1 files changed, 101 insertions, 0 deletions
diff --git a/crdt/src/doc.rs b/crdt/src/doc.rs
new file mode 100644
index 0000000..bbd24d0
--- /dev/null
+++ b/crdt/src/doc.rs
@@ -0,0 +1,101 @@
+use thiserror::Error;
+use uuid::Uuid;
+
+use crate::op::{ChangeSubdivisions, CreateGrid, Op, OpKind};
+
+/// An deterministically derived ID, e.g. a grid ID derived from the
+/// op ID which creates it.
+pub struct DerivedId {
+    base: String,
+    tag: &'static str,
+    index: usize,
+}
+
+impl ToString for DerivedId {
+    fn to_string(&self) -> String {
+        format!("{}:{}={}", self.base, self.tag, self.index)
+    }
+}
+
+trait DerivableId {
+    fn derive_id(&self, tag: &'static str, index: usize) -> DerivedId;
+}
+
+impl DerivableId for Uuid {
+    fn derive_id(&self, tag: &'static str, index: usize) -> DerivedId {
+        DerivedId {
+            base: self.to_string(),
+            tag,
+            index,
+        }
+    }
+}
+
+impl DerivableId for DerivedId {
+    fn derive_id(&self, tag: &'static str, index: usize) -> DerivedId {
+        DerivedId {
+            base: self.to_string(),
+            tag,
+            index,
+        }
+    }
+}
+
+#[derive(Default)]
+pub struct Doc {
+    pub(crate) grids: Vec<Grid>,
+}
+
+pub struct Grid {
+    pub(crate) id: DerivedId,
+    pub(crate) rows: Vec<Row>,
+}
+
+pub struct Row {
+    pub(crate) id: DerivedId,
+    pub(crate) cells: Vec<Cell>,
+}
+
+pub struct Cell {
+    pub(crate) id: DerivedId,
+}
+
+#[derive(Error, Debug)]
+pub enum ApplyOpError {}
+
+pub type ApplyOpResult = Result<(), ApplyOpError>;
+
+impl Doc {
+    pub fn apply_op(&mut self, op: &Op) -> ApplyOpResult {
+        match &op.kind {
+            OpKind::CreateGrid(data) => apply_create_grid(self, &op.id, data),
+            OpKind::ChangeSubdivisions(data) => apply_change_subdivisions(self, data),
+        }
+    }
+}
+
+fn apply_create_grid(doc: &mut Doc, op_id: &Uuid, data: &CreateGrid) -> ApplyOpResult {
+    let grid_id = op_id.derive_id("grid", 0);
+
+    let rows = (0..data.rows)
+        .map(|row_idx| {
+            let row_id = grid_id.derive_id("row", row_idx);
+
+            let cells = (0..data.base_cells_per_row)
+                .map(|cell_idx| Cell {
+                    id: row_id.derive_id("cell", cell_idx),
+                })
+                .collect();
+
+            Row { id: row_id, cells }
+        })
+        .collect();
+
+    doc.grids.push(Grid { id: grid_id, rows });
+
+    Ok(())
+}
+
+fn apply_change_subdivisions(doc: &mut Doc, data: &ChangeSubdivisions) -> ApplyOpResult {
+    todo!()
+}