feat: Add PluginPkg types to SDK command package (#127)

- Add PluginError and PluginErrors types for error handling
- Add PluginPkg struct with methods for plugin management
- Add NewPluginPkg constructor for creating plugin packages
- These types are being extracted from privateer core to enable shared functionality between OSS and Enterprise versions

Author: zohayb23

command/types.go

@@ -0,0 +1,83 @@
+package command
+
+import (
+	"fmt"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+
+	hcplugin "github.com/hashicorp/go-plugin"
+	"github.com/spf13/viper"
+)
+
+// PluginError retains an error object and the name of the pack that generated it
+type PluginError struct {
+	Plugin string
+	Err    error
+}
+
+// PluginErrors holds a list of errors and an Error() method
+// so it adheres to the standard Error interface
+type PluginErrors struct {
+	Errors []PluginError
+}
+
+func (e *PluginErrors) Error() string {
+	return fmt.Sprintf("Service Pack Errors: %v", e.Errors)
+}
+
+type PluginPkg struct {
+	Name          string
+	Path          string
+	ServiceTarget string
+	Command       *exec.Cmd
+	Result        string
+
+	Available  bool
+	Requested  bool
+	Successful bool
+	Error      error
+}
+
+func (p *PluginPkg) getBinary() (binaryName string, err error) {
+	p.Name = filepath.Base(strings.ToLower(p.Name)) // in some cases a filepath may arrive here instead of the base name; overwrite if so
+	if runtime.GOOS == "windows" && !strings.HasSuffix(p.Name, ".exe") {
+		p.Name = fmt.Sprintf("%s.exe", p.Name)
+	}
+	plugins, _ := hcplugin.Discover(p.Name, viper.GetString("binaries-path"))
+	if len(plugins) != 1 {
+		err = fmt.Errorf("failed to locate requested plugin '%s' at path '%s'", p.Name, viper.GetString("binaries-path"))
+		return
+	}
+	binaryName = plugins[0]
+
+	return
+}
+
+func (p *PluginPkg) queueCmd() {
+	cmd := exec.Command(p.Path)
+	flags := []string{
+		fmt.Sprintf("--config=%s", viper.GetString("config")),
+		fmt.Sprintf("--loglevel=%s", viper.GetString("loglevel")),
+		fmt.Sprintf("--service=%s", p.ServiceTarget),
+	}
+	for _, flag := range flags {
+		cmd.Args = append(cmd.Args, flag)
+		p.Command = cmd
+	}
+}
+
+func NewPluginPkg(pluginName string, serviceName string) *PluginPkg {
+	plugin := &PluginPkg{
+		Name: pluginName,
+	}
+	path, err := plugin.getBinary()
+	if err != nil {
+		plugin.Error = err
+	}
+	plugin.Path = path
+	plugin.ServiceTarget = serviceName
+	plugin.queueCmd()
+	return plugin
+}