#include <LPC17xx.h>
#include <stdbool.h>

/* ===================================================
 * SMART CALCULATOR - LPC1768 (Final v2)
 * Supports BIN, BASE4, OCT, DEC, and HEX
 * with 4x4 keypad, LCD, and 7-seg status display.
 *
 * Features:
 *  - Base-aware arithmetic and I/O
 *  - HEX: double MODE button press within 2s = operator mode
 *  - Hardware 1ms timing via SysTick
 * ===================================================
 */

/* 7-Segment patterns for 0–F */
const unsigned char seven_seg[16] = {
    0x3F, 0x06, 0x5B, 0x4F, 0x66, 0x6D, 0x7D, 0x07,
    0x7F, 0x6F, 0x77, 0x7C, 0x39, 0x5E, 0x79, 0x71
};

/* ===== Pin & Mode Definitions ===== */
#define COL_BASE 15
#define ROW_BASE 19
#define COL_MASK (0x0F << COL_BASE)
#define ROW_MASK (0x0F << ROW_BASE)

#define SEG_SHIFT 4
#define DIGIT_EN (1 << 23)

#define LCD_DATA_SHIFT 23
#define LCD_DATA_MASK (0x0F << LCD_DATA_SHIFT)
#define LCD_RS (1 << 27)
#define LCD_EN (1 << 28)

#define MODE_BUTTON (1 << 12)

/* Supported Bases */
#define MODE_BIN 2
#define MODE_BASE4 4
#define MODE_OCT 8
#define MODE_DEC 10
#define MODE_HEX 16

/* Operators */
#define OP_NONE 0
#define OP_ADD 1
#define OP_SUB 2
#define OP_MUL 3
#define OP_CLR 4
#define OP_RES 5

/* ===== Global Variables ===== */
unsigned int current_base;
unsigned int input_num;
unsigned int stored_num;
unsigned int result;
unsigned int operation;
unsigned char result_displayed;

unsigned int key, last_key, stable;
unsigned int button_state, last_button_state, button_stable;

unsigned char hex_operator_mode;
unsigned long last_mode_press_time;

/* Millisecond counter via SysTick */
volatile unsigned long sys_millis = 0;

/* ===== Function Declarations ===== */
void delay(volatile unsigned int d);
void lcd_delay(unsigned long r);
void lcd_write_nibble(unsigned char nibble, unsigned char is_data);
void lcd_cmd(unsigned char cmd);
void lcd_data(unsigned char data);
void lcd_init(void);
void lcd_print_str(const char *str);
void lcd_print_num(unsigned int num, unsigned int base);
void display_mode(void);
void display_input(void);
void display_result(void);
unsigned int scan_keypad(void);
unsigned int scan_mode_button(void);
unsigned int is_valid_digit(unsigned int key);
void change_mode(void);
void handle_mode_button(void);
void operate(unsigned int op);
void perform_operation(void);
unsigned char is_operator_active(unsigned int key);
unsigned int base_arith(unsigned int a, unsigned int b,
                        unsigned int op, unsigned int base);
unsigned long millis(void);

/* ===== Utility ===== */
void delay(volatile unsigned int d) {
    while (d--) __NOP();
}

void lcd_delay(unsigned long r) {
    volatile unsigned long i;
    for (i = 0; i < r; i++)
        ;
}

/* ===== SysTick Millisecond Tracker ===== */
void SysTick_Handler(void) {
    sys_millis++;
}

unsigned long millis(void) {
    return sys_millis;
}

/* ===== LCD Control ===== */
void lcd_write_nibble(unsigned char nibble, unsigned char is_data) {
    unsigned long temp;
    temp = (nibble & 0x0F) << LCD_DATA_SHIFT;
    LPC_GPIO0->FIOPIN = (LPC_GPIO0->FIOPIN & ~LCD_DATA_MASK) | temp;

    if (is_data)
        LPC_GPIO0->FIOSET = LCD_RS;
    else
        LPC_GPIO0->FIOCLR = LCD_RS;

    LPC_GPIO0->FIOSET = LCD_EN;
    lcd_delay(100);
    LPC_GPIO0->FIOCLR = LCD_EN;
    lcd_delay(250000);
}

void lcd_cmd(unsigned char cmd) {
    lcd_write_nibble(cmd >> 4, 0);
    lcd_write_nibble(cmd, 0);
}

void lcd_data(unsigned char data) {
    lcd_write_nibble(data >> 4, 1);
    lcd_write_nibble(data, 1);
}

void lcd_init(void) {
    lcd_delay(5000000);
    lcd_write_nibble(0x03, 0);
    lcd_delay(500000);
    lcd_write_nibble(0x03, 0);
    lcd_delay(500000);
    lcd_write_nibble(0x03, 0);
    lcd_delay(500000);
    lcd_write_nibble(0x02, 0);
    lcd_delay(500000);

    lcd_cmd(0x28);
    lcd_cmd(0x0C);
    lcd_cmd(0x01);
    lcd_delay(500000);
    lcd_cmd(0x06);
}

