chore: update lib-ot documentation again and rename some structs

frontend/rust-lib/flowy-folder/src/services/persistence/mod.rs

@@ -13,7 +13,7 @@ use flowy_folder_data_model::revision::{AppRevision, TrashRevision, ViewRevision
 use flowy_revision::disk::{RevisionRecord, RevisionState};
 use flowy_revision::mk_text_block_revision_disk_cache;
 use flowy_sync::{client_folder::FolderPad, entities::revision::Revision};
-use lib_ot::core::PlainTextDeltaBuilder;
+use lib_ot::core::TextDeltaBuilder;
 use std::sync::Arc;
 use tokio::sync::RwLock;
 pub use version_1::{app_sql::*, trash_sql::*, v1_impl::V1Transaction, view_sql::*, workspace_sql::*};
@@ -110,7 +110,7 @@ impl FolderPersistence {
     pub async fn save_folder(&self, user_id: &str, folder_id: &FolderId, folder: FolderPad) -> FlowyResult<()> {
         let pool = self.database.db_pool()?;
         let json = folder.to_json()?;
-        let delta_data = PlainTextDeltaBuilder::new().insert(&json).build().to_json_bytes();
+        let delta_data = TextDeltaBuilder::new().insert(&json).build().to_json_bytes();
         let revision = Revision::initial_revision(user_id, folder_id.as_ref(), delta_data);
         let record = RevisionRecord {
             revision,

frontend/rust-lib/flowy-folder/src/services/web_socket.rs

@@ -10,7 +10,7 @@ use flowy_sync::{
     },
 };
 use lib_infra::future::{BoxResultFuture, FutureResult};
-use lib_ot::core::{OperationTransform, PhantomAttributes, PlainTextDelta};
+use lib_ot::core::{OperationTransform, PhantomAttributes, TextDelta};
 use parking_lot::RwLock;
 use std::{sync::Arc, time::Duration};
 
@@ -56,7 +56,7 @@ struct FolderConflictResolver {
 }
 
 impl ConflictResolver<PhantomAttributes> for FolderConflictResolver {
-    fn compose_delta(&self, delta: PlainTextDelta) -> BoxResultFuture<DeltaMD5, FlowyError> {
+    fn compose_delta(&self, delta: TextDelta) -> BoxResultFuture<DeltaMD5, FlowyError> {
         let folder_pad = self.folder_pad.clone();
         Box::pin(async move {
             let md5 = folder_pad.write().compose_remote_delta(delta)?;
@@ -64,15 +64,12 @@ impl ConflictResolver<PhantomAttributes> for FolderConflictResolver {
         })
     }
 
-    fn transform_delta(
+    fn transform_delta(&self, delta: TextDelta) -> BoxResultFuture<TransformDeltas<PhantomAttributes>, FlowyError> {
-        &self,
-        delta: PlainTextDelta,
-    ) -> BoxResultFuture<TransformDeltas<PhantomAttributes>, FlowyError> {
         let folder_pad = self.folder_pad.clone();
         Box::pin(async move {
             let read_guard = folder_pad.read();
-            let mut server_prime: Option<PlainTextDelta> = None;
+            let mut server_prime: Option<TextDelta> = None;
-            let client_prime: PlainTextDelta;
+            let client_prime: TextDelta;
             if read_guard.is_empty() {
                 // Do nothing
                 client_prime = delta;
@@ -89,7 +86,7 @@ impl ConflictResolver<PhantomAttributes> for FolderConflictResolver {
         })
     }
 
-    fn reset_delta(&self, delta: PlainTextDelta) -> BoxResultFuture<DeltaMD5, FlowyError> {
+    fn reset_delta(&self, delta: TextDelta) -> BoxResultFuture<DeltaMD5, FlowyError> {
         let folder_pad = self.folder_pad.clone();
         Box::pin(async move {
             let md5 = folder_pad.write().reset_folder(delta)?;

frontend/rust-lib/flowy-grid/src/services/persistence/migration.rs

@@ -9,7 +9,7 @@ use flowy_revision::{mk_grid_block_revision_disk_cache, RevisionLoader, Revision
 use flowy_sync::client_grid::{make_grid_rev_json_str, GridRevisionPad};
 use flowy_sync::entities::revision::Revision;
 
