#include <Arduino.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

const uint32_t TEMP_PIN = A0;
const uint32_t LIGHT_PIN = A1;
const uint32_t THRESHOLD_PIN = A2;

const uint32_t KEY1_PIN = PB8;
const uint32_t KEY2_PIN = PB9;

const uint32_t GREEN_LED_PIN = PB12;
const uint32_t RED_LED_PIN = PB13;
const uint32_t BUZZER_PIN = PB14;
const uint32_t FAN_PIN = PB15;

const float ADC_REF_VOLTAGE = 3.3f;
const float ADC_MAX_VALUE = 4095.0f;

const unsigned long UI_UPDATE_MS = 200;
const unsigned long SERIAL_UPDATE_MS = 1000;
const unsigned long DEBOUNCE_MS = 30;
const unsigned long BUZZER_REARM_MS = 250;

LiquidCrystal_I2C lcd(0x27, 16, 2);

enum LightLevel {
  LIGHT_DARK,
  LIGHT_NORMAL,
  LIGHT_BRIGHT
};

struct ButtonState {
  bool stableLevel;
  bool lastRawLevel;
  unsigned long lastChangeMs;
};

struct SensorData {
  int tempAdc;
  int lightAdc;
  int thresholdAdc;
  float tempVoltage;
  float lightVoltage;
  float thresholdVoltage;
  float temperatureC;
  float thresholdC;
  LightLevel lightLevel;
};

ButtonState key1State = {HIGH, HIGH, 0};
ButtonState key2State = {HIGH, HIGH, 0};

SensorData data;

uint8_t lcdPage = 0;
bool alarmActive = false;
bool tempAlarm = false;
bool darkAlarm = false;
bool fanOn = false;
bool buzzerLatched = false;

unsigned long lastUiUpdateMs = 0;
unsigned long lastSerialUpdateMs = 0;
unsigned long buzzerRearmAtMs = 0;

float adcToVoltage(int adc) {
  return adc * ADC_REF_VOLTAGE / ADC_MAX_VALUE;
}

LightLevel classifyLight(int adc) {
  if (adc < 1365) {
    return LIGHT_DARK;
  }

  if (adc < 3000) {
    return LIGHT_NORMAL;
  }

  return LIGHT_BRIGHT;
}

const char *lightLevelText(LightLevel level) {
  switch (level) {
    case LIGHT_DARK:
      return "DARK";
    case LIGHT_BRIGHT:
      return "BRIGHT";
    case LIGHT_NORMAL:
    default:
      return "NORMAL";
  }
}

const char *onOffText(bool value) {
  return value ? "ON" : "OFF";
}

bool pressedEdge(uint32_t pin, ButtonState &state) {
  bool raw = digitalRead(pin);
  unsigned long now = millis();

  if (raw != state.lastRawLevel) {
    state.lastRawLevel = raw;
    state.lastChangeMs = now;
  }

  if ((now - state.lastChangeMs) >= DEBOUNCE_MS && raw != state.stableLevel) {
    state.stableLevel = raw;

    if (state.stableLevel == LOW) {
      return true;
    }
  }

  return false;
}

SensorData readSensors() {
  SensorData result;

  result.tempAdc = analogRead(TEMP_PIN);
  result.lightAdc = analogRead(LIGHT_PIN);
  result.thresholdAdc = analogRead(THRESHOLD_PIN);

  result.tempVoltage = adcToVoltage(result.tempAdc);
  result.lightVoltage = adcToVoltage(result.lightAdc);
  result.thresholdVoltage = adcToVoltage(result.thresholdAdc);

  result.temperatureC = result.tempVoltage * 100.0f;
  result.thresholdC = 20.0f + result.thresholdVoltage / ADC_REF_VOLTAGE * 60.0f;
  result.lightLevel = classifyLight(result.lightAdc);

  return result;
}

void updateAlarmAndOutputs(const SensorData &current) {
  unsigned long now = millis();

  tempAlarm = current.temperatureC >= current.thresholdC;
  darkAlarm = current.lightLevel == LIGHT_DARK;
  alarmActive = tempAlarm || darkAlarm;
  fanOn = tempAlarm;

