/**
 * Show the game selection view.
 *
 * <p>
 * The "hidden" class is added on the footer, the game_start elements and the game_mode_selection
 * elements are show. The body margin is also set to 0 by adding the ingame class.
 * </p>
 */
function showGameModeSelection() {
    document.getElementsByTagName("body")[0].classList.add("ingame");
    document.getElementsByTagName("footer")[0].classList.add("hidden");
    document.getElementsByClassName("game_start")[0].classList.add("hidden");
    document.getElementsByClassName("game_mode_selection")[0].classList.remove("hidden");
}

/**
 * Show the game selection view.
 *
 * <p>
 * The "hidden" class is removed on the footer, the game_start elements and the game_mode_selection
 * elements are hidden. The body margin is also set to its normal value by removing the ingame
 * class.
 * </p>
 */
function hideGameModeSelection() {
    document.getElementsByTagName("body")[0].classList.remove("ingame");
    document.getElementsByTagName("footer")[0].classList.remove("hidden");
    document.getElementsByClassName("game_start")[0].classList.remove("hidden");
    document.getElementsByClassName("game_mode_selection")[0].classList.add("hidden");
}

/**
 * Hide an error message on the first game_start_failed CSS element.
 *
 * <p>
 * The element will be hidden by removing the hidden CSS class on the element.
 * </p>
 */
function hideInvalidInputErrorMessage() {
    document.getElementsByClassName("game_start_failed")[0].classList.add("hidden");
}

/**
 * Show an error message on the first game_start_failed CSS element.
 *
 * <p>
 * The current error message text will be replaced by the given message and the element will be
 * shown, by removing the hidden CSS class on the element.
 * </p>
 *
 * @param {boolean} errorMessage the error message to show
 */
function showInvalidInputErrorMessage(errorMessage) {
    let gameStartFailedElement = document.getElementsByClassName("game_start_failed")[0];
    gameStartFailedElement.textContent = errorMessage;
    gameStartFailedElement.classList.remove("hidden");
}

/**
 * Determine whether a nickname is invalid.
 *
 * <p>
 * A nickname is invalid when it only contains spaces characters or is empty.
 * </p>
 *
 * @returns whether a nickname is invalid
 */
function isNickNameInvalid() {
    return document.getElementById("game_username").value.trim() == "";
}

/**
 * Determine whether a room code is invalid.
 *
 * <p>
 * A room code is invalid when it only contains spaces characters or is empty.
 * </p>
 *
 * @returns whether a room code is invalid
 */
function isRoomCodeInvalid() {
    return document.getElementById("game_room_code").value.trim() == "";
}

/**
 * Determine whether nickname and/or room code inputs are valid.
 *
 * <p>
 * The nickname validity is always checked, while the room code validity is checked only when
 * checkRoomCode is true (because when creating a room or playing on a solo match, the room code is
 * not used so checking it would be useless and would require a valid room code).
 * </p>
 *
 * @param {boolean} checkRoomCode whether the room code input should be checked
 * @returns whether the checked inputs are valid
 */
function areInputsValid(checkRoomCode) {
    if (isNickNameInvalid()) {
        showInvalidInputErrorMessage("Le nom saisi n'est pas valide.");
        return false;
    }

    if (checkRoomCode && isRoomCodeInvalid())  {
        showInvalidInputErrorMessage("Le code de salon saisi n'est pas valide.");
        return false;
    }

    return true;
}


/**
 * Handler for the multiplayer room creation button 
 */
function createMultiPlayerRoom() {
    if (!areInputsValid(false)) {
        return;
    }

    hideInvalidInputErrorMessage();

    startGame();
}

/**
 * Handler for the join room button 
 */
function joinMultiPlayerRoom() {
    if (!areInputsValid(true)) {
        return;
    }

    hideInvalidInputErrorMessage();

