// Base64 encoding/decoding utilities
const b64 = {
    encode: array => btoa(String.fromCharCode.apply(null, array)),
    decode: str => Uint8Array.from(atob(str), c => c.charCodeAt(0))
};

async function generateKeyPair() {
    const keyPair = await window.crypto.subtle.generateKey(
        {
            name: 'X25519',
            namedCurve: 'X25519',
        },
        true,
        ['deriveKey', 'deriveBits']
    );

    const privateKey = await window.crypto.subtle.exportKey('raw', keyPair.privateKey);
    const publicKey = await window.crypto.subtle.exportKey('raw', keyPair.publicKey);

    return {
        privateKey: b64.encode(new Uint8Array(privateKey)),
        publicKey: b64.encode(new Uint8Array(publicKey))
    };
}

document.addEventListener('DOMContentLoaded', async function() {
    const form = document.getElementById('subscription-form');
    const slider = document.getElementById('duration-slider');
    const durationDisplay = document.getElementById('duration-display');
    const priceDisplay = document.getElementById('price-display');
    const presetButtons = document.querySelectorAll('.duration-preset');
    const userIdInput = document.getElementById('user-id');
    const publicKeyInput = document.getElementById('public-key');
    const regenerateButton = document.getElementById('regenerate-keys');

    let currentKeyPair = null;

    function formatDuration(hours) {
        if (hours < 24) return `${hours} hour${hours === 1 ? '' : 's'}`;
        if (hours < 168) return `${hours / 24} day${hours === 24 ? '' : 's'}`;
        if (hours < 720) return `${Math.floor(hours / 168)} week${hours === 168 ? '' : 's'}`;
        return `${Math.floor(hours / 720)} month${hours === 720 ? '' : 's'}`;
    }

    async function generateNewKeys() {
        try {
            currentKeyPair = await generateKeyPair();
            publicKeyInput.value = currentKeyPair.publicKey;
            
            // Save private key to localStorage
            const keyData = {
                privateKey: currentKeyPair.privateKey,
                publicKey: currentKeyPair.publicKey,
                createdAt: new Date().toISOString()
            };
            localStorage.setItem(`vpn_keys_${userIdInput.value}`, JSON.stringify(keyData));
        } catch (error) {
            console.error('Failed to generate keys:', error);
            alert('Failed to generate WireGuard keys. Please try again.');
        }
    }

    async function initializeForm() {
        // Generate user ID
        userIdInput.value = crypto.randomUUID();
        
        // Generate initial keys
        await generateNewKeys();
    }

    async function updatePrice(hours) {
        try {
            const response = await fetch('/api/calculate-price', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({ hours: parseInt(hours) })
            });
            const data = await response.json();
            priceDisplay.textContent = data.price;
            durationDisplay.textContent = formatDuration(hours);
        } catch (error) {
            console.error('Error calculating price:', error);
        }
    }

    // Event listeners
    slider.addEventListener('input', () => updatePrice(slider.value));

    regenerateButton.addEventListener('click', generateNewKeys);

    presetButtons.forEach(button => {
        button.addEventListener('click', (e) => {
            const hours = e.target.dataset.hours;
            slider.value = hours;
            updatePrice(hours);
        });
    });

    form.addEventListener('submit', async (e) => {
        e.preventDefault();
        
        if (!currentKeyPair) {
            alert('No keys generated. Please refresh the page.');
            return;
        }
        
        try {
            const response = await fetch('/create-invoice', {
                method: 'POST',
                headers: {
                    'Content-Type': 'application/json'
                },
                body: JSON.stringify({
                    duration: parseInt(slider.value),
                    userId: userIdInput.value,
                    publicKey: currentKeyPair.publicKey
                })
            });
            
            if (!response.ok) {
                throw new Error('Failed to create invoice');
            }
            
            const data = await response.json();
            window.location.href = data.checkout_url;
            
        } catch (error) {
            console.error('Error creating invoice:', error);
            alert('Failed to create payment invoice. Please try again.');
        }
    });

    // Initialize the form
    await initializeForm();
    // Initial price calculation
    updatePrice(slider.value);
});