#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>

// LCD Pin Definitions (4-bit mode)
#define LCD_RS_PORT     PORTD
#define LCD_RS_DDR      DDRD
#define LCD_RS_PIN      PD0

#define LCD_EN_PORT     PORTD
#define LCD_EN_DDR      DDRD
#define LCD_EN_PIN      PD1

#define LCD_D4_PORT     PORTD
#define LCD_D4_DDR      DDRD
#define LCD_D4_PIN      PD4

#define LCD_D5_PORT     PORTD
#define LCD_D5_DDR      DDRD
#define LCD_D5_PIN      PD5

#define LCD_D6_PORT     PORTD
#define LCD_D6_DDR      DDRD
#define LCD_D6_PIN      PD6

#define LCD_D7_PORT     PORTD
#define LCD_D7_DDR      DDRD
#define LCD_D7_PIN      PD7

// Traffic Light Pins
#define PR_GREEN    PB0  // Park Road Green
#define PR_YELLOW   PB1  // Park Road Yellow
#define PR_RED      PB2  // Park Road Red
#define RS_GREEN    PB3  // Railway Street Green
#define RS_YELLOW   PB4  // Railway Street Yellow
#define RS_RED      PB5  // Railway Street Red
#define DS_GREEN    PC1  // Dam Street Green
#define DS_YELLOW   PC2  // Dam Street Yellow
#define DS_RED      PC3  // Dam Street Red

// Sensor Pins (Active-Low Buttons)
#define S0          PD2
#define S1          PD3
#define S2          PC4
#define S3          PC5
#define S4          PB6
#define S6          PB7  // Hazard Input

// States
typedef enum {
    HAZARD,
    PRT,  // Park Road Through
    RST,  // Railway Street Through
    DST   // Dam Street Through
} Phase;

// Global Variables
volatile Phase currentPhase = HAZARD;
volatile uint8_t sensors = 0;
volatile uint16_t timePeriod = 1000;  // Default: 1s
volatile uint32_t phaseTimer = 0;
volatile uint32_t systemTime = 0;
volatile uint8_t hazardFlag = 0;

// LCD Functions
void lcd_pulse_enable() {
    LCD_EN_PORT |= (1 << LCD_EN_PIN);
    _delay_us(1);
    LCD_EN_PORT &= ~(1 << LCD_EN_PIN);
    _delay_us(100);
}

void lcd_send_nibble(uint8_t nibble) {
    if (nibble & (1 << 0)) LCD_D4_PORT |= (1 << LCD_D4_PIN);
    else LCD_D4_PORT &= ~(1 << LCD_D4_PIN);
    
    if (nibble & (1 << 1)) LCD_D5_PORT |= (1 << LCD_D5_PIN);
    else LCD_D5_PORT &= ~(1 << LCD_D5_PIN);
    
    if (nibble & (1 << 2)) LCD_D6_PORT |= (1 << LCD_D6_PIN);
    else LCD_D6_PORT &= ~(1 << LCD_D6_PIN);
    
    if (nibble & (1 << 3)) LCD_D7_PORT |= (1 << LCD_D7_PIN);
    else LCD_D7_PORT &= ~(1 << LCD_D7_PIN);
    
    lcd_pulse_enable();
}

void lcd_send_byte(uint8_t data, uint8_t rs) {
    if (rs) LCD_RS_PORT |= (1 << LCD_RS_PIN);
    else LCD_RS_PORT &= ~(1 << LCD_RS_PIN);
    
    lcd_send_nibble(data >> 4);
    lcd_send_nibble(data & 0x0F);
    _delay_us(100);
}

void lcd_command(uint8_t cmd) {
    lcd_send_byte(cmd, 0);
}

void lcd_data(uint8_t data) {
    lcd_send_byte(data, 1);
}

void lcd_init() {
    // Configure LCD pins as outputs
    LCD_RS_DDR |= (1 << LCD_RS_PIN);
    LCD_EN_DDR |= (1 << LCD_EN_PIN);
    LCD_D4_DDR |= (1 << LCD_D4_PIN);
    LCD_D5_DDR |= (1 << LCD_D5_PIN);
    LCD_D6_DDR |= (1 << LCD_D6_PIN);
    LCD_D7_DDR |= (1 << LCD_D7_PIN);
    