-use lib_ot::core::PlainTextDeltaBuilder;
+use lib_ot::core::TextDeltaBuilder;
 use serde::{Deserialize, Serialize};
 use std::str::FromStr;
 use std::sync::Arc;
@@ -48,7 +48,7 @@ impl GridMigration {
         let pool = self.database.db_pool()?;
         let grid_rev_pad = self.get_grid_revision_pad(grid_id).await?;
         let json = grid_rev_pad.json_str()?;
-        let delta_data = PlainTextDeltaBuilder::new().insert(&json).build().to_json_bytes();
+        let delta_data = TextDeltaBuilder::new().insert(&json).build().to_json_bytes();
         let revision = Revision::initial_revision(&user_id, grid_id, delta_data);
         let record = RevisionRecord::new(revision);
         //

frontend/rust-lib/flowy-text-block/tests/editor/op_test.rs

@@ -342,11 +342,8 @@ fn apply_1000() {
 #[test]
 fn apply_test() {
     let s = "hello";
-    let delta_a = PlainTextDeltaBuilder::new().insert(s).build();
+    let delta_a = TextDeltaBuilder::new().insert(s).build();
-    let delta_b = PlainTextDeltaBuilder::new()
+    let delta_b = TextDeltaBuilder::new().retain(s.len()).insert(", AppFlowy").build();
-        .retain(s.len())
-        .insert(", AppFlowy")
-        .build();
 
     let after_a = delta_a.content_str().unwrap();
     let after_b = delta_b.apply(&after_a).unwrap();
@@ -384,7 +381,7 @@ fn invert() {
 #[test]
 fn invert_test() {
     let s = "hello world";
-    let delta = PlainTextDeltaBuilder::new().insert(s).build();
+    let delta = TextDeltaBuilder::new().insert(s).build();
     let invert_delta = delta.invert_str("");
     assert_eq!(delta.utf16_base_len, invert_delta.utf16_target_len);
     assert_eq!(delta.utf16_target_len, invert_delta.utf16_base_len);

shared-lib/flowy-sync/src/client_folder/builder.rs

@@ -7,7 +7,7 @@ use crate::{
 };
 
 use flowy_folder_data_model::revision::{TrashRevision, WorkspaceRevision};
-use lib_ot::core::{PhantomAttributes, PlainTextDelta, PlainTextDeltaBuilder};
+use lib_ot::core::{PhantomAttributes, TextDelta, TextDeltaBuilder};
 use serde::{Deserialize, Serialize};
 use std::sync::Arc;
 
@@ -35,7 +35,7 @@ impl FolderPadBuilder {
         self
     }
 
-    pub(crate) fn build_with_delta(self, mut delta: PlainTextDelta) -> CollaborateResult<FolderPad> {
+    pub(crate) fn build_with_delta(self, mut delta: TextDelta) -> CollaborateResult<FolderPad> {
         if delta.is_empty() {
             delta = default_folder_delta();
         }
@@ -61,7 +61,7 @@ impl FolderPadBuilder {
         Ok(FolderPad {
             workspaces: self.workspaces,
             trash: self.trash,
-            delta: PlainTextDeltaBuilder::new().insert(&json).build(),
+            delta: TextDeltaBuilder::new().insert(&json).build(),
         })
     }
 }

shared-lib/flowy-sync/src/client_folder/folder_pad.rs

@@ -400,14 +400,14 @@ impl FolderPad {
 }
 
 pub fn default_folder_delta() -> FolderDelta {
-    PlainTextDeltaBuilder::new()
+    TextDeltaBuilder::new()
         .insert(r#"{"workspaces":[],"trash":[]}"#)
         .build()
 }
 
 pub fn initial_folder_delta(folder_pad: &FolderPad) -> CollaborateResult<FolderDelta> {
     let json = folder_pad.to_json()?;
-    let delta = PlainTextDeltaBuilder::new().insert(&json).build();
+    let delta = TextDeltaBuilder::new().insert(&json).build();
     Ok(delta)
 }
 
