#include <Arduino.h>

/* ================= ПІНИ ================= */
#define DATA_PIN   PA7
#define CLOCK_PIN  PA5
#define LATCH_PIN  PA6
#define BTN_PIN    PB0

/* ================= ЗМІЙКА =================
   0 – CW
   1 – CCW
   2 – STOP
*/
uint8_t snakeMode = 0;
uint8_t snakePos  = 0;

/* ================= СЕГМЕНТИ ================= */
const uint8_t segDigits[10] = {
  0b00111111, 0b00000110, 0b01011011, 0b01001111, 0b01100110,
  0b01101101, 0b01111101, 0b00000111, 0b01111111, 0b01101111
};

uint8_t displayBuf[4] = {8, 0, 0, 0};

/* ================= 74HC595 ================= */
void shiftSend(uint16_t data) {
  digitalWrite(LATCH_PIN, LOW);
  shiftOut(DATA_PIN, CLOCK_PIN, MSBFIRST, data >> 8);
  shiftOut(DATA_PIN, CLOCK_PIN, MSBFIRST, data & 0xFF);
  digitalWrite(LATCH_PIN, HIGH);
}

/* ================= ЗАДАЧА 1: ІНДИКАТОР ================= */
void taskDisplay() {
  static uint8_t digit = 0;

  uint16_t data = (1 << digit) << 8;
  data |= segDigits[displayBuf[digit]];
  shiftSend(data);

  digit = (digit + 1) % 4;
}

/* ================= ЗАДАЧА 2: ЗМІЙКА ================= */
void taskSnake() {
  if (snakeMode == 2) return;

  for (int i = 0; i < 4; i++) displayBuf[i] = 0;
  displayBuf[snakePos] = 8;

  if (snakeMode == 0) {
    snakePos = (snakePos + 1) % 4;
  } else {
    snakePos = (snakePos == 0) ? 3 : snakePos - 1;
  }
}

/* ================= ЗАДАЧА 3: КНОПКА ================= */
void taskButton() {
  static uint8_t prev = HIGH;

  uint8_t cur = digitalRead(BTN_PIN);
  if (prev == HIGH && cur == LOW) {
    snakeMode++;
    if (snakeMode > 2) snakeMode = 0;
  }
  prev = cur;
}

/* ================= ЗАДАЧА 4: UART ================= */
float readTemp() {
  return 20.0 + (millis() % 1000) / 100.0;
}

float readVref() {
  return 1.10 + (millis() % 100) / 500.0;
}

void taskUART() {
  static String rx = "";

  while (Serial.available()) {
    char c = Serial.read();
    if (c == '\n' || c == '\r') {
      rx.trim();
      rx.toUpperCase();

      if (rx == "T MCU?") {
        Serial.print("T MCU=");
        Serial.print(readTemp(), 1);
        Serial.println("C");
      }
      else if (rx == "V REF?") {
        Serial.print("V REF=");
        Serial.print(readVref(), 2);
        Serial.println(" V");
      }
      else if (rx == "ALL SENS?") {
        Serial.print("T MCU=");
        Serial.print(readTemp(), 1);
        Serial.println("C");
        Serial.print("V REF=");
        Serial.print(readVref(), 2);
        Serial.println(" V");
      }
      else if (rx.length()) {
        Serial.println("ERROR");
      }

      rx = "";
    } else rx += c;
  }
}

/* ================= ДИСПЕТЧЕР ================= */
struct Task {
  void (*func)();
  uint32_t period;
  uint32_t lastRun;
};

Task tasks[] = {
  { taskDisplay,  2,   0 },
  { taskSnake,  300,  0 },
  { taskButton,  50,  0 },
  { taskUART,    1,   0 }
};

const uint8_t TASK_COUNT = sizeof(tasks) / sizeof(Task);

/* ================= SETUP ================= */
void setup() {
  pinMode(DATA_PIN, OUTPUT);
  pinMode(CLOCK_PIN, OUTPUT);
  pinMode(LATCH_PIN, OUTPUT);
  pinMode(BTN_PIN, INPUT_PULLUP);

  Serial.begin(115200);
  Serial.println("TASK DISPATCHER READY");
}

/* ================= LOOP ================= */
void loop() {
  uint32_t now = millis();

  for (uint8_t i = 0; i < TASK_COUNT; i++) {
    if (now - tasks[i].lastRun >= tasks[i].period) {
      tasks[i].lastRun = now;
      tasks[i].func();
    }
  }
}