feat: add necessary query entry for change_store

crates/loro-internal/src/oplog/change_store.rs

@@ -1,6 +1,7 @@
 use bytes::Bytes;
 use loro_common::{
-    Counter, HasId, HasIdSpan, HasLamportSpan, IdSpan, Lamport, LoroError, LoroResult, PeerID, ID,
+    Counter, HasId, HasIdSpan, HasLamportSpan, IdLp, IdSpan, Lamport, LoroError, LoroResult,
+    PeerID, ID,
 };
 use once_cell::sync::OnceCell;
 use rle::{HasLength, Mergable, RleCollection, RlePush};
@@ -89,7 +90,7 @@ impl ChangeStore {
         if block.peer == id.peer && block.counter_range.1 > id.counter {
             block.ensure_changes().unwrap();
             Some(BlockChangeRef {
-                change_index: block.get_change_index(id.counter).unwrap(),
+                change_index: block.get_change_index_by_counter(id.counter).unwrap(),
                 block: block.clone(),
             })
         } else {
@@ -97,6 +98,29 @@ impl ChangeStore {
         }
     }
 
+    pub fn get_change_by_idlp(&mut self, idlp: IdLp) -> Option<BlockChangeRef> {
+        // TODO: this can be optimized if we use a more customized tree structure
+        let mut iter = self
+            .kv
+            .range_mut(ID::new(idlp.peer, 0)..ID::new(idlp.peer, i32::MAX));
+        while let Some((_id, block)) = iter.next_back() {
+            if block.lamport_range.1 <= idlp.lamport {
+                return None;
+            }
+
+            if block.lamport_range.0 <= idlp.lamport {
+                block.ensure_changes().unwrap();
+                let index = block.get_change_index_by_lamport(idlp.lamport).unwrap();
+                return Some(BlockChangeRef {
+                    change_index: index,
+                    block: block.clone(),
+                });
+            }
+        }
+
+        None
+    }
+
     pub fn iter_changes(&mut self, id_span: IdSpan) -> impl Iterator<Item = BlockChangeRef> + '_ {
         self.kv
             .range_mut(id_span.id_start()..=id_span.id_end())
@@ -111,9 +135,11 @@ impl ChangeStore {
                     start = 0;
                     end = changes.len();
                 } else {
-                    start = block.get_change_index(id_span.counter.start).unwrap_or(0);
+                    start = block
+                        .get_change_index_by_counter(id_span.counter.start)
+                        .unwrap_or(0);
                     end = block
-                        .get_change_index(id_span.counter.end)
+                        .get_change_index_by_counter(id_span.counter.end)
                         .unwrap_or(changes.len());
                 }
 
@@ -123,6 +149,13 @@ impl ChangeStore {
                 })
             })
     }
+
+    pub fn change_num(&mut self) -> usize {
+        self.kv
+            .iter_mut()
+            .map(|(_, block)| block.change_num())
+            .sum()
+    }
 }
 
 pub struct BlockChangeRef {
@@ -283,7 +316,7 @@ impl ChangesBlock {
         }
     }
 
-    fn get_change_index(&self, counter: Counter) -> Option<usize> {
+    fn get_change_index_by_counter(&self, counter: Counter) -> Option<usize> {
         let changes = self.content.try_changes().unwrap();
         let r = changes.binary_search_by(|c| {
             if c.id.counter > counter {
@@ -301,9 +334,39 @@ impl ChangesBlock {
         }
     }
 
+    fn get_change_index_by_lamport(&self, lamport: Lamport) -> Option<usize> {
+        let changes = self.content.try_changes().unwrap();
+        let r = changes.binary_search_by(|c| {
+            if c.lamport > lamport {
+                Ordering::Greater
+            } else if (c.lamport + c.content_len() as Lamport) <= lamport {
+                Ordering::Less
+            } else {
+                Ordering::Equal
+            }
+        });
+
+        match r {
+            Ok(found) => Some(found),
+            Err(_) => None,
+        }
+    }
+
+    fn get_changes(&mut self) -> LoroResult<&Vec<Change>> {
+        self.content.changes()
+    }
+
     fn id(&self) -> ID {
         ID::new(self.peer, self.counter_range.0)
     }
+
+    pub fn change_num(&self) -> usize {
+        match &self.content {
+            ChangesBlockContent::Changes(c) => c.len(),
+            ChangesBlockContent::Bytes(b) => b.len_changes(),
+            ChangesBlockContent::Both(c, _) => c.len(),
+        }
+    }
 }
 
 #[derive(Clone)]
@@ -398,7 +461,7 @@ impl ChangesBlockBytes {
     fn serialize(changes: &[Change], a: &SharedArena) -> Self {
         let bytes = encode_block(changes, a);
         // TODO: Perf we can calculate header directly without parsing the bytes
-        let mut bytes = ChangesBlockBytes::new(Bytes::from(bytes));
+        let bytes = ChangesBlockBytes::new(Bytes::from(bytes));
         bytes.ensure_header().unwrap();
         bytes
     }
@@ -425,7 +488,7 @@ impl ChangesBlockBytes {
     }
 
     /// Length of the changes
-    fn len_changes(&mut self) -> usize {
+    fn len_changes(&self) -> usize {
         self.ensure_header().unwrap();
         self.header.get().unwrap().n_changes
     }