package agent

import (
	"strings"
	"testing"
)

func TestHostIfaceName_Format(t *testing.T) {
	got := HostIfaceName("0123456789abcdef0123456789abcdef")
	if !strings.HasPrefix(got, "flock") || len(got) != len("flock")+8 {
		t.Fatalf("HostIfaceName=%q (want flock + 8 hex)", got)
	}
}

func TestHostIfaceName_Determinism(t *testing.T) {
	a := HostIfaceName("container-xyz")
	b := HostIfaceName("container-xyz")
	if a != b {
		t.Fatalf("not deterministic: %s vs %s", a, b)
	}
}

func TestHostIfaceName_DifferentInputs(t *testing.T) {
	a := HostIfaceName("a")
	b := HostIfaceName("b")
	if a == b {
		t.Fatalf("collision on trivial inputs")
	}
}

// FuzzHostIfaceName ensures the host interface name generator never produces
// an output longer than IFNAMSIZ-1 (15 chars on Linux) and never panics.
// The name format is "flock" + 8 hex chars = 13 chars, always.
func FuzzHostIfaceName(f *testing.F) {
	f.Add("")
	f.Add("a")
	f.Add("/var/run/netns/abc")
	f.Add("0123456789abcdef0123456789abcdef")
	f.Add(longString("x", 64*1024)) // very long containerID
	f.Add("\x00\x00\x00")
	f.Add("ünïcødé/контейнер")

	f.Fuzz(func(t *testing.T, id string) {
		got := HostIfaceName(id)
		// Linux IFNAMSIZ is 16 (15 chars + NUL); ours must fit comfortably.
		if len(got) > 15 {
			t.Fatalf("HostIfaceName(%q)=%q exceeds 15 chars", id, got)
		}
		if !strings.HasPrefix(got, "flock") {
			t.Fatalf("HostIfaceName(%q)=%q missing prefix", id, got)
		}
		// Suffix must be lowercase hex (8 chars).
		suffix := got[len("flock"):]
		if len(suffix) != 8 {
			t.Fatalf("HostIfaceName(%q) suffix len=%d", id, len(suffix))
		}
		for _, c := range suffix {
			if !((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f')) {
				t.Fatalf("HostIfaceName(%q)=%q has non-hex suffix", id, got)
			}
		}
	})
}