package app

import (
	"fmt"
	"os"
	"os/exec"
	"strings"
	"time"
)

func transportWrapExecWithNetns(client TransportClient, command string) string {
	cmd := strings.TrimSpace(command)
	if cmd == "" || !transportNetnsEnabled(client) {
		return cmd
	}
	ns := transportNetnsName(client)
	if ns == "" {
		return cmd
	}
	name, args, err := transportNetnsExecCommand(client, ns, "/bin/sh", "-lc", cmd)
	if err != nil {
		return cmd
	}
	return shellJoinArgs(append([]string{name}, args...))
}

func transportResolveNetnsNsenterBin(client TransportClient) string {
	if explicit := strings.TrimSpace(transportConfigString(client.Config, "netns_nsenter_bin")); explicit != "" {
		return explicit
	}
	if p, err := exec.LookPath("nsenter"); err == nil {
		return strings.TrimSpace(p)
	}
	candidates := []string{
		"/usr/bin/nsenter",
		"/bin/nsenter",
		"/usr/sbin/nsenter",
		"/sbin/nsenter",
	}
	for _, cand := range candidates {
		if _, err := os.Stat(cand); err == nil {
			return cand
		}
	}
	return ""
}

func transportNetnsExecCommand(client TransportClient, ns string, command ...string) (string, []string, error) {
	if strings.TrimSpace(ns) == "" {
		return "", nil, fmt.Errorf("netns name is empty")
	}
	if len(command) == 0 {
		return "", nil, fmt.Errorf("netns command is empty")
	}
	mode := strings.ToLower(strings.TrimSpace(transportConfigString(client.Config, "netns_exec_mode")))
	useNsenter := false
	switch mode {
	case "ip", "ip-netns", "ip_netns":
		useNsenter = false
	case "nsenter":
		useNsenter = true
	case "", "auto":
		useNsenter = true
	default:
		useNsenter = true
	}
	if useNsenter {
		if bin := transportResolveNetnsNsenterBin(client); bin != "" {
			args := []string{"--net=/var/run/netns/" + ns, "--"}
			args = append(args, command...)
			return bin, args, nil
		}
	}
	ipBin := strings.TrimSpace(transportConfigString(client.Config, "netns_ip_bin"))
	if ipBin == "" {
		ipBin = "ip"
	}
	args := []string{"netns", "exec", ns}
	args = append(args, command...)
	return ipBin, args, nil
}

func transportRunInNetnsMust(timeout time.Duration, client TransportClient, ns string, command ...string) error {
	name, args, err := transportNetnsExecCommand(client, ns, command...)
	if err != nil {
		return err
	}
	return transportRunMust(timeout, name, args...)
}

func transportRunInNetnsSoft(timeout time.Duration, client TransportClient, ns string, command ...string) error {
	name, args, err := transportNetnsExecCommand(client, ns, command...)
	if err != nil {
		return err
	}
	return transportRunSoft(timeout, name, args...)
}