function viv() {
    let s = ".\n";
    for (let i in arr) {
        for (let j in arr[i]) {
            s += arr[i][j] + " ";
        }
        s = s.trim() + "\n";
    }
    console.log(s);
}

let snake_length_start = 4;
let snake_length = snake_length_start;
let snake_direction = 0; // 0 = right, 1 = down, 2 = left, 3 = up
var game_interval = null;
var game_ended_time = null;
var game_speed_start = 350;
var game_speed_min = 100;
var game_speed = game_speed_start;
var last_game_loop = null;

function rnd(min, max) { return Math.floor(Math.random() * (max - min + 1)) + min; }


function generateSnake() {    
    let start_pos_j = rnd(2, (arr[0].length / 3));
    let start_pos_i = rnd(2, 3);
    if (start_pos_i == 3) start_pos_i = 4;    
    

    for (let i = 0; i < snake_length; i++) {
        arr[start_pos_i][start_pos_j + i] = i + 1;
    }  
}

function getMaxBelow1000() {
    let maxVal = 0;
    for (let i = 0; i < arr.length; i++) {
        for (let j = 0; j < arr[i].length; j++) {
            if (arr[i][j] < 1000 && arr[i][j] > maxVal) {
                maxVal = arr[i][j];
            }
        }
    }
    return maxVal;
}

function printText(text) {
    $("#label_for_table").html(text);
}

function printTextOnScreen(text) {
    clearTextFromScreen();
    var el = $("<div id='onscreentext'></div>");
    el.css({
        'font-size': '40px',
        'text-align': 'center',
        'width': '100%',
        'position': 'absolute',
        'top': '330px',
        'z-index': '999'
    });
    var el_text = $("<span>" + text + "</span>");
    el_text.css({
        "text-shadow": "rgba(0, 0, 0, 0.2) 2px 2px 10px"
    });
    el.append(el_text);
    $("body").append(el);
    $("#inside_container").css({
        "opacity": "0.35",
        "pointer-events": "none",
    });
}

function clearTextFromScreen() {
    $("#onscreentext").remove();  
    $("#inside_container").css({
        "opacity": "1",
        "pointer-events": "auto",
    });  
}

function getScore() {
    return snake_length - snake_length_start;
}

function printScore() {
    printText("Отримано світла: " + getScore());
}

function sendScoreToLeaderboard(score) {
    let query = "https://api.svitlobot.in.ua/snakeGame/gameOverScore?score=" + score;
    $.get(query);
}

function gameOver() {
    let score = getScore();
    sendScoreToLeaderboard(score);
    printText("Отримано світла: " + score);
    printTextOnScreen("Game Over!<br>Натисніть WASD або ↑ ← → ↓");
    clearInterval(game_interval);
    game_interval = null;
    game_ended_time = new Date().getTime();
    printTable();
    viv();  
}

function moveSnake() {
    let head;
    let tail;

    let maxSnakeVal = getMaxBelow1000();

    // Find the head and the tail of the snake
    for (let i = 0; i < arr.length; i++) {
        for (let j = 0; j < arr[i].length; j++) {
            if (arr[i][j] === 1) {
                tail = [i, j];
            } else if (arr[i][j] === maxSnakeVal) {
                head = [i, j];
            }
        }
    }

    // Determine the new head position based on the direction
    let newHead = [...head];
    switch (snake_direction) {
        case 0:
            newHead[1]++;
            break;
        case 1:
            newHead[0]++;
            break;
        case 2:
            newHead[1]--;
            break;
        case 3:
            newHead[0]--;
            break;
    }

    if (newHead[0] >= arr.length) newHead[0] = 0;
    if (newHead[0] < 0) newHead[0] = arr.length - 1;
    if (newHead[1] >= arr[0].length) newHead[1] = 0;
    if (newHead[1] < 0) newHead[1] = arr[0].length - 1;
    

    let isAppleEaten = false;

    // Check for apple
    if (arr[newHead[0]][newHead[1]] === 1000) {
        // Add apple consumption logic here, e.g., increase snake length
        // For now, let's just reset the apple
        snake_length++;
        isAppleEaten = true;
        game_speed = getGameSpeed(getScore());
    }

    if (!isAppleEaten) {
        // Move the snake by incrementing all body parts
        for (let i = 0; i < arr.length; i++) {
            for (let j = 0; j < arr[i].length; j++) {
                if (arr[i][j] > 0 && arr[i][j] < 1000) {
                    arr[i][j]--;
                }
            }
        }
    }

    if (!isAppleEaten && arr[newHead[0]][newHead[1]] > 0) {
        arr[newHead[0]][newHead[1]] = -100;
        gameOver();
        return;
    }

    // Place the new head

    
    arr[newHead[0]][newHead[1]] = snake_length;

