feat(api): send X-Spoo-Client header on backend requests

.goreleaser.yaml

@@ -17,7 +17,7 @@ builds:
     goos: [linux, darwin, windows]
     goarch: [amd64, arm64]
     ldflags:
-      - -s -w -X main.version={{.Version}} -X main.commit={{.ShortCommit}}
+      - -s -w -X main.version={{.Version}} -X main.commit={{.ShortCommit}} -X github.com/spoo-me/spoo-cli/internal/api.Version={{.Version}}
 
 archives:
   - formats: [tar.gz]

internal/api/client.go

@@ -10,12 +10,27 @@ import (
 	"io"
 	"net/http"
 	"net/url"
+	"regexp"
 	"strings"
 	"time"
 
 	"github.com/spoo-me/spoo-cli/internal/auth"
 )
 
+// Version is the CLI release, injected by goreleaser via ldflags.
+var Version = "dev"
+
+var versionRe = regexp.MustCompile(`^[A-Za-z0-9._-]{1,16}$`)
+
+// clientHeader identifies the CLI (and its version, when well-formed) to
+// the backend so API traffic can be attributed per client.
+func clientHeader() string {
+	if versionRe.MatchString(Version) {
+		return "cli/" + Version
+	}
+	return "cli"
+}
+
 type Client struct {
 	base  string
 	http  *http.Client
@@ -24,8 +39,20 @@ type Client struct {
 
 func New(base string, store *auth.Store) *Client {
 	return &Client{
-		base:  strings.TrimRight(base, "/"),
-		http:  &http.Client{Timeout: 30 * time.Second},
+		base: strings.TrimRight(base, "/"),
+		http: &http.Client{
+			Timeout: 30 * time.Second,
+			// Go forwards custom headers on redirects, including
+			// cross-origin ones. Attribution belongs to the spoo API
+			// only, so drop it whenever a redirect leaves the original
+			// host. Go itself strips Authorization on cross-domain hops.
+			CheckRedirect: func(req *http.Request, via []*http.Request) error {
+				if req.URL.Host != via[0].URL.Host {
+					req.Header.Del("X-Spoo-Client")
+				}
+				return nil
+			},
+		},
 		store: store,
 	}
 }
@@ -96,6 +123,7 @@ func (c *Client) send(ctx context.Context, method, path string, query url.Values
 		return nil, err
 	}
 	req.Header.Set("User-Agent", "spoo-cli")
+	req.Header.Set("X-Spoo-Client", clientHeader())
 	if body != nil {
 		req.Header.Set("Content-Type", "application/json")
 	}

internal/api/client_test.go

@@ -44,6 +44,39 @@ func TestDoSendsBearerToken(t *testing.T) {
 	}
 }
 
+func TestDoSendsClientHeader(t *testing.T) {
+	var gotClient string
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		gotClient = r.Header.Get("X-Spoo-Client")
+		w.Write([]byte(`{}`))
+	}))
+	defer srv.Close()
+
+	c := New(srv.URL, newTestStore(t, nil))
+	if err := c.do(context.Background(), http.MethodGet, "/auth/me", nil, nil, nil); err != nil {
+		t.Fatal(err)
+	}
+	if gotClient != "cli/dev" {
+		t.Fatalf("X-Spoo-Client = %q, want cli/dev", gotClient)
+	}
+}
+
+func TestClientHeaderRejectsMalformedVersion(t *testing.T) {
+	orig := Version
+	defer func() { Version = orig }()
+	for version, want := range map[string]string{
+		"1.2.3":                  "cli/1.2.3",
+		"0.2.0-SNAPSHOT-697203b": "cli", // >16 chars
+		"1.0+meta":               "cli", // invalid charset
+		"":                       "cli",
+	} {
+		Version = version
+		if got := clientHeader(); got != want {
+			t.Errorf("clientHeader() with Version=%q = %q, want %q", version, got, want)
+		}
+	}
+}
+
 func TestDoParsesErrorEnvelope(t *testing.T) {
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusConflict)
@@ -97,3 +130,46 @@ func TestDoRefreshesOn401AndRetries(t *testing.T) {
 		t.Fatalf("store not updated after refresh: %+v", got)
 	}
 }
+
+func TestClientHeaderStrippedOnCrossOriginRedirect(t *testing.T) {
+	gotClient := "unset"
+	target := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		gotClient = r.Header.Get("X-Spoo-Client")
+		w.Write([]byte(`{}`))
+	}))
+	defer target.Close()
+
+	redirector := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		http.Redirect(w, r, target.URL+"/final", http.StatusFound)
+	}))
+	defer redirector.Close()
+
+	c := New(redirector.URL, newTestStore(t, nil))
+	if err := c.do(context.Background(), http.MethodGet, "/start", nil, nil, nil); err != nil {
+		t.Fatal(err)
+	}
+	if gotClient != "" {
+		t.Fatalf("X-Spoo-Client forwarded cross-origin = %q, want empty", gotClient)
+	}
+}
+
+func TestClientHeaderKeptOnSameHostRedirect(t *testing.T) {
+	gotClient := "unset"
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path == "/start" {
+			http.Redirect(w, r, "/final", http.StatusFound)
+			return
+		}
+		gotClient = r.Header.Get("X-Spoo-Client")
+		w.Write([]byte(`{}`))
+	}))
+	defer srv.Close()
+
+	c := New(srv.URL, newTestStore(t, nil))
+	if err := c.do(context.Background(), http.MethodGet, "/start", nil, nil, nil); err != nil {
+		t.Fatal(err)
+	}
+	if gotClient != "cli/dev" {
+		t.Fatalf("X-Spoo-Client after same-host redirect = %q, want cli/dev", gotClient)
+	}
+}

internal/api/inspect.go

@@ -28,6 +28,7 @@ func (c *Client) Inspect(ctx context.Context, shortCode string) (*InspectResult,
 		return nil, err
 	}
 	req.Header.Set("User-Agent", "spoo-cli")
+	req.Header.Set("X-Spoo-Client", clientHeader())
 	resp, err := noFollow.Do(req)
 	if err != nil {
 		return nil, err