// Package ssh builds and runs SSH port-forwarding commands.
package ssh

import (
	"errors"
	"fmt"

	"git.scuroneko.dev/ScuroNeko/est/internal/config"
)

func buildRemoteToLocalString(sourceIP, remoteIP string, sourcePort, remotePort uint16) string {
	if sourceIP == "" {
		sourceIP = "127.0.0.1"
	}
	if remoteIP == "" {
		remoteIP = "127.0.0.1"
	}
	return fmt.Sprintf("%s:%d:%s:%d", sourceIP, sourcePort, remoteIP, remotePort)
}
func buildLocalToRemoteString(sourceIP, remoteIP string, sourcePort, remotePort uint16) string {
	if sourceIP == "" {
		sourceIP = "127.0.0.1"
	}
	if remoteIP == "" {
		remoteIP = "127.0.0.1"
	}
	return fmt.Sprintf("%s:%d:%s:%d", remoteIP, remotePort, sourceIP, sourcePort)
}

var (
	// ErrEmptyHost is returned when a tunnel has no SSH destination.
	ErrEmptyHost = errors.New("empty host")
	// ErrEmptyLocalPort is returned when a tunnel has no local port.
	ErrEmptyLocalPort = errors.New("empty local port")
	// ErrEmptyRemotePort is returned when a tunnel has no remote port.
	ErrEmptyRemotePort = errors.New("empty remote port")
)

func validateArgs(entry config.ProxyEntry) error {
	if entry.Host == "" {
		return ErrEmptyHost
	}
	if entry.LocalPort == 0 {
		return ErrEmptyLocalPort
	}
	if entry.RemotePort == 0 {
		return ErrEmptyRemotePort
	}
	return nil
}
func prepareArgs(configPath string, entry config.ProxyEntry) ([]string, error) {
	if err := validateArgs(entry); err != nil {
		return nil, err
	}
	args := []string{"-N", "-T", "-o", "ExitOnForwardFailure=yes"}
	if configPath != "" {
		args = append(args, "-F", configPath)
	} else if configPath = getConfigOrEmpty(); configPath != "" {
		args = append(args, "-F", configPath)
	}
	if entry.IdentityFile != "" {
		args = append(args, "-i", entry.IdentityFile)
	}
	switch entry.Direction {
	case config.LocalToRemote:
		args = append(args, "-R", buildLocalToRemoteString(entry.LocalIP, entry.RemoteIP, entry.LocalPort, entry.RemotePort))
	case config.RemoteToLocal:
		args = append(args, "-L", buildRemoteToLocalString(entry.LocalIP, entry.RemoteIP, entry.LocalPort, entry.RemotePort))
	default:
		return nil, fmt.Errorf("invalid direction: %v; should be ltr on rtl", entry.Direction)
	}
	if entry.Host != "" {
		args = append(args, entry.Host)
	}
	return args, nil
}