gateway: install as a background service (launchd/systemd)

`memcode gateway install` writes an OS-native service unit that runs the gateway
in the current project — a launchd LaunchAgent on macOS, a systemd --user unit on
Linux — and prints the one command to start it. `gateway uninstall` removes it.
It writes the unit but doesn't run launchctl/systemctl itself, since activating a
system service is the operator's call. Unit generation is a pure, tested function.

Author: timothyerwin

cmd/gateway_install.go

@@ -0,0 +1,131 @@
+package cmd
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+
+	"github.com/spf13/cobra"
+
+	"github.com/memcode-ai/memcode/internal/atomicfile"
+)
+
+// gatewayInstallCmd installs the gateway as a managed background service so it
+// survives logout/reboot instead of living in a foreground terminal. It writes an
+// OS-native unit (launchd on macOS, systemd --user on Linux) that runs
+// `memcode gateway` in the current project, then prints how to start it.
+var gatewayInstallCmd = &cobra.Command{
+	Use:   "install",
+	Short: "Install the gateway as a background service (launchd/systemd)",
+	RunE: func(cmd *cobra.Command, args []string) error {
+		bin, err := os.Executable()
+		if err != nil {
+			return fmt.Errorf("locating memcode binary: %w", err)
+		}
+		workDir, err := os.Getwd()
+		if err != nil {
+			return err
+		}
+		home, err := os.UserHomeDir()
+		if err != nil {
+			return err
+		}
+		path, content, start, err := gatewayUnit(runtime.GOOS, home, bin, workDir)
+		if err != nil {
+			return err
+		}
+		if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+			return err
+		}
+		if err := atomicfile.WriteFile(path, []byte(content), 0o644); err != nil {
+			return err
+		}
+		cmd.Printf("Installed gateway service for %s\n", workDir)
+		cmd.Printf("Unit: %s\n", path)
+		cmd.Printf("Start it with:\n  %s\n", start)
+		return nil
+	},
+}
+
+// gatewayUninstallCmd removes the service unit. It doesn't stop a running service
+// (the user unloads it with the printed command); it just deletes the unit.
+var gatewayUninstallCmd = &cobra.Command{
+	Use:   "uninstall",
+	Short: "Remove the installed gateway service unit",
+	RunE: func(cmd *cobra.Command, args []string) error {
+		home, err := os.UserHomeDir()
+		if err != nil {
+			return err
+		}
+		path, _, _, err := gatewayUnit(runtime.GOOS, home, "", "")
+		if err != nil {
+			return err
+		}
+		if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
+			return err
+		}
+		cmd.Printf("Removed %s\n", path)
+		switch runtime.GOOS {
+		case "darwin":
+			cmd.Printf("Stop it (if running) with:\n  launchctl unload %s\n", path)
+		case "linux":
+			cmd.Printf("Stop it (if running) with:\n  systemctl --user disable --now memcode-gateway\n")
+		}
+		return nil
+	},
+}
+
+// gatewayUnit builds the service unit for goos: its file path, contents, and the
+// command to start it. bin/workDir may be empty when only the path is needed
+// (uninstall). Returns an error for an unsupported OS.
+func gatewayUnit(goos, home, bin, workDir string) (path, content, start string, err error) {
+	switch goos {
+	case "darwin":
+		path = filepath.Join(home, "Library", "LaunchAgents", "ai.memcode.gateway.plist")
+		content = fmt.Sprintf(`<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>Label</key><string>ai.memcode.gateway</string>
+	<key>ProgramArguments</key>
+	<array>
+		<string>%s</string>
+		<string>gateway</string>
+	</array>
+	<key>WorkingDirectory</key><string>%s</string>
+	<key>RunAtLoad</key><true/>
+	<key>KeepAlive</key><true/>
+	<key>StandardOutPath</key><string>%s/.memcode/gateway.log</string>
+	<key>StandardErrorPath</key><string>%s/.memcode/gateway.log</string>
+</dict>
+</plist>
+`, bin, workDir, workDir, workDir)
+		start = "launchctl load " + path
+		return path, content, start, nil
+	case "linux":
+		path = filepath.Join(home, ".config", "systemd", "user", "memcode-gateway.service")
+		content = fmt.Sprintf(`[Unit]
+Description=memcode gateway
+After=network-online.target
+
+[Service]
+ExecStart=%s gateway
+WorkingDirectory=%s
+Restart=always
+RestartSec=5
+
+[Install]
+WantedBy=default.target
+`, bin, workDir)
+		start = "systemctl --user daemon-reload && systemctl --user enable --now memcode-gateway"
+		return path, content, start, nil
+	default:
+		return "", "", "", fmt.Errorf("gateway install is not supported on %s (run `memcode gateway` directly)", goos)
+	}
+}
+
+func init() {
+	gatewayCmd.AddCommand(gatewayInstallCmd)
+	gatewayCmd.AddCommand(gatewayUninstallCmd)
+}

cmd/gateway_install_test.go

@@ -0,0 +1,48 @@
+package cmd
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestGatewayUnitDarwin(t *testing.T) {
+	path, content, start, err := gatewayUnit("darwin", "/Users/tim", "/usr/local/bin/memcode", "/work/proj")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.HasSuffix(path, "Library/LaunchAgents/ai.memcode.gateway.plist") {
+		t.Errorf("path = %q", path)
+	}
+	for _, want := range []string{"/usr/local/bin/memcode", "<string>gateway</string>", "/work/proj", "KeepAlive"} {
+		if !strings.Contains(content, want) {
+			t.Errorf("plist missing %q:\n%s", want, content)
+		}
+	}
+	if !strings.Contains(start, "launchctl load") {
+		t.Errorf("start cmd = %q", start)
+	}
+}
+
+func TestGatewayUnitLinux(t *testing.T) {
+	path, content, start, err := gatewayUnit("linux", "/home/tim", "/usr/bin/memcode", "/work/proj")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.HasSuffix(path, ".config/systemd/user/memcode-gateway.service") {
+		t.Errorf("path = %q", path)
+	}
+	for _, want := range []string{"ExecStart=/usr/bin/memcode gateway", "WorkingDirectory=/work/proj", "Restart=always"} {
+		if !strings.Contains(content, want) {
+			t.Errorf("unit missing %q:\n%s", want, content)
+		}
+	}
+	if !strings.Contains(start, "systemctl --user") {
+		t.Errorf("start cmd = %q", start)
+	}
+}
+
+func TestGatewayUnitUnsupported(t *testing.T) {
+	if _, _, _, err := gatewayUnit("plan9", "/home/tim", "/bin/memcode", "/work"); err == nil {
+		t.Error("an unsupported OS must return an error")
+	}
+}