@@ -434,7 +434,7 @@ mod tests {
     use chrono::Utc;
 
     use flowy_folder_data_model::revision::{AppRevision, TrashRevision, ViewRevision, WorkspaceRevision};
-    use lib_ot::core::{OperationTransform, PlainTextDelta, PlainTextDeltaBuilder};
+    use lib_ot::core::{OperationTransform, TextDelta, TextDeltaBuilder};
 
     #[test]
     fn folder_add_workspace() {
@@ -749,7 +749,7 @@ mod tests {
     fn test_folder() -> (FolderPad, FolderDelta, WorkspaceRevision) {
         let mut folder = FolderPad::default();
         let folder_json = serde_json::to_string(&folder).unwrap();
-        let mut delta = PlainTextDeltaBuilder::new().insert(&folder_json).build();
+        let mut delta = TextDeltaBuilder::new().insert(&folder_json).build();
 
         let mut workspace_rev = WorkspaceRevision::default();
         workspace_rev.name = "😁 my first workspace".to_owned();
@@ -791,7 +791,7 @@ mod tests {
     fn test_trash() -> (FolderPad, FolderDelta, TrashRevision) {
         let mut folder = FolderPad::default();
         let folder_json = serde_json::to_string(&folder).unwrap();
-        let mut delta = PlainTextDeltaBuilder::new().insert(&folder_json).build();
+        let mut delta = TextDeltaBuilder::new().insert(&folder_json).build();
 
         let mut trash_rev = TrashRevision::default();
         trash_rev.name = "🚽 my first trash".to_owned();
@@ -810,7 +810,7 @@ mod tests {
         (folder, delta, trash_rev)
     }
 
-    fn make_folder_from_delta(mut initial_delta: FolderDelta, deltas: Vec<PlainTextDelta>) -> FolderPad {
+    fn make_folder_from_delta(mut initial_delta: FolderDelta, deltas: Vec<TextDelta>) -> FolderPad {
         for delta in deltas {
             initial_delta = initial_delta.compose(&delta).unwrap();
         }

shared-lib/flowy-sync/src/client_grid/grid_block_revsion_pad.rs

@@ -4,13 +4,13 @@ use crate::util::{cal_diff, make_delta_from_revisions};
 use flowy_grid_data_model::revision::{
     gen_block_id, gen_row_id, CellRevision, GridBlockRevision, RowMetaChangeset, RowRevision,
 };
-use lib_ot::core::{OperationTransform, PhantomAttributes, PlainTextDelta, PlainTextDeltaBuilder};
+use lib_ot::core::{OperationTransform, PhantomAttributes, TextDelta, TextDeltaBuilder};
 use std::borrow::Cow;
 use std::collections::HashMap;
 use std::sync::Arc;
 
-pub type GridBlockRevisionDelta = PlainTextDelta;
+pub type GridBlockRevisionDelta = TextDelta;
-pub type GridBlockRevisionDeltaBuilder = PlainTextDeltaBuilder;
+pub type GridBlockRevisionDeltaBuilder = TextDeltaBuilder;
 
 #[derive(Debug, Clone)]
 pub struct GridBlockRevisionPad {
@@ -247,7 +247,7 @@ pub struct GridBlockMetaChange {
 
 pub fn make_grid_block_delta(block_rev: &GridBlockRevision) -> GridBlockRevisionDelta {
     let json = serde_json::to_string(&block_rev).unwrap();
-    PlainTextDeltaBuilder::new().insert(&json).build()
+    TextDeltaBuilder::new().insert(&json).build()
 }
 
 pub fn make_grid_block_revisions(user_id: &str, grid_block_meta_data: &GridBlockRevision) -> RepeatedRevision {

shared-lib/flowy-sync/src/client_grid/grid_revision_pad.rs

@@ -9,12 +9,12 @@ use flowy_grid_data_model::revision::{
     GridLayoutRevision, GridRevision, GridSettingRevision, GridSortRevision,
 };
 use lib_infra::util::move_vec_element;
-use lib_ot::core::{OperationTransform, PhantomAttributes, PlainTextDelta, PlainTextDeltaBuilder};
+use lib_ot::core::{OperationTransform, PhantomAttributes, TextDelta, TextDeltaBuilder};
 use std::collections::HashMap;
 use std::sync::Arc;
 
