Move Rojo server into root of the repository

src/snapshot/patch_compute.rs

@@ -0,0 +1,330 @@
+//! Defines the algorithm for computing a roughly-minimal patch set given an
+//! existing instance tree and an instance snapshot.
+
+use std::collections::{HashMap, HashSet};
+
+use rbx_dom_weak::{RbxId, RbxInstance, RbxTree, RbxValue};
+
+use super::{
+    patch::{PatchAddInstance, PatchSet, PatchUpdateInstance},
+    InstanceSnapshot,
+};
+
+pub fn compute_patch_set<'a>(
+    snapshot: &'a InstanceSnapshot,
+    tree: &RbxTree,
+    id: RbxId,
+) -> PatchSet<'a> {
+    let mut patch_set = PatchSet::new();
+    let mut context = ComputePatchContext::default();
+
+    compute_patch_set_internal(&mut context, snapshot, tree, id, &mut patch_set);
+
+    // Rewrite Ref properties to refer to instance IDs instead of snapshot IDs
+    // for all of the IDs that we know about so far.
+    rewrite_refs_in_updates(&context, &mut patch_set.updated_instances);
+    rewrite_refs_in_additions(&context, &mut patch_set.added_instances);
+
+    patch_set
+}
+
+#[derive(Default)]
+struct ComputePatchContext {
+    snapshot_id_to_instance_id: HashMap<RbxId, RbxId>,
+}
+
+fn rewrite_refs_in_updates(context: &ComputePatchContext, updates: &mut [PatchUpdateInstance]) {
+    for update in updates {
+        for property_value in update.changed_properties.values_mut() {
+            if let Some(RbxValue::Ref { value: Some(id) }) = property_value {
+                if let Some(&instance_id) = context.snapshot_id_to_instance_id.get(id) {
+                    *property_value = Some(RbxValue::Ref {
+                        value: Some(instance_id),
+                    });
+                }
+            }
+        }
+    }
+}
+
+fn rewrite_refs_in_additions(context: &ComputePatchContext, additions: &mut [PatchAddInstance]) {
+    for addition in additions {
+        rewrite_refs_in_snapshot(context, &mut addition.instance);
+    }
+}
+
+fn rewrite_refs_in_snapshot(context: &ComputePatchContext, snapshot: &mut InstanceSnapshot) {
+    for property_value in snapshot.properties.values_mut() {
+        if let RbxValue::Ref { value: Some(id) } = property_value {
+            if let Some(&instance_id) = context.snapshot_id_to_instance_id.get(id) {
+                *property_value = RbxValue::Ref {
+                    value: Some(instance_id),
+                };
+            }
+        }
+    }
+
+    for child in &mut snapshot.children {
+        rewrite_refs_in_snapshot(context, child);
+    }
+}
+
+fn compute_patch_set_internal<'a>(
+    context: &mut ComputePatchContext,
+    snapshot: &'a InstanceSnapshot,
+    tree: &RbxTree,
+    id: RbxId,
+    patch_set: &mut PatchSet<'a>,
+) {
+    if let Some(snapshot_id) = snapshot.snapshot_id {
+        context.snapshot_id_to_instance_id.insert(snapshot_id, id);
+    }
+
+    let instance = tree
+        .get_instance(id)
+        .expect("Instance did not exist in tree");
+
+    compute_property_patches(snapshot, instance, patch_set);
+    compute_children_patches(context, snapshot, tree, id, patch_set);
+}
+
+fn compute_property_patches(
+    snapshot: &InstanceSnapshot,
+    instance: &RbxInstance,
+    patch_set: &mut PatchSet,
+) {
+    let mut visited_properties = HashSet::new();
+    let mut changed_properties = HashMap::new();
+
+    let changed_name = if snapshot.name == instance.name {
+        None
+    } else {
+        Some(snapshot.name.clone().into_owned())
+    };
+
+    let changed_class_name = if snapshot.class_name == instance.class_name {
+        None
+    } else {
+        Some(snapshot.class_name.clone().into_owned())
+    };
+
+    for (name, snapshot_value) in &snapshot.properties {
+        visited_properties.insert(name.as_str());
+
+        match instance.properties.get(name) {
+            Some(instance_value) => {
+                if snapshot_value != instance_value {
+                    changed_properties.insert(name.clone(), Some(snapshot_value.clone()));
+                }
+            }
+            None => {
+                changed_properties.insert(name.clone(), Some(snapshot_value.clone()));
+            }
+        }
+    }
+
+    for name in instance.properties.keys() {
+        if visited_properties.contains(name.as_str()) {
+            continue;
+        }
+
+        changed_properties.insert(name.clone(), None);
+    }
+
+    if changed_properties.is_empty() && changed_name.is_none() {
+        return;
+    }
+
+    patch_set.updated_instances.push(PatchUpdateInstance {
+        id: instance.get_id(),
+        changed_name,
+        changed_class_name,
+        changed_properties,
+    });
+}
+
+fn compute_children_patches<'a>(
+    context: &mut ComputePatchContext,
+    snapshot: &'a InstanceSnapshot,
+    tree: &RbxTree,
+    id: RbxId,
+    patch_set: &mut PatchSet<'a>,
+) {
+    let instance = tree
+        .get_instance(id)
+        .expect("Instance did not exist in tree");
+
+    let instance_children = instance.get_children_ids();
+
+    let mut paired_instances = vec![false; instance_children.len()];
+
+    for snapshot_child in snapshot.children.iter() {
+        let matching_instance =
+            instance_children
+                .iter()
+                .enumerate()
+                .find(|(instance_index, instance_child_id)| {
+                    if paired_instances[*instance_index] {
+                        return false;
+                    }
+
