Make extension auto grab book id

index.js

@@ -23,6 +23,41 @@ function setDisabled(disabled) {
   kindleCheckbox.disabled = disabled;
 }
 
+function extractBookIdFromUrl(url) {
+  try {
+    const { pathname } = new URL(url);
+    const segments = pathname.split("/").filter(Boolean).reverse();
+    return segments.find((segment) => /^[0-9]{9,}$/.test(segment)) || null;
+  } catch (_) {
+    return null;
+  }
+}
+
+async function detectActiveBook() {
+  if (!chrome.tabs?.query) {
+    return;
+  }
+
+  try {
+    const [activeTab] = await chrome.tabs.query({ active: true, currentWindow: true });
+    if (!activeTab?.url || !activeTab.url.includes("/library/view/")) {
+      return;
+    }
+
+    const detectedBookId = extractBookIdFromUrl(activeTab.url);
+    if (!detectedBookId) {
+      return;
+    }
+
+    if (bookIdInput.value !== detectedBookId) {
+      bookIdInput.value = detectedBookId;
+      appendLog(`Detected book ID ${detectedBookId} from the active tab.`);
+    }
+  } catch (error) {
+    console.warn("SafariBooks Downloader: unable to detect active book.", error);
+  }
+}
+
 form.addEventListener("submit", async (event) => {
   event.preventDefault();
   const bookId = bookIdInput.value.trim();
@@ -48,3 +83,5 @@ form.addEventListener("submit", async (event) => {
     setDisabled(false);
   }
 });
+
+detectActiveBook();

manifest.json

@@ -32,7 +32,8 @@
   "permissions": [
     "downloads",
     "cookies",
-    "storage"
+    "storage",
+    "tabs"
   ],
   "host_permissions": [
     "https://learning.oreilly.com/*",

safaribooks/downloader.js

@@ -539,14 +539,83 @@ export class SafariBooksDownloader {
 
   async fetchImages() {
     for (const [relative, url] of this.imageDownloads.entries()) {
-      const response = await fetch(url, { credentials: "include" });
-      if (!response.ok) {
-        this.log(`Warning: unable to fetch image ${url} (status ${response.status})`);
+      const result = await this.fetchImageWithFallback(relative, url);
+      if (result) {
+        this.imageDownloads.set(relative, result);
+      }
+    }
+  }
+
+  async fetchImageWithFallback(relative, primaryUrl) {
+    const attempts = [];
+    const tried = new Set();
+
+    const queue = [primaryUrl, ...this.buildImageFallbackUrls(relative, primaryUrl)];
+    for (const candidate of queue) {
+      if (!candidate || tried.has(candidate)) {
         continue;
       }
-      const data = new Uint8Array(await response.arrayBuffer());
-      this.imageDownloads.set(relative, { data, sourceUrl: url });
+      tried.add(candidate);
+      try {
+        const response = await fetch(candidate, { credentials: "include" });
+        if (!response.ok) {
+          attempts.push(`${candidate} (status ${response.status})`);
+          continue;
+        }
+        const data = new Uint8Array(await response.arrayBuffer());
+        if (candidate !== primaryUrl) {
+          this.log(`Info: fetched image ${relative} via fallback ${candidate}`);
+        }
+        return { data, sourceUrl: candidate };
+      } catch (error) {
+        attempts.push(`${candidate} (${error.message})`);
+      }
     }
+
+    if (attempts.length) {
+      this.log(
+        `Warning: unable to fetch image ${primaryUrl}. Attempts: ${attempts.join("; ")}`
+      );
+    }
+    return null;
+  }
+
+  buildImageFallbackUrls(relative, url) {
+    const candidates = new Set();
+
+    if (url.includes("/Images/")) {
+      candidates.add(url.replace("/Images/", "/images/"));
+    }
+    if (url.includes("/images/")) {
+      candidates.add(url.replace("/images/", "/Images/"));
+    }
+
+    if (url.includes("/files/Images/")) {
+      const base = url.replace(/Images\/[^/]*$/i, "Images/");
+      ["cover.jpg", "cover.jpeg", "cover.png", "cover-large.jpg"].forEach((file) => {
+        candidates.add(`${base}${file}`);
+      });
+    }
+
+    const isbnMatch = url.match(/Images\/(\d{10,13})\.(jpg|jpeg|png|gif)$/i);
+    if (isbnMatch) {
+      const isbn = isbnMatch[1];
+      const sizes = ["600w", "400w", "250w", ""];
+      sizes.forEach((size) => {
+        const trimmedSize = size ? `/${size}` : "";
+        candidates.add(`https://learning.oreilly.com/library/cover/${isbn}${trimmedSize}/`);
+      });
+    }
+
+    if (this.bookInfo?.cover && url !== this.bookInfo.cover) {
+      candidates.add(this.bookInfo.cover);
+    }
+
+    if (relative && this.bookInfo?.cover_url) {
+      candidates.add(this.bookInfo.cover_url);
+    }
+
+    return Array.from(candidates).filter(Boolean);
   }
 
   async fetchCssImages() {