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

#define ADC_PIN 34
#define ENABLE_PIN 22
#define BLUE_PIN 12
#define GREEN_PIN 14
#define RED_PIN 27

#define DELAY 100 //milliseconds per cycle of loop
#define SAVEDELAY 15 * 1000 //number of loops between saves, change first number for seconds
#define ERRORDELAY 5 * 1000 //time between error code reset

float calibration = 1;
int serialPrint = 0;

int fileNum = 0;
String fileName;
File file;
void setup() {
  Serial.begin(115200);

  pinMode(ADC_PIN, INPUT);
  pinMode(ENABLE_PIN, INPUT);
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(BLUE_PIN, OUTPUT);
  pinMode(RED_PIN, OUTPUT);

  digitalWrite(RED_PIN, HIGH);
  digitalWrite(BLUE_PIN, HIGH);
  digitalWrite(GREEN_PIN, LOW);

  delay(500);
  while(digitalRead(ENABLE_PIN) != HIGH);//wait for enable high
  digitalWrite(BLUE_PIN, LOW);
  delay(500);
  if (!SD.begin()) { //MOSI:23, MISO:19, SCLK:18, CS:5
    Serial.println("SD card initialization failed.");
    return;
  }
  do {
    file.close();
    fileName = "/" + String(++fileNum) + ".txt";
    file = SD.open(fileName, FILE_READ);
  } while(file.size());

  file.close();
  SD.remove(fileName);
  delay(500);
  file = SD.open(fileName, FILE_WRITE);
  file.seek(file.size());
  if (!file) {
    Serial.println("Error opening file.");
    return;
  }
  Serial.print("Setup Successful\nSaving data to ");
  Serial.println(fileName);
  digitalWrite(RED_PIN, LOW);
  digitalWrite(GREEN_PIN, HIGH);
}

int len(char *string) {
  return sizeof(string) / sizeof(string[0]) - 1;
}
int startsWith(char *string, char *start) {
  for (int i = 0; i < len(string); i++) {
    if (string[i] != start[i]) {
      return 0;
    }
  }
  return 1;
}

void print(int i = 0, int length = 10) {
  
  file.seek(0);
  while(file.available() && i-- > 0) { //seek to line
    while(file.available() && file.read() != '\n');
  }
  if(!file.available()) {
    Serial.println("Value of i inputted is larger than number of measurements taken!");
    return;
  }
  Serial.print("Position :");
  Serial.println(file.position());

  char numChar[6]; i = 0;
  while(file.available() && length > 0) {
    if (file.peek() == '\n') {
      String numString = String(numChar);
      Serial.println(numString.substring(0, 5));

      file.read();
      strcpy(numChar, "");
      i = 0; length--;
    } else {
      numChar[i++] = file.read();
    }
  }
  file.seek(file.size());
  Serial.println(file.available());
  return;
}

void dumpFile(int num) {
  if(num == 0) {num = fileNum;}
  String name = "/" + String(num) + ".txt";
  file.close();
  file = SD.open(name, FILE_READ);
  int i = 0;
  Serial.print("Start Dump ");
  Serial.println(file.name());
  while(file.available()) {
    if(file.peek() == '\n') {i++;}
    char c[2] = {file.read(), '\0'};
    Serial.print(c);
  }
  Serial.print("File length: ");
  Serial.println(i);
  
  file.close();
  file = SD.open(fileName, FILE_WRITE);
  file.seek(file.size());
  return;
}

void calibrate(float reference) {
  float volts = analogRead(ADC_PIN) * 3.3 * 5810 / 3810 / pow(2, 12);
  calibration = reference / volts;
  file.print("Calibrated");
  return;
}

void stop() {
  Serial.println("Entering sleep\nPress boot button to restart");
  file.close();
  digitalWrite(BLUE_PIN, LOW);
  digitalWrite(GREEN_PIN, LOW);
  digitalWrite(RED_PIN, HIGH);
  delay(5000);
  esp_deep_sleep_start();
}

