1 files changed, 97 insertions, 0 deletions
diff --git a/src/dag_backend.rs b/src/dag_backend.rs
new file mode 100644
index 0000000..6a49146
--- /dev/null
+++ b/src/dag_backend.rs
@@ -0,0 +1,97 @@
+use anyhow::Result;
+use async_trait::async_trait;
+
+use crate::NodeId;
+use crate::Node;
+
+#[async_trait]
+pub trait DagBackend<Id, N>
+    where N: Node,
+          Id: NodeId + Send
+{
+    async fn get(&self, id: Id) -> Result<Option<N>>;
+    async fn put(&mut self, node: N) -> Result<Id>;
+}
+
+#[cfg(test)]
+mod tests {
+    use std::pin::Pin;
+
+    use anyhow::Result;
+    use anyhow::anyhow;
+    use async_trait::async_trait;
+    use tokio_test::block_on;
+
+    use crate::test_impl as test;
+    use crate::*;
+
+    #[test]
+    fn test_backend_get() {
+        let b = test::Backend(vec![Some(test::Node {
+            id: test::Id(0),
+            parents: vec![],
+            data: 42,
+        })]);
+
+        let node = tokio_test::block_on(b.get(test::Id(0)));
+        assert!(node.is_ok());
+        let node = node.unwrap();
+
+        assert!(node.is_some());
+        let node = node.unwrap();
+
+        assert_eq!(node.data, 42);
+        assert_eq!(node.id, test::Id(0));
+        assert!(node.parents.is_empty());
+    }
+
+    #[test]
+    fn test_backend_put() {
+        let mut b = test::Backend(vec![Some(test::Node {
+            id: test::Id(0),
+            parents: vec![],
+            data: 42,
+        })]);
+
+        let id = tokio_test::block_on(b.put({
+            test::Node {
+                id: test::Id(1),
+                parents: vec![],
+                data: 43,
+            }
+        }));
+
+        {
+            let node = tokio_test::block_on(b.get(test::Id(0)));
+            assert!(node.is_ok());
+            let node = node.unwrap();
+
+            assert!(node.is_some());
+            let node = node.unwrap();
+
+            assert_eq!(node.data, 42);
+            assert_eq!(node.id, test::Id(0));
+            assert!(node.parents.is_empty());
+        }
+        {
+            let node = tokio_test::block_on(b.get(test::Id(1)));
+            assert!(node.is_ok());
+            let node = node.unwrap();
+
+            assert!(node.is_some());
+            let node = node.unwrap();
+
+            assert_eq!(node.data, 43);
+            assert_eq!(node.id, test::Id(1));
+            assert!(node.parents.is_empty());
+        }
+        {
+            let node = tokio_test::block_on(b.get(test::Id(2)));
+            assert!(node.is_ok());
+            let node = node.unwrap();
+
+            assert!(node.is_none());
+        }
+    }
+
+}