package cli

import (
	"context"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"text/tabwriter"

	"banger/internal/buildinfo"
	"banger/internal/installmeta"
	"banger/internal/model"
	"banger/internal/paths"
	"banger/internal/system"

	"github.com/spf13/cobra"
)

const (
	systemBangerBin      = "/usr/local/bin/banger"
	systemBangerdBin     = "/usr/local/bin/bangerd"
	systemCompanionDir   = "/usr/local/lib/banger"
	systemCompanionAgent = systemCompanionDir + "/banger-vsock-agent"
	systemdUserUnitPath  = "/etc/systemd/system/" + installmeta.DefaultService
	systemdRootUnitPath  = "/etc/systemd/system/" + installmeta.DefaultRootHelperService
	systemCoverDirEnv    = "BANGER_SYSTEM_GOCOVERDIR"
	rootCoverDirEnv      = "BANGER_ROOT_HELPER_GOCOVERDIR"
)

func (d *deps) newSystemCommand() *cobra.Command {
	var owner string
	var purge bool
	cmd := &cobra.Command{
		Use:   "system",
		Short: "Install banger's owner-daemon and root-helper systemd units",
		Long: strings.TrimSpace(`
Banger ships as two services: an owner-user daemon for
orchestration and a narrow root helper for bridge/tap, NAT, and
Firecracker launch. 'banger system' installs, restarts, inspects,
and removes them.

First-run flow (must be run as root):

  sudo banger system install --owner $USER     install both services
  banger system status                         confirm they're up
  banger doctor                                check host readiness

After 'install', the owner user can run 'banger ...' day to day
without sudo. Subsequent invocations:

  sudo banger system restart                   bounce both services
  sudo banger system uninstall                 remove services + binaries
  sudo banger system uninstall --purge         also delete /var/lib/banger

See docs/privileges.md for the full trust model.
`),
		Example: strings.TrimSpace(`
  sudo banger system install --owner alice
  banger system status
  sudo banger system uninstall --purge
`),
		RunE: helpNoArgs,
	}
	installCmd := &cobra.Command{
		Use:   "install",
		Short: "Install or refresh the owner daemon and root helper",
		Args:  noArgsUsage("usage: banger system install [--owner USER]"),
		RunE: func(cmd *cobra.Command, args []string) error {
			return d.runSystemInstall(cmd.Context(), cmd.OutOrStdout(), owner)
		},
	}
	installCmd.Flags().StringVar(&owner, "owner", "", "login user who will operate banger day-to-day")

	statusCmd := &cobra.Command{
		Use:   "status",
		Short: "Show owner-daemon and root-helper status",
		Args:  noArgsUsage("usage: banger system status"),
		RunE: func(cmd *cobra.Command, args []string) error {
			return d.runSystemStatus(cmd.Context(), cmd.OutOrStdout())
		},
	}

	restartCmd := &cobra.Command{
		Use:   "restart",
		Short: "Restart the installed banger services",
		Args:  noArgsUsage("usage: banger system restart"),
		RunE: func(cmd *cobra.Command, args []string) error {
			if err := requireRoot(); err != nil {
				return err
			}
			if err := d.runSystemctl(cmd.Context(), "restart", installmeta.DefaultRootHelperService); err != nil {
				return err
			}
			if err := d.runSystemctl(cmd.Context(), "restart", installmeta.DefaultService); err != nil {
				return err
			}
			if err := d.waitForDaemonReady(cmd.Context(), paths.ResolveSystem().SocketPath); err != nil {
				return err
			}
			_, err := fmt.Fprintln(cmd.OutOrStdout(), "restarted")
			return err
		},
	}

	uninstallCmd := &cobra.Command{
		Use:   "uninstall",
		Short: "Remove the installed banger services",
		Args:  noArgsUsage("usage: banger system uninstall [--purge]"),
		RunE: func(cmd *cobra.Command, args []string) error {
			return d.runSystemUninstall(cmd.Context(), cmd.OutOrStdout(), purge)
		},
	}
	uninstallCmd.Flags().BoolVar(&purge, "purge", false, "also delete system-owned banger state and cache")

	cmd.AddCommand(installCmd, statusCmd, restartCmd, uninstallCmd)
	return cmd
}

func (d *deps) runSystemInstall(ctx context.Context, out io.Writer, ownerFlag string) error {
	if err := requireRoot(); err != nil {
		return err
	}
	meta, err := resolveInstallOwner(ownerFlag)
	if err != nil {
		return err
	}
	info := buildinfo.Current()
	meta.Version = info.Version
	meta.Commit = info.Commit
	meta.BuiltAt = info.BuiltAt
	meta.InstalledAt = model.Now()

