/**
 * KeepItGoing - Offline mini task app
 * Renders and edits tasks straight from IndexedDB while there's no network.
 * Reuses the .task-item/.task-checkbox/.priority-badge classes from
 * templates/tasks/_task_item.html for visual consistency with the real app.
 */

function formatDueDate(dateStr) {
    if (!dateStr) return '';
    const date = new Date(dateStr + 'T00:00:00');
    return date.toLocaleDateString(undefined, { month: 'short', day: 'numeric', year: 'numeric' });
}

function renderTaskItem(task) {
    const item = document.createElement('div');
    item.className = `task-item priority-${task.priority}${task.status === 'completed' ? ' completed' : ''}`;

    const toggleForm = document.createElement('button');
    toggleForm.type = 'button';
    toggleForm.className = `task-checkbox${task.status === 'completed' ? ' checked' : ''}`;
    toggleForm.setAttribute('aria-label', 'Toggle complete');
    if (task.status === 'completed') {
        toggleForm.innerHTML = '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="3"><path d="M5 13l4 4L19 7"/></svg>';
    }
    toggleForm.addEventListener('click', () => toggleTaskComplete(task.sync_id));

    const content = document.createElement('div');
    content.className = 'task-content';

    const title = document.createElement('div');
    title.className = 'task-title';
    title.textContent = task.title;
    content.appendChild(title);

    if (task.due_date) {
        const meta = document.createElement('div');
        meta.className = 'task-meta';
        meta.textContent = `📅 ${formatDueDate(task.due_date)}`;
        content.appendChild(meta);
    }

    const priorityBadge = document.createElement('span');
    priorityBadge.className = `priority-badge ${task.priority}`;
    priorityBadge.textContent = task.priority;

    item.appendChild(toggleForm);
    item.appendChild(content);
    item.appendChild(priorityBadge);

    return item;
}

async function toggleTaskComplete(syncId) {
    const tasks = await getAllTasks();
    const task = tasks.find((t) => t.sync_id === syncId);
    if (!task) return;

    task.status = task.status === 'completed' ? 'pending' : 'completed';
    task.updated_at = new Date().toISOString();
    task._dirty = true;
    await putLocalTask(task);
    renderOfflineTasks();
}

async function addOfflineTask(title) {
    const now = new Date().toISOString();
    const syncId = crypto.randomUUID();
    const task = {
        id: syncId,
        sync_id: syncId,
        parent: null,
        parent_sync_id: null,
        title: title,
        description: '',
        status: 'pending',
        priority: 'medium',
        due_date: null,
        due_time: null,
        reminder_at: null,
        recurrence: 'none',
        recurrence_rule: '',
        recurrence_end_date: null,
        tag_sync_ids: [],
        sort_order: 0,
        is_deleted: false,
        created_at: now,
        updated_at: now,
        _dirty: true,
        _pending_conflict_id: null,
    };
    await putLocalTask(task);
    renderOfflineTasks();
}

async function renderOfflineTasks() {
    const listEl = document.getElementById('offline-task-list');
    const emptyEl = document.getElementById('offline-empty-state');
    if (!listEl) return;

    const allTasks = await getAllTasks();
    const visibleTasks = allTasks
        .filter((t) => !t.is_deleted)
        .sort((a, b) => (a.due_date || '9999').localeCompare(b.due_date || '9999'));

    listEl.innerHTML = '';

    if (visibleTasks.length === 0) {
        const lastSyncToken = await getMeta('last_sync_token');
        emptyEl.textContent = lastSyncToken
            ? 'No tasks yet.'
            : "No offline data yet — connect once while online to sync your tasks.";
        emptyEl.hidden = false;
        listEl.hidden = true;
        return;
    }

    emptyEl.hidden = true;
    listEl.hidden = false;
    for (const task of visibleTasks) {
        listEl.appendChild(renderTaskItem(task));
    }
}

document.addEventListener('DOMContentLoaded', () => {
    renderOfflineTasks();

    const form = document.getElementById('offline-add-task-form');
    if (form) {
        form.addEventListener('submit', (event) => {
            event.preventDefault();
            const input = document.getElementById('offline-task-title');
            const title = input.value.trim();
            if (title) {
                addOfflineTask(title);
                input.value = '';
            }
        });
    }
});