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

void lcd_print_num(int num, unsigned int base) {
    char buffer[17];
    int i = 0;
    unsigned int unum;

    if (base == MODE_DEC) {
        if (num < 0) {
            lcd_data('-');
            num = -num;
        }
    }

    unum = (unsigned int)num;

    if (unum == 0) {
        lcd_data('0');
        return;
    }

    while (unum > 0 && i < 16) {
        unsigned int d = unum % base;
        buffer[i++] = (d < 10) ? ('0' + d) : ('A' + d - 10);
        unum /= base;
    }

    while (i > 0)
        lcd_data(buffer[--i]);
}

/* ===== Display Helpers ===== */
void display_mode(void) {
    lcd_cmd(0x80);
    lcd_print_str("Mode: ");
    if (current_base == MODE_BIN)
        lcd_print_str("BIN   ");
    else if (current_base == MODE_BASE4)
        lcd_print_str("BASE4 ");
    else if (current_base == MODE_OCT)
        lcd_print_str("OCT   ");
    else if (current_base == MODE_DEC)
        lcd_print_str("DEC   ");
    else {
        lcd_print_str("HEX");
        if (hex_operator_mode)
            lcd_print_str("[OPS]");
        else
            lcd_print_str("    ");
    }
}

void display_input(void) {
    lcd_cmd(0xC0);
    lcd_print_str("Input: ");
    lcd_print_num(input_num, current_base);
    lcd_print_str("       ");
}

void display_result(void) {
    lcd_cmd(0xC0);
    lcd_print_str("Result: ");
    lcd_print_num(result, current_base);
    lcd_print_str("       ");
}

/* ===== Keypad and Button ===== */
unsigned int scan_keypad(void) {
    unsigned int col, row, row_bits;
    for (col = 0; col < 4; col++) {
        LPC_GPIO0->FIOSET = COL_MASK;
        delay(50);
        LPC_GPIO0->FIOCLR = (1 << (COL_BASE + col));
        delay(200);
        row_bits = (LPC_GPIO0->FIOPIN & ROW_MASK) >> ROW_BASE;

        if (row_bits != 0x0F) {
            for (row = 0; row < 4; row++) {
                if (!(row_bits & (1 << row))) {
                    LPC_GPIO0->FIOSET = COL_MASK;
                    return col * 4 + row;
                }
            }
        }
    }
    LPC_GPIO0->FIOSET = COL_MASK;
    return 0xFF;
}

unsigned int scan_mode_button(void) {
    return ((LPC_GPIO2->FIOPIN & MODE_BUTTON) == 0) ? 1 : 0;
}

/* ===== Mode and Button ===== */
void change_mode(void) {
    if (current_base == MODE_DEC)
        current_base = MODE_BIN;
    else if (current_base == MODE_BIN)
        current_base = MODE_BASE4;
    else if (current_base == MODE_BASE4)
        current_base = MODE_OCT;
    else if (current_base == MODE_OCT)
        current_base = MODE_HEX;
    else
        current_base = MODE_DEC;

    display_mode();
    input_num = stored_num = result = 0;
    operation = OP_NONE;
    result_displayed = 0;
    display_input();
}

void handle_mode_button(void) {
    unsigned long now = millis();

    if (button_stable == 3 && button_state == 1) {
        if (current_base == MODE_HEX) {
            if ((now - last_mode_press_time) < 2000) {
                hex_operator_mode = !hex_operator_mode;
                display_mode();
                last_mode_press_time = 0;
            } else {
                last_mode_press_time = now;
            }
        } else {
            change_mode();
        }
    }
}

/* ===== Validation ===== */
unsigned int is_valid_digit(unsigned int key) {
    if (key >= 16)
        return 0;
    if (current_base == MODE_BIN && key >= 2)
        return 0;
    if (current_base == MODE_BASE4 && key >= 4)
        return 0;
    if (current_base == MODE_OCT && key >= 8)
        return 0;
    if (current_base == MODE_DEC && key >= 10)
        return 0;
    return 1;
}

