package update

import (
	"fmt"
	"io"
	"net"
	"os"
	"path/filepath"
	"time"

	"tea.chunkbyte.com/kato/go-worm/lib/config"
)

// Deploy saves exe and launches it on the alternate listen port (5032 <-> 5033).
func Deploy(currentAddr string, body io.Reader) (savedPath, nextAddr string, err error) {
	nextAddr, err = config.AlternateListenAddr(currentAddr)
	if err != nil {
		return "", "", err
	}
	if err := listenAvailable(nextAddr); err != nil {
		return "", "", err
	}

	dir, err := config.UpdatesDir()
	if err != nil {
		return "", "", err
	}
	if err := os.MkdirAll(dir, 0o700); err != nil {
		return "", "", err
	}

	name := fmt.Sprintf("update-%s.exe", time.Now().Format("20060102-150405"))
	savedPath = filepath.Join(dir, name)
	out, err := os.OpenFile(savedPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0o700)
	if err != nil {
		return "", "", err
	}

	var head [2]byte
	if _, err := io.ReadFull(body, head[:]); err != nil {
		_ = out.Close()
		_ = os.Remove(savedPath)
		return "", "", fmt.Errorf("invalid executable")
	}
	if head[0] != 'M' || head[1] != 'Z' {
		_ = out.Close()
		_ = os.Remove(savedPath)
		return "", "", fmt.Errorf("file is not a Windows executable")
	}
	if _, err := out.Write(head[:]); err != nil {
		_ = out.Close()
		_ = os.Remove(savedPath)
		return "", "", err
	}
	if _, err := io.Copy(out, body); err != nil {
		_ = out.Close()
		_ = os.Remove(savedPath)
		return "", "", err
	}
	if err := out.Close(); err != nil {
		_ = os.Remove(savedPath)
		return "", "", err
	}

	if err := deployLaunch(savedPath, nextAddr); err != nil {
		_ = os.Remove(savedPath)
		return "", "", err
	}
	return savedPath, nextAddr, nil
}

func listenAvailable(addr string) error {
	ln, err := net.Listen("tcp", addr)
	if err != nil {
		return fmt.Errorf("port %s is not available: %w", addr, err)
	}
	_ = ln.Close()
	return nil
}