#include <Arduino.h>
#include <cstdint>

// Pin assignments for the 7 segments (a-g)
const int segmentPins[] = {2, 3, 4, 5, 6, 7, 8}; // D2 to D8

/**
 * @brief Generates the 8-bit segment pattern for a Common Cathode 7-segment display.
 * Bit Map: [dp, g, f, e, d, c, b, a] (Bit 7 is dp, Bit 0 is a)
 * A '1' turns the segment ON (Common Cathode logic).
 * @param decimal_digit An integer from 0 to 9.
 * @return uint8_t The 8-bit pattern required to display the digit.
 */
uint8_t get_segment_pattern(int decimal_digit) {
    // Start with all segments OFF (0b00000000). dp is ignored.
    uint8_t pattern = 0x00; 
    
    switch (decimal_digit) {
        case 0: // 0: a, b, c, d, e, f (0x3F)
            pattern |= 0b00111111;
            break;
        case 1: // 1: b, c (0x06)
            pattern |= 0b00000110;
            break;
        case 2: // 2: a, b, d, e, g (0x5B)
            pattern |= 0b01011011;
            break;
        case 3: // 3: a, b, c, d, g (0x4F)
            pattern |= 0b01001111;
            break;
        case 4: // 4: b, c, f, g (0x66)
            pattern |= 0b01100110;
            break;
        case 5: // 5: a, c, d, f, g (0x6D)
            pattern |= 0b01101101;
            break;
        case 6: // 6: a, c, d, e, f, g (0x7D)
            pattern |= 0b01111101;
            break;
        case 7: // 7: a, b, c (0x07)
            pattern |= 0b00000111;
            break;
        case 8: // 8: a, b, c, d, e, f, g (0x7F)
            pattern |= 0b01111111;
            break;
        case 9: // 9: a, b, c, d, f, g (0x6F)
            pattern |= 0b01101111;
            break;
        default:
            pattern = 0x00; // All OFF for invalid input
    }
    return pattern;
}

/**
 * @brief Writes the 8-bit pattern to the designated Arduino pins.
 * @param pattern The 8-bit segment pattern to display.
 */
void displayDigit(uint8_t pattern) {
    // Iterate through segments a (Bit 0) to g (Bit 6)
    for (int i = 0; i < 7; i++) {
        // Check if the i-th bit (segment) is ON (1)
        if ((pattern >> i) & 0x01) {
            // Segment ON for Common Cathode
            digitalWrite(segmentPins[i], HIGH);
        } else {
            // Segment OFF
            digitalWrite(segmentPins[i], LOW);
        }
    }
}

void setup() {
    // Initialize all segment pins (D2 through D8) as outputs
    for (int i = 0; i < 7; i++) {
        pinMode(segmentPins[i], OUTPUT);
    }
}

void loop() {
    // Cycle through digits 0 to 9
    for (int i = 0; i <= 9; i++) {
        uint8_t segment_data = get_segment_pattern(i);
        displayDigit(segment_data);
        delay(500); // Pause for 500ms (as required)
    }
}