/* ===== Arithmetic per base (optimized) ===== */
int base_arith(int a, int b, unsigned int op, unsigned int base) {
    int r = 0;

    switch (op) {
        case OP_ADD:
            r = a + b;
            break;

        case OP_SUB:
            r = a - b;
            break;

        case OP_MUL:
            r = a * b;
            break;

        default:
            r = a;
            break;
    }

    // For non-decimal modes, keep everything positive and base-limited
    if (base != MODE_DEC) {
        if (r < 0)
            r = ((r % base) + base) % base;
        else
            r = r % (base * base * base * base * base); // safe wraparound for multi-digit bases
    }

    return r;
}

/* ===== Operation/Arithmetic Handling ===== */
void operate(unsigned int op) {
    stored_num = input_num;
    input_num = 0;
    operation = op;
    result_displayed = 0;
}

void perform_operation(void) {
    result = base_arith(stored_num, input_num, operation, current_base);
    display_result();
    input_num = result;
    operation = OP_NONE;
    result_displayed = 1;
}

/* ===== Key Classifier ===== */
unsigned char is_operator_active(unsigned int key) {
    if (key >= 11 && key <= 15) {
        if (current_base == MODE_HEX)
            return hex_operator_mode;
        else
            return 1;
    }
    return 0;
}

/* ===== MAIN ===== */
int main(void) {
    current_base = MODE_DEC;
    input_num = stored_num = result = 0;
    operation = OP_NONE;
    result_displayed = 0;
    key = last_key = 0xFF;
    stable = 0;
    button_stable = 0;
    button_state = last_button_state = 0;
    hex_operator_mode = 0;
    last_mode_press_time = 0;

    /* ===== SystemClock & SysTick Setup ===== */
    SystemCoreClockUpdate();
    SysTick_Config(SystemCoreClock / 1000);  // 1ms tick

    /* ===== Peripheral Init ===== */
    LPC_PINCON->PINSEL0 = 0;
    LPC_PINCON->PINSEL1 = 0;
    LPC_PINCON->PINSEL3 = 0;
    LPC_PINCON->PINSEL4 = 0;

    LPC_GPIO0->FIODIR |= COL_MASK;
    LPC_GPIO0->FIODIR &= ~ROW_MASK;
    LPC_GPIO0->FIOSET = COL_MASK;

    LPC_GPIO2->FIODIR &= ~MODE_BUTTON;

    LPC_GPIO0->FIODIR |= (0xFF << SEG_SHIFT);
    LPC_GPIO1->FIODIR |= DIGIT_EN;
    LPC_GPIO0->FIODIR |= LCD_DATA_MASK | LCD_RS | LCD_EN;

    lcd_init();
    display_mode();
    display_input();

    /* ===== Main Loop ===== */
    while (1) {
        key = scan_keypad();
        button_state = scan_mode_button();

        // Debounce keypad
        if (key == last_key)
            stable = (stable < 5) ? stable + 1 : stable;
        else {
            last_key = key;
            stable = 0;
        }

        // Debounce button
        if (button_state == last_button_state)
            button_stable = (button_stable < 5) ? button_stable + 1 : button_stable;
        else {
            last_button_state = button_state;
            button_stable = 0;
        }

        handle_mode_button();

        if (stable == 3 && key != 0xFF) {
            if (is_operator_active(key)) {
                switch (key) {
                    case 11: operate(OP_ADD); display_input(); break;
                    case 12: input_num = stored_num = result = 0;
                             operation = OP_NONE; display_input(); break;
                    case 13: operate(OP_SUB); display_input(); break;
                    case 14: operate(OP_MUL); display_input(); break;
                    case 15: perform_operation(); break;
                }
            } else if (is_valid_digit(key)) {
                result_displayed = 0;
                input_num = input_num * current_base + key;
                display_input();
            }
            stable = 5;
        }

        // Simple 7-seg base display
        LPC_GPIO0->FIOCLR = (0xFF << SEG_SHIFT);
        unsigned int segval = 0x3F;  // default '0'
        if (current_base == MODE_BIN) segval = seven_seg[2];
        else if (current_base == MODE_BASE4) segval = seven_seg[4];
        else if (current_base == MODE_OCT) segval = seven_seg[8];
        else if (current_base == MODE_DEC) segval = seven_seg[0];
        else if (current_base == MODE_HEX) segval = seven_seg[0xA];  // 'A' for HEX

        LPC_GPIO0->FIOSET = (segval << SEG_SHIFT);
        LPC_GPIO1->FIOSET = DIGIT_EN;

        delay(3000);
    }
}