package observability

import (
	"context"
	"errors"
	"testing"

	"github.com/prometheus/client_golang/prometheus"

	"evobgp/internal/store"
)

type failingMetricsBackend struct{ store.Backend }

func (failingMetricsBackend) ObserveStoreMetrics(context.Context) (int, int, int, map[string]int, error) {
	return 0, 0, 0, nil, errors.New("database unavailable")
}

type storedMetricsBackend struct{ store.Backend }

func (storedMetricsBackend) ObserveStoreMetrics(context.Context) (int, int, int, map[string]int, error) {
	return 12, 24, 1, map[string]int{"established": 1}, nil
}

type legacyStateBackend struct{ store.Backend }

func (legacyStateBackend) ObserveStoreMetrics(context.Context) (int, int, int, map[string]int, error) {
	return 0, 0, 2, map[string]int{" Established ": 1, "established": 1}, nil
}

func TestStoreMetricsCollectionErrorOmitsAggregates(t *testing.T) {
	metricsStore.Store(storeBackendHolder{backend: failingMetricsBackend{}})
	registry := prometheus.NewRegistry()
	if err := registry.Register(newMemoryStoreCollector()); err != nil {
		t.Fatal(err)
	}
	families, err := registry.Gather()
	if err != nil {
		t.Fatal(err)
	}
	if len(families) != 1 || families[0].GetName() != "evobgp_store_metrics_collection_success" {
		t.Fatalf("expected only collection status on error, got %v", families)
	}
	if got := families[0].Metric[0].Gauge.GetValue(); got != 0 {
		t.Fatalf("collection status = %v, want 0", got)
	}
}

func TestStoredRevisionMetricsDoNotClaimCurrentRoutes(t *testing.T) {
	metricsStore.Store(storeBackendHolder{backend: storedMetricsBackend{}})
	registry := prometheus.NewRegistry()
	if err := registry.Register(newMemoryStoreCollector()); err != nil {
		t.Fatal(err)
	}
	families, err := registry.Gather()
	if err != nil {
		t.Fatal(err)
	}
	values := make(map[string]float64)
	for _, family := range families {
		if len(family.Metric) > 0 && family.Metric[0].Gauge != nil {
			values[family.GetName()] = family.Metric[0].Gauge.GetValue()
		}
	}
	if values["evobgp_stored_revision_materialized_prefixes_sum"] != 24 || values["evobgp_materialized_prefixes_sum"] != 24 {
		t.Fatalf("stored revision and legacy sums must match: %v", values)
	}
	if values["evobgp_store_metrics_collection_success"] != 1 {
		t.Fatalf("successful collection not reported: %v", values)
	}
	if _, ok := values["evobgp_current_routes"]; ok {
		t.Fatal("historical revision sum must not be published as current routes")
	}
}

func TestCanonicalPeerStateBoundsNewLabelValues(t *testing.T) {
	if got := canonicalPeerState("Established"); got != "established" {
		t.Fatalf("state = %q", got)
	}
	if got := canonicalPeerState("unexpected peer text"); got != "other" {
		t.Fatalf("state = %q", got)
	}
}

func TestLegacyPeerStateLabelPreservedWhileNewLabelIsCanonical(t *testing.T) {
	metricsStore.Store(storeBackendHolder{backend: legacyStateBackend{}})
	registry := prometheus.NewRegistry()
	if err := registry.Register(newMemoryStoreCollector()); err != nil {
		t.Fatal(err)
	}
	families, err := registry.Gather()
	if err != nil {
		t.Fatal(err)
	}
	legacyRaw, newCanonical := false, false
	for _, family := range families {
		for _, metric := range family.Metric {
			if len(metric.Label) != 1 {
				continue
			}
			switch family.GetName() {
			case "evobgp_bgp_peer_sessions":
				if metric.Label[0].GetValue() == " Established " && metric.Gauge.GetValue() == 1 {
					legacyRaw = true
				}
			case "evobgp_stored_bgp_peer_session_state":
				if metric.Label[0].GetValue() == "established" && metric.Gauge.GetValue() == 2 {
					newCanonical = true
				}
			}
		}
	}
	if !legacyRaw || !newCanonical {
		t.Fatalf("legacy raw state preserved=%v, new canonical state aggregated=%v", legacyRaw, newCanonical)
	}
}