#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<fcntl.h>

typedef struct{

int index;
int num;

}proc;

/*
    The process parent receives N files from the user input. For each file it creates
    1 processes child. Each process child reads its file and count the number of
    characters. The first process sends the number to the second process, which reads
    the number, compares it the its own counter and send forward to the third process
    the greater between the two. The last process send the number to the process parent
    who read the pipe and prints the number in the standard output.
*/

void main(int argc, char **argv){

    proc myProc;

    int N=argc-1; // represents the number of argument (files)
    int i,j; // indexes
    proc msg; // the message received by parent
    int fd; // file descriptor
    int pid; // the process id returned by fork()
    char ch; // the buffer for file read
    int counter=0; // used to count the number of characters

    // declare and populate the N pipes (one for each child)
    int mypipe[N][2];
    for (j=0;j<N;j++)
        pipe(mypipe[j]); // populate with values

    // Create the N children
    for(i = 0; i < N; i++){

        pid=fork();

        if (pid < 0){
            printf("ERROR");
        }
        else if(pid == 0){

            // loop on pipes, close the ones not in use
            for (j=0;j<N;j++){
                if (i!=j) close(mypipe[j][1]);
                if(j!=i-1)close(mypipe[j][0]);
            }

        // Open file
        fd = open(argv[i+1], O_RDONLY);
        // Check if it was succefully opened
        if (fd < 0){
            printf("Error opeing the file %s \n", argv[i+1]);
            exit(1);
        }

        // Loop on file and read char by char
        while(read(fd, &ch, 1)>0){
            counter++;

        }

    //update struct info
        myProc.num = counter;
        myProc.index = i;

        // Close file after use
        close(fd);

        // If the porcess is not the first one
        if (i>0){
            // reading from previous
            read(mypipe[i-1][0], &msg, sizeof(proc));


            if (msg.num > myProc.num) {myProc.num=msg.num;myProc.index=msg.index;}
        }

        // Write on pipe the number of characters
        write(mypipe[i][1],&myProc,sizeof(proc));

        // Exit
        exit(0);
        }
    }
    // loop on pipes and close the ones not in use
    for (j=0;j<N;j++){
        close(mypipe[j][1]);
        if (j!=N-1) close(mypipe[j][0]);
    }

    read(mypipe[N-1][0],&msg,sizeof(proc));
    printf("MSG = %d with count %d \n", msg.index+1,msg.num);
}