// Navigation Router
function router(pageName) {
    const viewContainer = document.getElementById('app-view');
    const title = document.getElementById('page-title');
    const navItems = document.querySelectorAll('.nav-item');

    // Update Nav
    navItems.forEach(item => {
        if (item.dataset.page === pageName) item.classList.add('active');
        else item.classList.remove('active');
    });

    // Set Title
    title.textContent = pageName.charAt(0).toUpperCase() + pageName.slice(1);

    // Load View
    const template = document.getElementById(`view-${pageName}`);
    if (template) {
        viewContainer.innerHTML = '';
        viewContainer.appendChild(template.content.cloneNode(true));

        // Initialize view specific logic
        if (pageName === 'dashboard') loadDashboard();
        if (pageName === 'shop') loadShop();
        if (pageName === 'profile') loadProfile();

        // Re-init generic UI stuff like icons if new ones added
        if (window.lucide) lucide.createIcons();
    }
}

// Data Fetching
const API_BASE = '/api';

// Telegram Integration
let tgUser = null;
if (window.Telegram && window.Telegram.WebApp) {
    const tg = window.Telegram.WebApp;
    tg.ready();
    tgUser = tg.initDataUnsafe?.user;

    // Theme sync
    if (tg.colorScheme === 'dark') document.body.classList.add('dark');

    // Expand
    tg.expand();
}

// Fallback for browser testing
if (!tgUser) {
    console.warn("No Telegram user detected, using mock user");
    tgUser = { id: 123456789, first_name: 'Test', username: 'testuser' };
}

// Update UI with User Info
const sidebarName = document.getElementById('sidebar-name');
const sidebarAvatar = document.getElementById('sidebar-avatar');
if (sidebarName) sidebarName.textContent = tgUser.first_name || tgUser.username;
if (sidebarAvatar) sidebarAvatar.textContent = (tgUser.first_name || 'U')[0].toUpperCase();

async function loadDashboard() {
    try {
        const res = await fetch(`${API_BASE}/user/${tgUser.id}`);
        if (!res.ok) throw new Error("Failed to fetch user");
        const data = await res.json();

        const statusEl = document.getElementById('dash-status');
        const daysEl = document.getElementById('dash-days');
        const dataEl = document.getElementById('dash-data');
        const planEl = document.getElementById('sub-plan-name');
        const expireEl = document.getElementById('sub-expire-date');

        if (statusEl) statusEl.textContent = data.status;
        if (daysEl) daysEl.textContent = data.days_left;
        if (dataEl) dataEl.textContent = `${data.data_usage || 0} GB`;
        if (planEl) planEl.textContent = data.plan;
        if (expireEl) expireEl.textContent = data.expire_date;

        // Colorize status
        if (data.status === 'Active') {
            document.querySelector('.stat-info .value').style.color = '#4ade80';
        } else {
            document.querySelector('.stat-info .value').style.color = '#f87171';
        }

    } catch (e) {
        console.error(e);
        // Show error state?
    }
}

async function loadShop() {
    const container = document.getElementById('plans-container');
    if (!container) return;

    container.innerHTML = '<div class="loading-spinner">Loading plans...</div>';

    try {
        const res = await fetch(`${API_BASE}/plans`);
        if (!res.ok) throw new Error("Failed to fetch plans");
        const plans = await res.json();

        container.innerHTML = '';
        plans.forEach(plan => {
            const card = document.createElement('div');
            card.className = 'card glass plan-card';

            // Features list generation
            const features = [
                `${plan.data_limit} GB Data`,
                `${plan.days} Days`,
                'High Speed'
            ];

            card.innerHTML = `
                <div class="plan-name">${plan.name}</div>
                <div class="plan-price">${plan.price} XTR</div>
                <ul class="plan-features">
                    ${features.map(f => `<li>${f}</li>`).join('')}
                </ul>
                <button class="btn-primary" onclick="buyPlan('${plan.id}')">Buy for ${plan.price}</button>
            `;
            container.appendChild(card);
        });
    } catch (e) {
        container.innerHTML = 'Error loading plans.';
    }
}

async function buyPlan(planId) {
    if (!window.Telegram || !window.Telegram.WebApp) {
        alert("Payment only works inside Telegram!");
        return;
    }

    const btn = document.activeElement;
    const originalText = btn.innerText;
    btn.innerText = 'Creating Invoice...';
    btn.disabled = true;

    try {
        const res = await fetch(`${API_BASE}/create-invoice`, {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({
                user_id: tgUser.id,
                plan_id: planId
            })
        });

        const data = await res.json();

        if (data.invoice_link) {
            window.Telegram.WebApp.openInvoice(data.invoice_link, (status) => {
                if (status === 'paid') {
                    window.Telegram.WebApp.showAlert('Payment Successful! Subscription activated.');
                    router('dashboard');
                } else if (status === 'cancelled') {
                    // User cancelled
                } else {
                    window.Telegram.WebApp.showAlert('Payment failed or pending.');
                }
            });
        } else {
            window.Telegram.WebApp.showAlert('Error creating invoice: ' + data.error);
        }

    } catch (e) {
        window.Telegram.WebApp.showAlert('Network error');
        console.error(e);
    } finally {
        btn.innerText = originalText;
        btn.disabled = false;
    }
}

async function loadProfile() {
    document.getElementById('profile-tg-id').textContent = tgUser.id;
    document.getElementById('profile-username').value = '@' + (tgUser.username || 'unknown');
}

// Init
router('dashboard');