feat: add date-stepper buttons (Feature C) clamped to selected month

app.js

@@ -43,8 +43,13 @@ class DienstplanApp {
         // Duty management
         document.getElementById('add-duty-btn').addEventListener('click', () => this.addDuty());
         document.getElementById('employee-select-duty').addEventListener('change', () => this.loadDutiesForSelectedEmployee());
-        document.getElementById('month-select').addEventListener('change', () => this.loadDutiesForSelectedEmployee());
+
-        document.getElementById('year-select').addEventListener('change', () => this.loadDutiesForSelectedEmployee());
+        // Date stepper buttons (Feature C)
+        document.getElementById('duty-date-prev').addEventListener('click', () => this.stepDutyDate(-1));
+        document.getElementById('duty-date-next').addEventListener('click', () => this.stepDutyDate(+1));
+        document.getElementById('duty-date').addEventListener('change', () => this.updateDateStepperState());
+        document.getElementById('month-select').addEventListener('change', () => this.onDutyMonthChange());
+        document.getElementById('year-select').addEventListener('change', () => this.onDutyMonthChange());
 
         // Calculation
         document.getElementById('calculate-btn').addEventListener('click', () => this.calculateBonuses());
@@ -104,6 +109,8 @@ class DienstplanApp {
         // Set date input to today
         const today = new Date().toISOString().split('T')[0];
         document.getElementById('duty-date').value = today;
+
+        this.updateDateStepperState();
     }
 
     /**
@@ -265,6 +272,86 @@ class DienstplanApp {
         this.loadDutiesForSelectedEmployee();
     }
 
+    /**
+     * Step the duty-date input by +/-1 day, clamped to the currently selected month.
+     */
+    stepDutyDate(delta) {
+        const dateInput = document.getElementById('duty-date');
+        const monthSelect = document.getElementById('month-select');
+        const yearSelect  = document.getElementById('year-select');
+        const month = parseInt(monthSelect.value);
+        const year  = parseInt(yearSelect.value);
+        const lastDay = new Date(year, month, 0).getDate();
+
+        if (!dateInput.value) {
+            // Initialize to 1st of the selected month
+            dateInput.value = `${year}-${String(month).padStart(2, '0')}-01`;
+            this.updateDateStepperState();
+            return;
+        }
+        const cur = new Date(dateInput.value + 'T12:00:00');
+        // If outside selected month, snap to 1st
+        const inMonth = (cur.getFullYear() === year) && ((cur.getMonth() + 1) === month);
+        if (!inMonth) {
+            dateInput.value = `${year}-${String(month).padStart(2, '0')}-01`;
+            this.updateDateStepperState();
+            return;
+        }
+        const curDay = cur.getDate();
+        const newDay = curDay + delta;
+        if (newDay < 1 || newDay > lastDay) return; // clamp
+        const newDate = new Date(year, month - 1, newDay, 12, 0, 0);
+        const yyyy = newDate.getFullYear();
+        const mm   = String(newDate.getMonth() + 1).padStart(2, '0');
+        const dd   = String(newDate.getDate()).padStart(2, '0');
+        dateInput.value = `${yyyy}-${mm}-${dd}`;
+        this.updateDateStepperState();
+    }
+
+    /**
+     * Update the disabled state of the stepper buttons based on current date / month.
+     */
+    updateDateStepperState() {
+        const dateInput = document.getElementById('duty-date');
+        const monthSelect = document.getElementById('month-select');
+        const yearSelect  = document.getElementById('year-select');
+        const prevBtn = document.getElementById('duty-date-prev');
+        const nextBtn = document.getElementById('duty-date-next');
+        if (!dateInput || !prevBtn || !nextBtn) return;
+
+        const month = parseInt(monthSelect.value);
+        const year  = parseInt(yearSelect.value);
+        const lastDay = new Date(year, month, 0).getDate();
+
+        if (!dateInput.value) {
+            prevBtn.disabled = false;
+            nextBtn.disabled = false;
+            return;
+        }
+        const cur = new Date(dateInput.value + 'T12:00:00');
+        const inSelectedMonth = (cur.getFullYear() === year) && ((cur.getMonth() + 1) === month);
+        if (!inSelectedMonth) {
+            prevBtn.disabled = false;
+            nextBtn.disabled = false;
+            return;
+        }
+        prevBtn.disabled = cur.getDate() <= 1;
+        nextBtn.disabled = cur.getDate() >= lastDay;
+    }
+
+    /**
+     * Handle month/year change in the duty tab: set date to 1st of new month, refresh list, refresh stepper.
+     */
+    onDutyMonthChange() {
+        const monthSelect = document.getElementById('month-select');
+        const yearSelect  = document.getElementById('year-select');
+        const month = parseInt(monthSelect.value);
+        const year  = parseInt(yearSelect.value);
+        document.getElementById('duty-date').value = `${year}-${String(month).padStart(2, '0')}-01`;
+        this.updateDateStepperState();
+        this.loadDutiesForSelectedEmployee();
+    }
+
     /**
      * Load duties for the selected employee and month
      */

index.html

@@ -69,7 +69,11 @@
                 <!-- Add Duty Form -->
                 <div class="form-group">
                     <label for="duty-date">Datum:</label>
-                    <input type="date" id="duty-date">
+                    <div class="date-stepper">
+                        <button type="button" id="duty-date-prev" class="btn btn-secondary" aria-label="Vorheriger Tag">&lsaquo;</button>
+                        <input type="date" id="duty-date">
+                        <button type="button" id="duty-date-next" class="btn btn-secondary" aria-label="Nächster Tag">&rsaquo;</button>
+                    </div>
                 </div>
 
                 <div class="form-group">

styles.css

@@ -658,3 +658,29 @@ header h1 {
     color: #dc3545;
     font-weight: 600;
 }
+
+/* === Date Stepper === */
+.date-stepper {
+    display: grid;
+    grid-template-columns: auto 1fr auto;
+    gap: 6px;
+    align-items: stretch;
+}
+
+.date-stepper input[type="date"] {
+    /* override the .form-group width */
+    width: 100%;
+}
+
+.date-stepper button {
+    padding: 0 14px;
+    margin: 0;
+    font-size: 1.2rem;
+    line-height: 1;
+    min-width: 44px;
+}
+
+.date-stepper button:disabled {
+    opacity: 0.4;
+    cursor: not-allowed;
+}