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

void process_child(const char *command, char *parameters[])
{
    execvp(command, parameters);
}


char raw_commands[256][256];
char commands[256][256];
char *parameters[256][256];
int n_commands;

int main(int argc, char **argv)
{
    if (argc != 2) {
        printf("Usage: main \"cmd1 cmd_params.. | cmd2 cmd_params... \"");
        return 0;
    }

    int i, j, h, k;
    for (i=0; i<256; i++) {
            for (j=0; j<256; j++) {
                    parameters[i][j]=(char*)malloc(256*sizeof(char));
            }
    }
    i=0; j=0; h=0; k=0;
    int size=strlen(argv[1]);
    while (i<size) {
        if ((argv[1][i]==' ') && (j==0)) {
            j=1;
            h=0;
        }
        else if ((argv[1][i]==' ') && (j==1)) {
            k++;
            h=0;
        }
        else if (argv[1][i]=='|') {
            n_commands++;
            j=0;
            h=0;
            k=0;
        }
        else if (j==0) {
            commands[n_commands][h]=argv[1][i];
            h++;
        }
        else {
            parameters [n_commands][k][h]=argv[1][i];
            h++;
        }
        i++;
    }


        int fd_pipe[2]; // 0 -- input, 1 -- output
    for (i = 0; i < n_commands; ++i) {
                pipe(fd_pipe);

        int code = fork();
        if (!code) {
            // child

                        // if last command
                        if (i + 1 == n_commands) {
                                close(fd_pipe[1]);
                        } else {
                                dup2(fd_pipe[1], 1); // output to created pipe
                        }

                        close(fd_pipe[0]);

            process_child(commands[i], parameters[i]);
            return 0;
        } else {
            // parent

                        if (i + 1 == n_commands) {
                                // last command
                                close(fd_pipe[0]);
                        } else {
                                dup2(fd_pipe[0], 0); // receive input from pipe
                        }
                        close(fd_pipe[1]);
        }
    }

        for (i = 0; i < n_commands; ++i) {
                wait(NULL);
        }

    return 0;
}