	bangerBin, err := paths.BangerPath()
	if err != nil {
		return err
	}
	bangerdBin, err := paths.BangerdPath()
	if err != nil {
		return err
	}
	agentBin, err := paths.CompanionBinaryPath("banger-vsock-agent")
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(systemBangerBin), 0o755); err != nil {
		return err
	}
	if err := os.MkdirAll(systemCompanionDir, 0o755); err != nil {
		return err
	}
	if err := installFile(bangerBin, systemBangerBin, 0o755); err != nil {
		return err
	}
	if err := installFile(bangerdBin, systemBangerdBin, 0o755); err != nil {
		return err
	}
	if err := installFile(agentBin, systemCompanionAgent, 0o755); err != nil {
		return err
	}
	if err := installmeta.Save(installmeta.DefaultPath, meta); err != nil {
		return err
	}
	if err := paths.EnsureSystem(paths.ResolveSystem()); err != nil {
		return err
	}
	if err := os.WriteFile(systemdRootUnitPath, []byte(renderRootHelperSystemdUnit()), 0o644); err != nil {
		return err
	}
	if err := os.WriteFile(systemdUserUnitPath, []byte(renderSystemdUnit(meta)), 0o644); err != nil {
		return err
	}
	if err := d.runSystemctl(ctx, "daemon-reload"); err != nil {
		return err
	}
	if err := d.runSystemctl(ctx, "enable", installmeta.DefaultRootHelperService); err != nil {
		return err
	}
	if err := d.runSystemctl(ctx, "enable", installmeta.DefaultService); err != nil {
		return err
	}
	if err := d.runSystemctl(ctx, "restart", installmeta.DefaultRootHelperService); err != nil {
		return err
	}
	if err := d.runSystemctl(ctx, "restart", installmeta.DefaultService); err != nil {
		return err
	}
	if err := d.waitForDaemonReady(ctx, installmeta.DefaultSocketPath); err != nil {
		return err
	}
	if _, err := fmt.Fprintln(out, "installed"); err != nil {
		return err
	}
	w := tabwriter.NewWriter(out, 0, 8, 2, ' ', 0)
	fmt.Fprintf(w, "owner\t%s\n", meta.OwnerUser)
	fmt.Fprintf(w, "socket\t%s\n", installmeta.DefaultSocketPath)
	fmt.Fprintf(w, "helper_socket\t%s\n", installmeta.DefaultRootHelperSocketPath)
	fmt.Fprintf(w, "service\t%s\n", installmeta.DefaultService)
	fmt.Fprintf(w, "helper_service\t%s\n", installmeta.DefaultRootHelperService)
	return w.Flush()
}

func (d *deps) runSystemStatus(ctx context.Context, out io.Writer) error {
	layout := paths.ResolveSystem()
	active := d.systemctlQuery(ctx, "is-active", installmeta.DefaultService)
	if active == "" {
		active = "unknown"
	}
	enabled := d.systemctlQuery(ctx, "is-enabled", installmeta.DefaultService)
	if enabled == "" {
		enabled = "unknown"
	}
	helperActive := d.systemctlQuery(ctx, "is-active", installmeta.DefaultRootHelperService)
	if helperActive == "" {
		helperActive = "unknown"
	}
	helperEnabled := d.systemctlQuery(ctx, "is-enabled", installmeta.DefaultRootHelperService)
	if helperEnabled == "" {
		helperEnabled = "unknown"
	}
	w := tabwriter.NewWriter(out, 0, 8, 2, ' ', 0)
	fmt.Fprintf(w, "service\t%s\n", installmeta.DefaultService)
	fmt.Fprintf(w, "enabled\t%s\n", enabled)
	fmt.Fprintf(w, "active\t%s\n", active)
	fmt.Fprintf(w, "helper_service\t%s\n", installmeta.DefaultRootHelperService)
	fmt.Fprintf(w, "helper_enabled\t%s\n", helperEnabled)
	fmt.Fprintf(w, "helper_active\t%s\n", helperActive)
	fmt.Fprintf(w, "socket\t%s\n", layout.SocketPath)
	fmt.Fprintf(w, "helper_socket\t%s\n", installmeta.DefaultRootHelperSocketPath)
	fmt.Fprintf(w, "log\tjournalctl -u %s -u %s\n", installmeta.DefaultService, installmeta.DefaultRootHelperService)
	if ping, err := d.daemonPing(ctx, layout.SocketPath); err == nil {
		info := buildinfo.Normalize(ping.Version, ping.Commit, ping.BuiltAt)
		fmt.Fprintf(w, "pid\t%d\n", ping.PID)
		fmt.Fprintf(w, "version\t%s\n", info.Version)
		if info.Commit != "" {
			fmt.Fprintf(w, "commit\t%s\n", info.Commit)
		}
		if info.BuiltAt != "" {
			fmt.Fprintf(w, "built_at\t%s\n", info.BuiltAt)
		}
	}
	return w.Flush()
}

