package shutdown

import (
	"context"
	"net/http"
	"os"
	"os/signal"
	"time"

	syscall "golang.org/x/sys/unix"

	"edge-infra.dev/pkg/lib/logging"
)

type Graceful struct {
	term   chan os.Signal
	fail   chan error
	logger *logging.EdgeLogger
}

func NewGraceful() *Graceful {
	return &Graceful{
		term:   make(chan os.Signal),
		fail:   make(chan error),
		logger: logging.NewLogger(),
	}
}

// Serve graceful
func (g *Graceful) Serve(doWork func() error, teardown func(context.Context) error) error {
	go func() {
		signal.Notify(g.term, syscall.SIGINT, syscall.SIGTERM)
		<-g.term // waits for termination signal

		// context with 30s timeout
		ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
		defer cancel()

		// all teardown process must complete within 30 seconds
		g.fail <- teardown(ctx)
	}()

	// doWork blocks our code from exit, but will produce ErrServerClosed when stopped
	if err := doWork(); err != nil && err != http.ErrServerClosed {
		g.logger.Error(err, "doWork had an error")
		return err
	}

	// after server gracefully stopped, code proceeds here and waits for any error produced by teardown() process
	return <-g.fail
}