// Smart Thermostat - Slice 4: CLI User Interface (DEBUG)
// Platform: STM32F103C8T6 Blue Pill (Wokwi)
// NTC → A0 | Heater LED → A1 | UART → A9/A10

// ─── Config ───
#define NTC_PIN       A0
#define HEATER_PIN    A1
#define BAUD_RATE     115200
#define PID_INTERVAL  1000

// ─── PID Parameters ───
#define KP  2.0
#define KI  0.5
#define KD  0.1
#define INTEGRAL_MAX  50.0
#define INTEGRAL_MIN -50.0

// ─── PID State ───
float setpoint = 25.0;
float integral = 0.0;
float lastError = 0.0;
float pidOutput = 0.0;
unsigned long lastPidTime = 0;

// ─── CLI State ───
String inputBuffer = "";

// ─── Temperature ───
float readTemperature() {
  int raw = analogRead(NTC_PIN);
  return 50.0 - (raw / 1023.0) * 60.0;
}

// ─── PID ───
float computePID(float current, float target, float dt) {
  float error = target - current;

  integral += error * dt;
  if (integral > INTEGRAL_MAX) integral = INTEGRAL_MAX;
  if (integral < INTEGRAL_MIN) integral = INTEGRAL_MIN;

  float derivative = (error - lastError) / dt;
  lastError = error;

  float output = KP * error + KI * integral + KD * derivative;
  if (output > 100.0) output = 100.0;
  if (output < 0.0) output = 0.0;

  return output;
}

// ─── CLI Command Handler ───
void processCommand(String cmd) {
  cmd.trim();

  if (cmd.length() == 0) return;

  if (cmd.startsWith("SET_TEMP ")) {
    String valStr = cmd.substring(9);
    float val = valStr.toFloat();

    if (val == 0.0 && valStr != "0" && valStr != "0.0") {
      Serial.println("ERROR: Invalid temperature value");
      return;
    }

    if (val < -10.0 || val > 50.0) {
      Serial.println("ERROR: Temperature out of range (-10 ~ 50)");
      return;
    }

    setpoint = val;
    Serial.print("OK: Target set to ");
    Serial.print(setpoint, 1);
    Serial.println(" C");

  } else if (cmd == "STATUS") {
    float temp = readTemperature();
    Serial.print("Temp: ");
    Serial.print(temp, 1);
    Serial.print(" C | Target: ");
    Serial.print(setpoint, 1);
    Serial.print(" C | PID: ");
    Serial.print(pidOutput, 1);
    Serial.println("%");

  } else if (cmd == "HELP") {
    Serial.println("Commands:");
    Serial.println("  SET_TEMP <value>  Set target temperature (-10~50)");
    Serial.println("  STATUS            Show current state");
    Serial.println("  HELP              Show this help");

  } else {
    Serial.print("ERROR: Unknown command '");
    Serial.print(cmd);
    Serial.println("'");
  }
}

// ─── Serial RX (DEBUG VERSION) ───
void readSerial() {
  while (Serial.available()) {
    char c = (char)Serial.read();
    Serial.print("[RX:");
    Serial.print(c);
    Serial.println("]");
    if (c == '\n' || c == '\r') {
      if (inputBuffer.length() > 0) {
        processCommand(inputBuffer);
        inputBuffer = "";
      }
    } else {
      if (inputBuffer.length() < 64) {
        inputBuffer += c;
      }
    }
  }
}

// ─── Setup ───
void setup() {
  Serial.begin(BAUD_RATE);
  delay(100);
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(HEATER_PIN, OUTPUT);
  Serial.println("System OK");
  Serial.println("Type HELP for commands");
}

// ─── Main Loop ───
void loop() {
  readSerial();

  unsigned long now = millis();
  if (now - lastPidTime >= PID_INTERVAL) {
    float dt = (now - lastPidTime) / 1000.0;
    lastPidTime = now;

    float temp = readTemperature();
    pidOutput = computePID(temp, setpoint, dt);

    int pwmVal = (int)(pidOutput * 255.0 / 100.0);
    analogWrite(HEATER_PIN, pwmVal);

    digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));

    Serial.print("Temp: ");
    Serial.print(temp, 1);
    Serial.print(" C | Target: ");
    Serial.print(setpoint, 1);
    Serial.print(" C | PID: ");
    Serial.print(pidOutput, 1);
    Serial.println("%");
  }
}