chore: import upstream snapshot with attribution

cmd/micro/a2a/a2a.go

@@ -0,0 +1,86 @@
+// Package a2a provides the 'micro a2a' command for the Agent2Agent gateway.
+package a2a
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/urfave/cli/v2"
+	"go-micro.dev/v6/cmd"
+	"go-micro.dev/v6/gateway/a2a"
+	"go-micro.dev/v6/registry"
+)
+
+func init() {
+	cmd.Register(&cli.Command{
+		Name:  "a2a",
+		Usage: "Agent2Agent (A2A) protocol gateway",
+		Description: `Expose registered agents over the A2A protocol so other agents can
+discover and call them.
+
+Examples:
+  # Serve the A2A gateway over HTTP
+  micro a2a serve --address :4000 --base_url https://agents.example.com
+
+  # List agents and their A2A card URLs
+  micro a2a list
+
+Agents are discovered from the registry (the ones advertising type=agent);
+an Agent Card is generated for each from its registry metadata, and
+incoming A2A tasks are translated to the agent's Agent.Chat RPC. This is
+the agent-side analog of 'micro mcp', which exposes services as tools.`,
+		Subcommands: []*cli.Command{
+			{
+				Name:  "serve",
+				Usage: "Start the A2A gateway",
+				Flags: []cli.Flag{
+					&cli.StringFlag{Name: "address", Usage: "Address to listen on", Value: ":4000"},
+					&cli.StringFlag{Name: "base_url", Usage: "Public base URL for Agent Cards"},
+				},
+				Action: func(c *cli.Context) error {
+					return a2a.Serve(a2a.Options{
+						Registry: registry.DefaultRegistry,
+						Address:  c.String("address"),
+						BaseURL:  c.String("base_url"),
+					})
+				},
+			},
+			{
+				Name:   "list",
+				Usage:  "List agents and their A2A card URLs",
+				Flags:  []cli.Flag{&cli.StringFlag{Name: "base_url", Usage: "Public base URL for Agent Cards", Value: "http://localhost:4000"}},
+				Action: listAgents,
+			},
+		},
+	})
+}
+
+func listAgents(c *cli.Context) error {
+	base := strings.TrimRight(c.String("base_url"), "/")
+	svcs, err := registry.ListServices()
+	if err != nil {
+		return err
+	}
+	found := false
+	for _, s := range svcs {
+		recs, err := registry.GetService(s.Name)
+		if err != nil || len(recs) == 0 {
+			continue
+		}
+		meta := recs[0].Metadata
+		isAgent := meta != nil && meta["type"] == "agent"
+		if !isAgent && len(recs[0].Nodes) > 0 {
+			nm := recs[0].Nodes[0].Metadata
+			isAgent = nm != nil && nm["type"] == "agent"
+		}
+		if !isAgent {
+			continue
+		}
+		found = true
+		fmt.Printf("  \033[36m◆\033[0m %-20s %s/agents/%s\n", s.Name, base, s.Name)
+	}
+	if !found {
+		fmt.Println("  No agents registered.")
+	}
+	return nil
+}