var grid = document.getElementById("grid");

var cellsize = 60;
var width = Math.ceil(window.innerWidth / cellsize) + 1;
var height = Math.ceil(window.innerHeight / (cellsize*Math.sqrt(3)/2));

function xCoord(i, j) {
    var x = i + j/2;
    if (x > width - 1) {
        x = x - width;
    }
    return x;
}

function yCoord(i, j) {
    return Math.sqrt(3)*j/2;
}

var cells = new Array(width);
for (var i = 0; i < width; ++i) {
    cells[i] = new Array(height);
    for (var j = 0; j < height; ++j) {
        cells[i][j] = document.createElement("div");
        cells[i][j].classList.add("cell");
        cells[i][j].classList.add("alive");

        spiral = document.createElement("img");
        spiral.classList.add("spiral");
        spiral.src = "spiral.svg";
        cells[i][j].appendChild(spiral);

        hex = document.createElement("img");
        hex.classList.add("hex");
        hex.src = "hex.svg";
        cells[i][j].appendChild(hex);

        cells[i][j].style.position = "absolute";
        cells[i][j].style.left = xCoord(i, j)*cellsize + "px";
        cells[i][j].style.bottom = yCoord(i, j)*cellsize + "px";
        grid.appendChild(cells[i][j]);
    }
}

function prebirth(i, j) {
    cells[i][j].classList.add("birthing");
}
function prekill(i, j) {
    cells[i][j].classList.add("dying");
}
function birth(i, j) {
    cells[i][j].classList.remove("dead");
    cells[i][j].classList.add("alive");
}
function kill(i, j) {
    cells[i][j].classList.remove("alive");
    cells[i][j].classList.add("dead");
}
function update(i, j) {
    var cl = cells[i][j].classList;
    if (cl.contains("birthing")) {
        cl.remove("birthing");
        birth(i, j);
    }
    if (cl.contains("dying")) {
        cl.remove("dying");
        kill(i, j);
    }
}
function isAlive(i, j) {
    return !cells[i][j].classList.contains("dead");
}

function rotate(a) {
    a.push(a.shift());
}

function arraysEq(a, b) {
    if (a.length !== b.length) {
        return false;
    }

    for (var i = 0; i < a.length; ++i) {
        if (a[i] !== b[i]) {
            return false;
        }
    }

    return true;
}

function arraysRotatedEq(a, b) {
    if (a.length !== b.length) {
        return false;
    }

    for (var i = 0; i < a.length; ++i) {
        if (arraysEq(a, b)) {
            return true;
        }
        rotate(b);
    }

    return false;
}

function mod(m, n) {
    return ((m % n) + n) % n;
}

function ip(i) {
    return mod(i-1, width);
}
function is(i) {
    return mod(i+1, width);
}
function jp(j) {
    return mod(j-1, height);
}
function js(j) {
    return mod(j+1, height);
}

function ll(i, j) {
    return isAlive(ip(i), j);
}
function dl(i, j) {
    return isAlive(i, jp(j));
}
function dr(i, j) {
    return isAlive(is(i), jp(j));
}
function rr(i, j) {
    return isAlive(is(i), j);
}
function ur(i, j) {
    return isAlive(i, js(j));
}
function ul(i, j) {
    return isAlive(ip(i), js(j));
}

function neighbors(i, j) {
    return [ll(i, j), dl(i, j), dr(i, j), rr(i, j), ur(i, j), ul(i, j)];
}

function neighborsCount(i, j) {
    return neighbors(i, j).filter(function (b) { return b; }).length;
}

function golay(i, j) {
    var n = neighbors(i, j);
    var g1 = [true, true, false, false, false, false];
    var g2 = [true, false, true, false, false, false];
    return (arraysRotatedEq(n, g1) || arraysRotatedEq(n, g2));
}

function preston(i, j) {
    var n = neighbors(i, j);
    var p1 = [true, true, false, false, false, false];
    var p2 = [true, false, true, false, false, false];
    return (isAlive(i, j) && (arraysRotatedEq(n, p1) || arraysRotatedEq(n, p2))) || (!isAlive(i, j) && neighborsCount(i, j) === 2);
}

function golayStep() {
    for (var i = 0; i < width; ++i) {
        for (var j = 0; j < height; ++j) {
            if (golay(i, j)) {
                prebirth(i, j);
            } else {
                prekill(i, j);
            }
        }
    }

    for (var i = 0; i < width; ++i) {
        for (var j = 0; j < height; ++j) {
            update(i, j);
        }
    }
}

function prestonStep() {
    for (var i = 0; i < width; ++i) {
        for (var j = 0; j < height; ++j) {
            if (preston(i, j)) {
                prebirth(i, j);
            } else {
                prekill(i, j);
            }
        }
    }

    for (var i = 0; i < width; ++i) {
        for (var j = 0; j < height; ++j) {
            update(i, j);
        }
    }
}

for (var i = 0; i < width; ++i) {
    for (var j = 0; j < height; ++j) {
        if (Math.floor(Math.random()*2) === 0) {
            kill(i, j);
        }
    }
}

setInterval(prestonStep, 1000);