    // Initialization sequence
    _delay_ms(50);
    lcd_send_nibble(0x03);
    _delay_ms(5);
    lcd_send_nibble(0x03);
    _delay_us(100);
    lcd_send_nibble(0x03);
    lcd_send_nibble(0x02);  // Switch to 4-bit mode
    
    // Function set: 4-bit, 2-line, 5x8 dots
    lcd_command(0x28);
    // Display on, cursor off, blink off
    lcd_command(0x0C);
    // Clear display
    lcd_command(0x01);
    _delay_ms(2);
    // Entry mode set
    lcd_command(0x06);
}

void lcd_print(const char *str) {
    while (*str) {
        lcd_data(*str++);
    }
}

void lcd_print_number(uint32_t num) {
    char buffer[10];
    uint8_t i = 0;
    
    if (num == 0) {
        lcd_data('0');
        return;
    }
    
    while (num > 0) {
        buffer[i++] = '0' + (num % 10);
        num /= 10;
    }
    
    while (i > 0) {
        lcd_data(buffer[--i]);
    }
}

// Initialize Hardware
void init_hardware() {
    // Set sensor pins as inputs with pull-ups
    DDRD &= ~((1 << S0) | (1 << S1));
    DDRC &= ~((1 << S2) | (1 << S3));
    DDRB &= ~((1 << S4) | (1 << S6));
    PORTD |= (1 << S0) | (1 << S1);
    PORTC |= (1 << S2) | (1 << S3);
    PORTB |= (1 << S4) | (1 << S6);

    // Set traffic light pins as outputs
    DDRB |= (1 << PR_GREEN) | (1 << PR_YELLOW) | (1 << PR_RED) | 
            (1 << RS_GREEN) | (1 << RS_YELLOW) | (1 << RS_RED);
    DDRC |= (1 << DS_GREEN) | (1 << DS_YELLOW) | (1 << DS_RED);

    // ADC for potentiometer (PC0)
    ADMUX = (1 << REFS0);  // AVCC reference, ADC0
    ADCSRA = (1 << ADEN) | (1 << ADPS2) | (1 << ADPS1);  // Enable ADC, prescaler=64

    // Timer1 for phase timing (1ms interrupt)
    TCCR1B = (1 << WGM12) | (1 << CS11);  // CTC mode, prescaler=8
    OCR1A = 125;  // 1ms interrupt @ 1MHz
    TIMSK1 = (1 << OCIE1A);
}

// Timer1 Interrupt (Updates time period and system clock)
ISR(TIMER1_COMPA_vect) {
    static uint16_t adcCounter = 0;
    if (++adcCounter >= 1000) {  // Read ADC every 1s
        ADCSRA |= (1 << ADSC);
        while (ADCSRA & (1 << ADSC));
        uint16_t adcValue = ADC;
        timePeriod = 50 + (adcValue * 950) / 1023;  // Map to 50ms-1000ms
        adcCounter = 0;
    }
    phaseTimer++;
    systemTime++;
}

// Read Sensors (Active-Low)
uint8_t read_sensors() {
    uint8_t sensorState = 0;
    if (!(PIND & (1 << S0))) sensorState |= (1 << 0);
    if (!(PIND & (1 << S1))) sensorState |= (1 << 1);
    if (!(PINC & (1 << S2))) sensorState |= (1 << 2);
    if (!(PINC & (1 << S3))) sensorState |= (1 << 3);
    if (!(PINB & (1 << S4))) sensorState |= (1 << 4);
    if (!(PINB & (1 << S6))) sensorState |= (1 << 6);
    return sensorState;
}

