summercms/modules/pier/dispatch_test.go

package pier_test

import (
	"context"
	"encoding/json"
	"errors"
	"io"
	"net/http"
	"strings"
	"sync/atomic"
	"testing"
	"time"

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

type thingInput struct {
	ID    string   `json:"id" path:"id"`
	Tags  []string `json:"tags,omitempty" query:"tag"`
	Title string   `json:"title"`
	Note  string   `json:"note,omitempty"`
}

const invalidBody = `{"message":"The given data was invalid.","errors":{"title":["The title field is required."]}}`

// TestDispatch (D-11, D-13, D-14): a call's path and query fields fill the
// URL and the body is the agent's JSON minus them, without the fields the
// agent omitted (Pitfall 6); a multi-segment value for a single segment is
// refused before dispatch; the outer Authorization and Cookie never reach
// the route while the client address, X-Forwarded-For and Accept-Language
// do; a non-2xx answer is a tool error carrying the route's exact body as
// text and structured content; a 2xx array is wrapped as {"data": [...]};
// an answer above mcp.max_result_bytes is a fixed tool error; the per-call
// timeout cancels a hanging handler.
func TestDispatch(t *testing.T) {
	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()
	var thingHits atomic.Int64
	hangErr := make(chan error, 1)
	echo := func(w http.ResponseWriter, r *http.Request) {
		thingHits.Add(1)
		raw, _ := io.ReadAll(r.Body)
		w.Header().Set("Content-Type", "application/json")
		_ = json.NewEncoder(w).Encode(map[string]any{
			"id":     r.PathValue("id"),
			"tags":   r.URL.Query()["tag"],
			"body":   string(raw),
			"auth":   r.Header.Get("Authorization"),
			"cookie": r.Header.Get("Cookie"),
			"xff":    r.Header.Get("X-Forwarded-For"),
			"lang":   r.Header.Get("Accept-Language"),
			"remote": r.RemoteAddr,
		})
	}
	plugin := routePlugin{id: "test.disp",
		routes: []testRoute{
			{method: http.MethodPost, path: "/disp/things/{id}", mw: []string{"acme.auth"}, h: echo},
			{method: http.MethodPost, path: "/disp/invalid", mw: []string{"acme.auth"}, h: jsonRoute(http.StatusUnprocessableEntity, invalidBody)},
			{method: http.MethodGet, path: "/disp/list", mw: []string{"acme.auth"}, h: jsonRoute(http.StatusOK, `[1,2,3]`)},
			{method: http.MethodGet, path: "/disp/big", mw: []string{"acme.auth"}, h: jsonRoute(http.StatusOK, `"`+strings.Repeat("x", 2048)+`"`)},
			{method: http.MethodGet, path: "/disp/hang", mw: []string{"acme.auth"}, h: func(w http.ResponseWriter, r *http.Request) {
				<-r.Context().Done()
				hangErr <- r.Context().Err()
				w.WriteHeader(http.StatusServiceUnavailable)
			}},
		},
		tools: []pact.MCPTool{
			{Name: "thing", Method: "POST", Path: "/disp/things/{id}", Input: thingInput{}},
			{Name: "invalid", Method: "POST", Path: "/disp/invalid", Input: struct{}{}},
			{Name: "list", Method: "GET", Path: "/disp/list", Input: struct{}{}},
			{Name: "big", Method: "GET", Path: "/disp/big", Input: struct{}{}},
			{Name: "hang", Method: "GET", Path: "/disp/hang", Input: struct{}{}},
		}}
	app := newApp(t, appSpec{mcp: "enabled: false\nmax_result_bytes: 1024\ncall_timeout: 1s\n", guards: []pact.MCPGuard{&fakeGuard{}}})
	in := startInstance(t, app, plugin)
	cs := sdkClient(t, ctx, in.url(), "oas_at_test", clientOpts{headers: map[string]string{
		"Cookie":          "summer_session=outer; summer_admin=outer",
		"X-Forwarded-For": "203.0.113.9",
		"Accept-Language": "pl",
	}})
	call := func(name string, args map[string]any) *mcp.CallToolResult {
		t.Helper()
		res, err := cs.CallTool(ctx, &mcp.CallToolParams{Name: name, Arguments: args})
		if err != nil {
			t.Fatalf("%s: %v", name, err)
		}
		return res
	}

