// Copyright (c) 2026, Pim van Pelt <pim@ipng.ch>

package vpp

import (
	"net"
	"testing"
	"time"

	"git.ipng.ch/ipng/vpp-maglev/internal/config"
	"git.ipng.ch/ipng/vpp-maglev/internal/health"
)

// TestWarmupTrackerBasic pins the state-machine transitions the tracker
// owns: inMinDelay, isReleased, tryRelease, finishAll, isAllDone. Time
// is manipulated by backdating startAt — there is no hidden global
// clock, so a test can assert behaviour at any simulated point in
// the [0, maxDelay] window by rewinding startAt before each step.
func TestWarmupTrackerBasic(t *testing.T) {
	t.Run("min-delay gates everything", func(t *testing.T) {
		w := newWarmupTracker()
		w.configure(5*time.Second, 30*time.Second)

		// At t=0 we are inside min-delay.
		if !w.inMinDelay() {
			t.Error("t=0: expected inMinDelay=true")
		}
		if w.isReleased("fe1") {
			t.Error("t=0: expected isReleased(fe1)=false")
		}
		if w.tryRelease("fe1") {
			t.Error("t=0: tryRelease should fail inside min-delay")
		}
		if w.isAllDone() {
			t.Error("t=0: expected isAllDone=false")
		}
	})

	t.Run("per-VIP release after min-delay", func(t *testing.T) {
		w := newWarmupTracker()
		w.configure(5*time.Second, 30*time.Second)
		// Simulate t=10s by backdating startAt 10s into the past.
		w.startAt = time.Now().Add(-10 * time.Second)

		if w.inMinDelay() {
			t.Error("t=10s: expected inMinDelay=false")
		}
		if w.isReleased("fe1") {
			t.Error("t=10s: fe1 should not be released yet")
		}
		if !w.tryRelease("fe1") {
			t.Error("t=10s: tryRelease(fe1) should succeed")
		}
		if !w.isReleased("fe1") {
			t.Error("after tryRelease: isReleased(fe1) should be true")
		}
		// A second call returns true (already-released path).
		if !w.tryRelease("fe1") {
			t.Error("second tryRelease(fe1) should return true (already released)")
		}
		// Other VIPs are independent.
		if w.isReleased("fe2") {
			t.Error("releasing fe1 should not affect fe2")
		}
	})

	t.Run("finishAll opens all gates", func(t *testing.T) {
		w := newWarmupTracker()
		w.configure(5*time.Second, 30*time.Second)

		// Inside min-delay: fe1 not released.
		if w.isReleased("fe1") {
			t.Error("pre-finishAll: fe1 should not be released")
		}
		w.finishAll()
		if !w.isAllDone() {
			t.Error("post-finishAll: isAllDone should be true")
		}
		if !w.isReleased("fe1") {
			t.Error("post-finishAll: every frontend should be released")
		}
		if w.inMinDelay() {
			t.Error("post-finishAll: inMinDelay should be false")
		}
		// Second call is idempotent.
		w.finishAll()
	})

	t.Run("doneChan closes on finishAll", func(t *testing.T) {
		w := newWarmupTracker()
		w.configure(5*time.Second, 30*time.Second)

		select {
		case <-w.doneChan():
			t.Fatal("doneChan should not be readable before finishAll")
		default:
		}
		w.finishAll()
		select {
		case <-w.doneChan():
			// expected
		case <-time.After(100 * time.Millisecond):
			t.Fatal("doneChan should be readable after finishAll")
		}
	})

	t.Run("configure is idempotent after first call", func(t *testing.T) {
		w := newWarmupTracker()
		w.configure(5*time.Second, 30*time.Second)
		// Reload with shorter delays should be a no-op so a config
		// reload mid-warmup doesn't move the goalposts.
		w.configure(1*time.Second, 2*time.Second)
		if w.minDelay != 5*time.Second {
			t.Errorf("minDelay got %v, want %v", w.minDelay, 5*time.Second)
		}
		if w.maxDelay != 30*time.Second {
			t.Errorf("maxDelay got %v, want %v", w.maxDelay, 30*time.Second)
		}
	})
}

