#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <ctype.h>
#include <string.h>

int main()
{
    int pipe1[2];   // Pipe 1: Parent to Child
    int pipe2[2];   // Pipe 2: Child to Parent

    pid_t pid;

    char studentID[50];
    char receivedID[50];
    int digitCount = 0;

    // Create first pipe
    if (pipe(pipe1) == -1)
    {
        printf("Pipe 1 creation failed!\n");
        return 1;
    }

    // Create second pipe
    if (pipe(pipe2) == -1)
    {
        printf("Pipe 2 creation failed!\n");
        return 1;
    }

    // Create child process
    pid = fork();

    if (pid < 0)
    {
        printf("Fork failed!\n");
        return 1;
    }

    // Child Process
    else if (pid == 0)
    {
        // Close unused pipe ends
        close(pipe1[1]);   // Child does not write to pipe1
        close(pipe2[0]);   // Child does not read from pipe2

        // Read Student ID from Parent Process
        read(pipe1[0], receivedID, sizeof(receivedID));

        // Count digits in Student ID
        for (int i = 0; receivedID[i] != '\0'; i++)
        {
            if (isdigit(receivedID[i]))
            {
                digitCount++;
            }
        }

        // Send digit count back to Parent Process
        write(pipe2[1], &digitCount, sizeof(digitCount));

        // Close used pipe ends
        close(pipe1[0]);
        close(pipe2[1]);

        exit(0);
    }

    // Parent Process
    else
    {
        // Close unused pipe ends
        close(pipe1[0]);   // Parent does not read from pipe1
        close(pipe2[1]);   // Parent does not write to pipe2

        // Take Student ID input from user
        printf("Enter your Student ID: ");
        scanf("%s", studentID);

        // Send Student ID to Child Process
        write(pipe1[1], studentID, strlen(studentID) + 1);

        // Read digit count from Child Process
        read(pipe2[0], &digitCount, sizeof(digitCount));

        // Wait for Child Process to finish
        wait(NULL);

        // Display result
        printf("\n--- Result ---\n");
        printf("Original Student ID : %s\n", studentID);
        printf("Total Digits (Child Process) : %d\n", digitCount);

        // Close used pipe ends
        close(pipe1[1]);
        close(pipe2[0]);
    }

    return 0;
}