feat: support requests from registerProtocolHandler

This commit adds support for requests produced by navigator.registerProtocolHandler on gateways. Now one can register `dweb.link` as an URI handler for `ipfs://`:

```
navigator.registerProtocolHandler('ipfs', 'https://dweb.link/ipfs/?uri=%s', 'ipfs resolver')
```

Then opening `ipfs://QmbWqxBEKC3P8tqsKc98xmWNzrzDtRLMiMPL8wBuTGsMnR` will produce an HTTP GET call to:

```
https://dweb.link/ipfs?uri=ipfs%3A%2F%2FQmbWqxBEKC3P8tqsKc98xmWNzrzDtRLMiMPL8wBuTGsMnR
```

The query parameter `uri` will now be parsed and the given content identifier resolved via:

`https://dweb.link/ipfs/QmbWqxBEKC3P8tqsKc98xmWNzrzDtRLMiMPL8wBuTGsMnR`

core/corehttp/gateway_handler.go

@@ -181,6 +181,23 @@ func (i *gatewayHandler) getOrHeadHandler(w http.ResponseWriter, r *http.Request
 	}
 	originalUrlPath := prefix + requestURI.Path
 
+	// Query parameter handling to support requests produced by navigator.registerProtocolHandler.
+	// E.g. This code will redirect calls to /ipfs/?uri=ipfs%3A%2F%2Fcontent-identifier
+	// to /ipfs/content-identifier.
+	if uri := r.URL.Query().Get("uri"); uri != "" {
+		u, err := url.Parse(uri)
+		if err != nil {
+			webError(w, "failed to parse uri query parameter", err, http.StatusBadRequest)
+			return
+		}
+		if u.Scheme != "ipfs" && u.Scheme != "ipns" {
+			webError(w, "uri query parameter scheme must be ipfs or ipns", err, http.StatusBadRequest)
+			return
+		}
+		http.Redirect(w, r, gopath.Join("/", prefix, u.Scheme, u.Host), http.StatusMovedPermanently)
+		return
+	}
+
 	// Service Worker registration request
 	if r.Header.Get("Service-Worker") == "script" {
 		// Disallow Service Worker registration on namespace roots

core/corehttp/gateway_test.go

@@ -161,6 +161,44 @@ func matchPathOrBreadcrumbs(s string, expected string) bool {
 	return matched
 }
 
+func TestUriQueryRedirect(t *testing.T) {
+	ts, _, _ := newTestServerAndNode(t, mockNamesys{})
+
+	cid := "QmbWqxBEKC3P8tqsKc98xmWNzrzDtRLMiMPL8wBuTGsMnR"
+	for i, test := range []struct {
+		path     string
+		status   int
+		location string
+	}{
+		{"/ipfs/?uri=ipfs://" + cid, http.StatusMovedPermanently, "/ipfs/" + cid},
+		{"/ipfs/?uri=ipfs%3A%2F%2F" + cid, http.StatusMovedPermanently, "/ipfs/" + cid},
+		{"/ipfs?uri=ipfs://" + cid, http.StatusMovedPermanently, "/ipfs/?uri=ipfs://" + cid},
+		{"/ipfs/?uri=ipns://" + cid, http.StatusMovedPermanently, "/ipns/" + cid},
+		{"/ipns?uri=ipns://" + cid, http.StatusMovedPermanently, "/ipns/?uri=ipns://" + cid},
+		{"/ipns/?uri=ipfs://" + cid, http.StatusMovedPermanently, "/ipfs/" + cid},
+		{"/ipns/?uri=ipfs://" + cid, http.StatusMovedPermanently, "/ipfs/" + cid},
+		{"/ipfs/?uri=unsupported://" + cid, http.StatusBadRequest, ""},
+		{"/ipfs/?uri=" + cid, http.StatusBadRequest, ""},
+	} {
+
+		r, err := http.NewRequest(http.MethodGet, ts.URL+test.path, nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		resp, err := doWithoutRedirect(r)
+		defer resp.Body.Close()
+
+		if resp.StatusCode != test.status {
+			t.Errorf("(%d) got %d, expected %d from %s", i, resp.StatusCode, test.status, ts.URL+test.path)
+		}
+
+		locHdr := resp.Header.Get("Location")
+		if locHdr != test.location {
+			t.Errorf("(%d) location header got %s, expected %s from %s", i, locHdr, test.location, ts.URL+test.path)
+		}
+	}
+}
+
 func TestGatewayGet(t *testing.T) {
 	ns := mockNamesys{}
 	ts, api, ctx := newTestServerAndNode(t, ns)