class TodoApp {
    constructor() {
        this.tasks = [];
        this.currentFilter = 'all';
        this.initElements();
        this.initEventListeners();
        this.loadTasks();
        this.initFireworks();
    }
    
    initElements() {
        this.taskInput = document.getElementById('taskInput');
        this.addBtn = document.getElementById('addBtn');
        this.taskList = document.getElementById('taskList');
        this.emptyState = document.getElementById('emptyState');
        this.clearCompletedBtn = document.getElementById('clearCompleted');
        this.totalTasksEl = document.getElementById('totalTasks');
        this.completedTasksEl = document.getElementById('completedTasks');
        this.filterBtns = document.querySelectorAll('.filter-btn');
    }
    
    initEventListeners() {
        this.addBtn.addEventListener('click', () => this.addTask());
        this.taskInput.addEventListener('keypress', (e) => {
            if (e.key === 'Enter') this.addTask();
        });
        
        this.clearCompletedBtn.addEventListener('click', () => this.clearCompleted());
        
        this.filterBtns.forEach(btn => {
            btn.addEventListener('click', () => {
                this.filterBtns.forEach(b => b.classList.remove('active'));
                btn.classList.add('active');
                this.currentFilter = btn.dataset.filter;
                this.render();
            });
        });
    }
    
    initFireworks() {
        const canvas = document.getElementById('fireworks');
        this.fireworks = new Fireworks(canvas);
    }
    
    loadTasks() {
        const stored = localStorage.getItem('tasks');
        if (stored) {
            this.tasks = JSON.parse(stored);
        }
        this.render();
    }
    
    saveTasks() {
        localStorage.setItem('tasks', JSON.stringify(this.tasks));
    }
    
    addTask() {
        const text = this.taskInput.value.trim();
        if (!text) return;
        
        const task = {
            id: Date.now(),
            text: text,
            createdAt: new Date().toISOString(),
            completedAt: null,
            completed: false
        };
        
        this.tasks.unshift(task);
        this.taskInput.value = '';
        this.saveTasks();
        this.render();
    }
    
    toggleTask(id) {
        const task = this.tasks.find(t => t.id === id);
        if (!task) return;
        
        task.completed = !task.completed;
        task.completedAt = task.completed ? new Date().toISOString() : null;
        
        if (task.completed) {
            this.fireworks.start();
        }
        
        this.saveTasks();
        this.render();
    }
    
    deleteTask(id) {
        this.tasks = this.tasks.filter(t => t.id !== id);
        this.saveTasks();
        this.render();
    }
    
    clearCompleted() {
        this.tasks = this.tasks.filter(t => !t.completed);
        this.saveTasks();
        this.render();
    }
    
    formatDate(dateString) {
        const date = new Date(dateString);
        const now = new Date();
        const diff = now - date;
        const minutes = Math.floor(diff / 60000);
        const hours = Math.floor(diff / 3600000);
        const days = Math.floor(diff / 86400000);
        
        if (minutes < 1) return 'just now';
        if (minutes < 60) return `${minutes}m ago`;
        if (hours < 24) return `${hours}h ago`;
        if (days < 7) return `${days}d ago`;
        
        return date.toLocaleDateString();
    }
    
    getFilteredTasks() {
        switch (this.currentFilter) {
            case 'active':
                return this.tasks.filter(t => !t.completed);
            case 'completed':
                return this.tasks.filter(t => t.completed);
            default:
                return this.tasks;
        }
    }
    
    updateStats() {
        const total = this.tasks.length;
        const completed = this.tasks.filter(t => t.completed).length;
        
        this.totalTasksEl.textContent = `${total} ${total === 1 ? 'task' : 'tasks'}`;
        this.completedTasksEl.textContent = `${completed} completed`;
    }
    
    render() {
        const filteredTasks = this.getFilteredTasks();
        
        this.taskList.innerHTML = '';
        this.emptyState.classList.toggle('show', filteredTasks.length === 0);
        
        filteredTasks.forEach(task => {
            const taskEl = document.createElement('div');
            taskEl.className = `task-item ${task.completed ? 'completed' : ''}`;
            
            taskEl.innerHTML = `
                <div class="task-checkbox ${task.completed ? 'checked' : ''}" 
                     onclick="app.toggleTask(${task.id})"></div>
                <div class="task-content">
                    <div class="task-text">${this.escapeHtml(task.text)}</div>
                    <div class="task-timestamps">
                        <div class="timestamp">
                            📅 Created: ${this.formatDate(task.createdAt)}
                        </div>
                        ${task.completedAt ? `
                            <div class="timestamp">
                                ✅ Completed: ${this.formatDate(task.completedAt)}
                            </div>
                        ` : ''}
                    </div>
                </div>
                <button class="delete-btn" onclick="app.deleteTask(${task.id})">Delete</button>
            `;
            
            this.taskList.appendChild(taskEl);
        });
        
        this.updateStats();
    }
    
    escapeHtml(text) {
        const div = document.createElement('div');
        div.textContent = text;
        return div.innerHTML;
    }
}

// Initialize app
const app = new TodoApp();