#include <SPI.h>
#include <SD.h>
#include <LiquidCrystal_I2C.h>

const int WIDTH = 20;
const int HEIGHT = 4;

LiquidCrystal_I2C lcd0(0x27, WIDTH, HEIGHT);
LiquidCrystal_I2C lcd1(0x23, WIDTH, HEIGHT);

const int TRIGPIN = 2;
const int ECHOPIN = 3;
const int RESET_PIN = A0;


// New Stuff
const int LEDAPIN = 7;
const int LEDBPIN = 6;
const int LEDCPIN = 5;
const int LEDDPIN = 4;


const int ANS_CHANGE_THRESHOLD = 2000;
const int SCREEN_CHANGE_THRESHOLD = 1500;
const int INITIAL_SCREEN_FACTOR = 2;
const int EXTRA_SCROLLS = 2;
const int OPTION_CHANGE_THRESHOLD = 500;
const int NUM_QS = 1703;


File file;

const int arrayLength = 5;
int lines = 0;
String qArray[arrayLength];
int perm[arrayLength - 1];

void setup()
{
  digitalWrite(RESET_PIN, HIGH);
  pinMode(TRIGPIN, OUTPUT);
  pinMode(ECHOPIN, INPUT);
  pinMode(RESET_PIN, OUTPUT);
  // New Stuff
  pinMode(LEDAPIN, OUTPUT);
  pinMode(LEDBPIN, OUTPUT);
  pinMode(LEDCPIN, OUTPUT);
  pinMode(LEDDPIN, OUTPUT);

  digitalWrite(RESET_PIN, HIGH);
  Serial.begin(9600);
  delay(analogRead(A2));
  randomSeed(analogRead(A1)*analogRead(A2)+ analogRead(A3));
  Serial.println();

  lcd0.init();
  lcd0.backlight();
  lcd0.home();
  lcd0.noAutoscroll();

  lcd1.init();
  lcd1.backlight();
  lcd1.home();
  lcd1.noAutoscroll();

  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }
  Serial.print("Initializing SD card...");
  if (!SD.begin(10)) {
    while (1);
  }

  //open the file here
  lines = loadQuestions(String(random(NUM_QS)) + ".TXT", qArray);
  permute(lines - 1, perm);
  lcd0.setCursor(0, 0);
  //scrollQ(qArray[0]);
  displayAns(qArray, perm, lines, 0);
}

void loop() {
  //scroll answers
  static int screenInd = 0;
  static long lastS = 0;
  int numofScreens = INITIAL_SCREEN_FACTOR + qArray[0].length() / (WIDTH) - HEIGHT + EXTRA_SCROLLS;
  if (millis() - lastS > SCREEN_CHANGE_THRESHOLD) {
    lastS = millis();
    if (screenInd == 0 || screenInd > INITIAL_SCREEN_FACTOR) {
      printQScreen(qArray[0], max(screenInd - INITIAL_SCREEN_FACTOR, 0));
    }
    screenInd = (screenInd + 1) % (numofScreens);
  }

  //scroll questions
  static int optOffset = 0;
  static long lastScroll = 0;
  if (millis() - lastScroll > OPTION_CHANGE_THRESHOLD) {
    lastScroll = millis();
    displayAns(qArray, perm, lines, optOffset);
    optOffset++;
  }

  //lock in on choices
  static long lastChange = millis();
  static int lastChoice = 0;
  int dist = getDist();
  int choice = map(dist, 0, 120, 0, 6);
  if (lastChoice != choice) {
    lastChange = millis();
  }

  if (1 <= choice && choice < lines) {
    lcd1.cursor();
    lcd1.blink();
    lcd1.setCursor(19, choice - 1);
    if (millis() - lastChange > ANS_CHANGE_THRESHOLD) {
      feedbackAndReset(perm[choice - 1] == 0, qArray[1]);
    }
  } else {
    lcd1.noCursor();
    lcd1.noBlink();
  }

