// ==========================================
// Code to handle the actual gameplay
// ==========================================


// global variable for the timer which calls the 
// update function. You need this so you can cancel the timer
// later
var gTimer = null;

// constants to influence how easy the game is
const FRAME_RATE = 30;      
const TIME_TO_WIN = 10;    // how many seconds you need to survive
const MONSTER_SPEED = 5;    // speeds of the objects
const PLAYER_SPEED = 2;


// global variables for drawing on the canvas
var gCanvas = document.getElementById("gameSpace");
var gCtx = gCanvas.getContext("2d");

// when the game was started, for the timer
gStartTime = null;

// global variables for the objects on the screen
// they all need the same properties x,y,etc


var gMonster = {
    "x": 0,
    "y": 0,
    "xspeed": MONSTER_SPEED,
    "yspeed": MONSTER_SPEED,
    "width":50,
    "height":50,
    "colour": "#FF00FF"
}


// start the game
function startTheGame()
{
    // place player and monster in random places
    randomlyPlace(gMonster);

    // start the timer which calls the updater every 10th of a second
    gTimer = window.setInterval(updateGame,1000/FRAME_RATE);

    // start the keyboard listener
    addEventListener("keydown",handleKeyDown);

    // start the survival timer
    gStartTime = Date.now();
}


// when a key is pressed, decide what to do
function handleKeyDown(keyEvent)
{
    switch(keyEvent.key)
    {
        case "ArrowUp":
            // decide what happens
            break;
        case "ArrowDown":
            // decide what happens            
            break;
        // and more...
    }
}
// the main game loop. This function gets called for every frame of the game
function updateGame()
{
    // move the objects and get them to bounce or constrain
    // your code here

    // update the survival timer message
    // your code here
    
    // draw the players and monsters
    drawGame();

    // if the monster and player have collided, the game ends
    
    // your code here

    // if the player has survived enough time, the game ends

    // your code here

}

// display a message by freplacing the innerHTML of the message DIV
function displayMessage(text)
{
    // your code here
}

// compare the current time to the time the game started
// and return that, converted to seconds
function getTimeSurvived()
{
    var timeSurvived = (Date.now() - gStartTime)/1000;
    return timeSurvived;
}


// erase the current display and draw all the objects in the game
function drawGame()
{

    // erase the background

    // your code here

    // draw the objects

    // your code here
}

// draw a single object
function drawObject(thing)
{
    // set the context colour

    // use the context fillRect function
}

// stop the timer from calling the update function
function endTheGame()
{
    clearInterval(gTimer);
}

// move an object by adding the speeds to the coordinates
function moveObject(thing)
{
   // your code here
}