[feature] Update attachment format, receive + send focalPoint prop + use it on the frontend (#4052)

* [feature] Update attachment format, receive + send `focalPoint` prop + use it on the frontend

* whoops

* boop

* restore function signature of ExtractAttachments

internal/ap/extractfocus_test.go

@@ -0,0 +1,125 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package ap_test
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"testing"
+
+	"code.superseriousbusiness.org/activity/streams"
+	"github.com/stretchr/testify/suite"
+	"github.com/superseriousbusiness/gotosocial/internal/ap"
+)
+
+type ExtractFocusTestSuite struct {
+	APTestSuite
+}
+
+func (suite *ExtractFocusTestSuite) TestExtractFocus() {
+	ctx := context.Background()
+
+	type test struct {
+		data    string
+		expectX float32
+		expectY float32
+	}
+
+	for _, test := range []test{
+		{
+			// Fine.
+			data:    "-0.5, 0.5",
+			expectX: -0.5,
+			expectY: 0.5,
+		},
+		{
+			// Also fine.
+			data:    "1, 1",
+			expectX: 1,
+			expectY: 1,
+		},
+		{
+			// Out of range.
+			data:    "1.5, 1",
+			expectX: 0,
+			expectY: 0,
+		},
+		{
+			// Too many points.
+			data:    "1, 1, 0",
+			expectX: 0,
+			expectY: 0,
+		},
+		{
+			// Not enough points.
+			data:    "1",
+			expectX: 0,
+			expectY: 0,
+		},
+	} {
+		// Wrap provided test.data
+		// in a minimal Attachmentable.
+		const fmts = `{
+  "@context": [
+    "https://www.w3.org/ns/activitystreams",
+    {
+      "focalPoint": {
+        "@container": "@list",
+        "@id": "toot:focalPoint"
+      },
+      "toot": "http://joinmastodon.org/ns#"
+    }
+  ],
+  "focalPoint": [ %s ],
+  "type": "Image"
+}`
+
+		// Unmarshal test data.
+		data := fmt.Sprintf(fmts, test.data)
+		m := make(map[string]any)
+		if err := json.Unmarshal([]byte(data), &m); err != nil {
+			suite.FailNow(err.Error())
+		}
+
+		// Convert to type.
+		t, err := streams.ToType(ctx, m)
+		if err != nil {
+			suite.FailNow(err.Error())
+		}
+
+		// Convert to attachmentable.
+		attachmentable, ok := t.(ap.Attachmentable)
+		if !ok {
+			suite.FailNow("", "%T was not Attachmentable", t)
+		}
+
+		// Check extracted focus.
+		focus := ap.ExtractFocus(attachmentable)
+		if focus.X != test.expectX || focus.Y != test.expectY {
+			suite.Fail("",
+				"expected x=%.2f y=%.2f got x=%.2f y=%.2f",
+				test.expectX, test.expectY, focus.X, focus.Y,
+			)
+		}
+	}
+}
+
+func TestExtractFocusTestSuite(t *testing.T) {
+	suite.Run(t, new(ExtractFocusTestSuite))
+}