// RTC DS1307 I2C address
#define DS1307_ADDRESS 0x68

// Initialize ports for seven-segment display, switches, and buzzer
#define BUZZER_PIN 8
#define SWITCH_HOUR_PIN 2
#define SWITCH_MINUTE_PIN 3
#define SWITCH_ALARM_PIN 4

void init_ports() {
    DDRF = 0xFF;    // Set PORTF as output (for the segments)
    DDRK = 0x1F;    // Set lower 5 bits of PORTK as output (for digit select)
    DDRD &= ~(1 << SWITCH_HOUR_PIN | 1 << SWITCH_MINUTE_PIN | 1 << SWITCH_ALARM_PIN); // Set switch pins as input
    PORTD |= (1 << SWITCH_HOUR_PIN | 1 << SWITCH_MINUTE_PIN | 1 << SWITCH_ALARM_PIN); // Enable pull-up resistors
    DDRB |= (1 << BUZZER_PIN); // Set buzzer pin as output
}

// Function to start I2C communication
void i2c_start() {
    TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);
    while (!(TWCR & (1 << TWINT)));  // Wait for start to be transmitted
}

// Function to stop I2C communication
void i2c_stop() {
    TWCR = (1 << TWINT) | (1 << TWSTO) | (1 << TWEN);
}

// Function to write a byte over I2C
void i2c_write(uint8_t data) {
    TWDR = data;
    TWCR = (1 << TWINT) | (1 << TWEN);
    while (!(TWCR & (1 << TWINT)));  // Wait for the transmission to complete
}

// Function to read a byte from I2C (ack = 1 to acknowledge, ack = 0 for NACK)
uint8_t i2c_read(uint8_t ack) {
    TWCR = (1 << TWINT) | (1 << TWEN) | (ack << TWEA);
    while (!(TWCR & (1 << TWINT)));  // Wait for the data to be received
    return TWDR;
}

// Function to initialize RTC DS1307
void rtc_init() {
    i2c_start();
    i2c_write(DS1307_ADDRESS << 1);  // Send address + write bit
    i2c_write(0x00);                 // Start at register 0x00 (seconds)
    i2c_write(0x00);                 // Write 0 to seconds to start the clock
    i2c_stop();
}

// Function to read time from RTC DS1307
void rtc_get_time(uint8_t *hours, uint8_t *minutes) {
    i2c_start();
    i2c_write(DS1307_ADDRESS << 1);  // Send address + write bit
    i2c_write(0x00);                 // Start reading at register 0x00 (seconds)
    i2c_start();
    i2c_write((DS1307_ADDRESS << 1) | 1);  // Send address + read bit
    
    i2c_read(1);                     // Read seconds, but discard
    *minutes = i2c_read(1);           // Read minutes
    *hours = i2c_read(0);             // Read hours
    i2c_stop();
}

// Convert BCD to decimal
uint8_t bcd_to_dec(uint8_t val) {
    return ((val / 16 * 10) + (val % 16));
}

// Seven-segment display digit patterns for 0-9
long seven_segment[] = {
    0x3F, // 0
    0x06, // 1
    0x5B, // 2
    0x4F, // 3
    0x66, // 4
    0x6D, // 5
    0x7D, // 6
    0x07, // 7
    0x7F, // 8
    0x6F  // 9
};

// Function to display a number on 4-digit seven-segment display
void display_time(uint8_t hours, uint8_t minutes) {
    int digits[4] = {
        seven_segment[hours / 10],
        seven_segment[hours % 10],
        seven_segment[minutes / 10],
        seven_segment[minutes % 10]
    };

    int digit_select[4] = {0x1E, 0x1D, 0x1B, 0x17}; // Digit select for multiplexing

    for (int i = 0; i < 4; i++) {
        PORTF = digits[i];        // Output digit to seven-segment
        PORTK = digit_select[i];  // Select corresponding digit
        delay(5);                 // Short delay to allow multiplexing
        PORTK = 0x1F;             // Turn off all digits
    }
}

void setup() {
    init_ports();   // Initialize ports
    rtc_init();     // Initialize RTC
    Serial.begin(9600);
}

void loop() {
    static uint8_t alarm_hours = 0;
    static uint8_t alarm_minutes = 0;
    static bool alarm_set = false;
    
    uint8_t hours, minutes;

    // Get the current time from the RTC
    rtc_get_time(&hours, &minutes);

    // Convert BCD to decimal
    hours = bcd_to_dec(hours);
    minutes = bcd_to_dec(minutes);

    // Display time on the 4-digit seven-segment display
    display_time(hours, minutes);

    // Check for switch presses to set hours and minutes
    if (!(PIND & (1 << SWITCH_HOUR_PIN))) { // If hour switch is pressed
        alarm_hours = (alarm_hours + 1) % 24; // Increment hour
        delay(200); // Debounce delay
    }
    if (!(PIND & (1 << SWITCH_MINUTE_PIN))) { // If minute switch is pressed
        alarm_minutes = (alarm_minutes + 1) % 60; // Increment minute
        delay(200); // Debounce delay
    }
    if (!(PIND & (1 << SWITCH_ALARM_PIN))) { // If alarm switch is pressed
        alarm_set = true; // Set the alarm
        delay(200); // Debounce delay
    }

    // Check if the alarm time matches the current time
    if (alarm_set && hours == alarm_hours && minutes == alarm_minutes) {
        PORTB |= (1 << BUZZER_PIN); // Turn on the buzzer
        delay(1000);                 // Buzzer duration
        PORTB &= ~(1 << BUZZER_PIN); // Turn off the buzzer
        alarm_set = false;           // Reset alarm state
    }

    delay(1000);  // Update every second
}