#define _FILE_OFFSET_BITS 64 
#define _GNU_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <dirent.h>
#include <errno.h>

static int starts_with(const char *s, const char *t) {
    return strncmp(s, t, strlen(t)) == 0;
}

static int ends_with(const char *s, const char *t) {
    size_t slen = strlen(s);
    size_t tlen = strlen(t);
    if (tlen > slen) return 1;
    return strcmp(s + slen - tlen, t) == 0;
}

#define MODS_FOLDER "./mods/"

static void set_and_print_env(char *name, char *value) {
    fprintf(stderr, "Set %s = %s\n", name, value);
    setenv(name, value, 1);
}

static char *get_env_safe(const char *name) {
    char *ret = getenv(name);
    return ret != NULL ? ret : "";
}

int main(__attribute__((unused)) int argc, char *argv[]) {
    fprintf(stderr, "Configuring Game...\n");

    char *ld_path = NULL;
    char *cwd = getcwd(NULL, 0);
    asprintf(&ld_path, "%s:/usr/arm-linux-gnueabihf/lib:%s", cwd, get_env_safe("LD_LIBRARY_PATH"));
    free(cwd);
    set_and_print_env("LD_LIBRARY_PATH", ld_path);
    free(ld_path);
    
    char *ld_preload = NULL;
    asprintf(&ld_preload, "%s", get_env_safe("LD_PRELOAD"));
    int folder_name_length = strlen(MODS_FOLDER);
    DIR *dp = opendir(MODS_FOLDER);
    if (dp != NULL) {
        struct dirent *entry = NULL;
        errno = 0;
        while (1) {
            entry = readdir(dp);
            if (entry != NULL) {
                if (starts_with(entry->d_name, "lib") && ends_with(entry->d_name, ".so")) {
                    int name_length = strlen(entry->d_name);
                    int total_length = folder_name_length + name_length;
                    char name[total_length + 1];

                    for (int i = 0; i < folder_name_length; i++) {
                        name[i] = MODS_FOLDER[i];
                    }
                    for (int i = 0; i < name_length; i++) {
                        name[folder_name_length + i] = entry->d_name[i];
                    }
                    
                    name[total_length] = '\0';

                    asprintf(&ld_preload, "%s:%s", name, ld_preload);
                }
            } else if (errno != 0) {
                fprintf(stderr, "Error Reading Directory: %s\n", strerror(errno));
                exit(1);
            } else {
                break;
            }
        }
    } else {
        fprintf(stderr, "Error Opening Directory: %s\n", strerror(errno));
        exit(1);
    }
    closedir(dp);
    set_and_print_env("LD_PRELOAD", ld_preload);
    free(ld_preload);

    fprintf(stderr, "Starting Game...\n");
    return execve("./minecraft-pi", argv, environ);
}