package arp

import (
	"fmt"
	"net"
	"os"
	"strings"
)

// ARPEntry represents an entry in the ARP table
type ARPEntry struct {
	IP        net.IP
	HWType    int
	Flags     int
	HWAddress net.HardwareAddr
	Mask      string
	Device    string
}

// parseARPTable reads and parses ARP table from /proc/net/arp format
func parseARPTable(path string) ([]ARPEntry, error) {
	var entries []ARPEntry

	content, err := os.ReadFile(path)
	if err != nil {
		return entries, err
	}

	for _, line := range strings.Split(string(content), "\n") {
		fields := strings.Fields(line)
		if len(fields) > 5 {
			var entry ARPEntry

			// Parse HWType (hex format)
			if _, err := fmt.Sscanf(fields[1], "0x%x", &entry.HWType); err != nil {
				continue
			}

			// Parse Flags (hex format)
			if _, err := fmt.Sscanf(fields[2], "0x%x", &entry.Flags); err != nil {
				continue
			}

			// Parse IP address
			entry.IP = net.ParseIP(fields[0])
			if entry.IP == nil {
				continue
			}

			// Parse MAC address
			entry.HWAddress, err = net.ParseMAC(fields[3])
			if err != nil {
				continue
			}

			entry.Mask = fields[4]
			entry.Device = fields[5]

			entries = append(entries, entry)
		}
	}

	return entries, nil
}