	t.Run("argument split and request shape", func(t *testing.T) {
		res := call("disp_thing", map[string]any{"id": "abc", "tags": []string{"a", "b"}, "title": "T"})
		if res.IsError {
			t.Fatalf("isError: %s", resultText(t, res))
		}
		got := structured(t, res)
		if got["id"] != "abc" || got["body"] != `{"title":"T"}` {
			t.Fatalf("path and body = %v, %v", got["id"], got["body"])
		}
		if tags, _ := got["tags"].([]any); len(tags) != 2 || tags[0] != "a" || tags[1] != "b" {
			t.Fatalf("query tags = %v", got["tags"])
		}
		if got["auth"] != "" || got["cookie"] != "" {
			t.Fatalf("outer credentials reached the route: auth %q cookie %q", got["auth"], got["cookie"])
		}
		if got["xff"] != "203.0.113.9" || got["lang"] != "pl" || !strings.HasPrefix(got["remote"].(string), "127.0.0.1:") {
			t.Fatalf("forwarded request facts = xff %v lang %v remote %v", got["xff"], got["lang"], got["remote"])
		}
		if text := resultText(t, res); !strings.Contains(text, `"id":"abc"`) {
			t.Fatalf("text content = %s", text)
		}
	})

	t.Run("multi-segment value refused before dispatch", func(t *testing.T) {
		before := thingHits.Load()
		res := call("disp_thing", map[string]any{"id": "a/b", "title": "T"})
		if !res.IsError || !strings.Contains(resultText(t, res), "one non-empty path segment") {
			t.Fatalf("a/b = %+v", res)
		}
		res = call("disp_thing", map[string]any{"id": "abc"})
		if !res.IsError || !strings.Contains(resultText(t, res), "invalid arguments") {
			t.Fatalf("missing required title = %+v", res)
		}
		// The reflected schema refuses keys the input struct does not
		// declare (additionalProperties false), so nothing undeclared
		// reaches the route's body.
		res = call("disp_thing", map[string]any{"id": "abc", "title": "T", "user_id": 1})
		if !res.IsError || !strings.Contains(resultText(t, res), "invalid arguments") {
			t.Fatalf("undeclared key = %+v", res)
		}
		if thingHits.Load() != before {
			t.Fatal("a refused call reached the route")
		}
	})

	t.Run("route error is a tool error with its body", func(t *testing.T) {
		res := call("disp_invalid", nil)
		if !res.IsError || resultText(t, res) != invalidBody {
			t.Fatalf("422 = %+v %q", res, resultText(t, res))
		}
		got := structured(t, res)
		if got["message"] != "The given data was invalid." || got["errors"] == nil {
			t.Fatalf("422 structuredContent = %+v", got)
		}
	})

	t.Run("2xx array wrapped as data", func(t *testing.T) {
		res := call("disp_list", nil)
		data, _ := structured(t, res)["data"].([]any)
		if res.IsError || len(data) != 3 || data[0] != 1.0 || resultText(t, res) != "[1,2,3]" {
			t.Fatalf("array = %+v", res)
		}
	})

	t.Run("result above max_result_bytes", func(t *testing.T) {
		res := call("disp_big", nil)
		if !res.IsError || resultText(t, res) != "pier: the route's answer exceeds mcp.max_result_bytes" || strings.Contains(resultText(t, res), "xxxx") {
			t.Fatalf("big = %+v", res)
		}
	})

	t.Run("call timeout cancels the handler", func(t *testing.T) {
		start := time.Now()
		res := call("disp_hang", nil)
		if took := time.Since(start); took > 10*time.Second || took < 900*time.Millisecond {
			t.Fatalf("hang returned after %v, want about the 1s call_timeout", took)
		}
		if !res.IsError {
			t.Fatalf("hang = %+v, want a tool error", res)
		}
		select {
		case err := <-hangErr:
			if !errors.Is(err, context.DeadlineExceeded) {
				t.Fatalf("handler context ended with %v, want the deadline", err)
			}
		case <-time.After(5 * time.Second):
			t.Fatal("the hanging handler never saw its context end")
		}
	})
}