From 8fadafcd24720102870115287cff4e655df0ef5a Mon Sep 17 00:00:00 2001
From: Lucien Greathouse <me@lpghatguy.com>
Date: Mon, 17 Dec 2018 14:18:32 -0800
Subject: [PATCH] Track instance changes inside rbx_snapshot

---
 server/src/rbx_session.rs  | 30 ++++++++++++++++++----------
 server/src/rbx_snapshot.rs | 41 +++++++++++++++++++++++++++-----------
 2 files changed, 48 insertions(+), 23 deletions(-)

diff --git a/server/src/rbx_session.rs b/server/src/rbx_session.rs
index 1d4b7855..08ffb590 100644
--- a/server/src/rbx_session.rs
+++ b/server/src/rbx_session.rs
@@ -16,13 +16,19 @@ use crate::{
     rbx_snapshot::{RbxSnapshotInstance, reify_root, reconcile_subtree},
 };
 
-#[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
 pub struct InstanceChanges {
     pub added: HashSet<RbxId>,
     pub removed: HashSet<RbxId>,
     pub updated: HashSet<RbxId>,
 }
 
+impl InstanceChanges {
+    pub fn is_empty(&self) -> bool {
+        self.added.is_empty() && self.removed.is_empty() && self.updated.is_empty()
+    }
+}
+
 pub struct RbxSession {
     tree: RbxTree,
     paths_to_node_ids: PathMap<RbxId>,
@@ -67,7 +73,9 @@ impl RbxSession {
 
         let snapshot = snapshot_instances_from_imfs(&imfs, &closest_path)
             .expect("Could not generate instance snapshot");
-        reconcile_subtree(&mut self.tree, instance_id, &snapshot);
+
+        let mut changes = InstanceChanges::default();
+        reconcile_subtree(&mut self.tree, instance_id, &snapshot, &mut changes);
     }
 
     pub fn path_created(&mut self, path: &Path) {
@@ -108,15 +116,13 @@ impl RbxSession {
             },
         };
 
-        let removed_ids: HashSet<RbxId> = removed_subtree.iter_all_ids().collect();
+        let changes = InstanceChanges {
+            added: HashSet::new(),
+            removed: removed_subtree.iter_all_ids().collect(),
+            updated: HashSet::new(),
+        };
 
-        self.message_queue.push_messages(&[
-            InstanceChanges {
-                added: HashSet::new(),
-                removed: removed_ids,
-                updated: HashSet::new(),
-            }
-        ]);
+        self.message_queue.push_messages(&[changes]);
     }
 
     pub fn path_renamed(&mut self, from_path: &Path, to_path: &Path) {
@@ -148,7 +154,9 @@ fn construct_initial_tree(
         &project.tree,
     );
 
-    reify_root(&snapshot)
+    let mut changes = InstanceChanges::default();
+
+    reify_root(&snapshot, &mut changes)
 }
 
 fn construct_project_node<'a>(
diff --git a/server/src/rbx_snapshot.rs b/server/src/rbx_snapshot.rs
index 5d226fda..4a45afd0 100644
--- a/server/src/rbx_snapshot.rs
+++ b/server/src/rbx_snapshot.rs
@@ -7,6 +7,8 @@ use std::{
 
 use rbx_tree::{RbxTree, RbxId, RbxInstance, RbxValue};
 
+use crate::rbx_session::InstanceChanges;
+
 pub struct RbxSnapshotInstance<'a> {
     pub name: Cow<'a, str>,
     pub class_name: Cow<'a, str>,
@@ -15,30 +17,37 @@ pub struct RbxSnapshotInstance<'a> {
     pub source_path: Option<PathBuf>,
 }
 
-pub fn reify_root(snapshot: &RbxSnapshotInstance) -> RbxTree {
+pub fn reify_root(snapshot: &RbxSnapshotInstance, changes: &mut InstanceChanges) -> RbxTree {
     let instance = reify_core(snapshot);
     let mut tree = RbxTree::new(instance);
     let root_id = tree.get_root_id();
 
+    changes.added.insert(root_id);
+
     for child in &snapshot.children {
-        reify_subtree(child, &mut tree, root_id);
+        reify_subtree(child, &mut tree, root_id, changes);
     }
 
     tree
 }
 
-pub fn reify_subtree(snapshot: &RbxSnapshotInstance, tree: &mut RbxTree, parent_id: RbxId) {
+pub fn reify_subtree(snapshot: &RbxSnapshotInstance, tree: &mut RbxTree, parent_id: RbxId, changes: &mut InstanceChanges) {
     let instance = reify_core(snapshot);
     let id = tree.insert_instance(instance, parent_id);
 
+    changes.added.insert(id);
+
     for child in &snapshot.children {
-        reify_subtree(child, tree, id);
+        reify_subtree(child, tree, id, changes);
     }
 }
 
-pub fn reconcile_subtree(tree: &mut RbxTree, id: RbxId, snapshot: &RbxSnapshotInstance) {
-    reconcile_instance_properties(tree.get_instance_mut(id).unwrap(), snapshot);
-    reconcile_instance_children(tree, id, snapshot);
+pub fn reconcile_subtree(tree: &mut RbxTree, id: RbxId, snapshot: &RbxSnapshotInstance, changes: &mut InstanceChanges) {
+    if reconcile_instance_properties(tree.get_instance_mut(id).unwrap(), snapshot) {
+        changes.updated.insert(id);
+    }
+
+    reconcile_instance_children(tree, id, snapshot, changes);
 }
 
 fn reify_core(snapshot: &RbxSnapshotInstance) -> RbxInstance {
@@ -114,8 +123,12 @@ fn reconcile_instance_properties(instance: &mut RbxInstance, snapshot: &RbxSnaps
     has_diffs
 }
 
-fn reconcile_instance_children(tree: &mut RbxTree, id: RbxId, snapshot: &RbxSnapshotInstance) {
-    // TODO: enumerate and match up children, update props, construct and delete IDs
+fn reconcile_instance_children(
+    tree: &mut RbxTree,
+    id: RbxId,
+    snapshot: &RbxSnapshotInstance,
+    changes: &mut InstanceChanges
+) {
     let children_ids = tree.get_instance(id).unwrap().get_children_ids().to_vec();
     let child_count = children_ids.len().max(snapshot.children.len());
 
@@ -144,14 +157,18 @@ fn reconcile_instance_children(tree: &mut RbxTree, id: RbxId, snapshot: &RbxSnap
     }
 
     for child_snapshot in &children_to_add {
-        reify_subtree(child_snapshot, tree, id);
+        reify_subtree(child_snapshot, tree, id, changes);
     }
 
     for child_id in &children_to_remove {
-        tree.remove_instance(*child_id);
+        if let Some(subtree) = tree.remove_instance(*child_id) {
+            for id in subtree.iter_all_ids() {
+                changes.removed.insert(id);
+            }
+        }
     }
 
     for (child_id, child_snapshot) in &children_to_update {
-        reconcile_subtree(tree, *child_id, child_snapshot);
+        reconcile_subtree(tree, *child_id, child_snapshot, changes);
     }
 }
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