#include <Arduino.h>

#define CLK 13
#define DIN 11
#define CS  10
#define X_SEGMENTS   8
#define Y_SEGMENTS   4
#define NUM_SEGMENTS (X_SEGMENTS * Y_SEGMENTS)

byte fb[8 * NUM_SEGMENTS];
byte nextFb[8 * NUM_SEGMENTS];

void shiftOutAll(byte send_to_address, byte *send_this_data, int len) {
  digitalWrite(CS, LOW);
  shiftOut(DIN, CLK, MSBFIRST, send_to_address);
  for (int i = 0; i < len; i++) {
    shiftOut(DIN, CLK, MSBFIRST, send_this_data[i]);
  }
  digitalWrite(CS, HIGH);
}

void setup() {
  Serial.begin(115200);
  pinMode(CLK, OUTPUT);
  pinMode(DIN, OUTPUT);
  pinMode(CS, OUTPUT);
  byte initData[1] = {0x00};
  shiftOutAll(0x0f, initData, 1);
  byte intensityData[1] = {0x07};
  shiftOutAll(0x0b, intensityData, 1);
  byte scanLimitData[1] = {0x01};
  shiftOutAll(0x0c, scanLimitData, 1);
  byte powerDownData[1] = {0x0f};
  shiftOutAll(0x0a, powerDownData, 1);
  byte testModeData[1] = {0x00};
  shiftOutAll(0x09, testModeData, 1);
  randomSeed(analogRead(0));
  for (int i = 0; i < 1400; i++) {
    int x = random(0, X_SEGMENTS * 8);
    int y = random(0, Y_SEGMENTS * 8);
    set_pixel(x, y, true);
  }
}

void loop() {
  updateGameOfLife();
  show();
  delay(0);
}

void updateGameOfLife() {
  for (int i = 0; i < 8 * NUM_SEGMENTS; i++) {
    nextFb[i] = fb[i];
  }
  for (int y = 0; y < Y_SEGMENTS * 8; y++) {
    for (int x = 0; x < X_SEGMENTS * 8; x++) {
      int neighbors = countNeighbors(x, y);
      if (fb[y * X_SEGMENTS + x / 8] & (1 << (7 - (x % 8)))) {
        if (neighbors < 2 || neighbors > 3) {
          set_next_pixel(x, y, false);
        }
      } else {
        if (neighbors == 3) {
          set_next_pixel(x, y, true);
        }
      }
    }
  }
  for (int i = 0; i < 8 * NUM_SEGMENTS; i++) {
    fb[i] = nextFb[i];
  }
}

int countNeighbors(int x, int y) {
  int count = 0;
  for (int dy = -1; dy <= 1; dy++) {
    for (int dx = -1; dx <= 1; dx++) {
      if (dx == 0 && dy == 0) continue;
      int nx = (x + dx + X_SEGMENTS * 8) % (X_SEGMENTS * 8);
      int ny = (y + dy + Y_SEGMENTS * 8) % (Y_SEGMENTS * 8);
      if (fb[ny * X_SEGMENTS + nx / 8] & (1 << (7 - (nx % 8)))) count++;
    }
  }
  return count;
}

void set_next_pixel(uint8_t x, uint8_t y, bool state) {
  byte *addr = &nextFb[x / 8 + y * X_SEGMENTS];
  byte mask = 128 >> (x % 8);
  if (state) {
    *addr |= mask;
  } else {
    *addr &= ~mask;
  }
}

void set_pixel(uint8_t x, uint8_t y, bool state) {
  byte *addr = &fb[x / 8 + y * X_SEGMENTS];
  byte mask = 128 >> (x % 8);
  if (state) {
    *addr |= mask;
  } else {
    *addr &= ~mask;
  }
}

void show() {
  for (byte row = 0; row < 8; row++) {
    digitalWrite(CS, LOW);
    byte segment = NUM_SEGMENTS;
    while (segment--) {
      byte x = segment % X_SEGMENTS;
      byte y = segment / X_SEGMENTS * 8;
      byte addr = (row + y) * X_SEGMENTS;

      if (segment & X_SEGMENTS) {
        shiftOut(DIN, CLK, MSBFIRST, 8 - row);
        shiftOut(DIN, CLK, LSBFIRST, fb[addr + x]);
      } else {
        shiftOut(DIN, CLK, MSBFIRST, 1 + row);
        shiftOut(DIN, CLK, MSBFIRST, fb[addr - x + X_SEGMENTS - 1]);
      }
    }
    digitalWrite(CS, HIGH);
  }
}