summercms/modules/pier/mcp_seam_test.go

package pier_test

import (
	"context"
	"encoding/json"
	"io"
	"net/http"
	"net/http/httptest"
	"slices"
	"testing"
	"time"

	"git.golem15.com/golem15/summercms/modules/bouncer"
	"git.golem15.com/golem15/summercms/modules/pact"
	"git.golem15.com/golem15/summercms/modules/pier"
	"git.golem15.com/golem15/summercms/modules/wristband"
	"github.com/modelcontextprotocol/go-sdk/mcp"
)

// fixedMCPScopes is the MCP flavour's resolved list when ScopesSupported is empty.
var fixedMCPScopes = []string{"read", "write", "ai", "offline_access", "backend"}

// advertisedVerifier is the fake OAuth verifier plus a declared scope list.
type advertisedVerifier struct {
	acmeVerifier
	scopes []string
}

func (v advertisedVerifier) MCPScopesSupported() []string {
	return append([]string(nil), v.scopes...)
}

// TestMCPSeam is the tracer for one advertised scope list and one MCP call
// on the dispatch context: empty MCP metadata includes backend, a non-empty
// list is used as given, pier copies a verifier's advertised scopes (and
// keeps PRMScopes otherwise), and one frontend tool call observes MCPCall
// beside the bouncer dispatch marker.
func TestMCPSeam(t *testing.T) {
	opts := wristband.DefaultOptions()
	opts.Issuer = "https://issuer.example.test"
	opts.Resource = "https://resource.example.test/mcp"
	opts.ScopesSupported = nil
	empty := wristband.NewServer(opts)
	if got := metadataScopes(t, empty); !slices.Equal(got, fixedMCPScopes) {
		t.Fatalf("empty MCP scopes_supported = %v", got)
	}

	declared := append(append([]string(nil), fixedMCPScopes...), "acme:read")
	opts.ScopesSupported = declared
	listed := wristband.NewServer(opts)
	if got := metadataScopes(t, listed); !slices.Equal(got, declared) {
		t.Fatalf("declared MCP scopes_supported = %v", got)
	}

	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()

	advertised := append(append([]string(nil), fixedMCPScopes...), "acme:read")
	app := newApp(t, appSpec{
		verifier: advertisedVerifier{scopes: advertised},
		guards:   []pact.MCPGuard{&acmeGuard{}},
	})
	plugin := routePlugin{
		id: "test.acme",
		routes: []testRoute{{
			method: http.MethodPost,
			path:   "/acme/seam",
			mw:     []string{"acme.auth"},
			h:      seamHandler,
		}},
		tools: []pact.MCPTool{{
			Name:   "seam",
			Method: http.MethodPost,
			Path:   "/acme/seam",
			Input:  struct{}{},
		}},
	}
	in := startInstance(t, app, plugin)
	if got := prmScopes(t, in.srv.URL); !slices.Equal(got, advertised) {
		t.Fatalf("advertised PRM scopes = %v, want %v", got, advertised)
	}

	cs := sdkClient(t, ctx, in.url(), "oas_at_test", clientOpts{})
	res, err := cs.CallTool(ctx, &mcp.CallToolParams{Name: "acme_seam"})
	if err != nil {
		t.Fatalf("tools/call: %v", err)
	}
	if res.IsError {
		t.Fatalf("tools/call isError: %+v", res.Content)
	}
	body := structured(t, res)
	if body["ok"] != true || body["tool"] != "acme_seam" || body["dispatched"] != true || body["guard"] != "acme" {
		t.Fatalf("handler saw %+v, want MCPCall tool acme_seam and a dispatch", body)
	}
	if sid, _ := body["session"].(string); sid == "" || sid == "ephemeral" {
		t.Fatalf("session = %q, want the stateful session id", sid)
	}

	plain := startInstance(t, newApp(t, appSpec{
		verifier: acmeVerifier{},
		guards:   []pact.MCPGuard{&acmeGuard{}},
	}), plugin)
	if got := prmScopes(t, plain.srv.URL); !slices.Equal(got, pier.PRMScopes) {
		t.Fatalf("PRM without MCPAdvertisedScopes = %v, want %v", got, pier.PRMScopes)
	}
}

func metadataScopes(t *testing.T, srv *wristband.Server) []string {
	t.Helper()
	rec := httptest.NewRecorder()
	srv.Metadata(rec, httptest.NewRequest(http.MethodGet, "/.well-known/oauth-authorization-server", nil))
	if rec.Code != http.StatusOK {
		t.Fatalf("metadata status = %d", rec.Code)
	}
	var doc struct {
		Scopes []string `json:"scopes_supported"`
	}
	if err := json.Unmarshal(rec.Body.Bytes(), &doc); err != nil {
		t.Fatal(err)
	}
	return doc.Scopes
}

func prmScopes(t *testing.T, base string) []string {
	t.Helper()
	resp, err := http.Get(base + "/.well-known/oauth-protected-resource")
	if err != nil {
		t.Fatal(err)
	}
	defer resp.Body.Close()
	raw, _ := io.ReadAll(resp.Body)
	if resp.StatusCode != http.StatusOK {
		t.Fatalf("PRM status = %d body %s", resp.StatusCode, raw)
	}
	var doc struct {
		Scopes []string `json:"scopes_supported"`
	}
	if err := json.Unmarshal(raw, &doc); err != nil {
		t.Fatal(err)
	}
	return doc.Scopes
}

func seamHandler(w http.ResponseWriter, r *http.Request) {
	call, ok := pact.MCPCallFrom(r.Context())
	_, dispatched := bouncer.Dispatched(r.Context(), "acme")
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(map[string]any{
		"ok":         ok,
		"tool":       call.Tool,
		"session":    call.SessionID,
		"guard":      call.Subject.Guard,
		"dispatched": dispatched,
	})
}