#include <SD.h>
#include <SPI.h>

// Pin definition
#define SD_CS_PIN 5
#define TEMP_SENSOR_PIN 34

//Variables
File dataFile;
String filename = "/templog.csv";
int readingCount = 0;
unsigned long lastLogTimer = 0;
const unsigned long LOG_INTERVAL = 1000; // log data every 1 sec
unsigned long startTime = 0;

void setup() {
  // initialize serial
  Serial.begin(115200);
  delay(500);

  Serial.println("=========================");
  Serial.println("ESP32 temperature data logger");
  Serial.println("CSV format output");
  Serial.println("=========================");

  // initailize analog input
  analogReadResolution(12);
  pinMode(TEMP_SENSOR_PIN, INPUT);

  // initailize SD card
  Serial.print("Initializing SD card...");

  // Explicit SPI initialization for ESP32
  SPI.begin(18,19,23,5); // Pin SCK, MISO(DO), MOSI(DI), SS

  if (!SD.begin(SD_CS_PIN)) {
    Serial.println("FAILED");
    Serial.println("ERROR: SD card initailization failed");
    while(1){
      delay(500);
    }
  }
  Serial.println("SUCCESS");

  // CHeck card type
  uint8_t cardType = SD.cardType();
  Serial.print("SD card type: ");
  switch (cardType) {
    case CARD_MMC: Serial.println("MMC");
    case CARD_SD: Serial.println("SDSC");
    case CARD_SDHC: Serial.println("SDHC");
    default: Serial.println("UNKNOWN");
  }

  // Record start time
  startTime = millis();

  // create CSV File with header 
  Serial.println("==================================");
  Serial.println("CSV logging started");
  Serial.println("Columns: ID,DateTime,Timestamp_ms,Temp_c,Voltage_V,Raw_ADC,Status");
  Serial.println("=================================\n");
}

void loop() {
  unsigned long currentTime = millis();
  
  // Log at intervals
  if (currentTime - lastLogTimer >= LOG_INTERVAL) {
    lastLogTimer = currentTime;
    
    // Read sensor
    int rawValue = analogRead(TEMP_SENSOR_PIN);
    float voltage = rawValue * (3.3 / 4095.0);
    float temperature = readTemperature(rawValue, voltage);
    
    // Create datetime string (simulated: seconds since start)
    String dateTime = formatDateTime(currentTime);
    
    // Determine status based on temperature
    String status = getStatus(temperature);
    
    // Create CSV row
    // Format: ID,DateTime,Timestamp_ms,Temp_C,Voltage_V,Raw_ADC,Status
    String csvRow = String(readingCount) + "," + 
                    dateTime + "," + 
                    String(currentTime) + "," + 
                    String(temperature, 2) + "," + 
                    String(voltage, 3) + "," + 
                    String(rawValue) + "," + 
                    status + "\n";
    
    // Print to Serial (for monitoring)
    Serial.print("CSV Row: ");
    Serial.print(csvRow);
    
    // Write to SD card
    if (appendFile(filename, csvRow)) {
      Serial.println("  [SAVED TO SD]");
    } else {
      Serial.println("  [ERROR: SAVE FAILED]");
    }
    
    // Display CSV file contents every 5 readings
    if (readingCount % 5 == 0) {
      displayCSVFile();
    }
    
    readingCount++;
    Serial.println();
  }
  
  delay(100);
}

// ==================== CSV FUNCTIONS ====================

void createCSVFile() {
  if (!SD.exists(filename)) {
    Serial.println("Creating new CSV file with headers...");
    
    // CSV Header row
    String header = "ReadingID,DateTime,Timestamp_ms,Temperature_C,Voltage_V,Raw_ADC,Status\n";
    
    if (writeFile(filename, header)) {
      Serial.println("CSV headers written successfully");
    } else {
      Serial.println("ERROR: Failed to write CSV headers");
    }
  } else {
    // Count existing rows to continue numbering
    readingCount = countCSVRows();
    Serial.print("Existing CSV file found. Continuing from reading #");
    Serial.println(readingCount);
  }
}

void displayCSVFile() {
  Serial.println("\n========== CSV FILE CONTENTS ==========");
  Serial.println("----------------------------------------");
  
  File file = SD.open(filename, FILE_READ);
  if (!file) {
    Serial.println("ERROR: Cannot open CSV file");
    return;
  }
  
  int lineCount = 0;
  while (file.available()) {
    String line = file.readStringUntil('\n');
    if (line.length() > 0) {
      Serial.println(line);
      lineCount++;
    }
  }
  file.close();
  
  Serial.println("----------------------------------------");
  Serial.print("Total lines: ");
  Serial.println(lineCount);
  Serial.println("========================================\n");
}

int countCSVRows() {
  File file = SD.open(filename, FILE_READ);
  if (!file) return 0;
  
  int rows = 0;
  while (file.available()) {
    if (file.read() == '\n') rows++;
  }
  file.close();
  
  // Subtract 1 for header row
  return (rows > 0) ? rows - 1 : 0;
}

// ==================== SENSOR FUNCTIONS ====================

float readTemperature(int rawValue, float voltage) {
  // Map 0-3.3V to 0-100°C (adjust for your real sensor)
  float temperature = voltage * 30.3;
  
  // Add small random fluctuation
  temperature += random(-10, 11) * 0.05;
  
  return temperature;
}

String getStatus(float temp) {
  if (temp < 10) return "COLD";
  else if (temp < 25) return "NORMAL";
  else if (temp < 40) return "WARM";
  else return "HOT";
}

// Format time as HH:MM:SS (simulated from milliseconds)
String formatDateTime(unsigned long ms) {
  unsigned long totalSeconds = ms / 1000;
  int hours = (totalSeconds / 3600) % 24;
  int minutes = (totalSeconds / 60) % 60;
  int seconds = totalSeconds % 60;
  
  String dt = "";
  if (hours < 10) dt += "0";
  dt += String(hours) + ":";
  if (minutes < 10) dt += "0";
  dt += String(minutes) + ":";
  if (seconds < 10) dt += "0";
  dt += String(seconds);
  
  return dt;
}

// ==================== SD CARD FUNCTIONS ====================

bool writeFile(String path, String message) {
  File file = SD.open(path, FILE_WRITE);
  if (!file) return false;
  
  bool result = file.print(message);
  file.close();
  return result;
}

bool appendFile(String path, String message) {
  File file = SD.open(path, FILE_APPEND);
  if (!file) return false;
  
  bool result = file.print(message);
  file.close();
  return result;
}