  lightLEDs(choice);

  lastChoice = choice;
  delay(100);
}


int loadQuestions(String path, String arr[]) {
  file = SD.open(path, FILE_READ);
  int index = 0;
  while (file.available()) {
    //A inconsistent line length may lead to heap memory fragmentation
    arr[index] = file.readStringUntil('\n');
    arr[index].trim();

    index++;
  }
  file.close();
  return index;
}


void permute(int n, int perm[]) {
  int ord[n];
  for (int i = 0; i < n; i++) {
    ord[i] = i;
  }
  for (int i = 0; i < n; i++) {
    int ind = random(n - i);
    perm[i] = ord[ind];
    for (int j = ind; j < n - 1; j++) {
      ord[j] = ord[j + 1];
    }
  }
}

int getDist() {
  digitalWrite(TRIGPIN, LOW);
  delayMicroseconds(5);
  digitalWrite(TRIGPIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIGPIN, LOW);
  long duration = pulseIn(ECHOPIN, HIGH);
  int distance = duration * 0.34 / 2;
  Serial.println(distance);
  return distance;
}

void displayAns(String qArray[], int perm[], int lines, int offset) {
  for (int i = 0; i < lines - 1; i++) {
    lcd1.setCursor(0, i);
    int scrollsNeeded =
      qArray[perm[i] + 1].length() - (WIDTH - 2) + INITIAL_SCREEN_FACTOR + EXTRA_SCROLLS;
    if (scrollsNeeded <= INITIAL_SCREEN_FACTOR + EXTRA_SCROLLS) {
      lcd1.print(qArray[perm[i] + 1]);
    } else {
      int cur_off = offset % (scrollsNeeded) - INITIAL_SCREEN_FACTOR;

      if (-INITIAL_SCREEN_FACTOR < cur_off && cur_off < 1) {
        continue;
      }

      cur_off = max(cur_off, 0);
      lcd1.print("                   ");
      lcd1.setCursor(0, i);
      lcd1.print(qArray[perm[i] + 1].substring(cur_off, cur_off + WIDTH - 2));
    }
  }
}

void feedbackAndReset(bool correct, String ans) {
  lcd1.noCursor();
  lcd1.noBlink();
  lcd1.clear();
  lcd1.home();

  if (correct) {
    lcd1.print("Correct!");
  } else {
    lcd1.print("Incorrect.");
    lcd1.setCursor(0, 1);
    lcd1.print("Correct Answer is:");
    lcd1.setCursor(0, 2);
    lcd1.print(ans);
  }

  delay(1000);
  digitalWrite(RESET_PIN, LOW);
}

void printQScreen(String q, int s) {
  int qLen = q.length();
  int area = WIDTH * HEIGHT;

  if (qLen <= area) {
    for (int i = 0; i < qLen; i++) {
      int x = i % WIDTH;
      int y = i / WIDTH;
      lcd0.setCursor(x, y);
      lcd0.print(q[i]);
    }
    return;
  }

  lcd0.clear();
  for (int i = 0; i < area && ((s * WIDTH) + i) < qLen; i++) {
    int x = i % WIDTH;
    int y = i / WIDTH;
    lcd0.setCursor(x, y);
    lcd0.print(q[(s * WIDTH) + i]);
  }
}

void lightLEDs(int choice) {
  digitalWrite(LEDAPIN, LOW);
  digitalWrite(LEDBPIN, LOW);
  digitalWrite(LEDCPIN, LOW);
  digitalWrite(LEDDPIN, LOW);
  switch (choice)
  {
    case 1:
      digitalWrite(LEDAPIN, HIGH);
      break;
    case 2:
      digitalWrite(LEDBPIN, HIGH);
      break;
    case 3:
      digitalWrite(LEDCPIN, HIGH);
      break;
    case 4:
      digitalWrite(LEDDPIN, HIGH);
      break;
    default:
      break;
  }
}