refactor: rename "OpGroup" to "ContainerHistoryCache"

crates/loro-internal/src/history_cache.rs

@@ -19,13 +19,18 @@ use crate::{
     VersionVector,
 };
 
+/// A cache for the history of a container.
+///
+/// There are cases where a container needs a view of the history of the container.
+/// For example, when switching to an older version, a map container may need to know the value of a key at a certain version.
+/// This cache provides a faster way to do that than scanning the oplog.
 #[derive(Debug)]
-pub(crate) struct OpGroups {
+pub(crate) struct ContainerHistoryCache {
     arena: SharedArena,
     groups: FxHashMap<ContainerIdx, OpGroup>,
 }
 
-impl OpGroups {
+impl ContainerHistoryCache {
     pub(crate) fn fork(&self, arena: SharedArena) -> Self {
         let mut groups = FxHashMap::with_capacity_and_hasher(self.groups.len(), Default::default());
         for (container_idx, group) in self.groups.iter() {

crates/loro-internal/src/lib.rs

@@ -54,7 +54,7 @@ pub mod event;
 
 pub use error::{LoroError, LoroResult};
 pub mod estimated_size;
-pub(crate) mod group;
+pub(crate) mod history_cache;
 pub(crate) mod macros;
 pub(crate) mod state;
 pub mod undo;

crates/loro-internal/src/oplog.rs

@@ -16,7 +16,7 @@ use crate::container::list::list_op;
 use crate::dag::{Dag, DagUtils};
 use crate::encoding::ParsedHeaderAndBody;
 use crate::encoding::{decode_oplog, encode_oplog, EncodeMode};
-use crate::group::OpGroups;
+use crate::history_cache::ContainerHistoryCache;
 use crate::id::{Counter, PeerID, ID};
 use crate::op::{FutureInnerContent, ListSlice, RawOpContent, RemoteOp, RichOp};
 use crate::span::{HasCounterSpan, HasIdSpan, HasLamportSpan};
@@ -45,7 +45,7 @@ pub struct OpLog {
     pub(crate) dag: AppDag,
     pub(crate) arena: SharedArena,
     change_store: ChangeStore,
-    pub(crate) op_groups: OpGroups,
+    pub(crate) op_groups: ContainerHistoryCache,
     /// **lamport starts from 0**
     pub(crate) next_lamport: Lamport,
     pub(crate) latest_timestamp: Timestamp,
@@ -187,7 +187,7 @@ impl OpLog {
         Self {
             change_store: ChangeStore::new_mem(&arena, cfg.merge_interval.clone()),
             dag: AppDag::default(),
-            op_groups: OpGroups::new(arena.clone()),
+            op_groups: ContainerHistoryCache::new(arena.clone()),
             arena,
             next_lamport: 0,
             latest_timestamp: Timestamp::default(),