsbn;
+  }
+
   function renderRow(label, result) {
     if (result.found === true) {
       return `<div>✓ <a href="${result.url}" target="_blank" style="color:#7eb8f7;text-decoration:none">${label}</a></div>`;
@@ -232,15 +290,26 @@
     widget.querySelector('#__bl-results').textContent = 'Checking…';
 
     const isWaterstones = window.location.hostname.includes('waterstones.com');
-    const checksToRun = [checkAnna(isbn, title, author)];
-    if (!isWaterstones && isbn) checksToRun.push(checkWaterstones(isbn));
+    const cacheKeyFor = (site) => `${site}:${isbn || `${title}|${author}`}`;
+    const checksToRun = [
+      withCache(cacheKeyFor('anna'), () => checkAnna(isbn, title, author)),
+    ];
+    if (!isWaterstones && isbn) {
+      checksToRun.push(withCache(cacheKeyFor('waterstones'), () => checkWaterstones(isbn, title, author)));
+    }
+    if (isbn) {
+      checksToRun.push(withCache(cacheKeyFor('chezmonlibraire'), () => checkChezMonLibraire(isbn, title, author)));
+    }
 
     const results = await Promise.all(checksToRun);
-    const annaResult = results[0];
-    const waterstonesResult = isWaterstones ? null : results[1];
+    let idx = 0;
+    const annaResult = results[idx++];
+    const waterstonesResult = (!isWaterstones && isbn) ? results[idx++] : null;
+    const chezMonLibraireResult = isbn ? results[idx++] : null;
 
     let html = '';
-    if (!isWaterstones) html += renderRow('Waterstones', waterstonesResult);
+    if (waterstonesResult) html += renderRow('Waterstones', waterstonesResult);
+    if (chezMonLibraireResult) html += renderRow('Chez Mon Libraire', chezMonLibraireResult);
     html += renderRow("Anna's Archive", annaResult);
 
     widget.querySelector('#__bl-results').innerHTML = html;