Image editor

db/migrations/000004_add_image_lineage_indexes.down.sql

@@ -0,0 +1,4 @@
+BEGIN;
+DROP INDEX IF EXISTS image_table_root_id_idx;
+DROP INDEX IF EXISTS image_table_parent_id_idx;
+COMMIT;

db/migrations/000004_add_image_lineage_indexes.up.sql

@@ -0,0 +1,4 @@
+BEGIN;
+CREATE INDEX image_table_root_id_idx ON image_table(root_id);
+CREATE INDEX image_table_parent_id_idx ON image_table(parent_id);
+COMMIT;

db/migrations/000005_create_image_parent_table.down.sql

@@ -0,0 +1 @@
+DROP TABLE IF EXISTS image_parent_table;

db/migrations/000005_create_image_parent_table.up.sql

@@ -0,0 +1,39 @@
+BEGIN;
+
+CREATE TABLE image_parent_table (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    image_id UUID NOT NULL REFERENCES image_table(id) ON DELETE RESTRICT,
+    parent_image_id UUID NOT NULL REFERENCES image_table(id) ON DELETE RESTRICT,
+    relationship_type CHARACTER VARYING(50) NOT NULL,
+    created_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT now(),
+
+    CONSTRAINT image_parent_unique_relationship UNIQUE(image_id, parent_image_id, relationship_type)
+);
+
+CREATE INDEX image_parent_table_image_id_idx ON image_parent_table(image_id);
+CREATE INDEX image_parent_table_parent_image_id_idx ON image_parent_table(parent_image_id);
+
+-- Backfill from existing parent_id column
+INSERT INTO image_parent_table (image_id, parent_image_id, relationship_type)
+SELECT id, parent_id, 'base'
+FROM image_table
+WHERE parent_id IS NOT NULL AND deleted_at IS NULL;
+
+-- Backfill overlay relationships from changes JSON
+INSERT INTO image_parent_table (image_id, parent_image_id, relationship_type)
+SELECT
+    it.id,
+    (it.changes->'params'->>'overlay_image_id')::UUID,
+    'overlay'
+FROM image_table it
+WHERE it.changes != '{}'
+  AND it.changes->>'type' = 'watermark'
+  AND it.changes->'params'->>'overlay_image_id' IS NOT NULL
+  AND it.deleted_at IS NULL
+  AND EXISTS (
+    SELECT 1 FROM image_table ot
+    WHERE ot.id = (it.changes->'params'->>'overlay_image_id')::UUID
+    AND ot.deleted_at IS NULL
+  );
+
+COMMIT;

domainmodels/image.go

@@ -33,6 +33,7 @@ type Image struct {
 	Identifier      string
 	RootId          string
 	ParentId        string
+	Changes         string
 	UploaderIP      string
 	MIMEType        string
 	NominalWidth    int32

editing/changeset.go

@@ -0,0 +1,70 @@
+package editing
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+type ChangeSet struct {
+	Type   string          `json:"type"`
+	Params json.RawMessage `json:"params"`
+}
+
+// FetchImageFunc retrieves image bytes by image ID.
+type FetchImageFunc func(id string) ([]byte, error)
+
+// Editor applies a ChangeSet to base image bytes, producing new image bytes.
+type Editor interface {
+	Apply(base []byte, cs ChangeSet, fetchImage FetchImageFunc) ([]byte, string, error)
+}
+
+// ApplyResult holds the output of applying a ChangeSet.
+type ApplyResult struct {
+	Bytes       []byte
+	MIMEType    string
+	ChangesJSON []byte
+}
+
+// ApplyChangeSet orchestrates applying a change set: looks up the editor,
+// fetches the base image bytes, applies the edit, and serializes the changes.
+func ApplyChangeSet(cs ChangeSet, baseImageId string, fetchImage FetchImageFunc) (*ApplyResult, error) {
+	editor, err := GetEditor(cs.Type)
+	if err != nil {
+		return nil, err
+	}
+
+	baseBytes, err := fetchImage(baseImageId)
+	if err != nil {
+		return nil, fmt.Errorf("failed to fetch base image: %w", err)
+	}
+
+	resultBytes, resultMime, err := editor.Apply(baseBytes, cs, fetchImage)
+	if err != nil {
+		return nil, fmt.Errorf("failed to apply %s: %w", cs.Type, err)
+	}
+
+	changesJSON, err := json.Marshal(cs)
+	if err != nil {
+		return nil, fmt.Errorf("failed to serialize changes: %w", err)
+	}
+
+	return &ApplyResult{
+		Bytes:       resultBytes,
+		MIMEType:    resultMime,
+		ChangesJSON: changesJSON,
+	}, nil
+}
+
+var registry = map[string]Editor{}
+
+func Register(changeType string, editor Editor) {
+	registry[changeType] = editor
+}
+
+func GetEditor(changeType string) (Editor, error) {
+	e, ok := registry[changeType]
+	if !ok {
+		return nil, fmt.Errorf("unknown change type: %s", changeType)
+	}
+	return e, nil
+}

editing/changeset_test.go

@@ -0,0 +1,66 @@
+package editing
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func TestChangeSetSerialize(t *testing.T) {
+	params := WatermarkParams{
+		OverlayImageID: "abc-123",
+		Position:       WatermarkPosition{X: 0.9, Y: 0.9},
+		Anchor:         AnchorBottomRight,
+		Opacity:        0.5,
+		Scale:          0.15,
+	}
+	paramsJSON, err := json.Marshal(params)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cs := ChangeSet{
+		Type:   "watermark",
+		Params: paramsJSON,
+	}
+
+	data, err := json.Marshal(cs)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var decoded ChangeSet
+	if err := json.Unmarshal(data, &decoded); err != nil {
+		t.Fatal(err)
+	}
+	if decoded.Type != "watermark" {
+		t.Fatalf("expected type 'watermark', got '%s'", decoded.Type)
+	}
+
+	var decodedParams WatermarkParams
+	if err := json.Unmarshal(decoded.Params, &decodedParams); err != nil {
+		t.Fatal(err)
+	}
+	if decodedParams.OverlayImageID != "abc-123" {
+		t.Fatalf("expected overlay_image_id 'abc-123', got '%s'", decodedParams.OverlayImageID)
+	}
+	if decodedParams.Opacity != 0.5 {
+		t.Fatalf("expected opacity 0.5, got %f", decodedParams.Opacity)
+	}
+}
+
+func TestRegistryGetEditor(t *testing.T) {
+	editor, err := GetEditor("watermark")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if editor == nil {
+		t.Fatal("expected non-nil editor for 'watermark'")
+	}
+}
+
+func TestRegistryGetUnknownEditor(t *testing.T) {
+	_, err := GetEditor("nonexistent")
+	if err == nil {
+		t.Fatal("expected error for unknown editor type")
+	}
+}