Support SVG sources (closes #68)

The fetcher accepts image/svg+xml again and internal/magic detects SVG.
A raster format renders the SVG with librsvg at the density that makes
it cover the output size, so an enlarged SVG stays sharp; the rendered
size is held to MaxInputDimension. orig of an SVG at the orig size is
the SVG unchanged, cached as a variant; at any other size it is
ErrSVGNotOriginalSize, answered 400. The cache reads up to 1024 first
bytes of a file to find its format, as an SVG's root element can come
after a prolog. Tests that pinned SVG as refused now expect it to be
read.

Model: opus-5-5

internal/server/svg_internal_test.go

@@ -4,38 +4,114 @@ import (
 	"io"
 	"net/http"
 	"net/http/httptest"
+	"strings"
+	"sync/atomic"
 	"testing"
+
+	"sneak.berlin/go/pixa/internal/imageproxy"
+	"sneak.berlin/go/pixa/internal/imagerequest"
+	"sneak.berlin/go/pixa/internal/magic"
 )
 
-// TestImageProxyRefusesSVG requests an image the upstream answers as SVG,
-// in its own format (orig) and resized as PNG, through pixa's router,
-// upstream fetcher and image processor. pixa does not accept SVG as a
-// source, so each request is answered 415, never with an image.
-func TestImageProxyRefusesSVG(t *testing.T) {
-	t.Parallel()
+// testSVG is the SVG the upstream serves in the SVG tests below.
+const testSVG = `<svg xmlns="http://www.w3.org/2000/svg" width="64" height="48">` +
+	`<rect width="64" height="48"/></svg>`
+
+// startSVGUpstream starts an upstream that answers every request with
+// testSVG as image/svg+xml, and returns it with its count of requests.
+func startSVGUpstream(t *testing.T) (*httptest.Server, *atomic.Int64) {
+	t.Helper()
+
+	var requests atomic.Int64
 
 	upstream := httptest.NewServer(http.HandlerFunc(
 		func(w http.ResponseWriter, _ *http.Request) {
+			requests.Add(1)
 			w.Header().Set("Content-Type", "image/svg+xml")
-			_, _ = io.WriteString(w, `<svg xmlns="http://www.w3.org/2000/svg" `+
-				`width="64" height="48"><rect width="64" height="48"/></svg>`)
+			_, _ = io.WriteString(w, testSVG)
 		}))
 	t.Cleanup(upstream.Close)
 
+	return upstream, &requests
+}
+
+// TestImageProxyServesSVGAsItIs requests an SVG source in its own format
+// (orig) at the orig size through pixa's router, upstream fetcher, image
+// processor and cache, twice. Both answers are the SVG itself, never another
+// format, the second from the cache; the upstream is asked once. Scripts in
+// the SVG cannot run, as the Content-Security-Policy allows no inline
+// script. orig at another size is refused with 400.
+func TestImageProxyServesSVGAsItIs(t *testing.T) {
+	t.Parallel()
+
+	upstream, requests := startSVGUpstream(t)
+	s, _, _ := startImageProxy(t, upstream)
+	target := "/v1/image/" + upstreamHost + "/drawing.svg/orig.orig"
+
+	for _, wantCache := range []imageproxy.CacheStatus{
+		imageproxy.CacheMiss, imageproxy.CacheHit,
+	} {
+		rec := getImage(t, s, target)
+
+		if rec.Header().Get("Content-Type") != "image/svg+xml" ||
+			rec.Body.String() != testSVG {
+			t.Errorf("GET %s: %s %q, want image/svg+xml %q", target,
+				rec.Header().Get("Content-Type"), rec.Body.String(), testSVG)
+		}
+
+		if got := rec.Header().Get("X-Pixa-Cache"); got != string(wantCache) {
+			t.Errorf("GET %s: X-Pixa-Cache = %q, want %q", target, got, wantCache)
+		}
+
+		policy := rec.Header().Get("Content-Security-Policy")
+		if !strings.Contains(policy, "script-src 'self'") ||
+			strings.Contains(policy, "unsafe-inline") {
+			t.Errorf("GET %s: Content-Security-Policy = %q, want script-src "+
+				"'self' and no unsafe-inline", target, policy)
+		}
+	}
+
+	if requests.Load() != 1 {
+		t.Errorf("upstream requests = %d, want 1", requests.Load())
+	}
+
+	resized := "/v1/image/" + upstreamHost + "/drawing.svg/32x24.orig"
+
+	rec := httptest.NewRecorder()
+	s.ServeHTTP(rec, httptest.NewRequestWithContext(
+		t.Context(), http.MethodGet, resized, nil))
+	t.Logf("GET %s: %d %s", resized, rec.Code, rec.Body.String())
+
+	if rec.Code != http.StatusBadRequest {
+		t.Errorf("GET %s: %d %s, want 400", resized, rec.Code, rec.Body.String())
+	}
+}
+
+// TestImageProxyRendersSVG requests an SVG source as each raster format
+// through pixa's router, upstream fetcher and image processor. Each answer
+// is an image in that format.
+func TestImageProxyRendersSVG(t *testing.T) {
+	t.Parallel()
+
+	upstream, _ := startSVGUpstream(t)
 	s, _, _ := startImageProxy(t, upstream)
 
-	for _, sizeFormat := range []string{"64x48.orig", "32x24.png"} {
-		target := "/v1/image/" + upstreamHost + "/drawing.svg/" + sizeFormat
+	for _, format := range []imagerequest.Format{
+		imagerequest.FormatJPEG, imagerequest.FormatPNG, imagerequest.FormatGIF,
+		imagerequest.FormatWebP, imagerequest.FormatAVIF, imagerequest.FormatJXL,
+	} {
+		target := "/v1/image/" + upstreamHost + "/drawing.svg/32x24." +
+			string(format)
 
-		rec := httptest.NewRecorder()
-		s.ServeHTTP(rec, httptest.NewRequestWithContext(
-			t.Context(), http.MethodGet, target, nil))
-		t.Logf("GET %s: %d, Content-Type %s, body %s",
-			target, rec.Code, rec.Header().Get("Content-Type"), rec.Body.String())
+		rec := getImage(t, s, target)
+		detected, err := magic.DetectFormat(rec.Body.Bytes())
+		t.Logf("GET %s: %s, body in %q (%v)", target,
+			rec.Header().Get("Content-Type"), detected, err)
 
-		if rec.Code != http.StatusUnsupportedMediaType {
-			t.Errorf("GET %s status = %d, want %d",
-				target, rec.Code, http.StatusUnsupportedMediaType)
+		if rec.Header().Get("Content-Type") != format.MIMEType() ||
+			err != nil || detected != format {
+			t.Errorf("GET %s: %s, body in %q (%v); want %s", target,
+				rec.Header().Get("Content-Type"), detected, err, format.MIMEType())
 		}
 	}
 }