-pub type GridRevisionDelta = PlainTextDelta;
+pub type GridRevisionDelta = TextDelta;
-pub type GridRevisionDeltaBuilder = PlainTextDeltaBuilder;
+pub type GridRevisionDeltaBuilder = TextDeltaBuilder;
 
 pub struct GridRevisionPad {
     grid_rev: Arc<GridRevision>,
@@ -548,7 +548,7 @@ pub struct GridChangeset {
 
 pub fn make_grid_delta(grid_rev: &GridRevision) -> GridRevisionDelta {
     let json = serde_json::to_string(&grid_rev).unwrap();
-    PlainTextDeltaBuilder::new().insert(&json).build()
+    TextDeltaBuilder::new().insert(&json).build()
 }
 
 pub fn make_grid_revisions(user_id: &str, grid_rev: &GridRevision) -> RepeatedRevision {

shared-lib/flowy-sync/src/entities/folder.rs

@@ -1,7 +1,7 @@
 use flowy_derive::ProtoBuf;
-use lib_ot::core::PlainTextDelta;
+use lib_ot::core::TextDelta;
 
-pub type FolderDelta = PlainTextDelta;
+pub type FolderDelta = TextDelta;
 
 #[derive(ProtoBuf, Default, Debug, Clone, Eq, PartialEq)]
 pub struct FolderInfo {

shared-lib/flowy-sync/src/server_folder/folder_pad.rs

@@ -1,5 +1,5 @@
 use crate::{entities::folder::FolderDelta, errors::CollaborateError, synchronizer::RevisionSyncObject};
-use lib_ot::core::{OperationTransform, PhantomAttributes, PlainTextDelta};
+use lib_ot::core::{OperationTransform, PhantomAttributes, TextDelta};
 
 pub struct ServerFolder {
     folder_id: String,
@@ -20,13 +20,13 @@ impl RevisionSyncObject<PhantomAttributes> for ServerFolder {
         &self.folder_id
     }
 
-    fn compose(&mut self, other: &PlainTextDelta) -> Result<(), CollaborateError> {
+    fn compose(&mut self, other: &TextDelta) -> Result<(), CollaborateError> {
         let new_delta = self.delta.compose(other)?;
         self.delta = new_delta;
         Ok(())
     }
 
-    fn transform(&self, other: &PlainTextDelta) -> Result<(PlainTextDelta, PlainTextDelta), CollaborateError> {
+    fn transform(&self, other: &TextDelta) -> Result<(TextDelta, TextDelta), CollaborateError> {
         let value = self.delta.transform(other)?;
         Ok(value)
     }
@@ -35,7 +35,7 @@ impl RevisionSyncObject<PhantomAttributes> for ServerFolder {
         self.delta.to_json_str()
     }
 
-    fn set_delta(&mut self, new_delta: PlainTextDelta) {
+    fn set_delta(&mut self, new_delta: TextDelta) {
         self.delta = new_delta;
     }
 }

shared-lib/lib-ot/src/core/delta/builder.rs

@@ -1,9 +1,7 @@
 use crate::core::delta::{trim, Delta};
-use crate::core::operation::{Attributes, PhantomAttributes};
+use crate::core::operation::Attributes;
 use crate::core::Operation;
 
-pub type PlainTextDeltaBuilder = DeltaBuilder<PhantomAttributes>;
-
 /// A builder for creating new [Delta] objects.
 ///
 /// Note that all edit operations must be sorted; the start point of each
@@ -12,8 +10,8 @@ pub type PlainTextDeltaBuilder = DeltaBuilder<PhantomAttributes>;
 /// # Examples
 ///
 /// ```
-/// use lib_ot::core::PlainTextDeltaBuilder;
+/// use lib_ot::core::TextDeltaBuilder;
-/// let delta = PlainTextDeltaBuilder::new()
+/// let delta = TextDeltaBuilder::new()
 ///         .insert("AppFlowy")
 ///         .build();
 /// assert_eq!(delta.content_str().unwrap(), "AppFlowy");
@@ -74,13 +72,13 @@ where
     /// # Examples
     ///
     /// ```
-    /// use lib_ot::core::{OperationTransform, PlainTextDeltaBuilder};
+    /// use lib_ot::core::{OperationTransform, TextDeltaBuilder};
     ///
-    /// let delta = PlainTextDeltaBuilder::new()
+    /// let delta = TextDeltaBuilder::new()
     ///         .insert("AppFlowy...")
     ///         .build();
     ///
-    /// let changeset = PlainTextDeltaBuilder::new()
+    /// let changeset = TextDeltaBuilder::new()
     ///         .retain(8)
     ///         .delete(3)
     ///         .build();
@@ -110,9 +108,9 @@ where
     /// # Examples
     ///
     /// ```
-    /// use lib_ot::core::{OperationTransform, PlainTextDeltaBuilder};
+    /// use lib_ot::core::{OperationTransform, TextDeltaBuilder};
     /// use lib_ot::rich_text::{RichTextAttribute, RichTextDeltaBuilder};
-    /// let delta = PlainTextDeltaBuilder::new()
+    /// let delta = TextDeltaBuilder::new()
     ///         .retain(3)
     ///         .trim()
     ///         .build();