func (d *deps) runSystemUninstall(ctx context.Context, out io.Writer, purge bool) error {
	if err := requireRoot(); err != nil {
		return err
	}
	_ = d.runSystemctl(ctx, "disable", "--now", installmeta.DefaultService, installmeta.DefaultRootHelperService)
	_ = os.Remove(systemdUserUnitPath)
	_ = os.Remove(systemdRootUnitPath)
	_ = os.Remove(installmeta.DefaultPath)
	_ = os.Remove(installmeta.DefaultDir)
	_ = d.runSystemctl(ctx, "daemon-reload")
	_ = os.Remove(systemBangerdBin)
	_ = os.Remove(systemBangerBin)
	_ = os.RemoveAll(systemCompanionDir)
	if purge {
		_ = os.RemoveAll(paths.ResolveSystem().StateDir)
		_ = os.RemoveAll(paths.ResolveSystem().CacheDir)
		_ = os.RemoveAll(paths.ResolveSystem().RuntimeDir)
	}
	msg := "uninstalled"
	if purge {
		msg += " (purged state)"
	}
	_, err := fmt.Fprintln(out, msg)
	return err
}

func resolveInstallOwner(ownerFlag string) (installmeta.Metadata, error) {
	owner := strings.TrimSpace(ownerFlag)
	if owner == "" {
		owner = strings.TrimSpace(os.Getenv("SUDO_USER"))
	}
	if owner == "" {
		return installmeta.Metadata{}, errors.New("owner is required; pass --owner USER when installing without sudo")
	}
	if owner == "root" {
		return installmeta.Metadata{}, errors.New("refusing to install with root as the banger owner")
	}
	return installmeta.LookupOwner(owner)
}

func renderSystemdUnit(meta installmeta.Metadata) string {
	lines := []string{
		"[Unit]",
		"Description=banger daemon",
		"After=network-online.target",
		"Wants=network-online.target " + installmeta.DefaultRootHelperService,
		"After=" + installmeta.DefaultRootHelperService,
		"Requires=" + installmeta.DefaultRootHelperService,
		"",
		"[Service]",
		"Type=simple",
		"User=" + meta.OwnerUser,
		"ExecStart=" + systemBangerdBin + " --system",
		"Restart=on-failure",
		"RestartSec=1s",
		// KillMode=process: only signal the main PID on stop/restart.
		// The default (control-group) sends SIGKILL to every process in
		// the unit's cgroup, including descendants — and during `banger
		// update` we restart this unit, which would terminate any
		// in-flight subprocesses spawned by the daemon. The daemon
		// shuts its own children down explicitly when needed.
		"KillMode=process",
		"Environment=PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
		"Environment=TMPDIR=/run/banger",
		"UMask=0077",
		"NoNewPrivileges=yes",
		"PrivateMounts=yes",
		"ProtectSystem=strict",
		"ProtectHome=read-only",
		"ProtectControlGroups=yes",
		"ProtectKernelLogs=yes",
		"ProtectKernelModules=yes",
		"ProtectClock=yes",
		"ProtectHostname=yes",
		"RestrictSUIDSGID=yes",
		"LockPersonality=yes",
		"SystemCallArchitectures=native",
		"RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6 AF_NETLINK AF_VSOCK",
		"StateDirectory=banger",
		"StateDirectoryMode=0700",
		"CacheDirectory=banger",
		"CacheDirectoryMode=0700",
		"RuntimeDirectory=banger",
		"RuntimeDirectoryMode=0700",
	}
	if coverDir := strings.TrimSpace(os.Getenv(systemCoverDirEnv)); coverDir != "" {
		lines = append(lines, "Environment=GOCOVERDIR="+systemdQuote(coverDir))
	}
	if home := strings.TrimSpace(meta.OwnerHome); home != "" {
		lines = append(lines, "ReadOnlyPaths="+systemdQuote(home))
	}
	lines = append(lines,
		"",
		"[Install]",
		"WantedBy=multi-user.target",
		"",
	)
	return strings.Join(lines, "\n")
}

