4 files changed, 276 insertions, 9 deletions
diff --git a/internal/ap/extract.go b/internal/ap/extract.go
index cc8129f04..596e29b13 100644
--- a/internal/ap/extract.go
+++ b/internal/ap/extract.go
@@ -634,32 +634,38 @@ func ExtractContent(i WithContent) gtsmodel.Content {
 	return content
 }
 
-// ExtractAttachments attempts to extract barebones MediaAttachment objects from given AS interface type.
+// ExtractAttachments attempts to extract barebones
+// MediaAttachment objects from given AS interface type.
 func ExtractAttachments(i WithAttachment) ([]*gtsmodel.MediaAttachment, error) {
 	attachmentProp := i.GetActivityStreamsAttachment()
 	if attachmentProp == nil {
 		return nil, nil
 	}
 
-	var errs gtserror.MultiError
+	var (
+		attachments = make([]*gtsmodel.MediaAttachment, 0, attachmentProp.Len())
+		errs        gtserror.MultiError
+	)
 
-	attachments := make([]*gtsmodel.MediaAttachment, 0, attachmentProp.Len())
 	for iter := attachmentProp.Begin(); iter != attachmentProp.End(); iter = iter.Next() {
 		t := iter.GetType()
 		if t == nil {
 			errs.Appendf("nil attachment type")
 			continue
 		}
-		attachmentable, ok := t.(Attachmentable)
+
+		attachmentable, ok := ToAttachmentable(t)
 		if !ok {
-			errs.Appendf("incorrect attachment type: %T", t)
+			errs.Appendf("could not cast %T to Attachmentable", t)
 			continue
 		}
+
 		attachment, err := ExtractAttachment(attachmentable)
 		if err != nil {
 			errs.Appendf("error extracting attachment: %w", err)
 			continue
 		}
+
 		attachments = append(attachments, attachment)
 	}
 
@@ -681,7 +687,10 @@ func ExtractAttachment(i Attachmentable) (*gtsmodel.MediaAttachment, error) {
 		RemoteURL:   remoteURL.String(),
 		Description: ExtractDescription(i),
 		Blurhash:    ExtractBlurhash(i),
-		Processing:  gtsmodel.ProcessingStatusReceived,
+		FileMeta: gtsmodel.FileMeta{
+			Focus: ExtractFocus(i),
+		},
+		Processing: gtsmodel.ProcessingStatusReceived,
 	}, nil
 }
 
@@ -708,6 +717,50 @@ func ExtractBlurhash(i WithBlurhash) string {
 	return blurhashProp.Get()
 }
 
+// ExtractFocus parses a gtsmodel.Focus from the given Attachmentable's
+// `focalPoint` property, if Attachmentable can have `focalPoint`, and
+// `focalPoint` is set to a valid pair of floats. Otherwise, returns a
+// zero gtsmodel.Focus (ie., focus in the centre of the image).
+func ExtractFocus(attachmentable Attachmentable) gtsmodel.Focus {
+	focus := gtsmodel.Focus{}
+
+	withFocalPoint, ok := attachmentable.(WithFocalPoint)
+	if !ok {
+		return focus
+	}
+
+	focalPointProp := withFocalPoint.GetTootFocalPoint()
+	if focalPointProp == nil || focalPointProp.Len() != 2 {
+		return focus
+	}
+
+	xProp := focalPointProp.At(0)
+	if !xProp.IsXMLSchemaFloat() {
+		return focus
+	}
+
+	yProp := focalPointProp.At(1)
+	if !yProp.IsXMLSchemaFloat() {
+		return focus
+	}
+
+	x := xProp.Get()
+	if x < -1 || x > 1 {
+		return focus
+	}
+
+	y := yProp.Get()
+	if y < -1 || y > 1 {
+		return focus
+	}
+
+	// Looks good.
+	focus.X = float32(x)
+	focus.Y = float32(y)
+
+	return focus
+}
+
 // ExtractHashtags extracts a slice of minimal gtsmodel.Tags
 // from a WithTag. If an entry in the WithTag is not a hashtag,
 // or has a name that cannot be normalized, it will be ignored.
diff --git a/internal/ap/extractfocus_test.go b/internal/ap/extractfocus_test.go
new file mode 100644
index 000000000..9e7935740
--- /dev/null
+++ b/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))
+}
diff --git a/internal/ap/interfaces.go b/internal/ap/interfaces.go
index 1dcc6afef..28b5c0d20 100644
--- a/internal/ap/interfaces.go
+++ b/internal/ap/interfaces.go
@@ -165,6 +165,29 @@ func ToApprovable(t vocab.Type) (Approvable, bool) {
 	return approvable, true
 }
 
