From 06cd6b577dd7716f743ba112c0655ad7087cabfb Mon Sep 17 00:00:00 2001
From: Zixuan Chen <remch183@outlook.com>
Date: Wed, 17 Jul 2024 12:32:03 +0800
Subject: [PATCH] refactor: rename "OpGroup" to "ContainerHistoryCache"

---
 crates/loro-internal/src/{group.rs => history_cache.rs} | 9 +++++++--
 crates/loro-internal/src/lib.rs                         | 2 +-
 crates/loro-internal/src/oplog.rs                       | 6 +++---
 3 files changed, 11 insertions(+), 6 deletions(-)
 rename crates/loro-internal/src/{group.rs => history_cache.rs} (97%)

diff --git a/crates/loro-internal/src/group.rs b/crates/loro-internal/src/history_cache.rs
similarity index 97%
rename from crates/loro-internal/src/group.rs
rename to crates/loro-internal/src/history_cache.rs
index 2578da4d..bbe85fd8 100644
--- a/crates/loro-internal/src/group.rs
+++ b/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() {
diff --git a/crates/loro-internal/src/lib.rs b/crates/loro-internal/src/lib.rs
index 1a8ef965..90a42999 100644
--- a/crates/loro-internal/src/lib.rs
+++ b/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;
diff --git a/crates/loro-internal/src/oplog.rs b/crates/loro-internal/src/oplog.rs
index 2a7954d1..7ab3abd4 100644
--- a/crates/loro-internal/src/oplog.rs
+++ b/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(),