// Control Traffic Lights
void set_lights(Phase phase) {
    // Turn off all lights first
    PORTB &= ~((1 << PR_GREEN) | (1 << PR_YELLOW) | (1 << PR_RED) | 
             (1 << RS_GREEN) | (1 << RS_YELLOW) | (1 << RS_RED));
    PORTC &= ~((1 << DS_GREEN) | (1 << DS_YELLOW) | (1 << DS_RED));

    switch (phase) {
        case HAZARD:
            Serial.println("Flash yellow lights");
            // Flash yellow lights
            if (phaseTimer % 2000 < 1000) {
                PORTB |= (1 << PR_YELLOW) | (1 << RS_YELLOW);
                PORTC |= (1 << DS_YELLOW);
            }
            break;

        case PRT:
            Serial.println("Park Road green, others red");
            // Park Road green, others red
            PORTB |= (1 << PR_GREEN);
            PORTC |= (1 << DS_RED);
            PORTB |= (1 << RS_RED);
            break;

        case RST:
            Serial.println("Railway Street green, others red");
            // Railway Street green, others red
            PORTB |= (1 << RS_GREEN);
            PORTC |= (1 << DS_RED);
            PORTB |= (1 << PR_RED);
            break;

        case DST:
            Serial.println("Dam Street green, others red");
            // Dam Street green, others red
            PORTC |= (1 << DS_GREEN);
            PORTB |= (1 << PR_RED) | (1 << RS_RED);
            break;
    }
}

// State Machine Logic
void run_state_machine() {
    static uint8_t lastPhase = HAZARD;
   
    // Hazard mode override
    if (sensors & (1 << 6)) {  // S6 grounded
        hazardFlag = 1;
        currentPhase = HAZARD;
        phaseTimer = 0;
        set_lights(HAZARD);
        return;
    }

    // Exit hazard after 10s
    if (hazardFlag && phaseTimer >= 10000) {
        hazardFlag = 0;
        currentPhase = PRT;
        phaseTimer = 0;
    }

    // Normal operation
    if (!hazardFlag) {
        switch (currentPhase) {
            case PRT:
                if (phaseTimer >= (4 * timePeriod)) {
                    if (sensors & ((1 << 2) | (1 << 3) | (1 << 4))) {  // RST or DST sensors
                        if (lastPhase != RST) currentPhase = RST;
                        else currentPhase = DST;  // Avoid repeats
                        phaseTimer = 0;
                    }
                }
                break;

            case RST:
                if (phaseTimer >= (2 * timePeriod)) {
                    if (sensors & (1 << 4)) {  // DST sensor
                        currentPhase = DST;
                        phaseTimer = 0;
                    } else if (phaseTimer >= (3 * timePeriod)) {
                        currentPhase = PRT;
                        phaseTimer = 0;
                    }
                }
                break;

            case DST:
                if (phaseTimer >= (2 * timePeriod)) {
                    if (sensors & ((1 << 0) | (1 << 1))) {  // PRT sensors
                        currentPhase = PRT;
                        phaseTimer = 0;
                    } else if (phaseTimer >= (4 * timePeriod)) {
                        currentPhase = PRT;
                        phaseTimer = 0;
                    }
                }
                break;
        }
        lastPhase = currentPhase;
        set_lights(currentPhase);
    }
}

// Update LCD Display
void update_lcd() {
    lcd_command(0x01);  // Clear LCD
    _delay_ms(2);

    // Top Row: Sensors (S0-S6)
    lcd_command(0x80);  // Row 1, Column 1
    for (uint8_t i = 0; i < 7; i++) {
        lcd_data((sensors & (1 << i)) ? 'X' : '_');
    }

    // Top Row Right: Time Counter (5 digits)
    lcd_command(0x8B);  // Row 1, Column 12
    lcd_print_number(systemTime % 100000);

    // Bottom Row: Phase and Light State
    lcd_command(0xC0);  // Row 2, Column 1
    switch (currentPhase) {
        case HAZARD:
            lcd_print("HZD   ");
            break;
        case PRT:
            lcd_print("PRT G ");
            break;
        case RST:
            lcd_print("RST G ");
            break;
        case DST:
            lcd_print("DST G ");
            break;
    }
}

int main(void) {

  Serial.begin(115200);
    // Initialize hardware
    init_hardware();
    
    // Initialize LCD
    lcd_init();
    
    // Enable global interrupts
    sei();
    
    // Initial display
    lcd_print("Traffic Control");
    _delay_ms(1000);
    
    while (1) {
        // Read sensors
        sensors = read_sensors();
        
        // Run state machine
        run_state_machine();
        
        // Update LCD
        update_lcd();
        
        // Small delay for debounce
        _delay_ms(100);
    }
    
    return 0;
}void setup() {
  // put your setup code here, to run once:

}

void loop() {
  // put your main code here, to run repeatedly:

}