/**
 * 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,
 * and mirrors the dashboard's default filter/sort behavior (tasks/views.py
 * DashboardView) so offline mode isn't a degraded, unsorted, unfiltered view.
 */

const PRIORITY_ORDER = { urgent: 4, high: 3, medium: 2, low: 1 };

let currentFilter = 'all';
let currentSort = 'due_date';

function todayLocalStr() {
    const d = new Date();
    const y = d.getFullYear();
    const m = String(d.getMonth() + 1).padStart(2, '0');
    const day = String(d.getDate()).padStart(2, '0');
    return `${y}-${m}-${day}`;
}

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 applyFilter(tasks, filter) {
    const today = todayLocalStr();
    if (filter === 'completed') {
        return tasks.filter((t) => t.status === 'completed');
    }
    // Every other filter excludes completed by default, matching the
    // online dashboard's default behavior.
    const notCompleted = tasks.filter((t) => t.status !== 'completed');
    switch (filter) {
        case 'today':
            return notCompleted.filter((t) => t.due_date === today);
        case 'upcoming':
            return notCompleted.filter((t) => t.due_date && t.due_date > today);
        case 'overdue':
            return notCompleted.filter((t) => t.due_date && t.due_date < today && t.status !== 'cancelled');
        default:
            return notCompleted;
    }
}

function applySort(tasks, sort) {
    const sorted = [...tasks];
    const dueOrDefault = (t) => t.due_date || '9999-99-99';
    const priorityOf = (t) => PRIORITY_ORDER[t.priority] || 0;

    switch (sort) {
        case 'due_date_desc':
            sorted.sort((a, b) => dueOrDefault(b).localeCompare(dueOrDefault(a)) || priorityOf(b) - priorityOf(a));
            break;
        case 'priority':
            sorted.sort((a, b) => priorityOf(b) - priorityOf(a) || dueOrDefault(a).localeCompare(dueOrDefault(b)));
            break;
        case 'priority_low':
            sorted.sort((a, b) => priorityOf(a) - priorityOf(b) || dueOrDefault(a).localeCompare(dueOrDefault(b)));
            break;
        case 'due_date':
        default:
            sorted.sort((a, b) => dueOrDefault(a).localeCompare(dueOrDefault(b)) || priorityOf(b) - priorityOf(a));
            break;
    }
    return sorted;
}

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 nonDeleted = allTasks.filter((t) => !t.is_deleted);
    const visibleTasks = applySort(applyFilter(nonDeleted, currentFilter), currentSort);

    listEl.innerHTML = '';

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

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

function setActiveFilterButton(filter) {
    document.querySelectorAll('#offline-filter-tabs button').forEach((btn) => {
        const isActive = btn.dataset.filter === filter;
        btn.classList.toggle('btn-primary', isActive);
        btn.classList.toggle('btn-secondary', !isActive);
    });
}

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 = '';
            }
        });
    }

    document.querySelectorAll('#offline-filter-tabs button').forEach((btn) => {
        btn.addEventListener('click', () => {
            currentFilter = btn.dataset.filter;
            setActiveFilterButton(currentFilter);
            renderOfflineTasks();
        });
    });

    const sortSelect = document.getElementById('offline-sort-select');
    if (sortSelect) {
        sortSelect.value = currentSort;
        sortSelect.addEventListener('change', () => {
            currentSort = sortSelect.value;
            renderOfflineTasks();
        });
    }
});