package checker

import (
	"net"
	"testing"
)

func TestLowerFQDN(t *testing.T) {
	cases := []struct {
		in, want string
	}{
		{"Example.COM", "example.com."},
		{"example.com.", "example.com."},
		{"", "."},
		{"X", "x."},
		{"1.168.192.IN-ADDR.ARPA.", "1.168.192.in-addr.arpa."},
	}
	for _, c := range cases {
		if got := lowerFQDN(c.in); got != c.want {
			t.Errorf("lowerFQDN(%q)=%q, want %q", c.in, got, c.want)
		}
	}
}

func TestIsReverseArpa(t *testing.T) {
	cases := []struct {
		in   string
		want bool
	}{
		{"1.168.192.in-addr.arpa", true},
		{"in-addr.arpa", true},
		{"in-addr.arpa.", true},
		{"IN-ADDR.ARPA", true},
		{"ip6.arpa", true},
		{"0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa", true},
		{"example.com", false},
		{"arpa", false},
		{"in-addr.arpa.example.com", false},
		{"", false},
	}
	for _, c := range cases {
		if got := isReverseArpa(c.in); got != c.want {
			t.Errorf("isReverseArpa(%q)=%v, want %v", c.in, got, c.want)
		}
	}
}

func TestIsIPv6Arpa(t *testing.T) {
	cases := []struct {
		in   string
		want bool
	}{
		{"ip6.arpa", true},
		{"IP6.ARPA.", true},
		{"0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.", true},
		{"1.168.192.in-addr.arpa", false},
		{"in-addr.arpa", false},
		{"example.com", false},
	}
	for _, c := range cases {
		if got := isIPv6Arpa(c.in); got != c.want {
			t.Errorf("isIPv6Arpa(%q)=%v, want %v", c.in, got, c.want)
		}
	}
}

func TestReverseNameToIP_IPv4(t *testing.T) {
	cases := []struct {
		in   string
		want string // "" means nil
	}{
		{"42.1.168.192.in-addr.arpa", "192.168.1.42"},
		{"42.1.168.192.IN-ADDR.ARPA.", "192.168.1.42"},
		{"1.168.192.in-addr.arpa", ""}, // partial: only 3 labels
		{"a.b.c.d.in-addr.arpa", ""},   // non-numeric
		{"256.0.0.0.in-addr.arpa", ""}, // out of range parses with strconv but ParseIP fails
		{"1.2.3.4.5.in-addr.arpa", ""}, // too many
		{"in-addr.arpa", ""},           // apex, no labels
		{"example.com", ""},            // unrelated
	}
	for _, c := range cases {
		got := reverseNameToIP(c.in)
		switch {
		case c.want == "" && got != nil:
			t.Errorf("reverseNameToIP(%q)=%v, want nil", c.in, got)
		case c.want != "" && (got == nil || got.String() != c.want):
			t.Errorf("reverseNameToIP(%q)=%v, want %s", c.in, got, c.want)
		}
	}
}

func TestReverseNameToIP_IPv6(t *testing.T) {
	// 2001:db8::1 expanded reverse:
	// 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.
	full := "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa"
	got := reverseNameToIP(full)
	if got == nil {
		t.Fatalf("reverseNameToIP(%q) returned nil", full)
	}
	want := net.ParseIP("2001:db8::1")
	if !got.Equal(want) {
		t.Errorf("reverseNameToIP(%q)=%v, want %v", full, got, want)
	}

	// Partial / invalid IPv6 reverse names → nil.
	partials := []string{
		"d.0.1.0.0.2.ip6.arpa", // /24 zone, only 6 nibbles
		"ip6.arpa",             // apex
		"x.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa", // multi-char label
		"1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.ip6.arpa",   // 31 labels
	}
	for _, p := range partials {
		if r := reverseNameToIP(p); r != nil {
			t.Errorf("reverseNameToIP(%q)=%v, want nil", p, r)
		}
	}
}

func TestIPEqual(t *testing.T) {
	cases := []struct {
		addr string
		ip   net.IP
		want bool
	}{
		{"192.168.1.1", net.ParseIP("192.168.1.1"), true},
		{"192.168.1.1", net.ParseIP("192.168.1.2"), false},
		{"2001:db8::1", net.ParseIP("2001:0db8:0000::1"), true},
		{"::ffff:192.168.1.1", net.ParseIP("192.168.1.1"), true},
		{"not-an-ip", net.ParseIP("192.168.1.1"), false},
		{"", net.ParseIP("192.168.1.1"), false},
	}
	for _, c := range cases {
		if got := ipEqual(c.addr, c.ip); got != c.want {
			t.Errorf("ipEqual(%q,%v)=%v, want %v", c.addr, c.ip, got, c.want)
		}
	}
}

func TestSystemResolverFallback(t *testing.T) {
	// Force the fallback path: even if /etc/resolv.conf exists, the fallback
	// kicks in when the file is missing or has zero servers. We can't easily
	// remove /etc/resolv.conf in a test, so just assert the result is a valid
	// host:port and that FallbackResolver itself is well-formed.
	host, port, err := net.SplitHostPort(FallbackResolver)
	if err != nil {
		t.Fatalf("FallbackResolver = %q is not host:port: %v", FallbackResolver, err)
	}
	if host == "" || port == "" {
		t.Errorf("FallbackResolver = %q has empty host or port", FallbackResolver)
	}
	got := systemResolver()
	if _, _, err := net.SplitHostPort(got); err != nil {
		t.Errorf("systemResolver() = %q is not host:port: %v", got, err)
	}
}