feat: implement spaced repetition scheduler (#1178)

database.js

@@ -78,6 +78,11 @@ db.all("PRAGMA table_info(tasks)", (err, rows) => {
   if (!columnNames.includes("labels")) {
     db.run("ALTER TABLE tasks ADD COLUMN labels TEXT DEFAULT '[]'");
   }
+
+  // Revision stage
+  if (!columnNames.includes("revision_stage")) {
+    db.run("ALTER TABLE tasks ADD COLUMN revision_stage INTEGER DEFAULT 0");
+  }
 });
 
     // Pre-populate some subjects if empty

index.html

@@ -716,5 +716,16 @@ <h3 style="margin:0 0 12px; font-size:18px; font-weight:600;">New task</h3>
     </div>
   </div>
 </div>
+<div id="revision-modal" class="modal-backdrop" style="display:none; position:fixed; inset:0; z-index:9999; align-items:center; justify-content:center;">
+  <div class="modal-card" style="border-radius:12px; padding:20px; width:340px; box-shadow:0 12px 40px rgba(0,0,0,0.25); text-align:center;">
+    <h3 style="margin:0 0 8px; font-size:18px; font-weight:600;">Revision Complete! 🎉</h3>
+    <p style="font-size:14px; margin-bottom:16px; color:var(--color-text-secondary);">How difficult was it to recall this concept?</p>
+    <div style="display:flex; justify-content:space-between; gap:8px;">
+      <button id="rev-btn-easy" class="btn" style="flex:1; background:var(--color-text-success); color:white; border:none;">Easy</button>
+      <button id="rev-btn-medium" class="btn" style="flex:1; background:var(--color-text-warning); color:black; border:none;">Medium</button>
+      <button id="rev-btn-hard" class="btn" style="flex:1; background:var(--color-text-danger); color:white; border:none;">Hard</button>
+    </div>
+  </div>
+</div>
 </body>
 </html>

js/app.js

@@ -1168,7 +1168,12 @@ function renderTasks() {
           labelsHtml = t.labels.map(l => `<span class="task-pill" style="background:${getLabelColor(l)}; color:white;">${l}</span>`).join(' ');
         }
 
-  html += `
+        let revisionHtml = '';
+        if (t.revision_stage > 0) {
+          revisionHtml = `<span class="task-pill pill-purple" title="Spaced Repetition Stage ${t.revision_stage}">🔁 Stage ${t.revision_stage}</span>`;
+        }
+
+        html += `
             <div class="task-item 
               ${isUrgent ? 'urgent' : ''} 
               ${isHighPriority ? 'high-priority' : ''} 
@@ -1203,6 +1208,8 @@ function renderTasks() {
                   <span class="task-pill ${pillClass}">
                     ${sub.short_code}
                   </span>
+
+                  ${revisionHtml}
 
                   ${labelsHtml}
                 </div>
@@ -2280,3 +2287,57 @@ if (calendarDownloadBtn) {
     downloadCalendar();
   });
 }
+
+
+// ================= SPACED REPETITION (Issue 1178) =================
+window.showRevisionModal = function(task) {
+  const modal = document.getElementById('revision-modal');
+  if (!modal) return;
+  modal.style.display = 'flex';
+
+  const btnEasy = document.getElementById('rev-btn-easy');
+  const btnMedium = document.getElementById('rev-btn-medium');
+  const btnHard = document.getElementById('rev-btn-hard');
+
+  // Clone to remove old event listeners
+  const newEasy = btnEasy.cloneNode(true);
+  const newMedium = btnMedium.cloneNode(true);
+  const newHard = btnHard.cloneNode(true);
+  btnEasy.parentNode.replaceChild(newEasy, btnEasy);
+  btnMedium.parentNode.replaceChild(newMedium, btnMedium);
+  btnHard.parentNode.replaceChild(newHard, btnHard);
+
+  const handleFeedback = (difficulty) => {
+    modal.style.display = 'none';
+    let nextStage = task.revision_stage || 1;
+    if (difficulty === 'easy') nextStage += 1;
+    else if (difficulty === 'hard') nextStage = Math.max(1, nextStage - 1);
+
+    let daysToAdd = 1;
+    if (nextStage === 2) daysToAdd = 3;
+    else if (nextStage === 3) daysToAdd = 7;
+    else if (nextStage >= 4) daysToAdd = 14;
+
+    const revDate = new Date();
+    revDate.setDate(revDate.getDate() + daysToAdd);
+
+    let baseTitle = task.title;
+    if (baseTitle.startsWith('Revision: ')) {
+      baseTitle = baseTitle.replace('Revision: ', '');
+    }
+
+    store.addTasks([{
+      title: `Revision: ${baseTitle}`,
+      subject_id: task.subject_id,
+      due_at: revDate.toISOString(),
+      status: 'Not Started',
+      priority: task.priority,
+      revision_stage: nextStage
+    }]);
+  };
+
+  newEasy.addEventListener('click', () => handleFeedback('easy'));
+  newMedium.addEventListener('click', () => handleFeedback('medium'));
+  newHard.addEventListener('click', () => handleFeedback('hard'));
+};
+

