package agent

import (
	"net"
	"strings"
	"testing"
)

// allReady is a convenience isReady that says yes to every pod.
func allReady(_, _ string) bool { return true }

// readyOnly returns an isReady that only says yes to the named pods.
func readyOnly(want ...string) func(string, string) bool {
	set := map[string]struct{}{}
	for _, n := range want {
		set[n] = struct{}{}
	}
	return func(_, name string) bool {
		_, ok := set[name]
		return ok
	}
}

func TestResolveAnycastTargets_OnePodOneAnycast(t *testing.T) {
	allocs := []Allocation{{
		ContainerID: "c1", Namespace: "ns", PodName: "pod-a",
		State:       StateCommitted,
		IP6:         "2001:db8::1",
		Anycast:     []string{"2001:db8:a::1"},
	}}
	out := resolveAnycastTargets(allocs, allReady, nil)
	if len(out) != 1 {
		t.Fatalf("expected 1 anycast IP, got %d", len(out))
	}
	tgt, ok := out["2001:db8:a::1"]
	if !ok {
		t.Fatalf("missing target")
	}
	if len(tgt.nexthops) != 1 {
		t.Fatalf("expected 1 nexthop, got %d", len(tgt.nexthops))
	}
	if !tgt.nexthops[0].via.Equal(net.ParseIP("2001:db8::1")) {
		t.Fatalf("nexthop via wrong: %v", tgt.nexthops[0].via)
	}
}

// Two pods on the same node binding the same anycast IP must produce a
// SINGLE target with TWO nexthops. The previous behaviour (overwriting)
// was the bug this whole change exists to fix.
func TestResolveAnycastTargets_TwoPodsSameAnycast_MultiNexthop(t *testing.T) {
	allocs := []Allocation{
		{ContainerID: "c1", Namespace: "ns", PodName: "pod-a",
			State: StateCommitted, IP6: "2001:db8::2",
			Anycast: []string{"2001:db8:a::1"}},
		{ContainerID: "c2", Namespace: "ns", PodName: "pod-b",
			State: StateCommitted, IP6: "2001:db8::1",
			Anycast: []string{"2001:db8:a::1"}},
	}
	out := resolveAnycastTargets(allocs, allReady, nil)
	tgt := out["2001:db8:a::1"]
	if len(tgt.nexthops) != 2 {
		t.Fatalf("expected 2 nexthops, got %d", len(tgt.nexthops))
	}
	// Order should be sorted by canonical(via) — ::1 before ::2.
	if !tgt.nexthops[0].via.Equal(net.ParseIP("2001:db8::1")) {
		t.Fatalf("nexthops not sorted by via; got %v first", tgt.nexthops[0].via)
	}
	if !tgt.nexthops[1].via.Equal(net.ParseIP("2001:db8::2")) {
		t.Fatalf("nexthops not sorted by via; got %v second", tgt.nexthops[1].via)
	}
	// HostIface differs per pod (different containerID → different FNV).
	if tgt.nexthops[0].hostIface == tgt.nexthops[1].hostIface {
		t.Fatalf("expected distinct hostIfaces, both %q", tgt.nexthops[0].hostIface)
	}
}

// When one of the contributing pods goes NotReady, only the remaining
// Ready pod should appear in the target's nexthop set.
func TestResolveAnycastTargets_NotReadyDropped(t *testing.T) {
	allocs := []Allocation{
		{ContainerID: "c1", Namespace: "ns", PodName: "pod-a",
			State: StateCommitted, IP6: "2001:db8::1",
			Anycast: []string{"2001:db8:a::1"}},
		{ContainerID: "c2", Namespace: "ns", PodName: "pod-b",
			State: StateCommitted, IP6: "2001:db8::2",
			Anycast: []string{"2001:db8:a::1"}},
	}
	out := resolveAnycastTargets(allocs, readyOnly("pod-a"), nil)
	tgt := out["2001:db8:a::1"]
	if len(tgt.nexthops) != 1 {
		t.Fatalf("expected 1 nexthop after NotReady drop, got %d", len(tgt.nexthops))
	}
	if !tgt.nexthops[0].via.Equal(net.ParseIP("2001:db8::1")) {
		t.Fatalf("wrong surviving nexthop: %v", tgt.nexthops[0].via)
	}
}

// Pods that haven't reached Ready are excluded entirely from the target
// set. If no pod is Ready for an anycast IP, that IP is absent from the
// output (BIRD will withdraw from BGP, kernel route will be removed).
func TestResolveAnycastTargets_NoReadyPodsOmitsIP(t *testing.T) {
	allocs := []Allocation{
		{ContainerID: "c1", Namespace: "ns", PodName: "pod-a",
			State: StateCommitted, IP6: "2001:db8::1",
			Anycast: []string{"2001:db8:a::1"}},
	}
	out := resolveAnycastTargets(allocs, readyOnly( /* none */ ), nil)
	if _, ok := out["2001:db8:a::1"]; ok {
		t.Fatalf("anycast should be absent when no pod ready")
	}
}

