package trace

import (
	"context"
	"log/slog"
	"os"
	"time"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
	"go.opentelemetry.io/otel/sdk/resource"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.26.0"
)

func Init(ctx context.Context, serviceName string) func() {
	endpoint := os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT")
	if endpoint == "" {
		return func() {}
	}

	exp, err := otlptracegrpc.New(ctx,
		otlptracegrpc.WithEndpoint(endpoint),
		otlptracegrpc.WithInsecure(),
	)
	if err != nil {
		slog.Warn("trace exporter unavailable, tracing disabled", "err", err)
		return func() {}
	}

	res, err := resource.New(ctx,
		resource.WithAttributes(semconv.ServiceNameKey.String(serviceName)),
	)
	if err != nil {
		slog.Warn("trace resource error", "err", err)
	}

	tp := sdktrace.NewTracerProvider(
		sdktrace.WithBatcher(exp, sdktrace.WithBatchTimeout(5*time.Second)),
		sdktrace.WithResource(res),
	)
	otel.SetTracerProvider(tp)

	return func() {
		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		defer cancel()
		if err := tp.Shutdown(ctx); err != nil {
			slog.Error("trace shutdown", "err", err)
		}
	}
}