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

package checker

import (
	"context"
	"net"
	"testing"
	"time"

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

func makeTestConfig(interval time.Duration, fall, rise int) *config.Config {
	return &config.Config{
		HealthChecker: config.HealthCheckerConfig{TransitionHistory: 5},
		HealthChecks: map[string]config.HealthCheck{
			"icmp": {
				Type:     "icmp",
				Interval: interval,
				Timeout:  time.Second,
				Fall:     fall,
				Rise:     rise,
			},
		},
		Backends: map[string]config.Backend{
			"be0": {
				Address:     net.ParseIP("10.0.0.2"),
				HealthCheck: "icmp",
				Enabled:     true,
			},
		},
		Frontends: map[string]config.Frontend{
			"web": {
				Address:  net.ParseIP("192.0.2.1"),
				Protocol: "tcp",
				Port:     80,
				Pools: []config.Pool{
					{Name: "primary", Backends: map[string]config.PoolBackend{
						"be0": {Weight: 100},
					}},
				},
			},
		},
	}
}

func TestHealthCheckEqual(t *testing.T) {
	a := config.HealthCheck{
		Type:     "http",
		Interval: time.Second,
		Timeout:  2 * time.Second,
		Fall:     3,
		Rise:     2,
		HTTP:     &config.HTTPParams{Path: "/healthz", ResponseCodeMin: 200, ResponseCodeMax: 200},
	}
	b := a
	if !healthCheckEqual(a, b) {
		t.Error("identical configs should be equal")
	}
	b.Fall = 5
	if healthCheckEqual(a, b) {
		t.Error("different Fall should not be equal")
	}
	b = a
	b.FastInterval = 500 * time.Millisecond
	if healthCheckEqual(a, b) {
		t.Error("different FastInterval should not be equal")
	}
	b = a
	b.HTTP = &config.HTTPParams{Path: "/other", ResponseCodeMin: 200, ResponseCodeMax: 200}
	if healthCheckEqual(a, b) {
		t.Error("different HTTP.Path should not be equal")
	}
}

func TestStateMachineViaBackend(t *testing.T) {
	b := health.New("be0", net.ParseIP("10.0.0.2"), 2, 3)
	pass := health.ProbeResult{OK: true, Layer: health.LayerL7, Code: "L7OK"}
	fail := health.ProbeResult{OK: false, Layer: health.LayerL4, Code: "L4CON"}

	if !b.Record(fail, 5) {
		t.Error("first fail from Unknown should transition to Down")
	}
	if b.State != health.StateDown {
		t.Errorf("expected down, got %s", b.State)
	}
	if b.Record(pass, 5) {
		t.Error("should not transition after 1 pass (rise=2)")
	}
	if !b.Record(pass, 5) {
		t.Error("should transition to Up after 2 passes")
	}
	if b.State != health.StateUp {
		t.Errorf("expected up, got %s", b.State)
	}
}

func TestStaggerDelay(t *testing.T) {
	interval := 10 * time.Second
	if got := staggerDelay(interval, 0, 10); got != 0 {
		t.Errorf("pos=0: got %v, want 0", got)
	}
	if got := staggerDelay(interval, 5, 10); got != 5*time.Second {
		t.Errorf("pos=5/10: got %v, want 5s", got)
	}
	if got := staggerDelay(interval, 0, 1); got != 0 {
		t.Errorf("total=1: got %v, want 0", got)
	}
}

func TestReloadAddsBackend(t *testing.T) {
	cfg := makeTestConfig(10*time.Millisecond, 3, 2)
	c := New(cfg)

	newCfg := makeTestConfig(10*time.Millisecond, 3, 2)
	newCfg.Backends["be1"] = config.Backend{
		Address:     net.ParseIP("10.0.0.3"),
		HealthCheck: "icmp",
		Enabled:     true,
	}
	newCfg.Frontends["web2"] = config.Frontend{
		Address:  net.ParseIP("192.0.2.2"),
		Protocol: "tcp",
		Port:     443,
		Pools: []config.Pool{
			{Name: "primary", Backends: map[string]config.PoolBackend{
				"be1": {Weight: 100},
			}},
		},
	}

