/**
 * @file ip.c
 * @brief Display and configure IPv4 network configuration.
 *
 * Reads network interface information from /sys/net and displays
 * the current IPv4 configuration for all interfaces.
 *
 * Usage:
 *   ip              - Show all interfaces
 *   ip set <iface> <ip> <netmask> <gateway>  - Configure an interface
 *
 * Examples:
 *   ip
 *   ip set eth1 192.168.1.100 255.255.255.0 192.168.1.1
 */

#include "syscalls.h"

/**
 * Read the contents of a sysfs file into buf.
 * Returns number of bytes read, or -1 on failure.
 */
static int32_t read_sysfs(const char *path, char *buf, uint32_t size) {
    int32_t fd = open(path, 0);
    if (fd < 0) return -1;

    int32_t n = read(fd, buf, size - 1);
    close(fd);

    if (n > 0) {
        buf[n] = '\0';
        /* Strip trailing newline */
        for (int32_t i = n - 1; i >= 0; i--) {
            if (buf[i] == '\n' || buf[i] == '\r') buf[i] = '\0';
            else break;
        }
    } else {
        buf[0] = '\0';
    }
    return n;
}

/**
 * Build a sysfs path: /sys/net/<iface>/<file>
 */
static void build_path(char *out, uint32_t out_size,
                       const char *iface, const char *file) {
    /* Manual string concatenation */
    uint32_t pos = 0;
    const char *prefix = "/sys/net/";
    while (*prefix && pos < out_size - 1) out[pos++] = *prefix++;
    while (*iface && pos < out_size - 1) out[pos++] = *iface++;
    if (pos < out_size - 1) out[pos++] = '/';
    while (*file && pos < out_size - 1) out[pos++] = *file++;
    out[pos] = '\0';
}

/**
 * Show info for one interface.
 */
static void show_iface(const char *name) {
    char path[128];
    char val[64];

    puts(name);
    puts(":\n");

    /* MAC address */
    build_path(path, sizeof(path), name, "mac");
    if (read_sysfs(path, val, sizeof(val)) > 0) {
        puts("  MAC:     ");
        puts(val);
        puts("\n");
    }

    /* Link status */
    build_path(path, sizeof(path), name, "link");
    if (read_sysfs(path, val, sizeof(val)) > 0) {
        puts("  Link:    ");
        puts(val);
        puts("\n");
    }

    /* IP address */
    build_path(path, sizeof(path), name, "ip");
    if (read_sysfs(path, val, sizeof(val)) > 0) {
        puts("  IP:      ");
        puts(val);
        puts("\n");
    }

    /* Netmask */
    build_path(path, sizeof(path), name, "netmask");
    if (read_sysfs(path, val, sizeof(val)) > 0) {
        puts("  Netmask: ");
        puts(val);
        puts("\n");
    }

    /* Gateway */
    build_path(path, sizeof(path), name, "gateway");
    if (read_sysfs(path, val, sizeof(val)) > 0) {
        puts("  Gateway: ");
        puts(val);
        puts("\n");
    }
}

/**
 * Write a value to a sysfs file.
 */
static int32_t write_sysfs(const char *path, const char *value) {
    int32_t fd = open(path, 0);
    if (fd < 0) return -1;

    int32_t n = write(fd, value, strlen(value));
    close(fd);
    return n;
}

int main(void) {
    char arg1[64];

    /* Check if we have a subcommand */
    if (getenv("ARG1", arg1, sizeof(arg1)) < 0 || arg1[0] == '\0') {
        /* No arguments — show all interfaces */
        char name[128];
        uint32_t idx = 0;
        int found = 0;

        while (readdir("/sys/net", idx, name) >= 0) {
            show_iface(name);
            found = 1;
            idx++;
        }

        if (!found) {
            puts("No network interfaces found.\n");
        }
        return 0;
    }

    /* Check for "set" subcommand */
    if (strcmp(arg1, "set") == 0) {
        char iface_name[32], ip[32], netmask[32], gateway[32];
        char path[128];

        if (getenv("ARG2", iface_name, sizeof(iface_name)) < 0) {
            puts("Usage: ip set <iface> <ip> <netmask> <gateway>\n");
            return 1;
        }
        if (getenv("ARG3", ip, sizeof(ip)) < 0) {
            puts("Usage: ip set <iface> <ip> <netmask> <gateway>\n");
            return 1;
        }
        if (getenv("ARG4", netmask, sizeof(netmask)) < 0) {
            puts("Usage: ip set <iface> <ip> <netmask> <gateway>\n");
            return 1;
        }
        if (getenv("ARG5", gateway, sizeof(gateway)) < 0) {
            puts("Usage: ip set <iface> <ip> <netmask> <gateway>\n");
            return 1;
        }

        /* Write IP */
        build_path(path, sizeof(path), iface_name, "ip");
        if (write_sysfs(path, ip) < 0) {
            puts("Failed to set IP address\n");
            return 1;
        }

        /* Write netmask */
        build_path(path, sizeof(path), iface_name, "netmask");
        if (write_sysfs(path, netmask) < 0) {
            puts("Failed to set netmask\n");
            return 1;
        }

        /* Write gateway */
        build_path(path, sizeof(path), iface_name, "gateway");
        if (write_sysfs(path, gateway) < 0) {
            puts("Failed to set gateway\n");
            return 1;
        }

        puts("Configured ");
        puts(iface_name);
        puts(": ");
        puts(ip);
        puts(" / ");
        puts(netmask);
        puts(" gw ");
        puts(gateway);
        puts("\n");
        return 0;
    }

    puts("Unknown command: ");
    puts(arg1);
    puts("\nUsage: ip [set <iface> <ip> <netmask> <gateway>]\n");
    return 1;
}