package storage

import (
	"context"
	"errors"
	"testing"
	"time"

	"github.com/prometheus/client_golang/prometheus"
	dto "github.com/prometheus/client_model/go"
)

func newTestInstrumented() (*InstrumentedStore, *prometheus.HistogramVec, *prometheus.CounterVec) {
	dur := prometheus.NewHistogramVec(prometheus.HistogramOpts{
		Name:    "test_query_duration_seconds",
		Help:    "test",
		Buckets: []float64{0.001, 0.01, 0.1, 1},
	}, []string{"method"})
	errs := prometheus.NewCounterVec(prometheus.CounterOpts{
		Name: "test_query_errors_total",
		Help: "test",
	}, []string{"method"})

	store := NewMemoryStore()
	return NewInstrumentedStore(store, dur, errs), dur, errs
}

func getHistogramCount(h *prometheus.HistogramVec, method string) uint64 {
	m := &dto.Metric{}
	h.WithLabelValues(method).(prometheus.Histogram).Write(m)
	return m.GetHistogram().GetSampleCount()
}

func getCounterValue(c *prometheus.CounterVec, method string) float64 {
	m := &dto.Metric{}
	c.WithLabelValues(method).Write(m)
	return m.GetCounter().GetValue()
}

func TestInstrumentedStoreDelegation(t *testing.T) {
	s, dur, _ := newTestInstrumented()
	ctx := context.Background()

	// RecordLoginAttempt should delegate and record duration.
	err := s.RecordLoginAttempt(ctx, "root", "pass", "1.2.3.4", "US")
	if err != nil {
		t.Fatalf("RecordLoginAttempt: %v", err)
	}
	if c := getHistogramCount(dur, "RecordLoginAttempt"); c != 1 {
		t.Fatalf("expected 1 observation, got %d", c)
	}

	// CreateSession should delegate and return a valid ID.
	id, err := s.CreateSession(ctx, "1.2.3.4", "root", "bash", "US")
	if err != nil {
		t.Fatalf("CreateSession: %v", err)
	}
	if id == "" {
		t.Fatal("CreateSession returned empty ID")
	}
	if c := getHistogramCount(dur, "CreateSession"); c != 1 {
		t.Fatalf("expected 1 observation, got %d", c)
	}

	// GetDashboardStats should delegate.
	stats, err := s.GetDashboardStats(ctx)
	if err != nil {
		t.Fatalf("GetDashboardStats: %v", err)
	}
	if stats == nil {
		t.Fatal("GetDashboardStats returned nil")
	}
	if c := getHistogramCount(dur, "GetDashboardStats"); c != 1 {
		t.Fatalf("expected 1 observation, got %d", c)
	}
}

func TestInstrumentedStoreErrorCounting(t *testing.T) {
	dur := prometheus.NewHistogramVec(prometheus.HistogramOpts{
		Name:    "test_ec_query_duration_seconds",
		Help:    "test",
		Buckets: []float64{0.001, 0.01, 0.1, 1},
	}, []string{"method"})
	errs := prometheus.NewCounterVec(prometheus.CounterOpts{
		Name: "test_ec_query_errors_total",
		Help: "test",
	}, []string{"method"})

	es := &errorStore{}
	s := NewInstrumentedStore(es, dur, errs)
	ctx := context.Background()

	// Error should be counted.
	err := s.EndSession(ctx, "nonexistent", time.Now())
	if !errors.Is(err, errFake) {
		t.Fatalf("expected errFake, got %v", err)
	}
	if c := getHistogramCount(dur, "EndSession"); c != 1 {
		t.Fatalf("expected 1 observation, got %d", c)
	}
	if c := getCounterValue(errs, "EndSession"); c != 1 {
		t.Fatalf("expected error count 1, got %f", c)
	}

	// Successful call should not increment error counter.
	s2, _, errs2 := newTestInstrumented()
	err = s2.RecordLoginAttempt(ctx, "root", "pass", "1.2.3.4", "US")
	if err != nil {
		t.Fatalf("RecordLoginAttempt: %v", err)
	}
	if c := getCounterValue(errs2, "RecordLoginAttempt"); c != 0 {
		t.Fatalf("expected error count 0, got %f", c)
	}
}

// errorStore is a Store that returns errors for all methods.
type errorStore struct {
	MemoryStore
}

var errFake = errors.New("fake error")

func (s *errorStore) RecordLoginAttempt(context.Context, string, string, string, string) error {
	return errFake
}

func (s *errorStore) EndSession(context.Context, string, time.Time) error {
	return errFake
}

func TestInstrumentedStoreObserveErr(t *testing.T) {
	dur := prometheus.NewHistogramVec(prometheus.HistogramOpts{
		Name:    "test2_query_duration_seconds",
		Help:    "test",
		Buckets: []float64{0.001, 0.01, 0.1, 1},
	}, []string{"method"})
	errs := prometheus.NewCounterVec(prometheus.CounterOpts{
		Name: "test2_query_errors_total",
		Help: "test",
	}, []string{"method"})

	es := &errorStore{}
	s := NewInstrumentedStore(es, dur, errs)
	ctx := context.Background()

	err := s.RecordLoginAttempt(ctx, "root", "pass", "1.2.3.4", "US")
	if !errors.Is(err, errFake) {
		t.Fatalf("expected errFake, got %v", err)
	}
	if c := getCounterValue(errs, "RecordLoginAttempt"); c != 1 {
		t.Fatalf("expected error count 1, got %f", c)
	}
	if c := getHistogramCount(dur, "RecordLoginAttempt"); c != 1 {
		t.Fatalf("expected 1 observation, got %d", c)
	}
}

func TestInstrumentedStoreClose(t *testing.T) {
	s, _, _ := newTestInstrumented()
	if err := s.Close(); err != nil {
		t.Fatalf("Close: %v", err)
	}
}