    joinGame();
}

/**
 * Set the current theme for the game.
 *
 * <p>
 * The theme preference is read from the local storage.
 * </p>
 *
 * <p>
 * If accessing to the local storage is not allow, an error message which prevents playing the game
 * and requesting user to enable localStorage is shown, and the error is logged in the console.
 * </p>
 */
function setCurrentTheme() {
    const htmlElement = document.getElementsByTagName("html")[0];

    try {
        const currentTheme = localStorage.getItem("pref_theme");

        if (currentTheme == "light") {
            htmlElement.classList.remove("dark");
            htmlElement.classList.add("light");
        } else {
            // Use dark theme by default
            htmlElement.classList.remove("light");
            htmlElement.classList.add("dark");
        }

        const btn = document.getElementsByClassName("theme_switcher")[0];
        btn.addEventListener("pointerup", changeTheme);
    } catch (e) {
        console.error("Unable to set theme from localStorage", e);
        htmlElement.classList.add("dark");
    }
}

/**
 * Change the theme from the current theme to its opposite.
 *
 * <p>
 * If the current theme is "dark", it will become "light" and vice versa.
 * </p>
 *
 * <p>
 * The new theme is saved in the localStorage, if the browser allows this action; otherwise, an
 * error message is shown in the console.
 * </p>
 */
function changeTheme() {
    const currentTheme = localStorage.getItem("pref_theme");

    const htmlElement = document.getElementsByTagName("html")[0];
    let newTheme;
    if (currentTheme == "light") {
        htmlElement.classList.remove("light");
        htmlElement.classList.add("dark");
        newTheme = "dark";
    } else {
        htmlElement.classList.remove("dark");
        htmlElement.classList.add("light");
        newTheme = "light";
    }

    try {
        localStorage.setItem("pref_theme", newTheme);
    } catch (e) {
        console.error("Unable to save theme change to localStorage", e);
    }
}

/**
 * This function launches a single player game. It sends the api request to
 * create a game then it immediately start the game by sendind the startGame api
 */
async function startSoloGame(){

    if (!areInputsValid(false)) {
        return;
    }

    hideInvalidInputErrorMessage();

    username = document.getElementById("game_username").value;
    let data = {}
    data["username"] = username;
    await makeAPIRequest("createGame",data);
    start = makeAPIRequest("startGame");
    start.then(()=>{
        window.location.href = "/solo";
    })
}

/**
 * This function creates a multiplayer game by sending the createGame api call
 * then, if no error occured, redirects to the lobby page.
 */
async function startGame(){
    username = document.getElementById("game_username").value;
    let data = {}
    data["username"] = username;
    response = makeAPIRequest("createGame",data);
    response.then((value) => {
        if (value["error"] != 0){
            alert(value["msg"]);
        }
        else{
            gameid = value["game_id"]
            window.location.href = "/lobby/" + gameid;
        }
      });

}

/**
 * This function read the username and the room code in order to
 * join an already existing game, to do so it calls the joinGame endpoint
 * with the aftermentioned username and room code as parameter. 
 */
async function joinGame(){
    username = document.getElementById("game_username").value;
    gameid = document.getElementById("game_room_code").value;
    console.log(username);
    data = {}
    data["username"] = username;
    data["game_id"] = gameid;
    response = makeAPIRequest("joinGame",data);
    response.then((value)=>{
        console.log(value);
        if (value["error"] != 0){
            //alert(value["msg"]);
        }
        else{
            window.location.href = "/lobby/" + gameid;
        }
    })
}
// Set event listeners

document.getElementById("play_button").addEventListener("click", showGameModeSelection);
document.getElementById("back_button").addEventListener("click", hideGameModeSelection);
document.getElementById("start_solo_game_button").addEventListener("click", startSoloGame);
document.getElementById("create_room_button").addEventListener("click", createMultiPlayerRoom);
document.getElementById("join_room_button").addEventListener("click", joinMultiPlayerRoom);

// Execution of functions

setCurrentTheme();