Add plugins 'add' command (#219)

* Add plugins 'add' command

Implement 'mcpd config plugins add' command to add new plugins to a category.

Author: peteski22

cmd/config/plugins/add.go

@@ -2,24 +2,167 @@ package plugins
 
 import (
 	"fmt"
+	"maps"
+	"slices"
+	"strings"
 
 	"github.com/spf13/cobra"
 
-	"github.com/mozilla-ai/mcpd/v2/internal/cmd"
-	"github.com/mozilla-ai/mcpd/v2/internal/cmd/options"
+	internalcmd "github.com/mozilla-ai/mcpd/v2/internal/cmd"
+	cmdopts "github.com/mozilla-ai/mcpd/v2/internal/cmd/options"
+	"github.com/mozilla-ai/mcpd/v2/internal/config"
 )
 
-// NewAddCmd creates the add command for plugins.
-// TODO: Implement in a future PR.
-func NewAddCmd(baseCmd *cmd.BaseCmd, opt ...options.CmdOption) (*cobra.Command, error) {
+const (
+	flagFlow       = "flow"
+	flagRequired   = "required"
+	flagCommitHash = "commit-hash"
+)
+
+// AddCmd represents the command for adding a new plugin entry.
+// NOTE: Use NewAddCmd to create instances of AddCmd.
+type AddCmd struct {
+	*internalcmd.BaseCmd
+
+	// cfgLoader is used to load the configuration.
+	cfgLoader config.Loader
+
+	// category is the category to add the plugin to.
+	category config.Category
+
+	// flows is the list of flows.
+	flows []string
+
+	// required indicates if the plugin is required.
+	required bool
+
+	// commitHash is the optional commit hash for version validation.
+	commitHash string
+}
+
+// NewAddCmd creates a new add command for plugin entries.
+func NewAddCmd(baseCmd *internalcmd.BaseCmd, opt ...cmdopts.CmdOption) (*cobra.Command, error) {
+	opts, err := cmdopts.NewOptions(opt...)
+	if err != nil {
+		return nil, err
+	}
+
+	c := &AddCmd{
+		BaseCmd:   baseCmd,
+		cfgLoader: opts.ConfigLoader,
+	}
+
 	cobraCmd := &cobra.Command{
-		Use:   "add",
+		Use:   "add <plugin-name>",
 		Short: "Add a new plugin entry to a category",
-		Long:  "Add a new plugin entry to a category. The configuration is saved automatically.",
-		RunE: func(cmd *cobra.Command, args []string) error {
-			return fmt.Errorf("not yet implemented")
-		},
+		Long: `Add a new plugin entry to a category. The configuration is saved automatically.
+
+The plugin name must exactly match the name of the plugin binary file.
+
+This command creates new plugin entries only. If a plugin with the same name already exists
+in the category, the command fails with an error. To update an existing plugin, use the 'set' command.`,
+		Example: `  # Add new plugin with all fields
+  mcpd config plugins add jwt-auth --category=authentication --flow=request --required
+
+  # Add plugin with multiple flows
+  mcpd config plugins add metrics --category=observability --flow=request --flow=response --commit-hash=abc123
+
+  # Add without required flag (defaults to false)
+  mcpd config plugins add rbac --category=authorization --flow=response`,
+		RunE: c.run,
+		Args: cobra.ExactArgs(1), // plugin-name
 	}
 
+	allowedCategories := config.OrderedCategories()
+	cobraCmd.Flags().Var(
+		&c.category,
+		flagCategory,
+		fmt.Sprintf("Specify the category (one of: %s)", allowedCategories.String()),
+	)
+	_ = cobraCmd.MarkFlagRequired(flagCategory)
+
+	cobraCmd.Flags().StringArrayVar(
+		&c.flows,
+		flagFlow,
+		nil,
+		fmt.Sprintf(
+			"Flow during which, the plugin should execute (%s) (can be repeated)",
+			strings.Join(config.OrderedFlowNames(), ", "),
+		),
+	)
+	_ = cobraCmd.MarkFlagRequired(flagFlow)
+
+	cobraCmd.Flags().BoolVar(
+		&c.required,
+		flagRequired,
+		false,
+		"Optional, mark plugin as required",
+	)
+
+	cobraCmd.Flags().StringVar(
+		&c.commitHash,
+		flagCommitHash,
+		"",
+		"Optional, commit hash for runtime version validation",
+	)
+
 	return cobraCmd, nil
 }
+
+func (c *AddCmd) run(cmd *cobra.Command, args []string) error {
+	pluginName := strings.TrimSpace(args[0])
+	if pluginName == "" {
+		return fmt.Errorf("plugin name cannot be empty")
+	}
+
+	cfg, err := c.LoadConfig(c.cfgLoader)
+	if err != nil {
+		return err
+	}
+
+	if _, exists := cfg.Plugin(c.category, pluginName); exists {
+		return fmt.Errorf(
+			"plugin '%s' already exists in category '%s'\n\n"+
+				"To update an existing plugin, use: mcpd config plugins set %s --category=%s [flags]",
+			pluginName,
+			c.category,
+			pluginName,
+			c.category,
+		)
+	}
+
+	flows := config.ParseFlowsDistinct(c.flows)
+	if len(flows) == 0 {
+		return fmt.Errorf(
+			"at least one valid flow is required (%s)",
+			strings.Join(config.OrderedFlowNames(), ", "),
+		)
+	}
+
+	entry := config.PluginEntry{
+		Name:  pluginName,
+		Flows: slices.Sorted(maps.Keys(flows)),
+	}
+
+	// Set optional fields only if they were provided.
+	if cmd.Flags().Changed(flagRequired) {
+		entry.Required = &c.required
+	}
+
+	if c.commitHash != "" {
+		entry.CommitHash = &c.commitHash
+	}
+
+	if _, err := cfg.UpsertPlugin(c.category, entry); err != nil {
+		return err
+	}
+
+	_, _ = fmt.Fprintf(
+		cmd.OutOrStdout(),
+		"✓ Plugin '%s' added to category '%s'\n",
+		pluginName,
+		c.category,
+	)
+
+	return nil
+}