package dhcp

import (
	"encoding/binary"
	"testing"
)

func TestParseUdhcpdLeases(t *testing.T) {
	// Build a synthetic udhcpd lease file: 8-byte big-endian timestamp
	// header, then two 36-byte records.
	buf := make([]byte, 0, 8+36*3)
	header := make([]byte, 8)
	binary.BigEndian.PutUint64(header, 1714560000) // 2024-05-01
	buf = append(buf, header...)

	// Record 1: 192.168.1.42, aa:bb:cc:dd:ee:ff, "iPhone"
	r1 := make([]byte, 36)
	binary.BigEndian.PutUint32(r1[0:4], 3600)              // expires
	r1[4], r1[5], r1[6], r1[7] = 192, 168, 1, 42           // IP
	r1[8], r1[9], r1[10] = 0xaa, 0xbb, 0xcc                // MAC
	r1[11], r1[12], r1[13] = 0xdd, 0xee, 0xff              //
	copy(r1[14:34], "iPhone\x00")                          // hostname (NUL-padded)
	buf = append(buf, r1...)

	// Record 2: empty slot (all zero MAC/IP) — should be skipped
	r2 := make([]byte, 36)
	buf = append(buf, r2...)

	// Record 3: 10.0.0.1, b8:27:eb:11:22:33, no hostname
	r3 := make([]byte, 36)
	binary.BigEndian.PutUint32(r3[0:4], 7200)
	r3[4], r3[5], r3[6], r3[7] = 10, 0, 0, 1
	r3[8], r3[9], r3[10] = 0xb8, 0x27, 0xeb
	r3[11], r3[12], r3[13] = 0x11, 0x22, 0x33
	buf = append(buf, r3...)

	if !looksLikeUdhcpd(buf) {
		t.Fatalf("synthetic file not detected as udhcpd")
	}

	leases, err := parseUdhcpdLeases(buf)
	if err != nil {
		t.Fatalf("parseUdhcpdLeases: %v", err)
	}
	if len(leases) != 2 {
		t.Fatalf("expected 2 leases, got %d: %+v", len(leases), leases)
	}

	if leases[0].IP != "192.168.1.42" {
		t.Errorf("lease[0].IP = %q, want %q", leases[0].IP, "192.168.1.42")
	}
	if leases[0].MAC != "aa:bb:cc:dd:ee:ff" {
		t.Errorf("lease[0].MAC = %q, want %q", leases[0].MAC, "aa:bb:cc:dd:ee:ff")
	}
	if leases[0].Hostname != "iPhone" {
		t.Errorf("lease[0].Hostname = %q, want %q", leases[0].Hostname, "iPhone")
	}

	if leases[1].IP != "10.0.0.1" {
		t.Errorf("lease[1].IP = %q, want %q", leases[1].IP, "10.0.0.1")
	}
	if leases[1].MAC != "b8:27:eb:11:22:33" {
		t.Errorf("lease[1].MAC = %q, want %q", leases[1].MAC, "b8:27:eb:11:22:33")
	}
	if leases[1].Hostname != "" {
		t.Errorf("lease[1].Hostname = %q, want empty", leases[1].Hostname)
	}
}

func TestLooksLikeUdhcpdRejectsText(t *testing.T) {
	text := []byte("# The format of this file is documented in dhcpd.leases(5).\nlease 192.168.1.42 {\n  starts 0 2024/05/01 00:00:00;\n  hardware ethernet aa:bb:cc:dd:ee:ff;\n  client-hostname \"iPhone\";\n}\n")
	if looksLikeUdhcpd(text) {
		t.Errorf("ISC text file misdetected as udhcpd")
	}
}