package baseline

import (
	"math"
	"testing"
	"time"
)

func TestLearn_Basic(t *testing.T) {
	store := NewStore(StoreConfig{MinSamples: 10})
	
	// Create 50 data points with mean ~50 and some variance
	points := make([]MetricPoint, 50)
	now := time.Now()
	for i := 0; i < 50; i++ {
		points[i] = MetricPoint{
			Value:     50 + float64(i%10) - 5, // Values from 45-54
			Timestamp: now.Add(-time.Duration(50-i) * time.Minute),
		}
	}
	
	err := store.Learn("test-vm", "vm", "cpu", points)
	if err != nil {
		t.Fatalf("Learn failed: %v", err)
	}
	
	baseline, ok := store.GetBaseline("test-vm", "cpu")
	if !ok {
		t.Fatal("Baseline not found after learning")
	}
	
	// Check mean is around 50
	if math.Abs(baseline.Mean-50) > 1 {
		t.Errorf("Expected mean ~50, got %f", baseline.Mean)
	}
	
	// Check stddev is reasonable (should be ~3 for our data)
	if baseline.StdDev < 1 || baseline.StdDev > 5 {
		t.Errorf("Expected stddev ~3, got %f", baseline.StdDev)
	}
	
	if baseline.SampleCount != 50 {
		t.Errorf("Expected 50 samples, got %d", baseline.SampleCount)
	}
}

func TestLearn_InsufficientData(t *testing.T) {
	store := NewStore(StoreConfig{MinSamples: 50})
	
	// Only 10 points, not enough
	points := make([]MetricPoint, 10)
	for i := 0; i < 10; i++ {
		points[i] = MetricPoint{Value: float64(i)}
	}
	
	err := store.Learn("test-vm", "vm", "cpu", points)
	if err != nil {
		t.Fatalf("Learn should not error on insufficient data: %v", err)
	}
	
	_, ok := store.GetBaseline("test-vm", "cpu")
	if ok {
		t.Error("Should not have baseline with insufficient data")
	}
}

func TestIsAnomaly(t *testing.T) {
	store := NewStore(StoreConfig{MinSamples: 10})
	
	// Create stable data around 50 with low variance
	points := make([]MetricPoint, 100)
	for i := 0; i < 100; i++ {
		points[i] = MetricPoint{
			Value: 50 + float64(i%3) - 1, // Values 49, 50, 51
		}
	}
	
	store.Learn("test-vm", "vm", "cpu", points)
	
	// Test normal value
	isAnomaly, zScore := store.IsAnomaly("test-vm", "cpu", 50)
	if isAnomaly {
		t.Errorf("50 should not be anomaly, zScore=%f", zScore)
	}
	
	// Test slightly high - with stddev ~0.82, 51 is within 2 std devs
	isAnomaly, zScore = store.IsAnomaly("test-vm", "cpu", 51)
	if isAnomaly {
		t.Errorf("51 should not be anomaly with this variance, zScore=%f", zScore)
	}
	
	// Test very high (should be anomaly)
	isAnomaly, zScore = store.IsAnomaly("test-vm", "cpu", 60)
	if !isAnomaly {
		t.Errorf("60 should be anomaly, zScore=%f", zScore)
	}
	
	// Test very low (should be anomaly)
	isAnomaly, zScore = store.IsAnomaly("test-vm", "cpu", 40)
	if !isAnomaly {
		t.Errorf("40 should be anomaly, zScore=%f", zScore)
	}
}

func TestCheckAnomaly_Severity(t *testing.T) {
	store := NewStore(StoreConfig{MinSamples: 10})
	
	// Create very stable data with known statistics
	// Mean = 50, StdDev = 1
	points := make([]MetricPoint, 100)
	for i := 0; i < 100; i++ {
		// Alternate between 49, 50, 51 for stddev ~1
		points[i] = MetricPoint{Value: 50 + float64(i%3) - 1}
	}
	
	store.Learn("test-vm", "vm", "cpu", points)
	baseline, _ := store.GetBaseline("test-vm", "cpu")
	
	testCases := []struct {
		value            float64
		expectedSeverity AnomalySeverity
	}{
		{50, AnomalyNone},                     // Mean
		{50 + baseline.StdDev*1.5, AnomalyNone}, // 1.5 std devs - normal
		{50 + baseline.StdDev*2.2, AnomalyLow},  // 2.2 std devs
		{50 + baseline.StdDev*2.7, AnomalyMedium}, // 2.7 std devs
		{50 + baseline.StdDev*3.5, AnomalyHigh},   // 3.5 std devs
		{50 + baseline.StdDev*4.5, AnomalyCritical}, // 4.5 std devs
	}
	
	for _, tc := range testCases {
		severity, _, _ := store.CheckAnomaly("test-vm", "cpu", tc.value)
		if severity != tc.expectedSeverity {
			t.Errorf("Value %f: expected severity %s, got %s", tc.value, tc.expectedSeverity, severity)
		}
	}
}

func TestGetResourceBaseline(t *testing.T) {
	store := NewStore(StoreConfig{MinSamples: 10})
	
	// Learn multiple metrics
	cpuPoints := make([]MetricPoint, 50)
	memPoints := make([]MetricPoint, 50)
	for i := 0; i < 50; i++ {
		cpuPoints[i] = MetricPoint{Value: 30}
		memPoints[i] = MetricPoint{Value: 70}
	}
	
	store.Learn("test-vm", "vm", "cpu", cpuPoints)
	store.Learn("test-vm", "vm", "memory", memPoints)
	
	rb, ok := store.GetResourceBaseline("test-vm")
	if !ok {
		t.Fatal("Resource baseline not found")
	}
	
	if rb.ResourceType != "vm" {
		t.Errorf("Expected resource type 'vm', got '%s'", rb.ResourceType)
	}
	
	if len(rb.Metrics) != 2 {
		t.Errorf("Expected 2 metrics, got %d", len(rb.Metrics))
	}
	
	if rb.Metrics["cpu"] == nil {
		t.Error("CPU metric baseline missing")
	}
	
	if rb.Metrics["memory"] == nil {
		t.Error("Memory metric baseline missing")
	}
}

func TestPercentiles(t *testing.T) {
	values := []float64{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
	percentiles := computePercentiles(values)
	
	// P50 should be ~5.5 for 1-10
	if percentiles[50] < 5 || percentiles[50] > 6 {
		t.Errorf("P50 should be ~5.5, got %f", percentiles[50])
	}
	
	// P5 should be close to 1
	if percentiles[5] < 1 || percentiles[5] > 2 {
		t.Errorf("P5 should be ~1, got %f", percentiles[5])
	}
	
	// P95 should be close to 10
	if percentiles[95] < 9 || percentiles[95] > 10 {
		t.Errorf("P95 should be ~10, got %f", percentiles[95])
	}
}

func TestComputeStats(t *testing.T) {
	// Test mean and stddev with known values
	values := []float64{2, 4, 4, 4, 5, 5, 7, 9} // Mean = 5, Stddev = 2 (sample)
	
	mean := computeMean(values)
	if mean != 5 {
		t.Errorf("Expected mean 5, got %f", mean)
	}
	
	stddev := computeStdDev(values)
	// Sample stddev of [2,4,4,4,5,5,7,9] is approximately 2.14, not exactly 2
	if math.Abs(stddev-2.14) > 0.1 {
		t.Errorf("Expected stddev ~2.14, got %f", stddev)
	}
}