package awgserver

import "testing"

func TestIPAllocator_Basic(t *testing.T) {
	alloc, err := NewIPAllocator("10.14.0.0/24")
	if err != nil {
		t.Fatalf("NewIPAllocator() error: %v", err)
	}

	if got := alloc.ServerIP().String(); got != "10.14.0.1" {
		t.Errorf("ServerIP() = %s, want 10.14.0.1", got)
	}

	ip, err := alloc.Allocate(nil)
	if err != nil {
		t.Fatalf("Allocate() error: %v", err)
	}
	if ip != "10.14.0.2/32" {
		t.Errorf("first allocation = %s, want 10.14.0.2/32", ip)
	}
}

func TestIPAllocator_SkipsUsed(t *testing.T) {
	alloc, err := NewIPAllocator("10.14.0.0/24")
	if err != nil {
		t.Fatalf("NewIPAllocator() error: %v", err)
	}

	used := []string{"10.14.0.2/32", "10.14.0.3/32"}
	ip, err := alloc.Allocate(used)
	if err != nil {
		t.Fatalf("Allocate() error: %v", err)
	}
	if ip != "10.14.0.4/32" {
		t.Errorf("allocation = %s, want 10.14.0.4/32", ip)
	}
}

func TestIPAllocator_Exhaustion(t *testing.T) {
	alloc, err := NewIPAllocator("10.14.0.0/30") // Only 4 IPs: .0 (network), .1 (server), .2 (peer), .3 (broadcast)
	if err != nil {
		t.Fatalf("NewIPAllocator() error: %v", err)
	}

	ip, err := alloc.Allocate(nil)
	if err != nil {
		t.Fatalf("first Allocate() error: %v", err)
	}
	if ip != "10.14.0.2/32" {
		t.Errorf("allocation = %s, want 10.14.0.2/32", ip)
	}

	_, err = alloc.Allocate([]string{"10.14.0.2/32"})
	if err == nil {
		t.Errorf("expected error on exhausted subnet, got nil")
	}
}

func TestIPAllocator_16Subnet(t *testing.T) {
	alloc, err := NewIPAllocator("10.14.0.0/16")
	if err != nil {
		t.Fatalf("NewIPAllocator() error: %v", err)
	}

	ip, err := alloc.Allocate(nil)
	if err != nil {
		t.Fatalf("Allocate() error: %v", err)
	}
	if ip != "10.14.0.2/32" {
		t.Errorf("allocation = %s, want 10.14.0.2/32", ip)
	}
}