/*
SD_Card_Test
*/

#include <SPI.h>
#include "SdFat.h"
SdFat SD;

const int potPin = A0; // Analog input pin for potentiometer
int adcValue = 0; // Store raw ADC value
float voltage = 0.0;

unsigned long previousMillis = 0;
unsigned long interval = 5000;
const uint8_t chipSelect = 10;

const float GAMMA = 0.7;
const float RL10 = 50;

int ldrValue = 0;
float ldrVoltage = 0;
float resistance = 0;
float lux = 0;


File TimeFile;
File VoltFile;
File ADCFile;
File LuxFile;

void setup() {
  Serial.begin(9600);
  SD.begin(chipSelect); // Initialize the SD card module at the Chip Select (CS) pin
  SD.ls(LS_R | LS_SIZE);
}

void loop() {
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;

    potValues();

    TimeFile = SD.open("TIME.txt", FILE_WRITE);
    if (TimeFile) {
      TimeFile.println(currentMillis);
      TimeFile.close();
    }

    VoltFile = SD.open("VOLT.txt", FILE_WRITE);
    if (VoltFile) {
      VoltFile.println(voltage);
      VoltFile.close();
    }

    ADCFile = SD.open("ADC.txt", FILE_WRITE);
    if (ADCFile) {
      ADCFile.println(adcValue);
      ADCFile.close();
    }

    LuxFile = SD.open("LUX.txt", FILE_WRITE);
    if (LuxFile) {
      LuxFile.println(lux);
      LuxFile.close();
    }

    // After writing values, read back and print:
    printFile("TIME.txt");
    printFile("VOLT.txt");
    printFile("ADC.txt");
    printFile("LUX.txt");

  }

}

// === Functions ===
void potValues() {
  adcValue = analogRead(potPin);
  voltage = adcValue * (5.0 / 1024);
  
  // These constants should match the photoresistor's "gamma" and "rl10" attributes
  const float GAMMA = 0.7;
  const float RL10 = 50;
  // Convert the analog value into lux value:
  ldrValue = analogRead(A1);
  ldrVoltage = ldrValue / 1024. * 5;
  resistance = 2000 * ldrVoltage / (1 - ldrVoltage / 5);
  lux = pow(RL10 * 1e3 * pow(10, GAMMA) / resistance, (1 / GAMMA));
}

// === Function to dump file contents ===
void printFile(const char *filename) {
  File file = SD.open(filename);
  if (file) {
    Serial.print("Contents of ");
    Serial.println(filename);

    while (file.available()) {
      Serial.write(file.read()); // print character by character
    }
    file.close();
    Serial.println(); // add a blank line
  } else {
    Serial.print("Error opening ");
    Serial.println(filename);
  }
}