const restaurant_no = 5;

function shuffle(array, seed) {
    var m = array.length, t, i;
    while (m) {
      i = Math.floor(random(seed) * m--);
      t = array[m];
      array[m] = array[i];
      array[i] = t;
      ++seed 
    }
    return array;
}

function random(seed) {
    var x = Math.sin(seed++) * 10000; 
    return x - Math.floor(x);
}

async function fetchRestaurants() {
    const response = await fetch('restaurants.json');
    if (!response.ok) {
        throw new Error('Network response was not ok ' + response.statusText);
    }
    const data = await response.json();
    return data;
}

function getRandomRestaurants(restaurants, seed) {
    randomRestaurants = shuffle(restaurants, seed);
    return randomRestaurants.slice(0,restaurant_no);
}

function getDailySeed() {
    const today = new Date();
    return today.getFullYear() * 10000 + (today.getMonth() + 1) * 100 + today.getDate();
}

async function displayRestaurants(useRandomSeed = false) {
    const today = new Date();
    const day = today.getDay();
    const options = { weekday: 'long', year: 'numeric', month: 'long', day: 'numeric' };
    const formattedDate = today.toLocaleDateString(undefined, options);
    document.getElementById('currentDate').innerText = `Today is ${formattedDate}`;

    if (day === 0 || day === 6) {
        document.getElementById('restaurants').innerHTML = "No suggestions available today!";
        return;
    }

    try {
        const restaurants = await fetchRestaurants();
        const seed = useRandomSeed ? Math.floor(Math.random() * 1000000) : getDailySeed();
        const randomRestaurants = getRandomRestaurants(restaurants, seed);
        const firstThreeRestaurants = randomRestaurants.slice(0, 3);
        const bonusRestaurants = randomRestaurants.slice(3, 5);

        document.getElementById('restaurants').innerHTML = firstThreeRestaurants.map(restaurant => 
            `<a href="${restaurant[1]}" target="_blank">${restaurant[0]}</a>`
        ).join('<br>');
        document.getElementById('bonusRestaurants').innerHTML = bonusRestaurants.map(restaurant => 
            `<a href="${restaurant[1]}" target="_blank">${restaurant[0]}</a>`
        ).join('<br>');

        // Remove previous suggest again button
        const existingButton = document.querySelector('.suggest-again-button');
        if (existingButton) {
            existingButton.remove();
        }

        // Add new suggest again button
        const suggestButton = document.createElement('div');
        suggestButton.classList.add('suggest-again-button');
        suggestButton.style.cssText = 'text-align: center; margin-top: 20px;';
        suggestButton.innerHTML = '<button onclick="displayRestaurants(true)" style="padding:8px 16px; background-color:#4CAF50; color:white; border:none; border-radius:4px; cursor:pointer;">Suggest Again</button>';
        document.querySelector('.bonus-container').after(suggestButton);

    } catch (error) {
        const bestRestaurants = [
            ["돈비고고 (unlimited 돈까스 + 제육 (Pork) for 8.8K)", "https://naver.me/GGUfwvl9"],
            ["Taksim Kebab (Turkish, small place)", "https://maps.app.goo.gl/6rwGVo5qbT9xKZAMA"],
            ["강남역 파스타 (Pasta, large space)", "https://naver.me/xL1EJLfC"],
        ]
        document.getElementById('restaurants').innerHTML = "Failed to load restaurant suggestions. <br>Below are my personal suggestions based on your review!!";
        document.getElementById('bonusHeader').innerHTML = "";        
        document.getElementById('bonusRestaurants').innerHTML = bestRestaurants.map(restaurant => 
            `<a href="${restaurant[1]}" target="_blank">${restaurant[0]}</a>`
        ).join('<br>');

        // Remove previous suggest again button
        const existingButton = document.querySelector('.suggest-again-button');
        if (existingButton) {
            existingButton.remove();
        }

        // Add new suggest again button
        const suggestButton = document.createElement('div');
        suggestButton.classList.add('suggest-again-button');
        suggestButton.style.cssText = 'text-align: center; margin-top: 20px;';
        suggestButton.innerHTML = '<button onclick="displayRestaurants(true)" style="padding:8px 16px; background-color:#4CAF50; color:white; border:none; border-radius:4px; cursor:pointer;">Suggest Again</button>';
        document.querySelector('.bonus-container').after(suggestButton);
    }
}

window.onload = () => displayRestaurants(false);