// Pending allocations (CNI ADD partway through) are skipped even if the
// pod is Ready — we don't program kernel routes for partial setups.
func TestResolveAnycastTargets_PendingSkipped(t *testing.T) {
	allocs := []Allocation{
		{ContainerID: "c1", Namespace: "ns", PodName: "pod-a",
			State: StatePending, IP6: "2001:db8::1",
			Anycast: []string{"2001:db8:a::1"}},
	}
	out := resolveAnycastTargets(allocs, allReady, nil)
	if len(out) != 0 {
		t.Fatalf("pending allocations must be skipped")
	}
}

// Mixed v6+v4 anycast on the same pod produces two separate target
// entries, one per family, each anchored on the matching unicast IP.
func TestResolveAnycastTargets_MixedFamilies(t *testing.T) {
	allocs := []Allocation{{
		ContainerID: "c1", Namespace: "ns", PodName: "pod-a",
		State:       StateCommitted,
		IP6:         "2001:db8::1",
		IP4:         "10.0.0.1",
		Anycast:     []string{"2001:db8:a::1", "10.255.0.1"},
	}}
	out := resolveAnycastTargets(allocs, allReady, nil)
	if !out["2001:db8:a::1"].nexthops[0].via.Equal(net.ParseIP("2001:db8::1")) {
		t.Fatalf("v6 anycast should resolve via v6 unicast")
	}
	if !out["10.255.0.1"].nexthops[0].via.Equal(net.ParseIP("10.0.0.1").To4()) {
		t.Fatalf("v4 anycast should resolve via v4 unicast")
	}
}

// An anycast whose family has no matching unicast on the pod is skipped
// with a warning. Other anycast IPs on the same pod are unaffected.
func TestResolveAnycastTargets_FamilyMismatchWarns(t *testing.T) {
	allocs := []Allocation{{
		ContainerID: "c1", Namespace: "ns", PodName: "pod-a",
		State:       StateCommitted,
		IP6:         "2001:db8::1", // v6 only
		Anycast:     []string{"2001:db8:a::1", "10.255.0.1"},
	}}
	var warns []string
	out := resolveAnycastTargets(allocs, allReady, func(s string) { warns = append(warns, s) })
	if _, has := out["2001:db8:a::1"]; !has {
		t.Fatalf("v6 anycast should have been programmed")
	}
	if _, has := out["10.255.0.1"]; has {
		t.Fatalf("v4 anycast should have been skipped")
	}
	if len(warns) != 1 {
		t.Fatalf("expected 1 warning, got %d: %v", len(warns), warns)
	}
	if !strings.Contains(warns[0], "10.255.0.1") {
		t.Fatalf("warning should mention skipped IP: %q", warns[0])
	}
}

// Determinism: the same input must produce nexthops in the same order.
func TestResolveAnycastTargets_Determinism(t *testing.T) {
	allocs := []Allocation{
		{ContainerID: "z-late", Namespace: "ns", PodName: "z",
			State: StateCommitted, IP6: "2001:db8::5",
			Anycast: []string{"2001:db8:a::1"}},
		{ContainerID: "a-early", Namespace: "ns", PodName: "a",
			State: StateCommitted, IP6: "2001:db8::3",
			Anycast: []string{"2001:db8:a::1"}},
		{ContainerID: "m-mid", Namespace: "ns", PodName: "m",
			State: StateCommitted, IP6: "2001:db8::4",
			Anycast: []string{"2001:db8:a::1"}},
	}
	a := resolveAnycastTargets(allocs, allReady, nil)
	b := resolveAnycastTargets(allocs, allReady, nil)
	if !a["2001:db8:a::1"].equal(b["2001:db8:a::1"]) {
		t.Fatalf("same input produced unequal targets")
	}
	// Sorted by canonical(via): ::3, ::4, ::5
	via := a["2001:db8:a::1"].nexthops
	if !via[0].via.Equal(net.ParseIP("2001:db8::3")) ||
		!via[1].via.Equal(net.ParseIP("2001:db8::4")) ||
		!via[2].via.Equal(net.ParseIP("2001:db8::5")) {
		t.Fatalf("nexthops not stably sorted: %v %v %v", via[0].via, via[1].via, via[2].via)
	}
}

// equal()'s contract — different orderings are still considered equal
// AS LONG AS both sides have been canonicalised by resolveAnycastTargets.
// Across-call comparisons of resolver outputs must always match for the
// same logical input.
func TestAnycastTarget_Equal(t *testing.T) {
	a := anycastTarget{nexthops: []anycastNexthop{
		{hostIface: "f1", via: net.ParseIP("2001:db8::1")},
		{hostIface: "f2", via: net.ParseIP("2001:db8::2")},
	}}
	b := anycastTarget{nexthops: []anycastNexthop{
		{hostIface: "f1", via: net.ParseIP("2001:db8::1")},
		{hostIface: "f2", via: net.ParseIP("2001:db8::2")},
	}}
	if !a.equal(b) {
		t.Fatalf("equal targets reported unequal")
	}
	c := anycastTarget{nexthops: []anycastNexthop{
		{hostIface: "f1", via: net.ParseIP("2001:db8::1")},
	}}
	if a.equal(c) {
		t.Fatalf("targets with different lengths reported equal")
	}
	d := anycastTarget{nexthops: []anycastNexthop{
		{hostIface: "f1", via: net.ParseIP("2001:db8::1")},
		{hostIface: "f2", via: net.ParseIP("2001:db8::3")}, // diff IP
	}}
	if a.equal(d) {
		t.Fatalf("targets with different vias reported equal")
	}
}