#define _POSIX_C_SOURCE 200809L

/*
 * qfetch.c — dynamic & portable system information fetcher
 *
 * Goals:
 *  - Pure C (C99)
 *  - Heap-allocated strings (caller owns memory)
 *  - Portable across Linux, macOS, and BSD
 *  - Graceful fallbacks when platform-specific features are unavailable
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <pwd.h>
#include <sys/utsname.h>
#include <errno.h>

/* Platform-specific headers for macOS / BSD */
#if defined(__APPLE__) || defined(__FreeBSD__)
#include <sys/types.h>
#include <sys/sysctl.h>
#include <sys/time.h>
#include <time.h>
#endif

/*
 * Utility: duplicate a string or return "unknown" if NULL/empty.
 * Always returns heap-allocated memory.
 */
static char *dup_or_unknown(const char *s) {
    if (!s || !*s)
        return strdup("unknown");
    return strdup(s);
}

/*
 * Fetch system hostname using POSIX gethostname().
 * Buffer size is determined dynamically via sysconf().
 */
char *get_hostname(void) {
    long max = sysconf(_SC_HOST_NAME_MAX);
    if (max < 0)
        max = 256; /* fallback if limit is unavailable */

    char *buf = calloc(max + 1, 1);
    if (!buf)
        return dup_or_unknown(NULL);

    if (gethostname(buf, max) != 0) {
        free(buf);
        return dup_or_unknown(NULL);
    }
    return buf;
}

/*
 * Fetch current username via getpwuid().
 */
char *get_user(void) {
    struct passwd *pw = getpwuid(getuid());
    return pw ? dup_or_unknown(pw->pw_name) : dup_or_unknown(NULL);
}

/*
 * Fetch login shell name (basename only, e.g. "bash").
 */
char *get_shell(void) {
    struct passwd *pw = getpwuid(getuid());
    if (!pw || !pw->pw_shell)
        return dup_or_unknown(NULL);

    /* Extract basename from full path */
    const char *s = strrchr(pw->pw_shell, '/');
    return dup_or_unknown(s ? s + 1 : pw->pw_shell);
}

/*
 * Fetch kernel name and version using uname().
 */
char *get_kernel(void) {
    struct utsname u;
    if (uname(&u) != 0)
        return dup_or_unknown(NULL);

    size_t len = strlen(u.sysname) + strlen(u.release) + 2;
    char *buf = malloc(len);
    if (!buf)
        return dup_or_unknown(NULL);

    snprintf(buf, len, "%s %s", u.sysname, u.release);
    return buf;
}

/*
 * Fetch operating system / distribution name.
 * Linux: /etc/os-release
 * macOS/BSD: static identifier
 */
char *get_os(void) {
#if defined(__linux__)
    FILE *f = fopen("/etc/os-release", "r");
    if (!f)
        return dup_or_unknown("Linux");

    char line[512];
    while (fgets(line, sizeof line, f)) {
        if (strncmp(line, "PRETTY_NAME=", 12) == 0) {
            char *v = line + 12;
            v[strcspn(v, "\n")] = 0; /* strip newline */
            if (*v == '"') v++;
            char *e = strrchr(v, '"');
            if (e) *e = 0;
            fclose(f);
            return strdup(v);
        }
    }
    fclose(f);
    return dup_or_unknown("Linux");
#elif defined(__APPLE__)
    return dup_or_unknown("macOS");
#elif defined(__FreeBSD__)
    return dup_or_unknown("FreeBSD");
#else
    return dup_or_unknown("Unix");
#endif
}

/*
 * Fetch system uptime.
 * Linux: /proc/uptime
 * macOS/BSD: sysctl(KERN_BOOTTIME)
 */
char *get_uptime(void) {
#if defined(__linux__)
    FILE *f = fopen("/proc/uptime", "r");
    if (!f)
        return dup_or_unknown(NULL);

    double s;
    if (fscanf(f, "%lf", &s) != 1) {
        fclose(f);
        return dup_or_unknown(NULL);
    }
    fclose(f);
#elif defined(__APPLE__) || defined(__FreeBSD__)
    struct timeval boottime;
    size_t len = sizeof(boottime);
    int mib[2] = { CTL_KERN, KERN_BOOTTIME };

    if (sysctl(mib, 2, &boottime, &len, NULL, 0) != 0)
        return dup_or_unknown(NULL);

    time_t now = time(NULL);
    double s = difftime(now, boottime.tv_sec);
#else
    return dup_or_unknown("n/a");
#endif

    /* Convert seconds to human-readable format */
    int d = s / 86400;
    int h = ((int)s % 86400) / 3600;
    int m = ((int)s % 3600) / 60;

    char buf[64];
    if (d)
        snprintf(buf, sizeof buf, "%dd %dh %dm", d, h, m);
    else if (h)
        snprintf(buf, sizeof buf, "%dh %dm", h, m);
    else
        snprintf(buf, sizeof buf, "%dm", m);

    return strdup(buf);
}

/*
 * Fetch CPU model and core count.
 * Linux: /proc/cpuinfo
 * macOS/BSD: sysctl hw.model + hw.ncpu
 */
char *get_cpu(void) {
#if defined(__linux__)
    FILE *f = fopen("/proc/cpuinfo", "r");
    if (!f)
        return dup_or_unknown(NULL);

    char line[512];
    char model[256] = "";
    int cores = 0;

    while (fgets(line, sizeof line, f)) {
        if (strncmp(line, "model name", 10) == 0) {
            if (!*model) {
                char *p = strchr(line, ':');
                if (p) {
                    p += 2;
                    p[strcspn(p, "\n")] = 0;
                    strncpy(model, p, sizeof model - 1);
                }
            }
            cores++;
        }
    }
    fclose(f);

    if (!*model)
        return dup_or_unknown(NULL);

    char buf[512];
    snprintf(buf, sizeof buf, "%s (%d cores)", model, cores);
    return strdup(buf);
#elif defined(__APPLE__) || defined(__FreeBSD__)
    char model[256];
    size_t len = sizeof(model);

    if (sysctlbyname("hw.model", model, &len, NULL, 0) != 0)
        strncpy(model, "unknown", sizeof model);

    int cores = 0;
    len = sizeof(cores);
    sysctlbyname("hw.ncpu", &cores, &len, NULL, 0);

    char buf[512];
    snprintf(buf, sizeof buf, "%s (%d cores)", model, cores);
    return strdup(buf);
#else
    return dup_or_unknown("unknown cpu");
#endif
}

/*
 * Entry point.
 * Fetches all information, prints it, then frees memory.
 */
int main(void) {
    char *user   = get_user();
    char *host   = get_hostname();
    char *shell  = get_shell();
    char *os     = get_os();
    char *kernel = get_kernel();
    char *uptime = get_uptime();
    char *cpu    = get_cpu();

    printf("\n"
           "\033[1m\033[37mwelcome, %s\033[1;31m ♥\033[0m\n\n"
           "  \033[1;37m• \033[1;37mhost\033[0m     %s\n"
           "  \033[1;33m• \033[1;37mdistro\033[0m   %s\n"
           "  \033[1;32m• \033[1;37mshell\033[0m    %s\n"
           "  \033[1;36m• \033[1;37mcpu\033[0m      %s\n"
           "  \033[1;34m• \033[1;37mkernel\033[0m   %s\n"
           "  \033[1;35m• \033[1;37muptime\033[0m   %s\n\n",
           user, host, os, shell, cpu, kernel, uptime);

    /* Free all heap-allocated strings */
    free(user);
    free(host);
    free(shell);
    free(os);
    free(kernel);
    free(uptime);
    free(cpu);

    return 0;
}