shared-lib/lib-ot/src/core/delta/cursor.rs

@@ -29,14 +29,17 @@ where
     /// # Examples
     ///
     /// ```
-    /// use lib_ot::core::{DeltaIterator, Interval, Operation};
+    /// use lib_ot::core::{DeltaCursor, DeltaIterator, Interval, Operation};
     /// use lib_ot::rich_text::RichTextDelta;
     /// let mut delta = RichTextDelta::default();   
-    /// let op_1 = Operation::insert("123");    
+    /// delta.add(Operation::insert("123"));    
-    /// let op_2 = Operation::insert("4");
+    /// delta.add(Operation::insert("4"));
-    /// delta.add(op_1.clone());
+    ///
-    /// delta.add(op_2.clone());
+    /// let mut cursor = DeltaCursor::new(&delta, Interval::new(0, 3));
-    /// assert_eq!(DeltaIterator::from_interval(&delta, Interval::new(0, 3)).ops(), vec![op_1.clone()]);
+    /// assert_eq!(cursor.next_iv(), Interval::new(0,3));
+    /// assert_eq!(cursor.next_with_len(Some(2)).unwrap(), Operation::insert("12"));
+    /// assert_eq!(cursor.get_next_op().unwrap(), Operation::insert("3"));
+    /// assert_eq!(cursor.get_next_op(), None);
     /// ```
     pub fn new(delta: &'a Delta<T>, interval: Interval) -> DeltaCursor<'a, T> {
         // debug_assert!(interval.start <= delta.target_len);

shared-lib/lib-ot/src/core/delta/delta.rs

@@ -1,9 +1,10 @@
 use crate::errors::{ErrorBuilder, OTError, OTErrorCode};
 
 use crate::core::delta::{DeltaIterator, MAX_IV_LEN};
-use crate::core::flowy_str::OTString;
 use crate::core::interval::Interval;
 use crate::core::operation::{Attributes, Operation, OperationTransform, PhantomAttributes};
+use crate::core::ot_str::OTString;
+use crate::core::DeltaBuilder;
 use bytes::Bytes;
 use serde::de::DeserializeOwned;
 use std::{
@@ -14,12 +15,15 @@ use std::{
     str::FromStr,
 };
 
-pub type PlainTextDelta = Delta<PhantomAttributes>;
+pub type TextDelta = Delta<PhantomAttributes>;
+pub type TextDeltaBuilder = DeltaBuilder<PhantomAttributes>;
 
 /// A [Delta] contains list of operations that consists of 'Retain', 'Delete' and 'Insert' operation.
 /// Check out the [Operation] for more details. It describes the document as a sequence of
 /// operations.
 ///
+/// You could check [this](https://appflowy.gitbook.io/docs/essential-documentation/contribute-to-appflowy/architecture/backend/delta) out for more information.
+///
 /// If the [T] supports 'serde', that will enable delta to serialize to JSON or deserialize from
 /// a JSON string.
 ///
@@ -176,10 +180,10 @@ where
     /// # Examples
     ///
     /// ```
-    ///  use lib_ot::core::PlainTextDeltaBuilder;
+    ///  use lib_ot::core::TextDeltaBuilder;
     ///  let s = "hello";
-    ///  let delta_a = PlainTextDeltaBuilder::new().insert(s).build();
+    ///  let delta_a = TextDeltaBuilder::new().insert(s).build();
-    ///  let delta_b = PlainTextDeltaBuilder::new()
+    ///  let delta_b = TextDeltaBuilder::new()
     ///         .retain(s.len())
     ///         .insert(", AppFlowy")
     ///         .build();
@@ -233,9 +237,9 @@ where
     /// # Examples
     ///
     /// ```
-    ///  use lib_ot::core::PlainTextDeltaBuilder;
+    ///  use lib_ot::core::TextDeltaBuilder;
     ///  let s = "hello world";
-    ///  let delta = PlainTextDeltaBuilder::new().insert(s).build();
+    ///  let delta = TextDeltaBuilder::new().insert(s).build();
     ///  let invert_delta = delta.invert_str(s);
     ///  assert_eq!(delta.utf16_base_len, invert_delta.utf16_target_len);
     ///  assert_eq!(delta.utf16_target_len, invert_delta.utf16_base_len);

