feat: implement upload error handling and rate limiting improvements

data/html/index.html

@@ -25,6 +25,7 @@
       </div>
     </div>
   </div>
+  <div id="uploadError" class="upload-error" style="display: none" role="status" aria-live="polite"></div>
 
   <div class="duration-container">
     <label for="durationSlider">Duration: <span id="durationValue">5</span> min</label>
@@ -72,6 +73,17 @@
     const linkContainer = document.getElementById("linkContainer");
     const uploadedLink = document.getElementById("uploadedLink");
     const clipboardMessage = document.getElementById("clipboardMessage");
+    const uploadError = document.getElementById("uploadError");
+
+    function formatRetryAfter(seconds) {
+      const safeSeconds = Math.max(0, Math.floor(seconds));
+      const minutes = Math.floor(safeSeconds / 60);
+      const remainder = safeSeconds % 60;
+      if (minutes > 0) {
+        return `${minutes}m ${remainder}s`;
+      }
+      return `${remainder}s`;
+    }
 
     // Update duration display
     durationSlider.addEventListener("input", function () {
@@ -115,6 +127,8 @@
       };
 
       try {
+        uploadError.style.display = "none";
+        uploadError.textContent = "";
         const response = await fetch("/api/upload", {
           method: "POST",
           headers: {
@@ -123,10 +137,33 @@
           body: JSON.stringify(payload),
         });
 
-        const result = await response.json();
-        console.log(
-          `✅ Upload received!\n${JSON.stringify(result, null, 2)}`
-        );
+        let result = null;
+        try {
+          result = await response.json();
+        } catch (parseError) {
+          result = null;
+        }
+
+        if (!response.ok) {
+          const retryAfterSeconds = result && Number.isFinite(Number(result.retry_after_seconds))
+            ? Number(result.retry_after_seconds)
+            : null;
+          let errorMessage =
+            (result && result.error) ||
+            `Upload failed (${response.status})`;
+          if (retryAfterSeconds !== null) {
+            errorMessage += ` Try again in ${formatRetryAfter(retryAfterSeconds)}.`;
+          }
+          uploadError.textContent = errorMessage;
+          uploadError.style.display = "block";
+          return;
+        }
+
+        if (!result || !result.link) {
+          uploadError.textContent = "Upload failed (invalid response)";
+          uploadError.style.display = "block";
+          return;
+        }
 
         // Hide duration controls and buttons
         document.querySelector('label[for="durationSlider"]').style.display =
@@ -175,7 +212,8 @@
           };
         }
       } catch (error) {
-        console.log(`❌ Error: ${error.message}`);
+        uploadError.textContent = `Upload failed (${error.message})`;
+        uploadError.style.display = "block";
       }
     }
 
@@ -201,6 +239,8 @@
       resetBtn.style.display = "none";
       linkContainer.style.display = "none";
       clipboardMessage.style.display = "none";
+      uploadError.style.display = "none";
+      uploadError.textContent = "";
       uploadZone.focus();
     });