// +build windows

package utils

import (
	"fmt"
	"net"
	"os"
	"strings"
	"syscall"

	"github.com/valyala/tcplisten"
)

// CreateListener crates socket listener based on DSN definition.
func CreateListener(address string) (net.Listener, error) {
	dsn := strings.Split(address, "://")

	switch len(dsn) {
	case 1:
		// assume, that there is no prefix here [127.0.0.1:8000]
		return createTCPListener(dsn[0])
	case 2:
		// we got two part here, first part is the transport, second - address
		// [tcp://127.0.0.1:8000] OR [unix:///path/to/unix.socket] OR [error://path]
		// where error is wrong transport name
		switch dsn[0] {
		case "unix":
			// check of file exist. If exist, unlink
			if fileExists(dsn[1]) {
				err := syscall.Unlink(dsn[1])
				if err != nil {
					return nil, fmt.Errorf("error during the unlink syscall: error %v", err)
				}
			}
			return net.Listen(dsn[0], dsn[1])
		case "tcp":
			return createTCPListener(dsn[1])
			// not an tcp or unix
		default:
			return nil, fmt.Errorf("invalid Protocol ([tcp://]:6001, unix://file.sock), address: %s", address)
		}
		// wrong number of split parts
	default:
		return nil, fmt.Errorf("wrong number of parsed protocol parts, address: %s", address)
	}
}

func createTCPListener(addr string) (net.Listener, error) {
	cfg := tcplisten.Config{
		ReusePort:   true,
		DeferAccept: true,
		FastOpen:    true,
		Backlog:     0,
	}
	listener, err := cfg.NewListener("tcp4", addr)
	if err != nil {
		return nil, err
	}
	return listener, nil
}

// fileExists checks if a file exists and is not a directory before we
// try using it to prevent further errors.
func fileExists(filename string) bool {
	info, err := os.Stat(filename)
	if os.IsNotExist(err) {
		return false
	}
	return !info.IsDir()
}