//go:build linux || freebsd
// +build linux freebsd

package sftp

import (
	"fmt"
	"os"
	"path/filepath"

	"golang.org/x/crypto/ssh"
	"golang.org/x/crypto/ssh/knownhosts"
)

func hostKeyCallback(knownHostsPath string, insecure bool) (ssh.HostKeyCallback, error) {
	if insecure {
		return ssh.InsecureIgnoreHostKey(), nil
	}

	if knownHostsPath == "" {
		home, err := os.UserHomeDir()
		if err != nil {
			return nil, fmt.Errorf("known_hosts: %w", err)
		}
		knownHostsPath = filepath.Join(home, ".ssh", "known_hosts")
	}

	if _, err := os.Stat(knownHostsPath); err != nil {
		return nil, fmt.Errorf("known_hosts file not found: %s (use --ssh-insecure to skip host key check)", knownHostsPath)
	}

	return knownhosts.New(knownHostsPath)
}