package otel

import (
	"context"
	"errors"
	"time"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp"
	"go.opentelemetry.io/otel/propagation"
	"go.opentelemetry.io/otel/sdk/resource"
	"go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.32.0"
)

func SetupOTEL(ctx context.Context, traceEndpoint string) (shutdown func(context.Context) error, err error) {
	var shutdownFuncs []func(context.Context) error

	shutdown = func(ctx context.Context) error {
		var err error
		for _, fn := range shutdownFuncs {
			err = errors.Join(err, fn(ctx))
		}
		shutdownFuncs = nil
		return err
	}

	handlerErr := func(inErr error) {
		err = errors.Join(inErr, shutdown(ctx))
	}

	prop := newPropagator()
	otel.SetTextMapPropagator(prop)

	tracerProvider, err := newTracerProvider(ctx, traceEndpoint)
	if err != nil {
		handlerErr(err)
		return
	}
	shutdownFuncs = append(shutdownFuncs, tracerProvider.Shutdown)
	otel.SetTracerProvider(tracerProvider)

	return
}

func newPropagator() propagation.TextMapPropagator {
	return propagation.NewCompositeTextMapPropagator(
		propagation.TraceContext{},
		propagation.Baggage{},
	)
}

func newTracerProvider(ctx context.Context, traceEndpoint string) (*trace.TracerProvider, error) {
	traceExporter, err := otlptracehttp.New(ctx,
		otlptracehttp.WithEndpoint(traceEndpoint),
		otlptracehttp.WithInsecure(),
	)
	if err != nil {
		return nil, err
	}

	traceResource, err := resource.New(ctx, resource.WithAttributes(
		semconv.ServiceNamespaceKey.String("t-juice.club"),
		semconv.ServiceName("labmon"),
	))
	if err != nil {
		return nil, err
	}
	tracerProvider := trace.NewTracerProvider(
		trace.WithBatcher(traceExporter, trace.WithBatchTimeout(time.Second)),
		trace.WithResource(traceResource),
	)

	return tracerProvider, nil
}