	ctx, cancel := context.WithCancel(context.Background())
	cancel()

	if err := c.Reload(ctx, newCfg); err != nil {
		t.Fatalf("Reload: %v", err)
	}

	c.mu.RLock()
	_, ok := c.workers["be1"]
	c.mu.RUnlock()
	if !ok {
		t.Error("new backend not added after Reload")
	}
}

func TestReloadRemovesBackend(t *testing.T) {
	cfg := makeTestConfig(10*time.Millisecond, 3, 2)
	c := New(cfg)

	ctx, cancel := context.WithCancel(context.Background())
	cancel()

	// Seed a worker manually.
	c.mu.Lock()
	wCtx, wCancel := context.WithCancel(context.Background())
	c.workers["be0"] = &worker{
		backend: health.New("be0", net.ParseIP("10.0.0.2"), 2, 3),
		hc:      cfg.HealthChecks["icmp"],
		entry:   cfg.Backends["be0"],
		cancel:  wCancel,
	}
	c.mu.Unlock()
	_ = wCtx

	// Remove all frontends → be0 is no longer active.
	newCfg := &config.Config{
		HealthChecker: cfg.HealthChecker,
		HealthChecks:  cfg.HealthChecks,
		Backends:      cfg.Backends,
		Frontends:     map[string]config.Frontend{},
	}

	if err := c.Reload(ctx, newCfg); err != nil {
		t.Fatalf("Reload: %v", err)
	}

	c.mu.RLock()
	_, ok := c.workers["be0"]
	c.mu.RUnlock()
	if ok {
		t.Error("removed backend still present after Reload")
	}
}

func TestSharedBackendProbedOnce(t *testing.T) {
	// be0 is referenced by two frontends — only one worker should exist.
	cfg := makeTestConfig(10*time.Millisecond, 3, 2)
	cfg.Frontends["web-tls"] = config.Frontend{
		Address:  net.ParseIP("192.0.2.3"),
		Protocol: "tcp",
		Port:     443,
		Pools: []config.Pool{
			{Name: "primary", Backends: map[string]config.PoolBackend{
				"be0": {Weight: 100},
			}},
		},
	}

	c := New(cfg)
	names := activeBackendNames(c.cfg)
	if len(names) != 1 || names[0] != "be0" {
		t.Errorf("expected exactly one active backend, got %v", names)
	}
}

func TestSubscribe(t *testing.T) {
	cfg := makeTestConfig(10*time.Millisecond, 1, 1)
	c := New(cfg)

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	go c.fanOut(ctx)

	ch, unsub := c.Subscribe()
	defer unsub()

	e := Event{
		FrontendName: "web",
		BackendName:  "be0",
		Backend:      net.ParseIP("10.0.0.2"),
		Transition: health.Transition{
			From: health.StateUnknown,
			To:   health.StateUp,
		},
	}
	c.mu.Lock()
	c.emit(e)
	c.mu.Unlock()

	select {
	case got := <-ch:
		if got.FrontendName != "web" {
			t.Errorf("event FrontendName: got %q, want web", got.FrontendName)
		}
		if got.BackendName != "be0" {
			t.Errorf("event BackendName: got %q, want be0", got.BackendName)
		}
		if got.Transition.To != health.StateUp {
			t.Errorf("event To state: got %s, want up", got.Transition.To)
		}
	case <-time.After(time.Second):
		t.Error("timed out waiting for event")
	}
}

func TestSetFrontendPoolBackendWeight(t *testing.T) {
	cfg := makeTestConfig(time.Hour, 3, 2)
	c := New(cfg)

	// Valid weight change.
	fe, err := c.SetFrontendPoolBackendWeight("web", "primary", "be0", 42)
	if err != nil {
		t.Fatalf("SetFrontendPoolBackendWeight: %v", err)
	}
	if fe.Pools[0].Backends["be0"].Weight != 42 {
		t.Errorf("weight: got %d, want 42", fe.Pools[0].Backends["be0"].Weight)
	}
	// Persisted in live config.
	got, _ := c.GetFrontend("web")
	if got.Pools[0].Backends["be0"].Weight != 42 {
		t.Errorf("config weight: got %d, want 42", got.Pools[0].Backends["be0"].Weight)
	}

