package main

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"time"

	"git.loyso.art/frx/kurious/internal/common/config"
	"git.loyso.art/frx/kurious/pkg/xdefault"

	"github.com/gorilla/mux"
	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
	"go.opentelemetry.io/otel/exporters/stdout/stdoutmetric"
	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
	"go.opentelemetry.io/otel/propagation"
	"go.opentelemetry.io/otel/sdk/metric"
	"go.opentelemetry.io/otel/sdk/resource"
	"go.opentelemetry.io/otel/sdk/trace"
)

var webtracer = otel.Tracer("kuriweb")

type shutdownFunc func(context.Context) error

func setupOtelSDK(ctx context.Context, cfg config.Trace) (shutdown shutdownFunc, err error) {
	var shutdownFuncs []shutdownFunc

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

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

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

	tracerProvider, err := newTraceProvider(ctx, cfg.Endpoint, cfg.LicenseKey)
	if err != nil {
		return nil, handleError(err)
	}
	shutdownFuncs = append(shutdownFuncs, tracerProvider.Shutdown)
	otel.SetTracerProvider(tracerProvider)

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

	return shutdown, nil
}

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

const defaultNewRelicEndpoint = "otlp.eu01.nr-data.net:443"

func newTraceProvider(ctx context.Context, endpoint, licensekey string) (traceProvider *trace.TracerProvider, err error) {
	opts := make([]trace.TracerProviderOption, 0, 2)
	opts = append(
		opts,
		trace.WithSampler(trace.AlwaysSample()),
		trace.WithResource(resource.Default()),
	)

	if licensekey != "" {
		endpoint = xdefault.WithFallback(endpoint, defaultNewRelicEndpoint)
		client, err := otlptracegrpc.New(
			ctx,
			otlptracegrpc.WithEndpoint(endpoint),
			otlptracegrpc.WithHeaders(map[string]string{
				"api-key": licensekey,
			}),
		)
		if err != nil {
			return nil, fmt.Errorf("making grpc client: %w", err)
		}

		opts = append(opts, trace.WithBatcher(client, trace.WithBatchTimeout(time.Second*10)))
	} else {
		traceExporter, err := stdouttrace.New(
			stdouttrace.WithPrettyPrint())
		if err != nil {
			return nil, err
		}

		opts = append(
			opts,
			trace.WithBatcher(traceExporter, trace.WithBatchTimeout(time.Second*5)),
		)
	}

	traceProvider = trace.NewTracerProvider(opts...)

	return traceProvider, nil
}

func newMeterProvider() (*metric.MeterProvider, error) {
	metricExporter, err := stdoutmetric.New()
	if err != nil {
		return nil, err
	}

	meterProvider := metric.NewMeterProvider(
		metric.WithReader(metric.NewPeriodicReader(metricExporter,
			// Default is 1m. Set to 3s for demonstrative purposes.
			metric.WithInterval(60*time.Second))),
	)
	return meterProvider, nil
}

func muxHandleFunc(router *mux.Router, path string, hf http.HandlerFunc) *mux.Route {
	h := otelhttp.WithRouteTag(path, hf)
	return router.Handle(path, h)
}