package main

import (
	"context"
	"errors"
	"time"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc"
	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
	"go.opentelemetry.io/otel/log/global"
	"go.opentelemetry.io/otel/propagation"
	"go.opentelemetry.io/otel/sdk/log"
	"go.opentelemetry.io/otel/sdk/metric"
	"go.opentelemetry.io/otel/sdk/trace"
)

// setupOTelSDK bootstraps the OpenTelemetry pipeline.
// If it does not return an error, make sure to call shutdown for proper cleanup.
func setupOTelSDK(ctx context.Context) (func(context.Context) error, error) {
	var shutdownFuncs []func(context.Context) error
	var err error

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

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

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

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

	meterProvider, err := newMeterProvider()
	if err != nil {
		handleErr(err)
		return shutdown, err
	}
	shutdownFuncs = append(shutdownFuncs, meterProvider.Shutdown)
	otel.SetMeterProvider(meterProvider)

	loggerProvider, err := newLoggerProvider()
	if err != nil {
		handleErr(err)
		return shutdown, err
	}
	shutdownFuncs = append(shutdownFuncs, loggerProvider.Shutdown)
	global.SetLoggerProvider(loggerProvider)

	return shutdown, err
}

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

func newTracerProvider() (*trace.TracerProvider, error) {
	traceExporter, err := otlptracegrpc.New(context.Background())
	if err != nil {
		return nil, err
	}

	tracerProvider := trace.NewTracerProvider(
		trace.WithBatcher(traceExporter,
			trace.WithBatchTimeout(time.Second)),
	)
	return tracerProvider, nil
}

func newMeterProvider() (*metric.MeterProvider, error) {
	exporter, err := otlpmetricgrpc.New(context.Background())
	if err != nil {
		return nil, err
	}

	provider := metric.NewMeterProvider(metric.WithReader(metric.NewPeriodicReader(exporter)))
	return provider, nil
}

func newLoggerProvider() (*log.LoggerProvider, error) {
	logExporter, err := otlploggrpc.New(context.Background())
	if err != nil {
		return nil, err
	}

	loggerProvider := log.NewLoggerProvider(
		log.WithProcessor(log.NewBatchProcessor(logExporter)),
	)
	return loggerProvider, nil
}