#include <SPI.h>

#define CLK 52
#define DIN 51
#define CS  53
#define X_SEGMENTS   4
#define Y_SEGMENTS   1  // Adjusted to 1 because we're using a single row of 4 segments
#define NUM_SEGMENTS (X_SEGMENTS * Y_SEGMENTS)

// A framebuffer to hold the state of the entire matrix of LEDs
byte fb[8 * NUM_SEGMENTS];

const byte alphabet[5][8] = {
  {0b01111110, 0b10001001, 0b10001001, 0b10001001, 0b10001001, 0b01111110, 0b00000000, 0b00000000}, // H
  {0b00000000, 0b00000000, 0b00000000, 0b11111111, 0b00000000, 0b00000000, 0b00000000, 0b00000000}, // E
  {0b01111100, 0b10000010, 0b10000001, 0b10000001, 0b10000001, 0b10000010, 0b01111100, 0b00000000}, // L
  {0b01111100, 0b10000010, 0b10000001, 0b10000001, 0b10000001, 0b10000010, 0b01111100, 0b00000000}, // L
  {0b01111100, 0b10000010, 0b10000001, 0b10000001, 0b10000001, 0b10000010, 0b01111100, 0b00000000}  // O
};

void shiftAll(byte send_to_address, byte send_this_data) {
  digitalWrite(CS, LOW);
  for (int i = 0; i < NUM_SEGMENTS; i++) {
    SPI.transfer(send_to_address);
    SPI.transfer(send_this_data);
  }
  digitalWrite(CS, HIGH);
}

void setup() {
  Serial.begin(115200);
  pinMode(CLK, OUTPUT);
  pinMode(DIN, OUTPUT);
  pinMode(CS, OUTPUT);
  SPI.beginTransaction(SPISettings(16000000, MSBFIRST, SPI_MODE0));

  // Setup each MAX7219
  shiftAll(0x0f, 0x00); //display test register - test mode off
  shiftAll(0x0b, 0x07); //scan limit register - display digits 0 thru 7
  shiftAll(0x0c, 0x01); //shutdown register - normal operation
  shiftAll(0x0a, 0x0f); //intensity register - max brightness
  shiftAll(0x09, 0x00); //decode mode register - No decode
  
  // Clear the framebuffer
  memset(fb, 0, sizeof(fb));
  
  // Load "HELLO" into the framebuffer
  displayText("HELLO");
  
  show(); // Display the initial text
}

void displayText(const char* text) {
  int length = strlen(text);
  for (int i = 0; i < length; i++) {
    char c = text[i];
    int index = c - 'H';  // Index based on the ASCII value of 'H'
    
    if (index >= 0 && index < 5) { // 'H', 'E', 'L', 'L', 'O' are the first 5 letters in our array
      for (int row = 0; row < 8; row++) {
        fb[i * 8 + row] = alphabet[index][row];
      }
    }
  }
}

void loop() {
  // Add scrolling or other dynamic effects here, if desired.
}

// Send the framebuffer data to the display
void show() {
  for (byte row = 0; row < 8; row++) {
    digitalWrite(CS, LOW);
    byte segment = NUM_SEGMENTS;
    while (segment--) {
      byte x = segment % X_SEGMENTS;
      byte addr = row * X_SEGMENTS;
      
      SPI.transfer(row + 1);  // Send the row number
      SPI.transfer(fb[addr + x]);  // Send the corresponding data
    }
    digitalWrite(CS, HIGH);
  }
}