package telemetry

import (
	"context"
	"time"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
	"go.opentelemetry.io/otel/propagation"
	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
	"go.opentelemetry.io/otel/sdk/resource"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.26.0"

	"gitea.nik4nao.com/nik/home-services/ha-gateway/internal/config"
)

// Setup initialises OTel trace and metric providers. If cfg.OTELEndpoint is
// empty, no-op providers are installed and Setup returns immediately. The
// returned shutdown func flushes and closes both exporters.
func Setup(ctx context.Context, cfg *config.Config, version string) (shutdown func(context.Context) error, err error) {
	if cfg.OTELEndpoint == "" {
		// Local dev — no telemetry.
		return func(context.Context) error { return nil }, nil
	}

	res, err := resource.New(ctx,
		resource.WithAttributes(
			semconv.ServiceName("ha-gateway"),
			semconv.ServiceVersion(version),
		),
	)
	if err != nil {
		return nil, err
	}

	// Trace exporter.
	traceExp, err := otlptracegrpc.New(ctx,
		otlptracegrpc.WithEndpoint(cfg.OTELEndpoint),
		otlptracegrpc.WithInsecure(),
	)
	if err != nil {
		return nil, err
	}
	tp := sdktrace.NewTracerProvider(
		sdktrace.WithBatcher(traceExp),
		sdktrace.WithResource(res),
	)
	otel.SetTracerProvider(tp)
	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(
		propagation.TraceContext{},
		propagation.Baggage{},
	))

	// Metric exporter.
	metricExp, err := otlpmetricgrpc.New(ctx,
		otlpmetricgrpc.WithEndpoint(cfg.OTELEndpoint),
		otlpmetricgrpc.WithInsecure(),
	)
	if err != nil {
		_ = tp.Shutdown(ctx)
		return nil, err
	}
	mp := sdkmetric.NewMeterProvider(
		sdkmetric.WithReader(sdkmetric.NewPeriodicReader(metricExp,
			sdkmetric.WithInterval(30*time.Second))),
		sdkmetric.WithResource(res),
	)
	otel.SetMeterProvider(mp)

	return func(ctx context.Context) error {
		if err := tp.Shutdown(ctx); err != nil {
			return err
		}
		return mp.Shutdown(ctx)
	}, nil
}