1 files changed, 100 insertions, 6 deletions

diff --git a/crdt/src/lib.rs b/crdt/src/lib.rs
index 4c41dd0..c0214b3 100644
--- a/crdt/src/lib.rs
+++ b/crdt/src/lib.rs
@@ -1,9 +1,19 @@
 mod vector_clock;
 
+use std::fmt::Display;
+
 use uuid::Uuid;
 
 use crate::vector_clock::VectorClock;
 
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum Error {
+    #[error("object with ID {0} not found")]
+    NotFound(DerivedId),
+}
+
 #[derive(Default)]
 pub struct Doc {
     ops: Vec<Op>,
@@ -26,17 +36,18 @@ impl Doc {
         });
     }
 
-    pub fn realize(&self) -> RealizedDoc {
+    pub fn realize(&self) -> Result<RealizedDoc, Error> {
         let mut realized = RealizedDoc::default();
 
         for op in &self.ops {
-            op.apply(&mut realized);
+            op.apply(&mut realized)?;
         }
 
-        realized
+        Ok(realized)
     }
 }
 
+#[derive(Debug)]
 pub struct Op {
     id: Uuid,
     payload: OpPayload,
@@ -44,7 +55,7 @@ pub struct Op {
 }
 
 impl Op {
-    fn apply(&self, realized: &mut RealizedDoc) {
+    fn apply(&self, realized: &mut RealizedDoc) -> Result<(), Error> {
         match &self.payload {
             OpPayload::CreateGrid {
                 rows,
@@ -70,42 +81,109 @@ impl Op {
                     rows,
                 });
             }
+
+            OpPayload::ChangeSubdivisions {
+                grid_id,
+                row_id,
+                start_cell_id,
+                end_cell_id,
+                subdivisions,
+            } => {
+                let grid = realized
+                    .grids
+                    .iter_mut()
+                    .find(|g| g.id == *grid_id)
+                    .ok_or(Error::NotFound(grid_id.clone()))?;
+
+                let row = grid
+                    .rows
+                    .iter_mut()
+                    .find(|r| r.id == *row_id)
+                    .ok_or(Error::NotFound(row_id.clone()))?;
+
+                let start_cell_idx = row
+                    .cells
+                    .iter()
+                    .position(|c| c.id == *start_cell_id)
+                    .ok_or(Error::NotFound(start_cell_id.clone()))?;
+
+                let end_cell_idx = row
+                    .cells
+                    .iter()
+                    .position(|c| c.id == *end_cell_id)
+                    .ok_or(Error::NotFound(end_cell_id.clone()))?;
+
+                let (i, j) = if start_cell_idx <= end_cell_idx {
+                    (start_cell_idx, end_cell_idx)
+                } else {
+                    (end_cell_idx, start_cell_idx)
+                };
+
+                row.cells.splice(
+                    i..(j + 1),
+                    (0..*subdivisions).map(|subdivision_idx| Cell {
+                        id: self.id.derive_id("cell", subdivision_idx),
+                    }),
+                );
+            }
         }
+
+        Ok(())
     }
 }
 
+#[derive(Debug)]
 pub enum OpPayload {
     CreateGrid {
         rows: usize,
         base_cells_per_row: usize,
     },
+
+    ChangeSubdivisions {
+        grid_id: DerivedId,
+        row_id: DerivedId,
+        start_cell_id: DerivedId,
+        end_cell_id: DerivedId,
+        subdivisions: usize,
+    },
 }
 
-#[derive(Default)]
+#[derive(Default, Debug)]
 pub struct RealizedDoc {
     grids: Vec<Grid>,
 }
 
+#[derive(Debug)]
 pub struct Grid {
     id: DerivedId,
     rows: Vec<Row>,
 }
 
+#[derive(Debug)]
 pub struct Row {
     id: DerivedId,
     cells: Vec<Cell>,
 }
 
+#[derive(Debug)]
 pub struct Cell {
     id: DerivedId,
 }
 
+#[derive(PartialEq, Eq, Debug, Clone)]
 pub struct DerivedId {
+    // TODO These IDs can be interned on the Doc
     id: Uuid,
     tag: &'static str,
     index: usize,
 }
 
+impl Display for DerivedId {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}:{}:{}", self.id, self.tag, self.index)
+    }
+}
+
 trait DerivableId {
     fn derive_id(&self, tag: &'static str, index: usize) -> DerivedId;
 }
@@ -138,7 +216,7 @@ mod tests {
             },
         );
 
-        let realized = doc.realize();
+        let realized = doc.realize().unwrap();
 
         assert!(realized.grids.len() == 1);
 
@@ -149,5 +227,21 @@ mod tests {
         let row = grid.rows.first().unwrap();
 
         assert!(row.cells.len() == 16);
+
+        doc.append_op(
+            &actor_id,
+            OpPayload::ChangeSubdivisions {
+                grid_id: grid.id.clone(),
+                row_id: row.id.clone(),
+                start_cell_id: row.cells[0].id.clone(),
+                end_cell_id: row.cells[3].id.clone(),
+                subdivisions: 3,
+            },
+        );
+
+        let realized2 = doc.realize().unwrap();
+
+        assert_eq!(realized2.grids[0].rows[0].cells.len(), 15);
+        assert_eq!(realized2.grids[0].rows[1].cells.len(), 16);
     }
 }