package app

import (
	"context"
	"fmt"

	"github.com/go-kit/log/level"
	"github.com/grafana/dskit/services"
	"github.com/weaveworks/common/server"

	util_log "github.com/grafana/tempo/pkg/util/log"
)

// NewServerService constructs service from Server component.
// servicesToWaitFor is called when server is stopping, and should return all
// services that need to terminate before server actually stops.
// N.B.: this function is NOT Cortex specific, please let's keep it that way.
// Passed server should not react on signals. Early return from Run function is considered to be an error.
func NewServerService(serv *server.Server, servicesToWaitFor func() []services.Service) services.Service {
	serverDone := make(chan error, 1)

	runFn := func(ctx context.Context) error {
		go func() {
			defer close(serverDone)
			serverDone <- serv.Run()
		}()

		select {
		case <-ctx.Done():
			return nil
		case err := <-serverDone:
			if err != nil {
				return err
			}
			return fmt.Errorf("server stopped unexpectedly")
		}
	}

	stoppingFn := func(_ error) error {
		// wait until all modules are done, and then shutdown server.
		for _, s := range servicesToWaitFor() {
			_ = s.AwaitTerminated(context.Background())
		}

		// shutdown HTTP and gRPC servers (this also unblocks Run)
		serv.Shutdown()

		// if not closed yet, wait until server stops.
		<-serverDone
		level.Info(util_log.Logger).Log("msg", "server stopped")
		return nil
	}

	return services.NewBasicService(nil, runFn, stoppingFn)
}

// DisableSignalHandling puts a dummy signal handler
func DisableSignalHandling(config *server.Config) {
	config.SignalHandler = make(ignoreSignalHandler)
}

type ignoreSignalHandler chan struct{}

func (dh ignoreSignalHandler) Loop() {
	<-dh
}

func (dh ignoreSignalHandler) Stop() {
	close(dh)
}
