From ab4b6a99d7828154fc803870bbb2f18835d6470b Mon Sep 17 00:00:00 2001
From: Ethan Lee <ethanalee@google.com>
Date: Wed, 11 Mar 2026 21:00:08 +0000
Subject: internal/api: implement module metadata endpoint

Change-Id: Id6b8686012803c88c9b7ea71e4b1c0058b7967b0
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/754861
Auto-Submit: Ethan Lee <ethanalee@google.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
kokoro-CI: kokoro <noreply+kokoro@google.com>
---
 internal/api/api.go      | 54 ++++++++++++++++++++++++++++++++
 internal/api/api_test.go | 81 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 135 insertions(+)

(limited to 'internal/api')

diff --git a/internal/api/api.go b/internal/api/api.go
index d27e49b0..97c3b5a1 100644
--- a/internal/api/api.go
+++ b/internal/api/api.go
@@ -158,6 +158,60 @@ func ServePackage(w http.ResponseWriter, r *http.Request, ds internal.DataSource
 	return serveJSON(w, http.StatusOK, resp)
 }
 
+// ServeModule handles requests for the v1 module metadata endpoint.
+func ServeModule(w http.ResponseWriter, r *http.Request, ds internal.DataSource) (err error) {
+	defer derrors.Wrap(&err, "ServeModule")
+
+	modulePath := strings.TrimPrefix(r.URL.Path, "/v1/module/")
+	if modulePath == "" {
+		return serveErrorJSON(w, http.StatusBadRequest, "missing module path", nil)
+	}
+
+	var params ModuleParams
+	if err := ParseParams(r.URL.Query(), &params); err != nil {
+		return serveErrorJSON(w, http.StatusBadRequest, err.Error(), nil)
+	}
+
+	requestedVersion := params.Version
+	if requestedVersion == "" {
+		requestedVersion = version.Latest
+	}
+
+	// For modules, we can use GetUnitMeta on the module path.
+	um, err := ds.GetUnitMeta(r.Context(), modulePath, modulePath, requestedVersion)
+	if err != nil {
+		if errors.Is(err, derrors.NotFound) {
+			return serveErrorJSON(w, http.StatusNotFound, err.Error(), nil)
+		}
+		return err
+	}
+
+	resp := Module{
+		Path:              um.ModulePath,
+		Version:           um.Version,
+		IsStandardLibrary: stdlib.Contains(um.ModulePath),
+		IsRedistributable: um.IsRedistributable,
+	}
+	// RepoURL needs to be extracted from source info if available
+	if um.SourceInfo != nil {
+		resp.RepoURL = um.SourceInfo.RepoURL()
+	}
+
+	if params.Readme {
+		readme, err := ds.GetModuleReadme(r.Context(), um.ModulePath, um.Version)
+		if err == nil && readme != nil {
+			resp.Readme = &Readme{
+				Filepath: readme.Filepath,
+				Contents: readme.Contents,
+			}
+		}
+	}
+
+	// Future: handle licenses param.
+
+	return serveJSON(w, http.StatusOK, resp)
+}
+
 // needsResolution reports whether the version string is a sentinel like "latest" or "master".
 func needsResolution(v string) bool {
 	return v == version.Latest || v == version.Master || v == version.Main
diff --git a/internal/api/api_test.go b/internal/api/api_test.go
index e087b13e..f61c8581 100644
--- a/internal/api/api_test.go
+++ b/internal/api/api_test.go
@@ -166,3 +166,84 @@ func TestServePackage(t *testing.T) {
 		})
 	}
 }
+
+func TestServeModule(t *testing.T) {
+	ctx := context.Background()
+	ds := fakedatasource.New()
+
+	const (
+		modulePath = "example.com"
+		version    = "v1.2.3"
+	)
+
+	ds.MustInsertModule(ctx, &internal.Module{
+		ModuleInfo: internal.ModuleInfo{
+			ModulePath: modulePath,
+			Version:    version,
+		},
+		Units: []*internal.Unit{{
+			UnitMeta: internal.UnitMeta{
+				Path: modulePath,
+				ModuleInfo: internal.ModuleInfo{
+					ModulePath: modulePath,
+					Version:    version,
+				},
+			},
+			Readme: &internal.Readme{Filepath: "README.md", Contents: "Hello world"},
+		}},
+	})
+
+	for _, test := range []struct {
+		name       string
+		url        string
+		wantStatus int
+		want       *Module
+	}{
+		{
+			name:       "basic module metadata",
+			url:        "/v1/module/example.com?version=v1.2.3",
+			wantStatus: http.StatusOK,
+			want: &Module{
+				Path:    modulePath,
+				Version: version,
+			},
+		},
+		{
+			name:       "module with readme",
+			url:        "/v1/module/example.com?version=v1.2.3&readme=true",
+			wantStatus: http.StatusOK,
+			want: &Module{
+				Path:    modulePath,
+				Version: version,
+				Readme: &Readme{
+					Filepath: "README.md",
+					Contents: "Hello world",
+				},
+			},
+		},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			r := httptest.NewRequest("GET", test.url, nil)
+			w := httptest.NewRecorder()
+
+			err := ServeModule(w, r, ds)
+			if err != nil {
+				t.Fatalf("ServeModule returned error: %v", err)
+			}
+
+			if w.Code != test.wantStatus {
+				t.Errorf("status = %d, want %d", w.Code, test.wantStatus)
+			}
+
+			if test.want != nil {
+				var got Module
+				if err := json.Unmarshal(w.Body.Bytes(), &got); err != nil {
+					t.Fatalf("json.Unmarshal: %v", err)
+				}
+				if diff := cmp.Diff(test.want, &got); diff != "" {
+					t.Errorf("mismatch (-want +got):\n%s", diff)
+				}
+			}
+		})
+	}
+}
-- 
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