#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Keypad.h>

LiquidCrystal_I2C lcd(0x27, 20, 4);

const byte ROW_NUM    = 4; // Four rows
const byte COLUMN_NUM = 4; // Four columns
char keys[ROW_NUM][COLUMN_NUM] = {
  {'1','2','3'},
  {'4','5','6'},
  {'7','8','9'},
  {'*','0','#'}
};
byte pin_rows[ROW_NUM] = {9, 8, 7, 6}; // Connect to the row pinouts of the keypad
byte pin_column[COLUMN_NUM] = {5, 4, 3, 2}; // Connect to the column pinouts of the keypad

Keypad keypad = Keypad(makeKeymap(keys), pin_rows, pin_column, ROW_NUM, COLUMN_NUM);

int numUsers = 0;
unsigned long elapsedTimes[8] = {0};  // Store elapsed time for each user
unsigned long timerStartTimes[8];      // Store the start time for each user
bool timersRunning[8] = {false};       // Store the running state for each user

unsigned long lastUpdateTime = 0;
unsigned long lastMillisecondUpdate = 0; // Track the last update time for milliseconds
const unsigned long updateInterval = 50;  // Update every 50 ms
const unsigned long millisecondInterval = 50; // Update milliseconds every 50 ms

bool userSelectionInProgress;  // Flag to prevent toggling during user selection
bool resetButtonPressed = false; // Declare the resetButtonPressed flag globally

void setup() {
  lcd.init();           // Initialize the I2C LCD
  lcd.backlight();      // Turn on the backlight
  lcd.setCursor(0, 0);  // Set the cursor to the first row, first column
  Serial.begin(9600);   // Initialize Serial for debugging

  // Display "How many users?" prompt on the LCD
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("How many users?");
  lcd.setCursor(0, 1);
  lcd.print("{1-8}");
}

void loop() {
    char key = keypad.getKey();  // Get the pressed key from the keypad
 
    if (keypad.getState() == PRESSED) {  // Check if a key is pressed and handle only when the state is PRESSED 

        if (key >= '1' && key <= '8' && numUsers ==0 ) { // Handle user selection (1-8)
          userSelectionInProgress = true;
            numUsers = key - '0'; // Set number of users (1 to 8)

            // Display selected number of users on the LCD  
            lcd.clear();
            lcd.setCursor(0, 0);
            lcd.print("Selected: " + String(numUsers) + " users");
            delay(500); // Delay to give time to read the LCD  
            lcd.clear();

            for (int i =0 ; i < 8; i++) {  // Ensure all timers are stopped when users are selected  
                timersRunning[i] = false;  // Stop all timers  
                elapsedTimes[i] =0 ;        // Reset elapsed times  
            }
        }

        if (key == '9') { // Handle "All" button press (Button 9)
            if (resetButtonPressed) {
                resetAllTimers();  // Reset all timers if reset button is also pressed  
                resetButtonPressed = false;  // Reset the flag after reset  
            } else {
                toggleAllTimers();  // Toggle all timers when button 9 is pressed without reset  
            }
        }

        if (key == '0') { // Handle "Reset" button press (Button )
            resetButtonPressed = true;  // Set flag indicating Reset button is pressed  
        }
  
        if (key >= '1' && key <= '8') { // Handle user button presses (1-8) to start/stop their respective timers

        if (userSelectionInProgress)
            return;

            int userIndex = key - '1';  // Get the user index (-7)

            if (timersRunning[userIndex]) {
                timersRunning[userIndex] = false; // Stop the timer  
                elapsedTimes[userIndex] += millis() - timerStartTimes[userIndex]; // Add elapsed time  
            } else {
                timerStartTimes[userIndex] = millis();  // Start the timer  
                timersRunning[userIndex] = true;
            }

            if (resetButtonPressed) { // If the reset button () was pressed while a user button was pressed, reset that user's timer  
                resetUserTimer(userIndex);  // Reset the selected user's timer  
                resetButtonPressed = false; // Reset the flag after the reset is performed  
            }
        }
    }

    if (millis() - lastUpdateTime >= updateInterval) { // Update the screen only at controlled intervals  
        lastUpdateTime = millis();
        updateTimers();  // Update the timer display  
    }
    userSelectionInProgress = false;  // Reset the flag once the selection is complete
}

void updateTimers() { // Function to update the timers on the screen
  for (int i = 0; i < numUsers; i++) {
    unsigned long elapsedTime = elapsedTimes[i];
    if (timersRunning[i]) {
      elapsedTime = millis() - timerStartTimes[i] + elapsedTimes[i];  // Calculate running timer
    }

    int minutes = (elapsedTime / 1000) / 60;
    int seconds = (elapsedTime / 1000) % 60;
    int milliseconds = elapsedTime % 1000;

    // Update the LCD display for each user
    int row = i % 4;  // 4 users per row
    int col = (i / 4) * 11;  // First 4 users in column 0, second 4 users in column 10

    lcd.setCursor(col, row);
    lcd.print(i + 1);   // Print user number
    lcd.print(")");     // Divider

    lcd.print(formatTime(minutes));    // Print timer formatted as 00:00:0
    lcd.print(":");
    lcd.print(formatTime(seconds));
    lcd.print(":");
    lcd.print(milliseconds / 100);  // Display only the first digit of milliseconds (as 00:00:0)
  }
}

String formatTime(int timeUnit) { // Single formatTime function 
  if (timeUnit < 10) {
    return "0" + String(timeUnit);  // Add leading zero if timeUnit < 10
  } else return String(timeUnit);
}

void resetUserTimer(int userIndex) { // Function to handle user timer reset
  elapsedTimes[userIndex] = 0;  // Reset the user's elapsed time
  timersRunning[userIndex] = false;  // Stop the timer
  timerStartTimes[userIndex] = millis(); // Set the start time to current time
  updateTimers(); // Update the timer display after resetting
}

void resetAllTimers() { // Function to reset all timers
  for (int i = 0; i < numUsers; i++) {
    elapsedTimes[i] = 0;  // Reset the elapsed time for each user
    timersRunning[i] = false;  // Stop the timer
    timerStartTimes[i] = millis(); // Set the start time to current time
  }
}

void toggleAllTimers() { // Function to toggle all timers (start any stopped timers or stop all if all are running)
  bool allRunning = true;

  // Check if all timers are running
  for (int i = 0; i < numUsers; i++) {
    if (!timersRunning[i]) {
      allRunning = false;
      break;
    }
  }

  if (allRunning) { // If all timers are running, stop all of them
    for (int i = 0; i < numUsers; i++) {
      timersRunning[i] = false;
      elapsedTimes[i] += millis() - timerStartTimes[i];  // Add elapsed time before stopping
    }
  } else { // If not all timers are running, start the stopped ones
    for (int i = 0; i < numUsers; i++) {
      if (!timersRunning[i]) {
        timerStartTimes[i] = millis();  // Start the timer
        timersRunning[i] = true;
      }
    }
  }
}