shared-lib/lib-ot/src/core/delta/iterator.rs

@@ -7,17 +7,26 @@ use std::ops::{Deref, DerefMut};
 
 pub(crate) const MAX_IV_LEN: usize = i32::MAX as usize;
 
-/// Retain the 'n' characters with the attributes. Use 'retain' instead if you don't
+/// [DeltaIterator] is used to iterate over a delta.
-/// need any attributes.
 /// # Examples
 ///
+/// You could check [this](https://appflowy.gitbook.io/docs/essential-documentation/contribute-to-appflowy/architecture/backend/delta) out for more information.
+///
 /// ```
-/// use lib_ot::rich_text::{RichTextAttribute, RichTextDelta, RichTextDeltaBuilder};
+///  use lib_ot::core::{DeltaIterator, Interval, Operation};
+///  use lib_ot::rich_text::RichTextDelta;
+///  let mut delta = RichTextDelta::default();
+///  delta.add(Operation::insert("123"));
+///  delta.add(Operation::insert("4"));
+///  assert_eq!(
+///     DeltaIterator::from_interval(&delta, Interval::new(0, 2)).ops(),
+///     vec![Operation::insert("12")]
+///  );
 ///
-/// let mut attribute = RichTextAttribute::Bold(true);
+///  assert_eq!(
-/// let delta = RichTextDeltaBuilder::new().retain_with_attributes(7, attribute.into()).build();
+///     DeltaIterator::from_interval(&delta, Interval::new(1, 3)).ops(),
-///
+///     vec![Operation::insert("23")]
-/// assert_eq!(delta.to_json_str(), r#"[{"retain":7,"attributes":{"bold":true}}]"#);
+///  );
 /// ```
 pub struct DeltaIterator<'a, T: Attributes> {
     cursor: DeltaCursor<'a, T>,

shared-lib/lib-ot/src/core/mod.rs

@@ -1,9 +1,9 @@
 mod delta;
-mod flowy_str;
 mod interval;
 mod operation;
+mod ot_str;
 
 pub use delta::*;
-pub use flowy_str::*;
 pub use interval::*;
 pub use operation::*;
+pub use ot_str::*;

