package features

import (
	"testing"
	"time"
)

func TestDetectSpikesIgnoresChronicPatterns(t *testing.T) {
	at := time.Date(2026, 9, 19, 12, 0, 0, 0, time.UTC)
	cfg := SpikeConfig{Window: 5 * time.Minute, BaselineWindows: 12}
	var events []Event
	add := func(sig string, n int, when time.Time) {
		for i := 0; i < n; i++ {
			events = append(events, Event{Timestamp: when.Add(time.Duration(i) * time.Second), Service: "api", IsError: true, PatternSignature: sig})
		}
	}
	// chronic poller: 50 errors in every window, including the current one
	for w := 0; w <= 12; w++ {
		add("poll-401", 50, at.Add(-time.Duration(w+1)*cfg.Window))
	}
	if got := DetectSpikes(events, at, cfg); len(got) != 0 {
		t.Fatalf("chronic pattern alone alerted: %+v", got)
	}
	// a novel failure appears in the current window
	add("db-timeout", 20, at.Add(-cfg.Window))
	got := DetectSpikes(events, at, cfg)
	if len(got) != 1 || got[0].Patterns[0].Signature != "db-timeout" || !got[0].Patterns[0].Novel {
		t.Fatalf("expected db-timeout spike, got %+v", got)
	}
}

func TestDetectSpikesRequiresMinimumExcess(t *testing.T) {
	at := time.Date(2026, 9, 19, 12, 0, 0, 0, time.UTC)
	events := []Event{}
	for i := 0; i < 3; i++ {
		events = append(events, Event{Timestamp: at.Add(-time.Minute), Service: "api", IsError: true, PatternSignature: "x"})
	}
	if got := DetectSpikes(events, at, SpikeConfig{}); len(got) != 0 {
		t.Fatalf("3 errors should stay under the floor: %+v", got)
	}
}

func TestBaselineTrimIgnoresEarlierStorm(t *testing.T) {
	at := time.Date(2026, 9, 19, 12, 0, 0, 0, time.UTC)
	cfg := SpikeConfig{Window: 5 * time.Minute, BaselineWindows: 10}
	var events []Event
	add := func(sig string, n int, when time.Time) {
		for i := 0; i < n; i++ {
			events = append(events, Event{Timestamp: when.Add(time.Duration(i) * time.Millisecond), Service: "api", IsError: true, PatternSignature: sig})
		}
	}
	// one earlier storm in 1 of 10 baseline windows, then a smaller repeat now
	add("storm", 1000, at.Add(-6*cfg.Window))
	add("storm", 60, at.Add(-cfg.Window))
	got := DetectSpikes(events, at, cfg)
	if len(got) != 1 || got[0].Patterns[0].BaselineMean != 0 {
		t.Fatalf("storm baseline should be trimmed to 0, got %+v", got)
	}
}

func TestSuppressorCooldownAndEscalation(t *testing.T) {
	at := time.Date(2026, 9, 19, 12, 0, 0, 0, time.UTC)
	spike := func(at time.Time, count int) []Spike {
		return []Spike{{Service: "api", WindowEnd: at, Patterns: []PatternDelta{{Signature: "x", Count: count, Excess: float64(count)}}}}
	}
	s := NewSuppressor(30 * time.Minute)
	if len(s.Filter(spike(at, 20))) != 1 {
		t.Fatal("first alert should pass")
	}
	if len(s.Filter(spike(at.Add(5*time.Minute), 22))) != 0 {
		t.Fatal("repeat inside cooldown should be suppressed")
	}
	if len(s.Filter(spike(at.Add(10*time.Minute), 45))) != 1 {
		t.Fatal("2x escalation should re-alert")
	}
	if len(s.Filter(spike(at.Add(50*time.Minute), 46))) != 1 {
		t.Fatal("alert after cooldown should pass")
	}
}

func TestDetectSpikesWarmupGuard(t *testing.T) {
	at := time.Date(2026, 9, 19, 12, 0, 0, 0, time.UTC)
	cfg := SpikeConfig{Window: 5 * time.Minute, BaselineWindows: 12, WarmupWindows: 6}
	var events []Event
	for i := 0; i < 20; i++ {
		events = append(events, Event{Timestamp: at.Add(-time.Minute).Add(time.Duration(i) * time.Second), Service: "api", IsError: true, PatternSignature: "new"})
	}
	cfg.DataSince = at.Add(-10 * time.Minute) // data began 10 min ago: cold
	if got := DetectSpikes(events, at, cfg); len(got) != 0 {
		t.Fatalf("alerted during warm-up: %+v", got)
	}
	cfg.DataSince = at.Add(-2 * time.Hour) // warm
	if got := DetectSpikes(events, at, cfg); len(got) != 1 {
		t.Fatalf("expected alert once warm, got %+v", got)
	}
	cfg.DataSince = time.Time{} // guard disabled
	if got := DetectSpikes(events, at, cfg); len(got) != 1 {
		t.Fatalf("guard should be off when DataSince is zero")
	}
}