#include <SPI.h>                                                    // Include libraries
#include <SD.h>                                                     // ,,
#include <Wire.h>                                                   // ,,
#include <TimeLib.h>                                                // ,,
#include <DS1307RTC.h>                                              // ,,
#include <LiquidCrystal_I2C.h>                                      // ,,
#define aref_voltage 4.99                                           // Uncomment the used analog reference voltage
//#define aref_voltage 1.111                                        // ,,
//#define aref_voltage 3.35                                         // ,,
LiquidCrystal_I2C lcd(0x27, 16, 2);                                 // Set up lcd display
int tempPin = A0;                                                   // TMP36 middle pin
int illPin = A1;                                                    // Photoresistor
double illuminanceInput;                                            // Raw illuminance output variable
int buttonPin = 9;                                                  // Toggle button (record/standby)
int buttonState = LOW;                                              // Default low
int tmpInput;                                                       // Raw TMP36 output variable
double temp;                                                        // Calculated temperature variable
double illuminance;                                                 // Calculated illuminance percentage
unsigned long measureTime;                                          // Time of measuring variable (millis)
unsigned long currentTime;                                          // Current time (millis)
unsigned long deltaTime;                                            // Difference between measureTime and currentTime
unsigned long measureInterval = 2000;                               // Logging interval (5 mins when actually logging data)
File Data;                                                          // SD data file

void setup() {
  Serial.begin(9600);                                               // Start serial comms
  //analogReference(INTERNAL);                                      // Uncomment if using internal 1.111 v reference voltage
  //analogReference(EXTERNAL);                                      // Uncomment if using external 3.35 v reference voltage
  pinMode(buttonPin, INPUT);                                        // Set toggle button pin to input
  lcd.init();                                                       // Start lcd
  lcd.backlight();                                                  // ,,
  lcd.clear();                                                      // Clear lcd
  lcd.setCursor(0, 0);                                              // Set lcd cursor (column, row)
  lcd.print("Initializing SD");
  delay(500);                                                       // Check whether SD card is present/working correctly
  if (!SD.begin(10)) {
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Failed! Check SD");
    lcd.setCursor(0, 1);
    lcd.print("and reset");
    while (1);                                                      // If not, wait for reset
  }
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Done!");
  delay(500);
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Press S to log");                                      // Print standby instructions
  lcd.setCursor(0, 1);
  lcd.print("temperature");
}

void loop() {
  standby:                                                          // Standby goto point
  buttonState = digitalRead(buttonPin);                             // Check state of button
  if (buttonState == LOW) {                                         // Return to start of standby loop if button was not pressed
    goto standby;                                                   // ,,
  } else {                                                          // Go to measure loop if button was pressed
    delay(250);                                                     // Wait 250 ms to prevent bouncing
    lcd.clear();                                                    // Clear lcd
    Data = SD.open("data.txt", FILE_WRITE);
    if (Data) {
      goto measure;                                                 // Go to measure loop
    } else {
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Failed! Check SD");
      lcd.setCursor(0, 1);
      lcd.print("and reset");
      while (1);
    }
  }
  measure:                                                          // Measure goto point
  illuminanceInput = analogRead(illPin);                            // Read raw photoresistor value
  illuminance = (double) (illuminanceInput / 1023 * 100);           // Calculate illuminance percentage
  tmpInput = analogRead(tempPin);                                   // Read raw TMP36 value
  temp = (double) ((tmpInput * aref_voltage / 1024 - 0.5) * 100);   // Calculate temperature in C
  lcd.setCursor(0, 0);                                              // Set lcd cursor and print temperature, illuminance, and recording
  lcd.print("T=");                                                  // ,,
  lcd.setCursor(2, 0);                                              // ,,
  lcd.print(temp);                                                  // ,,
  lcd.setCursor(8, 0);                                              // ,,
  lcd.print("I=");                                                  // ,,
  lcd.setCursor(10, 0);                                             // ,,
  lcd.print(illuminance);                                           // ,,
  lcd.setCursor(14, 0);                                             // ,,
  lcd.print("%");                                                   // ,,
  lcd.setCursor(0, 1);                                              // ,,
  lcd.print("Logging");                                             // ,,
  tmElements_t tm;                                                  // No idea why this has to be here, but doesn't work without it
  RTC.read(tm);                                                     // Read DS3231 RTC
  Data.print(tm.Day);                                               // Print date, time, temperature, and illuminance in SD card file
  Data.print("/");                                                  // ,,
  Data.print(tm.Month);                                             // ,,
  Data.print("/");                                                  // ,,
  Data.print(tmYearToCalendar(tm.Year));                            // ,,
  Data.print(",");                                                  // ,,
  Data.print(tm.Hour);                                              // ,,
  Data.print(":");                                                  // ,,
  Data.print(tm.Minute);                                            // ,,
  Data.print(":");                                                  // ,,
  Data.print(tm.Second);                                            // ,,
  Data.print(",");                                                  // ,,
  Data.print(temp);                                                 // ,,
  Data.print(",");                                                  // ,,
  Data.print(illuminance);                                          // ,,
  Data.println();                                                   // ,,
  measureTime = millis();                                           // Store time of measuring
  goto wait;                                                        // Go to wait loop after taking measurement

  wait:                                                             // Wait goto point
  buttonState = digitalRead(buttonPin);                             // Check state of button
  if (buttonState == LOW) {                                         // Check whether set logging interval has passed if button was not pressed
    currentTime = millis();                                         // Store current time
    deltaTime = (currentTime - measureTime);                        // Calculate time between last measurement and current time
    if (deltaTime > measureInterval) {                              // Go to measure loop to take next measurement if set logging interval has passed
      lcd.clear();                                                  // Clear lcd
      goto measure;                                                 // Go to measure loop
    } else {                                                        // Go back to start of wait loop if set logging interval has not passed
      goto wait;                                                    // Go to wait loop
    }
  } else {                                                          // Go back to standby loop if button was pressed
    delay(250);                                                     // Wait 250 ms to prevent bouncing
    Data.close();
    lcd.clear();                                                    // Clear lcd
    lcd.setCursor(0, 0);                                            // Set lcd cursor
    lcd.print("Press S to log");                                    // Print standby loop instructions
    lcd.setCursor(0, 1);
    lcd.print("temperature");
    goto standby;                                                   // Go to standby loop
  }
}