#include <Arduino.h>

// Output shift register pins
constexpr uint8_t outClk   = 27;
constexpr uint8_t outData  = 13;
constexpr uint8_t outLatch = 14;

// Input shift register pins
constexpr uint8_t inClk    = 17;
constexpr uint8_t inData   = 5;
constexpr uint8_t inLatch  = 16;

// Delay constant
constexpr uint8_t wt = 20;

// Forward declarations
uint8_t ReadInput();
void WriteOutput(uint32_t);
uint8_t debounce();

void setup() {
  pinMode(outClk, OUTPUT);
  pinMode(outData, OUTPUT);
  pinMode(outLatch, OUTPUT);

  pinMode(inClk, OUTPUT);
  pinMode(inData, INPUT);
  pinMode(inLatch, OUTPUT);

  digitalWrite(inLatch, HIGH);
  digitalWrite(inClk, LOW);
  digitalWrite(outClk, LOW);
  digitalWrite(outData, LOW);
  digitalWrite(outLatch, LOW);

  Serial.begin(115200);
}

// Button debouncing: returns 255 on timeout
uint8_t debounce() {
  uint32_t startTime = millis();
  uint8_t first = ReadInput();
  delay(10);
  if (first == ReadInput()) return first;

  while (millis() - startTime < 1000) {
    first = ReadInput();
    delay(10);
    if (first == ReadInput()) return first;
  }
  return 255; // Timeout
}

void loop() {
  union {
    uint32_t val = 0;
    struct {
      uint32_t dummy : 16;
      bool Led[8];
    };
  } outputs;

  union {
    uint8_t val = 0;
    struct {
      bool Btn[8];
    };
  } inputs, oldInputs;

  uint8_t cnt = 0;

  const uint8_t to7digits[] = {
    0x3F, 0x06, 0x5B, 0x4F, 0x66,
    0x6D, 0x7D, 0x07, 0x7F, 0x6F
  };

  uint8_t digits = 0;

  while (true) {
    // Rotate 4-bit digit pattern
    digits = ((digits << 1) | ((digits & 0x08) ? 1 : 0)) & 0x0F;

    inputs.val = debounce();

    if (inputs.val != oldInputs.val) {
      if (inputs.Btn[0] && cnt < 9) cnt++;
      if (inputs.Btn[1] && cnt > 0) cnt--;
      Serial.print("Inputs: "); Serial.print(inputs.val);
      Serial.print(" | Old: "); Serial.print(oldInputs.val);
      Serial.print(" | Cnt: "); Serial.println(cnt);
    }

    uint32_t outputVal =
      (static_cast<uint32_t>(inputs.val) << 16) |
      (static_cast<uint32_t>(digits) << 8) |
      static_cast<uint32_t>(to7digits[cnt]);

    WriteOutput(outputVal);
    oldInputs = inputs;
  }
}

uint8_t ReadInput() {
  uint8_t data = 0;

  digitalWrite(inLatch, HIGH);
  digitalWrite(inLatch, LOW);
  digitalWrite(inLatch, HIGH);

  for (uint8_t i = 0; i < 8; ++i) {
    data <<= 1;
    data |= digitalRead(inData);
    digitalWrite(inClk, HIGH);
    digitalWrite(inClk, LOW);
  }

  return ~data;
}

void WriteOutput(uint32_t data) {
  digitalWrite(outLatch, LOW);
  for (int8_t i = 23; i >= 0; --i) {
    digitalWrite(outData, (data >> i) & 0x01);
    digitalWrite(outClk, HIGH);
    digitalWrite(outClk, LOW);
  }
  digitalWrite(outLatch, HIGH);
}