  if (alarmActive && now >= buzzerRearmAtMs) {
    buzzerLatched = true;
  }

  if (!alarmActive) {
    buzzerRearmAtMs = 0;
  }

  digitalWrite(GREEN_LED_PIN, alarmActive ? LOW : HIGH);
  digitalWrite(RED_LED_PIN, alarmActive ? HIGH : LOW);
  digitalWrite(FAN_PIN, fanOn ? HIGH : LOW);
  digitalWrite(BUZZER_PIN, buzzerLatched ? HIGH : LOW);
}

void printLcdLine(uint8_t row, String text) {
  if (text.length() > 16) {
    text = text.substring(0, 16);
  }

  while (text.length() < 16) {
    text += ' ';
  }

  lcd.setCursor(0, row);
  lcd.print(text);
}

void updateLcd() {
  if (lcdPage == 0) {
    String line1 = "T:";
    line1 += String(data.temperatureC, 1);
    line1 += "C TH:";
    line1 += String(data.thresholdC, 0);

    String line2 = "STAT:";
    line2 += alarmActive ? "ALARM" : "NORMAL";

    printLcdLine(0, line1);
    printLcdLine(1, line2);
  } else {
    String line1 = "L:";
    line1 += data.lightAdc;
    line1 += " ";
    line1 += lightLevelText(data.lightLevel);

    String line2 = "F:";
    line2 += onOffText(fanOn);
    line2 += " B:";
    line2 += onOffText(buzzerLatched);

    printLcdLine(0, line1);
    printLcdLine(1, line2);
  }
}

void printSerialHeader() {
  Serial1.println("Smart Sensing System Started");
  Serial1.println("Time(ms),Temp(C),Threshold(C),LightADC,LightLevel,Alarm,Fan,Buzzer,Page");
}

void printSerialData() {
  Serial1.print(millis());
  Serial1.print(",T=");
  Serial1.print(data.temperatureC, 1);
  Serial1.print("C,TH=");
  Serial1.print(data.thresholdC, 1);
  Serial1.print("C,LIGHT=");
  Serial1.print(data.lightAdc);
  Serial1.print(",");
  Serial1.print(lightLevelText(data.lightLevel));
  Serial1.print(",ALARM=");
  Serial1.print(onOffText(alarmActive));
  Serial1.print(",FAN=");
  Serial1.print(onOffText(fanOn));
  Serial1.print(",BUZ=");
  Serial1.print(onOffText(buzzerLatched));
  Serial1.print(",PAGE=");
  Serial1.println(lcdPage + 1);
}

void handleButtons() {
  if (pressedEdge(KEY1_PIN, key1State)) {
    lcdPage = (lcdPage + 1) % 2;
    updateLcd();
  }

  if (pressedEdge(KEY2_PIN, key2State)) {
    buzzerLatched = false;
    buzzerRearmAtMs = millis() + BUZZER_REARM_MS;
    digitalWrite(BUZZER_PIN, LOW);
  }
}

void setup() {
  Serial1.begin(115200);
  delay(200);
  printSerialHeader();

  analogReadResolution(12);

  pinMode(KEY1_PIN, INPUT_PULLUP);
  pinMode(KEY2_PIN, INPUT_PULLUP);

  pinMode(GREEN_LED_PIN, OUTPUT);
  pinMode(RED_LED_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(FAN_PIN, OUTPUT);

  digitalWrite(GREEN_LED_PIN, LOW);
  digitalWrite(RED_LED_PIN, LOW);
  digitalWrite(BUZZER_PIN, LOW);
  digitalWrite(FAN_PIN, LOW);

  Wire.setSDA(PB7);
  Wire.setSCL(PB6);
  Wire.begin();

  lcd.init();
  lcd.backlight();
  printLcdLine(0, "STM32 Sensing");
  printLcdLine(1, "System Ready");
  delay(500);

  data = readSensors();
  updateAlarmAndOutputs(data);
  updateLcd();

  printSerialData();
}

void loop() {
  unsigned long now = millis();

  handleButtons();

  if ((now - lastUiUpdateMs) >= UI_UPDATE_MS) {
    lastUiUpdateMs = now;

    data = readSensors();
    updateAlarmAndOutputs(data);
    updateLcd();
  }

  if ((now - lastSerialUpdateMs) >= SERIAL_UPDATE_MS) {
    lastSerialUpdateMs = now;
    printSerialData();
  }
}