func renderRootHelperSystemdUnit() string {
	lines := []string{
		"[Unit]",
		"Description=banger root helper",
		"After=network-online.target",
		"Wants=network-online.target",
		"",
		"[Service]",
		"Type=simple",
		"ExecStart=" + systemBangerdBin + " --root-helper",
		"Restart=on-failure",
		"RestartSec=1s",
		// KillMode=process is load-bearing: the helper unit's cgroup is
		// where every banger-launched firecracker process lives (see
		// validateFirecrackerPID). Without this, `systemctl restart
		// bangerd-root.service` — which `banger update` runs — would
		// SIGKILL every in-flight VM along with the helper because
		// systemd's default KillMode=control-group nukes the whole cgroup.
		// With process mode, only the helper PID is signaled; firecracker
		// children survive, the new helper instance re-attaches via the
		// helper RPC, daemon reconcile re-seeds in-memory state, VM keeps
		// running. `banger system uninstall` and the daemon's vm-stop
		// path explicitly stop firecracker processes when actually needed.
		"KillMode=process",
		"Environment=PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
		"Environment=TMPDIR=" + installmeta.DefaultRootHelperRuntimeDir,
		"UMask=0077",
		"NoNewPrivileges=yes",
		"PrivateTmp=yes",
		"PrivateMounts=yes",
		"ProtectSystem=strict",
		"ProtectHome=yes",
		"ProtectControlGroups=yes",
		"ProtectKernelLogs=yes",
		"ProtectKernelModules=yes",
		"ProtectClock=yes",
		"ProtectHostname=yes",
		"RestrictSUIDSGID=yes",
		"LockPersonality=yes",
		"SystemCallArchitectures=native",
		"RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6 AF_NETLINK AF_VSOCK",
		"CapabilityBoundingSet=CAP_CHOWN CAP_DAC_OVERRIDE CAP_FOWNER CAP_KILL CAP_MKNOD CAP_NET_ADMIN CAP_NET_RAW CAP_SETGID CAP_SETUID CAP_SYS_ADMIN CAP_SYS_CHROOT",
		"ReadWritePaths=/var/lib/banger",
		"RuntimeDirectory=banger-root",
		"RuntimeDirectoryMode=0711",
	}
	if coverDir := strings.TrimSpace(os.Getenv(rootCoverDirEnv)); coverDir != "" {
		lines = append(lines, "Environment=GOCOVERDIR="+systemdQuote(coverDir))
	}
	lines = append(lines,
		"",
		"[Install]",
		"WantedBy=multi-user.target",
		"",
	)
	return strings.Join(lines, "\n")
}

func systemdQuote(value string) string {
	return strconv.Quote(strings.TrimSpace(value))
}

func installFile(sourcePath, targetPath string, mode os.FileMode) error {
	if err := os.MkdirAll(filepath.Dir(targetPath), 0o755); err != nil {
		return err
	}
	tempPath := targetPath + ".tmp"
	_ = os.Remove(tempPath)
	if err := system.CopyFilePreferClone(sourcePath, tempPath); err != nil {
		return err
	}
	if err := os.Chmod(tempPath, mode); err != nil {
		_ = os.Remove(tempPath)
		return err
	}
	if err := os.Rename(tempPath, targetPath); err != nil {
		_ = os.Remove(tempPath)
		return err
	}
	return nil
}

func requireRoot() error {
	if os.Geteuid() == 0 {
		return nil
	}
	return errors.New("this command requires root; run it with sudo")
}

func (d *deps) runSystemctl(ctx context.Context, args ...string) error {
	_, err := d.hostCommandOutput(ctx, "systemctl", args...)
	return err
}

func (d *deps) systemctlQuery(ctx context.Context, args ...string) string {
	output, err := d.hostCommandOutput(ctx, "systemctl", args...)
	if err == nil {
		return strings.TrimSpace(string(output))
	}
	msg := strings.TrimSpace(string(output))
	if msg != "" {
		return msg
	}
	msg = strings.TrimSpace(err.Error())
	if idx := strings.LastIndex(msg, ": "); idx >= 0 {
		return strings.TrimSpace(msg[idx+2:])
	}
	return msg
}