Ping-pong console game

pong.c

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdbool.h>
#include <time.h>
#include <sys/select.h>
#include <string.h>

#define MIN(a, b) (((a) < (b)) ? (a) : (b))
#define MAX(a, b) (((a) > (b)) ? (a) : (b))

#define AI_MODE 1
const int TABLE_WIDTH = 21;
const int TABLE_HEIGHT = 12;
const int RACKET_OFFSET = 1;
const int RACKET_SIZE = 3;

void clrscr()
{
    system("clear");
}

void printHorizontalLine()
{
    printf("+");
    for (int i = 0; i < TABLE_WIDTH; i++)
    {
        printf("—");
    }
    printf("+");
    printf("\n\r");
}

struct
{
    int x, y;
    int vx, vy;
} ball;

struct
{
    int A, B;
} racket;
struct
{
    int A, B;
} score;

void initScore()
{
    score.A = 0;
    score.B = 0;
}

void resetGame()
{
    ball.x = TABLE_WIDTH / 2;
    ball.y = TABLE_HEIGHT / 2;
    ball.vx = rand() % 2 ? 1 : -1;
    ball.vy = rand() % 2 ? 1 : -1;
    racket.A = TABLE_HEIGHT / 2 - 2;
    racket.B = TABLE_HEIGHT / 2 - 2;
}

char scoreBuffer[16];
void printScoreLine() {
    sprintf(scoreBuffer, "%3d : %-d", score.A, score.B);
    int scoreLength = strlen(scoreBuffer);
    
    printf("|");
    int half = TABLE_WIDTH / 2 - scoreLength / 2;
    for (int i = 1; i < half; i++)
        printf(" ");
    printf("%3d : %-3d", score.A, score.B);
    for (int i = half + scoreLength; i < TABLE_WIDTH - 1; i++)
        printf(" ");
    printf("|");
    printf("\n\r");
}

void printTable()
{
    clrscr();
    printHorizontalLine();
    for (int j = 0; j < TABLE_HEIGHT; j++)
    {
        printf("|");
        for (int i = 0; i < TABLE_WIDTH; i++)
        {
            if (i == ball.x && j == ball.y)
            {
                printf("*");
                continue;
            }
            if (i == RACKET_OFFSET && (j >= racket.A) && (j < racket.A + RACKET_SIZE))
            {
                printf("|");
                continue;
            }
            if (i == (TABLE_WIDTH - 1 - RACKET_OFFSET) && (j >= racket.B) && (j < racket.B + RACKET_SIZE))
            {
                printf("|");
                continue;
            }
            printf(" ");
        }
        printf("|");
        printf("\n\r");
    }
    printHorizontalLine();
    printScoreLine();
    printHorizontalLine();
}

void moveBall()
{
    ball.x += ball.vx;
    ball.y += ball.vy;
}

void checkState()
{
    // check horizontal borders
    if (ball.x == 0 || ball.x == TABLE_WIDTH - 1)
    {
        if (ball.x == 0)
        {
            score.B++;
        }
        else
        {
            score.A++;
        }
        resetGame();
        return;
    }
    // chek vertical borders
    if (ball.y < 0 || ball.y > TABLE_HEIGHT - 1)
    {
        ball.vy *= -1;
        ball.y += ball.vy;
    }
    // check racket is inside the table
    racket.A = MAX(0, MIN(racket.A, TABLE_HEIGHT - RACKET_SIZE));
    racket.B = MAX(0, MIN(racket.B, TABLE_HEIGHT - RACKET_SIZE));
    // check racket collision
    bool hitRocketA = ball.x == RACKET_OFFSET && (ball.y >= racket.A && ball.y < racket.A + RACKET_SIZE);
    bool hitRocketB = ball.x == (TABLE_WIDTH - 1 - RACKET_OFFSET) && (ball.y >= racket.B && ball.y < racket.B + RACKET_SIZE);
    if (hitRocketA || hitRocketB)
    {
        ball.vx *= -1;
        ball.x += 2 * ball.vx;

        int mode = rand() % 5;
        if (mode == 0)
        {
            ball.vy = 0;
        }
        else
        {
            if (ball.vy == 0)
            {
                ball.vy = rand() % 2 ? 1 : -1;
            }
            else if (mode == 1)
            {
                ball.vy *= -1;
            }
        }
    }
}

fd_set read_fds;
int fd;
struct timeval tv = {0, 1000};

#define BUFFER_SIZE 32
char buffer[BUFFER_SIZE];
bool readInput()
{
    FD_ZERO(&read_fds);
    FD_SET(fd, &read_fds);
    int toRead = 0;
    toRead = select(fd + 1, &read_fds, NULL, NULL, &tv);
    if (toRead < 1) {
        return true;
    }

    int readed = read(0, buffer, BUFFER_SIZE);
    int va = 0, vb = 0;
    for (int i = 0; i < readed; i++)
    {
        switch (buffer[i])
        {
        case 'a':
            va = -1;
            break;
        case 'z':
            va = 1;
            break;
        case 'k':
            vb = -1;
            break;
        case 'm':
            vb = +1;
            break;
        case 'q':
            return false;
        case 10:
            break;
        }
    }
    racket.A += va;
    racket.B += vb;
    return true;
}

void aiStep()
{
    if (ball.vx < 0)
    {
        if (racket.A + 1 < ball.y)
        {
            racket.A++;
        }
        else if (racket.A + 1 > ball.y)
        {
            racket.A--;
        }
    }
    else
    {
        if (racket.B + 1 < ball.y)
        {
            racket.B++;
        }
        else if (racket.B + 1 > ball.y)
        {
            racket.B--;
        }
    }
}

bool assertState() {
    if (ball.x < 0 || ball.x > TABLE_WIDTH - 1)
    {
        printf("Ball out of table\n\r");
        return false;
    }
    if (ball.y < 0 || ball.y > TABLE_HEIGHT - 1)
    {
        printf("Ball out of table\n\r");
        return false;
    }
    if (racket.A < 0 || racket.A > TABLE_HEIGHT - RACKET_SIZE)
    {
        printf("Racket A out of table\n\r");
        return false;
    }
    if (racket.B < 0 || racket.B > TABLE_HEIGHT - RACKET_SIZE)
    {
        printf("Racket B out of table\n\r");
        return false;
    }
    return true;
}

int main()
{
    if (!AI_MODE)
    {
        system("/bin/stty -icanon min 1");
        fd = fileno(stdin);
        FD_ZERO(&read_fds);
        FD_SET(fd, &read_fds);
    }
    srand(time(NULL));

    initScore();
    resetGame();
    printTable();
    unsigned long long counter = 0;
    while (true)
    {
        moveBall();
        if (AI_MODE)
        {
            aiStep();
        }
        else
        {
            if (!readInput())
                break;
        }
        checkState();
        if (!assertState()) {
            break;
        }

        printf("\n\r");
        printTable();
        printf("%llu\n\r", counter);

        usleep(100 * 1000);
        counter += 1;
    }

    if (!AI_MODE)
    {
        system("/bin/stty -raw");
    }
    return 0;
}