	// Out-of-range weight.
	if _, err := c.SetFrontendPoolBackendWeight("web", "primary", "be0", 101); err == nil {
		t.Error("expected error for weight 101")
	}

	// Unknown frontend.
	if _, err := c.SetFrontendPoolBackendWeight("nope", "primary", "be0", 50); err == nil {
		t.Error("expected error for unknown frontend")
	}

	// Unknown pool.
	if _, err := c.SetFrontendPoolBackendWeight("web", "nope", "be0", 50); err == nil {
		t.Error("expected error for unknown pool")
	}

	// Unknown backend.
	if _, err := c.SetFrontendPoolBackendWeight("web", "primary", "nope", 50); err == nil {
		t.Error("expected error for unknown backend in pool")
	}
}

func TestEnableDisable(t *testing.T) {
	cfg := makeTestConfig(time.Hour, 3, 2)
	c := New(cfg)

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	go c.fanOut(ctx)

	// Seed a worker as EnableBackend/DisableBackend require one in c.workers.
	wCtx, wCancel := context.WithCancel(ctx)
	c.mu.Lock()
	c.runCtx = ctx
	c.workers["be0"] = &worker{
		backend: health.New("be0", net.ParseIP("10.0.0.2"), 2, 3),
		hc:      cfg.HealthChecks["icmp"],
		entry:   cfg.Backends["be0"],
		cancel:  wCancel,
	}
	c.mu.Unlock()
	_ = wCtx

	b, ok := c.DisableBackend("be0")
	if !ok {
		t.Fatal("DisableBackend: not found")
	}
	if b.Health.State != health.StateDisabled {
		t.Errorf("after disable: state=%s, want disabled", b.Health.State)
	}
	if b.Config.Enabled {
		t.Error("after disable: Enabled should be false")
	}

	// Backend should still be visible after disable.
	snap, ok := c.GetBackend("be0")
	if !ok {
		t.Fatal("GetBackend after disable: not found")
	}
	if snap.Config.Enabled {
		t.Error("GetBackend after disable: Enabled should be false")
	}

	b, ok = c.EnableBackend("be0")
	if !ok {
		t.Fatal("EnableBackend: not found")
	}
	if b.Health.State != health.StateUnknown {
		t.Errorf("after enable: state=%s, want unknown", b.Health.State)
	}
	if !b.Config.Enabled {
		t.Error("after enable: Enabled should be true")
	}
}

func TestPauseResume(t *testing.T) {
	cfg := makeTestConfig(time.Hour, 3, 2)
	c := New(cfg)

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	go c.fanOut(ctx)

	c.mu.Lock()
	c.runCtx = ctx
	_, wCancel := context.WithCancel(ctx)
	c.workers["be0"] = &worker{
		backend: health.New("be0", net.ParseIP("10.0.0.2"), 2, 3),
		hc:      cfg.HealthChecks["icmp"],
		entry:   cfg.Backends["be0"],
		cancel:  wCancel,
		wakeCh:  make(chan struct{}, 1),
	}
	c.mu.Unlock()

	b, err := c.PauseBackend("be0")
	if err != nil {
		t.Fatalf("PauseBackend: %v", err)
	}
	if b.Health.State != health.StatePaused {
		t.Errorf("after pause: %s", b.Health.State)
	}

	b, err = c.ResumeBackend("be0")
	if err != nil {
		t.Fatalf("ResumeBackend: %v", err)
	}
	if b.Health.State != health.StateUnknown {
		t.Errorf("after resume: %s", b.Health.State)
	}

	// Pause/resume on a disabled backend must return an error.
	c.mu.Lock()
	c.workers["be0"].entry.Enabled = false
	c.mu.Unlock()
	if _, err := c.PauseBackend("be0"); err == nil {
		t.Error("PauseBackend on disabled backend: expected error")
	}
	if _, err := c.ResumeBackend("be0"); err == nil {
		t.Error("ResumeBackend on disabled backend: expected error")
	}
}