#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <semaphore.h>
#include <sys/shm.h>
#include <fcntl.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include "semadefs.h"

int main(int argc, char* argv[]){
    int fd_read_file;
    if (argc < 2){
        fprintf(stderr, "No address of file.\n");
        return 1;
    }
    int file_index = 1;
    if ((strcmp(argv[1], "-h") == 0)){
        printf("Usage: [key] <filename>.\nKeys:\n-h: show this help.\n-i: ignore another running client.\n");
        return 0;
    }
    else if (strcmp(argv[1], "-i") == 0){
        if (argc < 3){
            fprintf(stderr, "No address of file.\n");
            return 1;
        }
        file_index = 2;
        if (remove("/dev/shm/sem.clientlock") < 0){                          //delete semaphore semaphore
            if (errno == ENOENT){}
            else {
                perror("");
                return 1;
            }
        }
    }
    Message *message_ptr;
    key_t key;
    sem_t* sem_blocker;
    int shmem_id, sem_proc_id, semval;
    int n_reader = -1;
    fd_read_file = open(argv[file_index], O_RDONLY);
    //open given file
    if (fd_read_file < 0) {
        perror("An error occured while trying to open file");
        return 1;
    }
    //generate key
    if ((key = ftok(shfname, 'A')) < 0){
        fprintf (stderr, "Server wasn't runned\n");
        return 1;
    }
    //getting memory id
    if ((shmem_id = shmget(key, sizeof(Message), IPC_CREAT | 0666)) < 0){
        perror("Cannot create shared memory space");
        return 1;
    }
    //attaching memory
    if ((message_ptr = (Message *)shmat(shmem_id, 0, 0)) < 0){
        perror("Cannot attach shared memory");
        return 1;
    }
    //getting semaphores
    if ((sem_proc_id = semget(key, 1, IPC_CREAT | 0666)) < 0){
        perror("An error occured while accessing semaphore");
        return 1;
    }
    //get blocker semaphore
    if ((sem_blocker = sem_open("/clientlock", O_CREAT, IPC_CREAT | 0666, 0)) == SEM_FAILED){
        perror ("An error occured while creating locker semaphore");
        return 1;
    }
    //check locks from another clients
    if (sem_getvalue(sem_blocker, &semval) < 0){
        perror ("An error occured while accessing semaphore");
    }
    if (semval > 0){
        fprintf(stderr, "Another client is running.\n");
        return 1;
    }
    //set lock from another clients
    if (sem_post(sem_blocker) < 0){
        perror("An error occured while doing semaphore operation");
        return 1;
    }
    while (n_reader!=0){
        //wait for unlocking, then lock memory
        if (semop(sem_proc_id, &client_start, 1) < 0){
            perror("An error occured while doing semaphore operation");
            return 1;
        }
        if ((n_reader = read(fd_read_file, message_ptr->buff, BUF_SIZE)) < 0){
            perror("An error occured while reading to shared memory");
            return 1;
        }
        message_ptr->size = n_reader;
        //unlock memory
        if (semop(sem_proc_id, &client_end, 1) < 0){
            perror("An error occured while doing semaphore operation");
            return 1;
        }
    }
    //detatch from memory
    if (shmdt(message_ptr) < 0){
        perror("Message error");
        return 1;
    }
    if (sem_close(sem_blocker) < 0){
        perror ("Semaphore destroying error");
        return 1;
    }
    if (remove("/dev/shm/sem.clientlock") < 0){
        perror("Semaphore destroying error");
        return 1;
    }
    //and successfully return
    return 0;
}