shared-lib/lib-ot/src/core/operation/operation.rs

@@ -1,5 +1,5 @@
-use crate::core::flowy_str::OTString;
 use crate::core::interval::Interval;
+use crate::core::ot_str::OTString;
 use crate::errors::OTError;
 use serde::{Deserialize, Serialize, __private::Formatter};
 use std::fmt::Display;
@@ -21,9 +21,9 @@ pub trait OperationTransform {
     /// # Examples
     ///
     /// ```
-    ///  use lib_ot::core::{OperationTransform, PlainTextDeltaBuilder};
+    ///  use lib_ot::core::{OperationTransform, TextDeltaBuilder};
-    ///  let document = PlainTextDeltaBuilder::new().build();
+    ///  let document = TextDeltaBuilder::new().build();
-    ///  let delta = PlainTextDeltaBuilder::new().insert("abc").build();
+    ///  let delta = TextDeltaBuilder::new().insert("abc").build();
     ///  let new_document = document.compose(&delta).unwrap();
     ///  assert_eq!(new_document.content_str().unwrap(), "abc".to_owned());
     /// ```
@@ -50,9 +50,9 @@ pub trait OperationTransform {
     /// # Examples
     ///
     /// ```
-    /// use lib_ot::core::{OperationTransform, PlainTextDeltaBuilder};
+    /// use lib_ot::core::{OperationTransform, TextDeltaBuilder};
-    /// let original_document = PlainTextDeltaBuilder::new().build();
+    /// let original_document = TextDeltaBuilder::new().build();
-    /// let delta = PlainTextDeltaBuilder::new().insert("abc").build();
+    /// let delta = TextDeltaBuilder::new().insert("abc").build();
     ///
     /// let undo_delta = delta.invert(&original_document);
     /// let new_document = original_document.compose(&delta).unwrap();
@@ -67,8 +67,8 @@ pub trait OperationTransform {
 /// Each operation can carry attributes. For example, the [RichTextAttributes] has a list of key/value attributes.
 /// Such as { bold: true, italic: true }.  
 ///
-/// Because [Operation] is generic over the T, so you must specify the T. For example, the [PlainTextDelta]. It use
+///Because [Operation] is generic over the T, so you must specify the T. For example, the [TextDelta] uses
-/// use [PhantomAttributes] as the T. [PhantomAttributes] does nothing, just a phantom.
+///[PhantomAttributes] as the T. [PhantomAttributes] does nothing, just a phantom.
 ///
 pub trait Attributes: Default + Display + Eq + PartialEq + Clone + Debug + OperationTransform {
     fn is_empty(&self) -> bool {
@@ -90,6 +90,8 @@ pub trait Attributes: Default + Display + Eq + PartialEq + Clone + Debug + Opera
 /// * Retain
 /// * Insert
 ///
+/// You could check [this](https://appflowy.gitbook.io/docs/essential-documentation/contribute-to-appflowy/architecture/backend/delta) out for more information.
+///
 /// The [T] should support serde if you want to serialize/deserialize the operation
 /// to json string. You could check out the operation_serde.rs for more information.
 ///

shared-lib/lib-ot/src/core/operation/operation_serde.rs

@@ -1,5 +1,5 @@
-use crate::core::flowy_str::OTString;
 use crate::core::operation::{Attributes, Insert, Operation, Retain};
+use crate::core::ot_str::OTString;
 use serde::{
     de,
     de::{MapAccess, SeqAccess, Visitor},

shared-lib/lib-ot/src/core/ot_str.rs

@@ -86,8 +86,8 @@ impl OTString {
     /// assert_eq!(iter.skip(OTString::from("ab一二").utf16_len()).next().unwrap(), "👋".to_string());
     /// ```
     #[allow(dead_code)]
-    pub fn utf16_code_point_iter(&self) -> FlowyUtf16CodePointIterator {
+    pub fn utf16_code_point_iter(&self) -> OTUtf16CodePointIterator {
-        FlowyUtf16CodePointIterator::new(self, 0)
+        OTUtf16CodePointIterator::new(self, 0)
     }
 }
 
@@ -218,21 +218,21 @@ impl<'a> Iterator for Utf16CodeUnitIterator<'a> {
     }
 }
 
-pub struct FlowyUtf16CodePointIterator<'a> {
+pub struct OTUtf16CodePointIterator<'a> {
     s: &'a OTString,
     offset: usize,
 }
 
-impl<'a> FlowyUtf16CodePointIterator<'a> {
+impl<'a> OTUtf16CodePointIterator<'a> {
     pub fn new(s: &'a OTString, offset: usize) -> Self {
-        FlowyUtf16CodePointIterator { s, offset }
+        OTUtf16CodePointIterator { s, offset }
     }
 }
 
 use crate::core::interval::Interval;
 use std::str;
 
-impl<'a> Iterator for FlowyUtf16CodePointIterator<'a> {
+impl<'a> Iterator for OTUtf16CodePointIterator<'a> {
     type Item = String;
 
     fn next(&mut self) -> Option<Self::Item> {
@@ -278,8 +278,8 @@ pub fn len_utf8_from_first_byte(b: u8) -> usize {
 
 #[cfg(test)]
 mod tests {
-    use crate::core::flowy_str::OTString;
     use crate::core::interval::Interval;
+    use crate::core::ot_str::OTString;
 
     #[test]
     fn flowy_str_code_unit() {