#include <SPI.h>

const uint8_t LATCH_PIN = 10;
const uint8_t LATCH_PIN_MASK = PB2;
const uint8_t OE_PIN = 12;
const uint8_t OE_PIN_MASK = PB4;

const int NUM_ROWS = 8;

uint16_t matrix[NUM_ROWS] = {
  0b1111111111111111,
  0b1000000000000001,
  0b1000000000000001,
  0b1000000000000001,
  0b1000000000000001,
  0b1000000000000001,
  0b1000000000000001,
  0b1111111111111111,
};
uint8_t currentRow = 0;

void setPixel(uint8_t x, uint8_t y) {
  if (x >= 16 || y >= NUM_ROWS)
    return;
  matrix[y] |= (1 << (16 - 1 - x));
}

void clearPixel(uint8_t x, uint8_t y) {
  if (x >= 16 || y >= NUM_ROWS)
    return;
  matrix[y] &= ~(1 << (16 - 1 - x));
}

static inline uint8_t reverse8(uint8_t b) {
  b = (b & 0xF0) >> 4 | (b & 0x0F) << 4;
  b = (b & 0xCC) >> 2 | (b & 0x33) << 2;
  b = (b & 0xAA) >> 1 | (b & 0x55) << 1;
  return b;
}

void showRow(uint8_t row) {
  uint8_t rowByte = ~(1 << row);
  uint8_t colA = (matrix[row] >> 8) & 0xFF;
  uint8_t colB  = matrix[row] & 0xFF;

  PORTB &= ~(1 << LATCH_PIN_MASK);
  PORTB |= (1 << OE_PIN_MASK);
  SPI.transfer(rowByte);  // Row multiplexing SR
  SPI.transfer(reverse8(colB));   // Region B SR
  SPI.transfer(reverse8(colA));   // Rebion A SR
  PORTB |= (1 << LATCH_PIN_MASK);
  PORTB &= ~(1 << OE_PIN_MASK);
}

void setupTimer()
{
	OCR2A = 200;			      // compare match at 200 ticks
	TCCR2A = (1 << WGM21);	// CTC mode
	TCCR2B = (1 << CS21);	  // prescaler 8
	TCNT2 = 0x00;			      // clear counter
	TIMSK2 = (1 << OCIE2A); // enable compare match interrupt
}

void setup() {
  pinMode(LATCH_PIN, OUTPUT);
  digitalWrite(LATCH_PIN, HIGH);

  SPI.begin();
  SPI.beginTransaction(SPISettings(8000000, MSBFIRST, SPI_MODE0));

  // setupTimer();
}


void loop() {
  memset(matrix, 0, NUM_ROWS * sizeof(uint16_t));
  static float phase = 0;
  for (uint8_t x = 0; x < 16; x++) {
    float angle = (x / 16.0) * 2 * PI + phase;
    float value = sin(angle);
    uint8_t y = (uint8_t)((value + 1) * 3.5);
    setPixel(x, y);
  }
  phase += 0.3;
  if (phase > 2 * PI) phase -= 2 * PI; // Wrap around

  for (uint8_t r = 0; r < NUM_ROWS; ++r) {
    showRow(r);
    // matrix[r] = ~matrix[r];
    // delayMicroseconds(1000);
    delay(10);
  }
}

// ISR(TIMER2_COMPA_vect)
// {
//   showRow(currentRow++);
//   if(currentRow >= NUM_ROWS)
//     currentRow = 0;
// }