1 files changed, 29 insertions, 11 deletions
diff --git a/src/document/store.rs b/src/document/store.rs
index 4d9bc74..cc67f77 100644
--- a/src/document/store.rs
+++ b/src/document/store.rs
@@ -1102,17 +1102,15 @@ fn write_value(
     value: &JsonValue,
 ) -> Result<(), StoreError> {
     match value {
-        JsonValue::Object(object) => {
-            let id = put_object(doc, parent, slot, ObjType::Map)?;
-            for (child_key, child_value) in object {
-                write_value(doc, &id, Slot::Key(child_key), child_value)?;
-            }
-        }
-        JsonValue::Array(items) => {
-            let id = put_object(doc, parent, slot, ObjType::List)?;
-            for (index, item) in items.iter().enumerate() {
-                write_value(doc, &id, Slot::Index(index), item)?;
-            }
+        JsonValue::Object(_) | JsonValue::Array(_) => {
+            // A new tree in one go, not an operation at a time.
+            let tree = hydrated(value)?;
+            let (prop, insert): (Prop, bool) = match slot {
+                Slot::Key(key) => (key.into(), false),
+                Slot::Index(index) => (index.into(), true),
+                Slot::At(index) => (index.into(), false),
+            };
+            doc.batch_create_object(parent, prop, &tree, insert)?;
         }
         scalar => {
             let scalar = json_scalar(scalar)?.expect("neither an object nor an array");
@@ -1123,6 +1121,26 @@ fn write_value(
     Ok(())
 }
 
+/// `value` as Automerge holds it: maps, lists and scalars as `write_value` stores them.
+fn hydrated(value: &JsonValue) -> Result<automerge::hydrate::Value, StoreError> {
+    use automerge::hydrate;
+    Ok(match value {
+        JsonValue::Object(object) => {
+            let mut map = std::collections::HashMap::new();
+            for (key, value) in object {
+                map.insert(key.clone(), hydrated(value)?);
+            }
+            hydrate::Value::Map(hydrate::Map::from(map))
+        }
+        JsonValue::Array(items) => {
+            hydrate::Value::from(items.iter().map(hydrated).collect::<Result<Vec<_>, _>>()?)
+        }
+        scalar => {
+            hydrate::Value::from(json_scalar(scalar)?.expect("neither an object nor an array"))
+        }
+    })
+}
+
 fn json_to_automerge(
     doc: &mut impl Transactable,
     parent: &ObjId,