refactor: add has id

crates/loro-core/src/change.rs

@@ -5,10 +5,10 @@
 //!
 //! In future, we may also use [Change] to represent a transaction. But this decision is postponed.
 
-
 use crate::{
     id::{Counter, ID},
     op::Op,
+    span::HasId,
 };
 use rle::{HasLength, Mergable, RleVec};
 use smallvec::SmallVec;
@@ -121,3 +121,9 @@ impl Mergable<ChangeMergeCfg> for Change {
             && self.lamport + self.len() as Lamport == other.lamport
     }
 }
+
+impl HasId for Change {
+    fn id_start(&self) -> ID {
+        self.id
+    }
+}

crates/loro-core/src/op.rs

@@ -1,7 +1,7 @@
 use crate::{
     container::ContainerID,
     id::{Counter, ID},
-    span::IdSpan,
+    span::{HasId, IdSpan},
 };
 use rle::{HasLength, Mergable, RleVec, Sliceable};
 mod insert_content;
@@ -124,3 +124,9 @@ impl Sliceable for Op {
         }
     }
 }
+
+impl HasId for Op {
+    fn id_start(&self) -> ID {
+        self.id
+    }
+}

crates/loro-core/src/span.rs

@@ -155,6 +155,28 @@ impl Mergable for IdSpan {
     }
 }
 
+pub trait HasId {
+    fn id_start(&self) -> ID;
+}
+
+pub trait HasIdSpan: HasId + HasLength {
+    fn id_end(&self) -> ID {
+        self.id_start().inc(self.len() as i32)
+    }
+
+    fn id_last(&self) -> ID {
+        self.id_start().inc(self.len() as i32 - 1)
+    }
+}
+impl<T: HasId + HasLength> HasIdSpan for T {}
+
+impl HasId for IdSpan {
+    #[inline]
+    fn id_start(&self) -> ID {
+        self.min_id()
+    }
+}
+
 #[cfg(test)]
 mod test_id_span {
     use rle::RleVec;