From 7d912937cc7a271cd4c85fa1108094055ffe730f Mon Sep 17 00:00:00 2001
From: Josh Kingsley <josh@joshkingsley.me>
Date: Sat, 15 Nov 2025 23:50:55 +0200
Subject: feat(crdt): add duration to Cell

---
 crdt/src/lib.rs | 96 +++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 90 insertions(+), 6 deletions(-)

(limited to 'crdt/src')

diff --git a/crdt/src/lib.rs b/crdt/src/lib.rs
index 3983692..7b426fc 100644
--- a/crdt/src/lib.rs
+++ b/crdt/src/lib.rs
@@ -2,6 +2,7 @@ mod vector_clock;
 
 use std::{collections::BTreeSet, fmt::Display};
 
+use num_rational::Ratio;
 use uuid::Uuid;
 
 use crate::vector_clock::VectorClock;
@@ -93,11 +94,14 @@ impl Op {
                 rows,
                 base_cells_per_row,
             } => {
+                let duration: Ratio<u32> = Ratio::new(1, *base_cells_per_row as u32);
+
                 let rows = (0..*rows)
                     .map(|row_idx| {
                         let cells = (0..*base_cells_per_row)
                             .map(|cell_idx| Cell {
                                 id: self.id.derive_id("cell", cell_idx),
+                                duration,
                             })
                             .collect();
 
@@ -151,10 +155,16 @@ impl Op {
                     (end_cell_idx, start_cell_idx)
                 };
 
+                let span_duration: Ratio<u32> =
+                    row.cells[i..j + 1].iter().map(|cell| cell.duration).sum();
+
+                let duration: Ratio<u32> = span_duration / *subdivisions as u32;
+
                 row.cells.splice(
                     i..(j + 1),
                     (0..*subdivisions).map(|subdivision_idx| Cell {
                         id: self.id.derive_id("cell", subdivision_idx),
+                        duration,
                     }),
                 );
             }
@@ -200,9 +210,10 @@ pub struct Row {
 #[derive(Debug)]
 pub struct Cell {
     id: DerivedId,
+    duration: Ratio<u32>,
 }
 
-#[derive(PartialEq, Eq, Debug, Clone)]
+#[derive(PartialEq, Eq, Debug, Clone, Copy)]
 pub struct DerivedId {
     // TODO These IDs can be interned on the Doc
     id: Uuid,
@@ -270,13 +281,58 @@ mod tests {
         let actor1 = Uuid::now_v7();
         let actor2 = Uuid::now_v7();
 
-        let doc = Doc::from_ops(
+        let mut doc1 = Doc::from_ops(
             &actor1,
             &[OpPayload::CreateGrid {
                 rows: 4,
                 base_cells_per_row: 16,
             }],
         );
+
+        let mut doc2 = doc1.clone();
+
+        {
+            let realized = doc1.realize().unwrap();
+
+            doc1.append_op(
+                &actor1,
+                OpPayload::ChangeSubdivisions {
+                    grid_id: realized.grids[0].id,
+                    row_id: realized.grids[0].rows[0].id,
+                    start_cell_id: realized.grids[0].rows[0].cells[0].id,
+                    end_cell_id: realized.grids[0].rows[0].cells[3].id,
+                    subdivisions: 3,
+                },
+            );
+
+            doc2.append_op(
+                &actor2,
+                OpPayload::ChangeSubdivisions {
+                    grid_id: realized.grids[0].id,
+                    row_id: realized.grids[0].rows[0].id,
+                    start_cell_id: realized.grids[0].rows[0].cells[0].id,
+                    end_cell_id: realized.grids[0].rows[0].cells[3].id,
+                    subdivisions: 3,
+                },
+            );
+        }
+
+        doc1.merge(&doc2);
+
+        assert_eq!(doc1.ops.len(), 3);
+
+        let realized = doc1.realize().unwrap();
+
+        let grid = &realized.grids[0];
+        let row = &grid.rows[0];
+
+        assert_eq!(
+            row.cells
+                .iter()
+                .map(|cell| cell.duration)
+                .sum::<Ratio<u32>>(),
+            Ratio::ONE
+        );
     }
 
     #[test]
@@ -296,15 +352,23 @@ mod tests {
         {
             let realized = doc.realize().unwrap();
 
-            assert!(realized.grids.len() == 1);
+            assert_eq!(realized.grids.len(), 1);
 
             let grid = realized.grids.first().unwrap();
 
-            assert!(grid.rows.len() == 4);
+            assert_eq!(grid.rows.len(), 4);
 
             let row = grid.rows.first().unwrap();
 
-            assert!(row.cells.len() == 16);
+            assert_eq!(row.cells.len(), 16);
+
+            assert_eq!(
+                row.cells
+                    .iter()
+                    .map(|cell| cell.duration)
+                    .sum::<Ratio<u32>>(),
+                Ratio::ONE
+            );
 
             doc.append_op(
                 &actor_id,
@@ -327,6 +391,14 @@ mod tests {
             let grid = &realized.grids[0];
             let row = &grid.rows[0];
 
+            assert_eq!(
+                row.cells
+                    .iter()
+                    .map(|cell| cell.duration)
+                    .sum::<Ratio<u32>>(),
+                Ratio::ONE
+            );
+
             doc.append_op(
                 &actor_id,
                 OpPayload::ChangeSubdivisions {
@@ -341,8 +413,20 @@ mod tests {
 
         {
             let realized = doc.realize().unwrap();
-            assert_eq!(realized.grids[0].rows[0].cells.len(), 12);
+
+            let grid = &realized.grids[0];
+            let row = &grid.rows[0];
+
+            assert_eq!(row.cells.len(), 12);
             assert_eq!(realized.grids[0].rows[1].cells.len(), 16);
+
+            assert_eq!(
+                row.cells
+                    .iter()
+                    .map(|cell| cell.duration)
+                    .sum::<Ratio<u32>>(),
+                Ratio::ONE
+            );
         }
     }
 }
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