+                    let instance_child = tree
+                        .get_instance(**instance_child_id)
+                        .expect("Instance did not exist in tree");
+
+                    if snapshot_child.name == instance_child.name
+                        && snapshot_child.class_name == instance_child.class_name
+                    {
+                        paired_instances[*instance_index] = true;
+                        return true;
+                    }
+
+                    false
+                });
+
+        match matching_instance {
+            Some((_, instance_child_id)) => {
+                compute_patch_set_internal(
+                    context,
+                    snapshot_child,
+                    tree,
+                    *instance_child_id,
+                    patch_set,
+                );
+            }
+            None => {
+                patch_set.added_instances.push(PatchAddInstance {
+                    parent_id: id,
+                    instance: snapshot_child.clone(),
+                });
+            }
+        }
+    }
+
+    for (instance_index, instance_child_id) in instance_children.iter().enumerate() {
+        if paired_instances[instance_index] {
+            continue;
+        }
+
+        patch_set.removed_instances.push(*instance_child_id);
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    use std::borrow::Cow;
+
+    use maplit::hashmap;
+    use rbx_dom_weak::RbxInstanceProperties;
+
+    /// This test makes sure that rewriting refs in instance update patches to
+    /// instances that already exists works. We should be able to correlate the
+    /// snapshot ID and instance ID during patch computation and replace the
+    /// value before returning from compute_patch_set.
+    #[test]
+    fn rewrite_ref_existing_instance_update() {
+        let tree = RbxTree::new(RbxInstanceProperties {
+            name: "foo".to_owned(),
+            class_name: "foo".to_owned(),
+            properties: HashMap::new(),
+        });
+
+        let root_id = tree.get_root_id();
+
+        // This snapshot should be identical to the existing tree except for the
+        // addition of a prop named Self, which is a self-referential Ref.
+        let snapshot_id = RbxId::new();
+        let snapshot = InstanceSnapshot {
+            snapshot_id: Some(snapshot_id),
+            properties: hashmap! {
+                "Self".to_owned() => RbxValue::Ref {
+                    value: Some(snapshot_id),
+                }
+            },
+
+            name: Cow::Borrowed("foo"),
+            class_name: Cow::Borrowed("foo"),
+            children: Vec::new(),
+        };
+
+        let patch_set = compute_patch_set(&snapshot, &tree, root_id);
+
+        let expected_patch_set = PatchSet {
+            updated_instances: vec![PatchUpdateInstance {
+                id: root_id,
+                changed_name: None,
+                changed_class_name: None,
+                changed_properties: hashmap! {
+                    "Self".to_owned() => Some(RbxValue::Ref {
+                        value: Some(root_id),
+                    }),
+                },
+            }],
+            added_instances: Vec::new(),
+            removed_instances: Vec::new(),
+        };
+
+        assert_eq!(patch_set, expected_patch_set);
+    }
+
+    /// The same as rewrite_ref_existing_instance_update, except that the
+    /// property is added in a new instance instead of modifying an existing
+    /// one.
+    #[test]
+    fn rewrite_ref_existing_instance_addition() {
+        let tree = RbxTree::new(RbxInstanceProperties {
+            name: "foo".to_owned(),
+            class_name: "foo".to_owned(),
+            properties: HashMap::new(),
+        });
+
+        let root_id = tree.get_root_id();
+
+        // This patch describes the existing instance with a new child added.
+        let snapshot_id = RbxId::new();
+        let snapshot = InstanceSnapshot {
+            snapshot_id: Some(snapshot_id),
+            children: vec![InstanceSnapshot {
+                properties: hashmap! {
+                    "Self".to_owned() => RbxValue::Ref {
+                        value: Some(snapshot_id),
+                    },
+                },
+
+                snapshot_id: None,
+                name: Cow::Borrowed("child"),
+                class_name: Cow::Borrowed("child"),
+                children: Vec::new(),
+            }],
+
+            properties: HashMap::new(),
+            name: Cow::Borrowed("foo"),
+            class_name: Cow::Borrowed("foo"),
+        };
+
+        let patch_set = compute_patch_set(&snapshot, &tree, root_id);
+
+        let expected_patch_set = PatchSet {
+            added_instances: vec![PatchAddInstance {
+                parent_id: root_id,
+                instance: InstanceSnapshot {
+                    snapshot_id: None,
+                    properties: hashmap! {
+                        "Self".to_owned() => RbxValue::Ref {
+                            value: Some(root_id),
+                        },
+                    },
+                    name: Cow::Borrowed("child"),
+                    class_name: Cow::Borrowed("child"),
+                    children: Vec::new(),
+                },
+            }],
+            updated_instances: Vec::new(),
+            removed_instances: Vec::new(),
+        };
+
+        assert_eq!(patch_set, expected_patch_set);
+    }
+}