}

function spawnApple() {
    let applePlaced = false;

    while (!applePlaced) {
        let i = rnd(0, arr.length - 1);
        let j = rnd(0, arr[0].length - 1);

        let maxSnakeVal = getMaxBelow1000();
        let head = [];

        // Find the head of the snake
        for (let x = 0; x < arr.length; x++) {
            for (let y = 0; y < arr[x].length; y++) {
                if (arr[x][y] === maxSnakeVal) {
                    head = [x, y];
                }
            }
        }

        let distance = Math.abs(head[0] - i) + Math.abs(head[1] - j);

        // Check if the position is valid
        if (arr[i][j] === 0 && distance > 5 && distance < 20) {
            arr[i][j] = 1000;
            applePlaced = true;
        }
    }
}

function checkApple() {
   for (let i = 0; i < arr.length; i++) {
        for (let j = 0; j < arr[i].length; j++) {
            if (arr[i][j] == 1000) return;
        }
    }    
    spawnApple();
}

let last_key_press = 0;
let movementInputArray = [];

function changeDirection(new_direction) {

    if (!game_interval) {
        startGame();
    }

    let t = new Date().getTime();
    let diff = t - last_key_press;
    let trs = game_speed;

    if (diff < trs) {
        movementInputArray.push(new_direction);
    } else {
        movementInputArray = [new_direction];
    }
    last_key_press = t;
}

function setButtonListeners() {

    for (let i = 0; i < 4; i++) {
        $("#btn_control_" + i).on("click", function(){
            changeDirection(i);    
        });    
    }

      
}

function keyboardListener(event) {    
    switch (event.key) {
        case 'ArrowUp':
        case 'w':
        case 'W':
        case 'ц':
        case 'Ц':
            changeDirection(3);
            break;
        case 'ArrowDown':
        case 's':
        case 'S':
        case 'ы':
        case 'Ы':
            changeDirection(1);
            break;
        case 'ArrowLeft':
        case 'a':
        case 'A':
        case 'ф':
        case 'Ф':
            changeDirection(2);
            break;
        case 'ArrowRight':
        case 'd':
        case 'D':
        case 'в':
        case 'В':
            changeDirection(0);
            break;
    }
}

function handleMovementInput() {
    if (!movementInputArray || movementInputArray.length == 0) return;

    let direction = movementInputArray[0];
    if (Math.abs(snake_direction - direction) == 2 && movementInputArray.length != 2) {        
      movementInputArray.shift();      
      return; // opposite movement
    }
    if (movementInputArray.length > 1 && (Math.abs(snake_direction - direction) == 2 || snake_direction == direction)) {  
      //swap
      
      if (Math.abs(movementInputArray[1] - snake_direction) != 2) snake_direction = movementInputArray[1];
      movementInputArray[1] = direction;
      movementInputArray.shift();
      return;
    }

    snake_direction = direction;
    movementInputArray.shift();
}

function getGameSpeed(score) {
    const max_score = 25;

    if (score < 0) {
        throw new Error("Score must be a positive number.");
    }

    var max_speed = game_speed_start * 0.7;

    // Calculate the speed factor (linear decrease)
    const speedFactor = (max_speed - game_speed_min) / max_score;
    
    // Calculate the new speed
    let newSpeed = max_speed - (score * speedFactor);

    // Ensure the speed doesn't go below the minimum speed
    if (score >= max_score) {
        newSpeed = game_speed_min;
    }

    return newSpeed;
}

function gameLoop() {
    

    /* let s = "";
    for (let i = 0; i < movementInputArray.length; i++) {
        s += movementInputArray[i];
        if (i != movementInputArray - 1) s += ", ";
    }
    printText("Moves: " + s); */

    let t = new Date().getTime();
    if (last_game_loop) {
        if (t - last_game_loop < game_speed) return;
    }
    last_game_loop = t;

    handleMovementInput();

    moveSnake();
    if (!game_interval) return;
    //viv();
    printTable();
    checkApple();    
    printScore();



    
}

function initGameState() {
    //clear array
    for (let i = 0; i < arr.length; i++) {
        for (let j = 0; j < arr[0].length; j++) {
            arr[i][j] = 0;
        }
    }  
     
    movementInputArray = []
    snake_length = snake_length_start;
    snake_direction = 0; 
    game_speed = game_speed_start;  

    generateSnake();
    spawnApple(); 
    printTable();
}

function startGame() {
    if (game_ended_time) {
        if (new Date().getTime() - game_ended_time < 400) return;
        initGameState();           
    }    

    game_interval = setInterval(gameLoop, 10);
    clearTextFromScreen();
}

function initGame() {
    setButtonListeners();
    initGameState();   

    document.addEventListener('keydown', keyboardListener);

    printTextOnScreen("Натисніть WASD або ↑ ← → ↓");
    
}