package grpcadapter

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

	ledgerv1 "gl/gen/ledger/v1"

	"google.golang.org/grpc"
	"google.golang.org/grpc/reflection"
)

type ServerConfig struct {
	Host            string
	Port            int
	ShutdownTimeout time.Duration
}

func Run(ctx context.Context, cfg ServerConfig, handler ledgerv1.GeneralLedgerServiceServer) error {
	listener, err := net.Listen("tcp", fmt.Sprintf("%s:%d", cfg.Host, cfg.Port))
	if err != nil {
		return fmt.Errorf("listen for grpc: %w", err)
	}
	return runWithListener(ctx, cfg.ShutdownTimeout, listener, handler)
}

func runWithListener(ctx context.Context, shutdownTimeout time.Duration, listener net.Listener, handler ledgerv1.GeneralLedgerServiceServer) error {
	defer listener.Close()

	server := grpc.NewServer()
	ledgerv1.RegisterGeneralLedgerServiceServer(server, handler)
	reflection.Register(server)

	serveErr := make(chan error, 1)
	go func() { serveErr <- server.Serve(listener) }()

	select {
	case err := <-serveErr:
		if errors.Is(err, grpc.ErrServerStopped) {
			return nil
		}
		return fmt.Errorf("serve grpc: %w", err)
	case <-ctx.Done():
	}

	stopped := make(chan struct{})
	go func() {
		server.GracefulStop()
		close(stopped)
	}()

	timer := time.NewTimer(shutdownTimeout)
	defer timer.Stop()
	select {
	case <-stopped:
	case <-timer.C:
		server.Stop()
		<-stopped
	}

	err := <-serveErr
	if err != nil && !errors.Is(err, grpc.ErrServerStopped) {
		return fmt.Errorf("serve grpc: %w", err)
	}
	return nil
}