void statistics(int num) {
  if(num == 0) {num = fileNum;}
  String name = "/" + String(num) + ".txt";
  file.close();
  file = SD.open(name, FILE_READ);
  file.seek(0);
  float min, max;
  double sum = 0;
  
  unsigned long i = 0;
  String numString = "";
  while (file.available()) {
    if (file.peek() == '\n') {
      numString.trim();
      float f = numString.toFloat();
      sum += f;
      if(f < min) {
        min = f;
      }
      if(f > max) {
        max = f;
      }
      
      file.read();
      i++;
      numString = "";
    } else {
      char c[2] = {file.read(), '\0'};
      numString.concat(c);
    }
    
  }
  sum /= i;
  Serial.print("File length: ");
  Serial.println(i);
  float average = (float) sum;

  file.close();
  SD.remove("/stats.txt");
  file = SD.open("/stats.txt", FILE_WRITE);
  file.println(String(min, 3));
  file.println(String(max, 3));
  file.println(String(average, 3));

  Serial.println("min: " + String(min, 3));
  Serial.println("max: " + String(max, 3));
  Serial.println("average: " + String(average, 3));                                                   
  
  file.close();
  file = SD.open(fileName, FILE_WRITE);
  file.seek(file.size());
  return;
}

void serialEvent() {
  String command = Serial.readStringUntil('\n');
  char args[10][10];
  int j = 0, k = 0;
  for (int i = 0; i < command.length(); i++) {
    if (command.charAt(i) == ' ') {
      j++; k = 0;
    } else {
      args[j][k++] = command.charAt(i);
    }
  }
  
  if (startsWith(args[0], "print")) {
    print(String(args[1]).toInt(), String(args[2]).toInt());
  } else if (startsWith(args[0], "stop")) {
    stop();
  } else if (startsWith(args[0], "calibrate")) {
    calibrate(String(args[1]).toFloat());
  } else if (startsWith(args[0], "stats")) {
    statistics(String(args[1]).toInt());
  } else if(startsWith(args[0], "dump")) {
    dumpFile(String(args[1]).toInt());
  } else if(startsWith(args[0], "serial")) {
    serialPrint = String(args[1]).toInt();
  } else {
    Serial.println("Unknown command");
  }
  return;
}

unsigned long measureTime = millis();
unsigned long saveTime = millis();
unsigned long errorTime = millis();
unsigned long prevFileSize = 0;
int fileError = 0;
void loop() {
  if(measureTime - millis() > DELAY) {
    measureTime = millis();
    float volts = analogRead(ADC_PIN) * calibration * 3.3 * 5810 / 3810 / pow(2, 12); //undoes adc, and 5v to 3.3v divider
    file.println(String(volts, 3));
    if(serialPrint) {Serial.println(String(volts, 3));}
    if(volts <= 0.05 && !fileError) {
      digitalWrite(BLUE_PIN, HIGH);
      digitalWrite(GREEN_PIN, LOW);
    }
    if(volts >= 4.5 && !fileError) {
      digitalWrite(BLUE_PIN, HIGH);
      digitalWrite(GREEN_PIN, HIGH);
    }
  }
  if(saveTime - millis() > SAVEDELAY) {
    saveTime = millis();
    file.close();
    file = SD.open(fileName, FILE_WRITE);
    file.seek(file.size());
    
    if(file && file.size() > prevFileSize) {
      digitalWrite(RED_PIN, LOW);
      digitalWrite(GREEN_PIN, HIGH);
      fileError = 0;
      prevFileSize = file.size();
    } else {
      digitalWrite(RED_PIN, HIGH);
      digitalWrite(GREEN_PIN, LOW);
      digitalWrite(BLUE_PIN, LOW);
      fileError = 1;
    }
  }
  if(errorTime - millis() > ERRORDELAY) {
    digitalWrite(BLUE_PIN, LOW);
    if(!fileError) digitalWrite(GREEN_PIN, HIGH);
  }

  if(digitalRead(ENABLE_PIN) == LOW) {stop();}
  if (Serial.available()) {serialEvent();}
}