// staticStateSource is a minimal StateSource for allBackendsKnown tests.
// It holds a fixed config and a static backend-state map; BackendState
// returns (state, true) for entries in the map and (StateUnknown, false)
// for everything else — matching how checker.Checker would report a
// backend that isn't under its watch.
type staticStateSource struct {
	cfg    *config.Config
	states map[string]health.State
}

func (s *staticStateSource) Config() *config.Config { return s.cfg }
func (s *staticStateSource) BackendState(name string) (health.State, bool) {
	st, ok := s.states[name]
	return st, ok
}

// TestAllBackendsKnown pins the per-VIP release precondition. A
// frontend is eligible for release during the warmup phase iff every
// backend it references has reached a non-Unknown state. StateDown,
// StatePaused, and StateDisabled all count as "known" — the property
// is "has the checker reported at least once", not "is healthy".
func TestAllBackendsKnown(t *testing.T) {
	ip := func(s string) net.IP { return net.ParseIP(s) }
	fe := config.Frontend{
		Address:  ip("192.0.2.1"),
		Protocol: "tcp",
		Port:     80,
		Pools: []config.Pool{
			{Name: "primary", Backends: map[string]config.PoolBackend{
				"b1": {Weight: 100},
				"b2": {Weight: 100},
			}},
			{Name: "fallback", Backends: map[string]config.PoolBackend{
				"b3": {Weight: 100},
			}},
		},
	}

	cases := []struct {
		name   string
		states map[string]health.State
		want   bool
	}{
		{
			name: "all up → known",
			states: map[string]health.State{
				"b1": health.StateUp, "b2": health.StateUp, "b3": health.StateUp,
			},
			want: true,
		},
		{
			name: "mixed up/down/disabled → known",
			// All of up, down, paused, disabled are "non-Unknown" and
			// therefore counts as known; allBackendsKnown is about
			// "has the checker reported once", not about health.
			states: map[string]health.State{
				"b1": health.StateDown, "b2": health.StateDisabled, "b3": health.StatePaused,
			},
			want: true,
		},
		{
			name: "one still unknown → not known",
			states: map[string]health.State{
				"b1": health.StateUp, "b2": health.StateUnknown, "b3": health.StateUp,
			},
			want: false,
		},
		{
			name:   "backend not reported at all (checker doesn't know it) → not known",
			states: map[string]health.State{"b1": health.StateUp, "b2": health.StateUp},
			want:   false,
		},
		{
			name: "fallback pool unknown → not known",
			states: map[string]health.State{
				"b1": health.StateUp, "b2": health.StateUp, "b3": health.StateUnknown,
			},
			want: false,
		},
	}

	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			src := &staticStateSource{cfg: &config.Config{}, states: tc.states}
			got := allBackendsKnown(fe, src)
			if got != tc.want {
				t.Errorf("got %v, want %v", got, tc.want)
			}
		})
	}
}

// TestWarmupTrackerZeroDelays pins the "warmup disabled" escape hatch:
// with both delays set to 0, tryRelease succeeds immediately and
// isReleased returns true for every frontend without needing any
// state transitions. This is the configuration an operator picks
// when they'd rather take the brief startup black-hole than wait
// out the warmup — typically for tests and dev setups.
func TestWarmupTrackerZeroDelays(t *testing.T) {
	w := newWarmupTracker()
	w.configure(0, 0)
	if w.inMinDelay() {
		t.Error("min=0: expected inMinDelay=false immediately")
	}
	if !w.tryRelease("fe1") {
		t.Error("min=0: tryRelease should succeed immediately")
	}
	if !w.isReleased("fe1") {
		t.Error("min=0: isReleased(fe1) should be true after tryRelease")
	}
}