Add participant unregistration feature and update UI for activity participants

Author: briefjo

src/app.py

@@ -105,3 +105,18 @@ def signup_for_activity(activity_name: str, email: str):
     # Add student
     activity["participants"].append(email)
     return {"message": f"Signed up {email} for {activity_name}"}
+
+
+@app.delete("/activities/{activity_name}/signup")
+def unregister_from_activity(activity_name: str, email: str):
+    """Unregister a student from an activity"""
+    if activity_name not in activities:
+        raise HTTPException(status_code=404, detail="Activity not found")
+
+    activity = activities[activity_name]
+
+    if email not in activity["participants"]:
+        raise HTTPException(status_code=400, detail="Student not signed up for this activity")
+
+    activity["participants"].remove(email)
+    return {"message": f"Unregistered {email} from {activity_name}"}

src/static/app.js

@@ -20,11 +20,24 @@ document.addEventListener("DOMContentLoaded", () => {
 
         const spotsLeft = details.max_participants - details.participants.length;
 
+        const participantsList = details.participants
+          .map(
+            (p) =>
+              `<li><span class="participant-email">${p}</span><button class="remove-btn" data-activity="${name}" data-email="${p}" title="Remove ${p}">&#x2715;</button></li>`
+          )
+          .join("");
+
         activityCard.innerHTML = `
           <h4>${name}</h4>
           <p>${details.description}</p>
           <p><strong>Schedule:</strong> ${details.schedule}</p>
           <p><strong>Availability:</strong> ${spotsLeft} spots left</p>
+          <div class="participants-section">
+            <strong>Participants:</strong>
+            <ul class="participants-list">
+              ${participantsList || "<li class='no-participants'>No participants yet</li>"}
+            </ul>
+          </div>
         `;
 
         activitiesList.appendChild(activityCard);
@@ -62,6 +75,7 @@ document.addEventListener("DOMContentLoaded", () => {
         messageDiv.textContent = result.message;
         messageDiv.className = "success";
         signupForm.reset();
+        fetchActivities();
       } else {
         messageDiv.textContent = result.detail || "An error occurred";
         messageDiv.className = "error";
@@ -81,6 +95,41 @@ document.addEventListener("DOMContentLoaded", () => {
     }
   });
 
+  // Handle participant removal
+  activitiesList.addEventListener("click", async (event) => {
+    const btn = event.target.closest(".remove-btn");
+    if (!btn) return;
+
+    const activity = btn.dataset.activity;
+    const email = btn.dataset.email;
+
+    try {
+      const response = await fetch(
+        `/activities/${encodeURIComponent(activity)}/signup?email=${encodeURIComponent(email)}`,
+        { method: "DELETE" }
+      );
+
+      const result = await response.json();
+
+      if (response.ok) {
+        messageDiv.textContent = result.message;
+        messageDiv.className = "success";
+        fetchActivities();
+      } else {
+        messageDiv.textContent = result.detail || "An error occurred";
+        messageDiv.className = "error";
+      }
+
+      messageDiv.classList.remove("hidden");
+      setTimeout(() => messageDiv.classList.add("hidden"), 5000);
+    } catch (error) {
+      messageDiv.textContent = "Failed to unregister. Please try again.";
+      messageDiv.className = "error";
+      messageDiv.classList.remove("hidden");
+      console.error("Error unregistering:", error);
+    }
+  });
+
   // Initialize app
   fetchActivities();
 });

src/static/styles.css

@@ -74,6 +74,53 @@ section h3 {
   margin-bottom: 8px;
 }
 
+.participants-section {
+  margin-top: 10px;
+  padding-top: 10px;
+  border-top: 1px solid #e0e0e0;
+}
+
+.participants-list {
+  list-style: none;
+  padding: 0;
+  margin-top: 6px;
+}
+
+.participants-list li {
+  padding: 4px 10px;
+  margin-bottom: 4px;
+  background-color: #e8eaf6;
+  color: #1a237e;
+  border-radius: 12px;
+  font-size: 14px;
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+  margin-right: 4px;
+}
+
+.remove-btn {
+  background: none;
+  border: none;
+  color: #c62828;
+  cursor: pointer;
+  font-size: 12px;
+  padding: 0 2px;
+  line-height: 1;
+  border-radius: 50%;
+  transition: background-color 0.2s;
+}
+
+.remove-btn:hover {
+  background-color: #ffcdd2;
+}
+
+.participants-list li.no-participants {
+  background-color: transparent;
+  color: #999;
+  font-style: italic;
+}
+
 .form-group {
   margin-bottom: 15px;
 }