js/store.js

@@ -214,6 +214,27 @@ export const store = {
 
       if (newStatus === 'Done') {
         triggerConfetti();
+
+        // SPACED REPETITION LOGIC (Issue 1178)
+        if (!task.revision_stage || task.revision_stage === 0) {
+          // Schedule first revision 1 day later
+          const revDate = new Date();
+          revDate.setDate(revDate.getDate() + 1);
+
+          this.addTasks([{
+            title: `Revision: ${task.title}`,
+            subject_id: task.subject_id,
+            due_at: revDate.toISOString(),
+            status: 'Not Started',
+            priority: task.priority,
+            revision_stage: 1
+          }]);
+        } else {
+          // It's already a revision task, ask for feedback
+          if (window.showRevisionModal) {
+            window.showRevisionModal(task);
+          }
+        }
       }
 
       try {

server.js

@@ -377,8 +377,8 @@ app.post('/api/tasks', (req, res) => {
     let errors = [];
 
     const stmt = db.prepare(`INSERT INTO tasks 
-      (id, subject_id, title, due_at, status, priority, confidence_score, notes, estimated_duration, is_estimated_duration_min, labels) 
-      VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`);
+      (id, subject_id, title, due_at, status, priority, confidence_score, notes, estimated_duration, is_estimated_duration_min, labels, revision_stage) 
+      VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`);
 
 
     let pending = tasks.length;
@@ -439,6 +439,7 @@ app.post('/api/tasks', (req, res) => {
               Number.isFinite(Number(t.estimated_duration)) ? Number(t.estimated_duration) : null,
               t.is_estimated_duration_min === 0 ? 0 : 1,
               typeof t.labels === 'string' ? t.labels : JSON.stringify(t.labels || []),
+              t.revision_stage || 0,
               function (insertErr) {
                 if (insertErr) {
                   errors.push({ task: t, error: insertErr.message });
@@ -481,7 +482,7 @@ app.post('/api/tasks', (req, res) => {
 // ================= UPDATE =================
 app.put('/api/tasks/:id', (req, res) => {
 
-  const { status, archived, title, subject_id, due_at, notes, priority, estimated_duration, is_estimated_duration_min,labels } = req.body;
+  const { status, archived, title, subject_id, due_at, notes, priority, estimated_duration, is_estimated_duration_min,labels, revision_stage } = req.body;
 
 
   let query = 'UPDATE tasks SET ';
@@ -498,6 +499,7 @@ app.put('/api/tasks/:id', (req, res) => {
   if (estimated_duration !== undefined) { updates.push('estimated_duration = ?'); params.push(Number.isFinite(Number(estimated_duration)) ? Number(estimated_duration) : null); }
   if (is_estimated_duration_min !== undefined) { updates.push('is_estimated_duration_min = ?'); params.push(is_estimated_duration_min === 0 ? 0 : 1); }
   if (labels !== undefined) { updates.push('labels = ?'); params.push(typeof labels === 'string' ? labels : JSON.stringify(labels)); }
+  if (revision_stage !== undefined) { updates.push('revision_stage = ?'); params.push(revision_stage); }
 
   if (updates.length === 0) {
     return res.status(400).json({ error: 'No fields to update' });