//Game options
var framerate = 150;
var gColumns = 60;
var gRows = 140;
var tileWidth = 12;
var paused = true;
var deleteMode = false;

//Canvas properties
var canvas_width = gRows * tileWidth;
var canvas_height = gColumns * tileWidth;


//Tiles in game of life
var tiles = {
    tiles: [...Array(gRows)].map(x => Array(gColumns).fill(0)), //<< x*y array with all values set to zero
    tempTiles: [...Array(gRows)].map(x => Array(gColumns).fill(0)), //<< same as above

    //One iteration of game of life
    iterate: function() {
        myGameArea.clear(); //Remove graphics

        //Create temporary 2D array of new values
        for (var x = 0; x < gRows; x++)
            for (var y = 0; y < gColumns; y++) {
                if (![2, 3].includes(this.getNeighbors(x, y))) {
                    this.tempTiles[x][y] = 0;
                } //cell dies if number of neighbors are not 2 or 3
                else if (this.getNeighbors(x, y) == 3) {
                    this.tempTiles[x][y] = 1;
                } //cell is born if there are exactly 3 neighbors
                else {
                    this.tempTiles[x][y] = this.tiles[x][y];
                } //cell remains unchanged otherwise

                //Draw new graphics
                if (this.tempTiles[x][y] == 1) {
                    drawCell(x, y);
                }
            }

        //Replace old values with new values
        for (var x = 0; x < gRows; x++) {
            for (var y = 0; y < gColumns; y++) {
                this.tiles[x][y] = this.tempTiles[x][y];
            }
        }
    },

    //returns number of neighboring cells for cell at position x, y
    getNeighbors: function(x, y) {
        let neighbors = 0;

        if (x != 0) {
            if (y != 0) neighbors += this.tiles[x - 1][y - 1];
            neighbors += this.tiles[x - 1][y];
            if (y < gColumns - 1) neighbors += this.tiles[x - 1][y + 1];
        }
        if (y != 0) neighbors += this.tiles[x][y - 1];
        if (y < gColumns) neighbors += this.tiles[x][y + 1];
        if (x < gRows - 1) {
            if (y != 0) neighbors += this.tiles[x + 1][y - 1];
            neighbors += this.tiles[x + 1][y];
            if (y < gColumns - 1) neighbors += this.tiles[x + 1][y + 1];
        }

        return neighbors;
    },

    //Sets all cells to zero
    clear: function() {
        this.tiles = [...Array(gRows)].map(x => Array(gColumns).fill(0)); //<< x*y array with all values set to zero
    }
}


//Initializes canvas and event listeners (starts when HTML has loaded)
function startGame() {
    myGameArea.start();

    myGameArea.canvas.onclick = function(e) { //<< Mouse click event listener
        //outer edges of tiles is set to 0 to simplify neighbor calculation code
        //therefore we use x+1 and y+1
        var x = Math.floor(e.offsetX / tileWidth);
        var y = Math.floor(e.offsetY / tileWidth);

        if (!deleteMode) {
            tiles.tiles[x][y] = 1;
            drawCell(x, y);
        } else {
            tiles.tiles[x][y] = 0;
            unDrawCell(x, y);
        }

        //output some info to console
        console.log("coords: ", x, y);
        console.log("neighbors: ", tiles.getNeighbors(x + 1, y + 1));
    }
}

//HTML5 canvas
var myGameArea = {
    canvas: document.createElement("canvas"),

    start: function() {
        this.canvas.width = canvas_width;
        this.canvas.height = canvas_height;
        this.canvas.style.position = "absolute";
        this.canvas.style.top = "100px";
        this.canvas.style.left = "100px";

        this.context = this.canvas.getContext("2d");
        document.body.insertBefore(this.canvas, document.body.childNodes[0]);
        this.frameNo = 0;
        this.interval = setInterval(updateGameArea, 1000 / framerate);
        drawGrid(gColumns, gRows, tileWidth);
    },

    clear: function() {
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
        drawGrid(gColumns, gRows);
    }
}

//Fill one tile in grid with color
function drawCell(x, y) {
    ctx = myGameArea.context;
    ctx.fillStyle = "#ff0000";
    ctx.fillRect(x * tileWidth, y * tileWidth, tileWidth, tileWidth);
    drawGrid(tiles.columns, tiles.rows, tileWidth);
}

//Remove graphics from tile in grid
function unDrawCell(x, y) {
    ctx = myGameArea.context;
    ctx.fillStyle = "#ffffff";
    ctx.clearRect(x * tileWidth, y * tileWidth, tileWidth, tileWidth);
    drawGrid(tiles.columns, tiles.rows, tileWidth);
}

//Display grid on screen
function drawGrid(columns, rows, size) {
    //Style parameters
    ctx = myGameArea.context;
    ctx.lineWidth = 1;
    ctx.strokeStyle = "#7F7F7F";

    //By adding 0.5 the lines are displayed sharper
    for (var i = 1; i <= columns; i++) {
        ctx.moveTo(0, i * size + 0.5);
        ctx.lineTo(canvas_width, i * size + 0.5);
        ctx.stroke();
    }

    for (var i = 1; i <= rows; i++) {
        ctx.moveTo(i * size + 0.5, 0);
        ctx.lineTo(i * size + 0.5, canvas_height);
        ctx.stroke();
    }
}

//Toggles between eraser and pencil
function toggleDrawMode() {
    deleteMode = !deleteMode;
    if (deleteMode) {
        document.getElementById("drawModeEnabled").innerHTML = "You are erasing";
    } else {
        document.getElementById("drawModeEnabled").innerHTML = "You are drawing";
    }
}

//Set all cells to zero and removes graphics
function clearCells() {
    console.log("attempting to clear cells");
    tiles.clear();
    myGameArea.clear();
}

//Toggles pause and updates text on screen
function togglePause() {
    paused = !paused;

    if (paused) {
        document.getElementById("gameIsPaused").innerHTML = "You are paused";
    } else {
        document.getElementById("gameIsPaused").innerHTML = "You are unpaused";
    }
}

//This function runs every frame
function updateGameArea() {
    if (!paused) {
        myGameArea.frameNo += 1;
        tiles.iterate();
        drawGrid(gColumns, gRows);
    }
}