#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dlfcn.h>

#define MAX_LINE 4096

typedef int (*replace_func_t)(char*, int, int*);

int main(int argc, char *argv[]) {
    if (argc != 5) {
        fprintf(stderr, "Usage: %s <input.txt> <output.txt> <max_replacements> <libpath>\n", argv[0]);
        return 1;
    }
    FILE *fin = fopen(argv[1], "r");
    if (!fin) { perror("fopen input"); return 1; }
    FILE *fout = fopen(argv[2], "w");
    if (!fout) { perror("fopen output"); fclose(fin); return 1; }
    int cap = atoi(argv[3]);
    if (cap < 0) { fprintf(stderr, "invalid cap\n"); fclose(fin); fclose(fout); return 1; }

    void *lib = dlopen(argv[4], RTLD_LAZY);
    if (!lib) { fprintf(stderr, "dlopen error: %s\n", dlerror()); fclose(fin); fclose(fout); return 1; }
    replace_func_t replace = (replace_func_t) dlsym(lib, "replace_char_line");
    if (!replace) { fprintf(stderr, "dlsym error: %s\n", dlerror()); fclose(fin); fclose(fout); dlclose(lib); return 1; }

    int total = 0;
    char line[MAX_LINE];
    while (fgets(line, sizeof(line), fin)) {
        if (line[0] == '\0' || line[0] == '\n') {
            fputs(line, fout);
            continue;
        }
        int key = (unsigned char)line[0];
        if (cap > 0) {
            int repl_line = replace(line, key, &cap);
            total += repl_line;
        }
        fputc(line[0], fout);
        fputs(line + 1, fout);
    }
    fclose(fin); fclose(fout);
    dlclose(lib);
    printf("total_replacements: %d\n", total);
    return 0;
}