#include <stdio.h>
#include <stdlib.h>
#include <zconf.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <string.h>

#define piperead 0
#define pipewrite 1

int pipe_fd1[2];
int pipe_fd2[2];

int getFileDimension(const char* fileName){
    struct stat st;
    if(stat(fileName, &st) != 0){
        perror("File doesn't exist\n");
    }
    return st.st_size;
}

char* getNCharFromEndFile(char* fileInput, int n){
    int fd = open(fileInput, O_RDONLY);
    if(fd==-1)perror("open");

    int resL=lseek(fd,-n,SEEK_END);
    if(resL==-1)perror("lseek");

    char *buffer = malloc(sizeof(char));
    int res = read(fd, buffer, 1);
    if(res==-1)perror("read");
    return buffer;
}
char* getNCharFromFile(char* fileInput, int n){
    int fd = open(fileInput, O_RDONLY);
    if(fd==-1)perror("open");

    int resL=lseek(fd,n,SEEK_SET);
    if(resL==-1)perror("lseek");

    char *buffer = malloc(sizeof(char));
    int res = read(fd, buffer, 1);
    if(res==-1)perror("read");
    return buffer;
}

void padre(char* fileInput);
void figlio1(char* fileInput);
void figlio2(char *string);

int main(int argc, char* argv[]) {
    printf("%s\n", argv[1]);
    printf("%s\n", argv[2]);

    if(argc!=3)
        exit(999);

    pid_t sons[2]; //array di pid per i processi

    if (pipe(pipe_fd1)==-1){
        fprintf(stderr, "Pipe Failed" );
        return 1;
    }
    if (pipe(pipe_fd2)==-1){
        fprintf(stderr, "Pipe Failed" );
        return 1;
    }

    switch(sons[0]=fork()){ //Figlio 1
        case -1: perror("Errore fork 1"); break;
        case 0:{
              figlio1(argv[1]);
        } break;
        default:
            switch(sons[1]=fork()){ //Figlio 2
                case -1: perror("Errore fork 2"); break;
                case 0:{
                    figlio2(argv[2]);
                } break;
                default:
                    padre(argv[1]);
                    exit(0);
                    break;
            }
            break;
    }

    waitpid(sons[0],NULL,0);
    waitpid(sons[1],NULL,0);

    return 0;
}

void figlio2(char *fileOutput) {
    char* readFromFiglio1 = malloc(sizeof(char));

    int fd = open(fileOutput, O_WRONLY | O_CREAT | O_APPEND);

    while((read(pipe_fd2[piperead],readFromFiglio1,1))>0){
        printf("Figlio 2 deve scrivere: %s\n",readFromFiglio1);
        write(fd,readFromFiglio1,1);
    }
    close(fd);
    close(pipe_fd2[piperead]);
}
void figlio1(char* fileInput) {
    close(pipe_fd1[pipewrite]);
    close(pipe_fd2[piperead]);

    int index = 0;
    char* readFromPadre = malloc(sizeof(char));
    while((read(pipe_fd1[piperead],readFromPadre,1))>0){
        char* readFromFiglio1 = getNCharFromFile(fileInput,index);
        printf("Padre: %s, Figlio: %s, Index; %d\n",readFromPadre, readFromFiglio1,index);

        if(strcmp(readFromPadre,readFromFiglio1)==0)
            write(pipe_fd2[pipewrite], readFromPadre, 1);
        index++;
    }

    close(pipe_fd2[pipewrite]);
}

void padre(char* fileInput) {
    close(pipe_fd1[piperead]);
    close(pipe_fd2[pipewrite]);

    int lenght = getFileDimension(fileInput);
    for(int i=1; i<lenght+1;i++){
       char* c = getNCharFromEndFile(fileInput,i);
       write(pipe_fd1[pipewrite], c, 1);
    }
    close(pipe_fd1[pipewrite]);

}