+// IsAttachmentable returns whether AS vocab type name
+// is something that can be cast to Attachmentable.
+func IsAttachmentable(typeName string) bool {
+	switch typeName {
+	case ObjectAudio,
+		ObjectDocument,
+		ObjectImage,
+		ObjectVideo:
+		return true
+	default:
+		return false
+	}
+}
+
+// ToAttachmentable safely tries to cast vocab.Type as Attachmentable.
+func ToAttachmentable(t vocab.Type) (Attachmentable, bool) {
+	attachmentable, ok := t.(Attachmentable)
+	if !ok || !IsAttachmentable(t.GetTypeName()) {
+		return nil, false
+	}
+	return attachmentable, true
+}
+
 // Activityable represents the minimum activitypub interface for representing an 'activity'.
 // (see: IsActivityable() for types implementing this, though you MUST make sure to check
 // the typeName as this bare interface may be implementable by non-Activityable types).
@@ -628,9 +651,11 @@ type WithBlurhash interface {
 	SetTootBlurhash(vocab.TootBlurhashProperty)
 }
 
-// type withFocalPoint interface {
-// 	// TODO
-// }
+// WithFocalPoint represents an object with TootFocalPointProperty.
+type WithFocalPoint interface {
+	GetTootFocalPoint() vocab.TootFocalPointProperty
+	SetTootFocalPoint(vocab.TootFocalPointProperty)
+}
 
 // WithHref represents an activity with ActivityStreamsHrefProperty
 type WithHref interface {
diff --git a/internal/ap/properties.go b/internal/ap/properties.go
index ea925457a..589639337 100644
--- a/internal/ap/properties.go
+++ b/internal/ap/properties.go
@@ -560,6 +560,70 @@ func SetApprovedBy(with WithApprovedBy, approvedBy *url.URL) {
 	abProp.Set(approvedBy)
 }
 
+// GetMediaType returns the string contained in
+// the MediaType property of 'with', if set.
+func GetMediaType(with WithMediaType) string {
+	mtProp := with.GetActivityStreamsMediaType()
+	if mtProp == nil || !mtProp.IsRFCRfc2045() {
+		return ""
+	}
+	return mtProp.Get()
+}
+
+// SetMediaType sets the given string
+// on the MediaType property of 'with'.
+func SetMediaType(with WithMediaType, mediaType string) {
+	mtProp := with.GetActivityStreamsMediaType()
+	if mtProp == nil {
+		mtProp = streams.NewActivityStreamsMediaTypeProperty()
+		with.SetActivityStreamsMediaType(mtProp)
+	}
+	mtProp.Set(mediaType)
+}
+
+// AppendName appends the given name
+// vals to the Name property of 'with'.
+func AppendName(with WithName, name ...string) {
+	if len(name) == 0 {
+		return
+	}
+	nameProp := with.GetActivityStreamsName()
+	if nameProp == nil {
+		nameProp = streams.NewActivityStreamsNameProperty()
+		with.SetActivityStreamsName(nameProp)
+	}
+	for _, name := range name {
+		nameProp.AppendXMLSchemaString(name)
+	}
+}
+
+// AppendSummary appends the given summary
+// vals to the Summary property of 'with'.
+func AppendSummary(with WithSummary, summary ...string) {
+	if len(summary) == 0 {
+		return
+	}
+	summaryProp := with.GetActivityStreamsSummary()
+	if summaryProp == nil {
+		summaryProp = streams.NewActivityStreamsSummaryProperty()
+		with.SetActivityStreamsSummary(summaryProp)
+	}
+	for _, summary := range summary {
+		summaryProp.AppendXMLSchemaString(summary)
+	}
+}
+
+// SetBlurhash sets the given string
+// on the Blurhash property of 'with'.
+func SetBlurhash(with WithBlurhash, mediaType string) {
+	bProp := with.GetTootBlurhash()
+	if bProp == nil {
+		bProp = streams.NewTootBlurhashProperty()
+		with.SetTootBlurhash(bProp)
+	}
+	bProp.Set(mediaType)
+}
+
 // extractIRIs extracts just the AP IRIs from an iterable
 // property that may contain types (with IRIs) or just IRIs.
 //