document.addEventListener('DOMContentLoaded', function () {
    // --- ELEMENTS ---
    const createAlarmForm = document.getElementById('createAlarmForm');
    const alarmList = document.getElementById('alarmList');
    const noAlarmsMessage = document.getElementById('noAlarmsMessage');
    const alarmModalEl = document.getElementById('alarmModal');
    const alarmModal = new bootstrap.Modal(alarmModalEl);
    const dismissAlarmBtn = document.getElementById('dismissAlarmBtn');
    const alarmSound = document.getElementById('alarmSound');
    const alarmModalMessage = document.getElementById('alarmModalMessage');

    // --- STATE ---
    let isAlarmModalShown = false;

    // --- FUNCTIONS ---

    /**
     * Handles the submission of the create alarm form.
     */
    const handleCreateAlarm = async (e) => {
        e.preventDefault();
        const timeInput = document.getElementById('alarmTime');
        const labelInput = document.getElementById('alarmLabel');

        const formData = new FormData();
        formData.append('action', 'create');
        formData.append('alarm_time', timeInput.value);
        formData.append('label', labelInput.value);

        try {
            const response = await fetch('api/alarms.php', {
                method: 'POST',
                body: formData
            });
            const result = await response.json();

            if (result.success) {
                addAlarmToList(result.id, timeInput.value, labelInput.value);
                timeInput.value = '';
                labelInput.value = '';
                if (noAlarmsMessage) {
                    noAlarmsMessage.style.display = 'none';
                }
            } else {
                alert('Error: ' + result.message);
            }
        } catch (error) {
            console.error('Failed to create alarm:', error);
            alert('An error occurred while creating the alarm.');
        }
    };

    /**
     * Handles the click on a delete alarm form.
     */
    const handleDeleteAlarm = async (e) => {
        if (!e.target.closest('.delete-alarm-form')) return;
        e.preventDefault();
        
        const form = e.target.closest('.delete-alarm-form');
        const alarmId = form.querySelector('input[name="alarm_id"]').value;
        
        if (!confirm('Are you sure you want to delete this alarm?')) return;

        const formData = new FormData(form);

        try {
            const response = await fetch('api/alarms.php', {
                method: 'POST',
                body: formData
            });
            const result = await response.json();

            if (result.success) {
                const listItem = form.closest('li');
                listItem.remove();
                if (!alarmList.querySelector('li')) {
                    if (noAlarmsMessage) {
                        noAlarmsMessage.style.display = 'block';
                    }
                }
            } else {
                alert('Error: ' + result.message);
            }
        } catch (error) {
            console.error('Failed to delete alarm:', error);
            alert('An error occurred while deleting the alarm.');
        }
    };

    /**
     * Adds a new alarm item to the DOM.
     */
    const addAlarmToList = (id, time, label, isActive = true) => {
        const date = new Date(`1970-01-01T${time}`);
        const formattedTime = date.toLocaleTimeString('en-US', { hour: 'numeric', minute: '2-digit', hour12: true });

        const li = document.createElement('li');
        li.className = 'list-group-item d-flex justify-content-between align-items-center';
        li.dataset.id = id;
        li.innerHTML = `
            <div class="d-flex align-items-center">
                <div class="form-check form-switch me-3">
                    <input class="form-check-input toggle-alarm-switch" type="checkbox" role="switch" id="toggle-${id}" ${isActive ? 'checked' : ''}>
                    <label class="form-check-label" for="toggle-${id}"></label>
                </div>
                <div>
                    <span class="fw-bold fs-5">${formattedTime}</span>
                    <span class="text-muted ms-2">${escapeHTML(label)}</span>
                </div>
            </div>
            <form class="delete-alarm-form">
                <input type="hidden" name="action" value="delete">
                <input type="hidden" name="alarm_id" value="${id}">
                <button type="submit" class="btn btn-sm btn-outline-danger">
                    <i data-feather="trash-2" class="align-text-bottom"></i>
                </button>
            </form>
        `;
        alarmList.appendChild(li);
        feather.replace();
    };

    /**
     * Handles toggling the active state of an alarm.
     */
    const handleToggleAlarm = async (e) => {
        if (!e.target.classList.contains('toggle-alarm-switch')) return;

        const switchEl = e.target;
        const listItem = switchEl.closest('li');
        const alarmId = listItem.dataset.id;
        const isActive = switchEl.checked ? 1 : 0;

        const formData = new FormData();
        formData.append('action', 'toggle');
        formData.append('alarm_id', alarmId);
        formData.append('is_active', isActive);

        try {
            const response = await fetch('api/alarms.php', {
                method: 'POST',
                body: formData
            });
            const result = await response.json();

            if (!result.success) {
                alert('Error: ' + result.message);
                // Revert the switch on failure
                switchEl.checked = !switchEl.checked;
            }
        } catch (error) {
            console.error('Failed to toggle alarm:', error);
            alert('An error occurred while updating the alarm.');
            // Revert the switch on failure
            switchEl.checked = !switchEl.checked;
        }
    };

    /**
     * Checks the server for any due alarms.
     */
    const checkAlarms = async () => {
        if (isAlarmModalShown) return; // Don't check if an alarm is already ringing

        try {
            const response = await fetch('api/alarms.php?action=check');
            const result = await response.json();

            if (result.success && result.alarms.length > 0) {
                const alarm = result.alarms[0];
                triggerAlarm(alarm);
            }
        } catch (error) {
            console.error('Error checking alarms:', error);
        }
    };

    /**
     * Triggers the visual and audible alarm.
     */
    const triggerAlarm = (alarm) => {
        isAlarmModalShown = true;
        if (alarm.label) {
            alarmModalMessage.textContent = alarm.label;
        } else {
            alarmModalMessage.textContent = 'Time to write your notes.';
        }
        alarmModal.show();
        alarmSound.play().catch(e => console.error("Audio play failed:", e));
    };

    /**
     * Dismisses the alarm and redirects to the note page.
     */
    const dismissAlarm = () => {
        alarmSound.pause();
        alarmSound.currentTime = 0;
        alarmModal.hide();
        isAlarmModalShown = false;

        const today = new Date();
        const dateString = today.getFullYear() + '-' + String(today.getMonth() + 1).padStart(2, '0') + '-' + String(today.getDate()).padStart(2, '0');
        window.location.href = `note.php?date=${dateString}`;
    };

    const escapeHTML = (str) => {
        const p = document.createElement('p');
        p.appendChild(document.createTextNode(str));
        return p.innerHTML;
    }

    // --- EVENT LISTENERS ---
    if (createAlarmForm) {
        createAlarmForm.addEventListener('submit', handleCreateAlarm);
    }

    if (alarmList) {
        alarmList.addEventListener('click', handleDeleteAlarm);
        alarmList.addEventListener('change', handleToggleAlarm);
    }

    if (dismissAlarmBtn) {
        dismissAlarmBtn.addEventListener('click', dismissAlarm);
    }

    // --- INITIALIZATION ---
    setInterval(checkAlarms, 5000); // Check for alarms every 5 seconds
});