#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <dlfcn.h>

#define RBUFSZ 4096
#define WBUFSZ 4096

static void die_perror(const char *what, const char *path, int exit_code) {
    int saved = errno;
    char msg[512];
    if (path) {
        snprintf(msg, sizeof(msg), "%s: %s: %s\n", what, path, strerror(saved));
    } else {
        snprintf(msg, sizeof(msg), "%s: %s\n", what, strerror(saved));
    }
    (void) write(STDERR_FILENO, msg, strlen(msg));
    _exit(exit_code);
}

static long long parse_ll(const char *s) {
    char *end = NULL;
    errno = 0;
    long long v = strtoll(s, &end, 10);
    if (errno != 0 || end == s || *end != '\0' || v < 0) {
        errno = EINVAL;
        return -1;
    }
    return v;
}

int main(int argc, char *argv[]) {
    if (argc != 5) {
        const char *usage =
                "Usage: lab2_var12 <input.txt> <output.txt> <max_replacements> <library.so>\n"
                "Variant 12: Load text processing library dynamically and process file.\n"
                "Library should provide 'process_text' function.\n";
        (void) write(STDERR_FILENO, usage, strlen(usage));
        return -1;
    }

    const char *in_path = argv[1];
    const char *out_path = argv[2];
    long long cap = parse_ll(argv[3]);
    const char *lib_path = argv[4];

    if (cap < 0) {
        die_perror("invalid max_replacements", argv[3], -1);
    }

    // Динамически загружаем библиотеку
    void *lib_handle = dlopen(lib_path, RTLD_LAZY);
    if (!lib_handle) {
        const char *error_msg = dlerror();
        char msg[512];
        snprintf(msg, sizeof(msg), "dlopen failed: %s\n", error_msg ? error_msg : "unknown error");
        (void) write(STDERR_FILENO, msg, strlen(msg));
        return -1;
    }

    // Получаем указатель на функцию обработки текста
    long long (*process_text)(const char*, const char*, long long) =
        (long long (*)(const char*, const char*, long long)) dlsym(lib_handle, "process_text");

    if (!process_text) {
        const char *error_msg = dlerror();
        char msg[512];
        snprintf(msg, sizeof(msg), "dlsym failed: %s\n", error_msg ? error_msg : "unknown error");
        (void) write(STDERR_FILENO, msg, strlen(msg));
        dlclose(lib_handle);
        return -1;
    }

    // Вызываем функцию из библиотеки
    long long result = process_text(in_path, out_path, cap);

    if (result < 0) {
        die_perror("process_text failed", NULL, -1);
    }

    // Закрываем библиотеку
    dlclose(lib_handle);

    // Выводим результат
    char res[64];
    int m = snprintf(res, sizeof(res), "%lld\n", result);
    if (m > 0) {
        (void) write(STDOUT_FILENO, res, (size_t) m);
    }

    return 0;
}