From 6013177bfc5b3f3ee6b97abe36900fb22e8632e6 Mon Sep 17 00:00:00 2001
From: Matthias Beyer <mail@beyermatthias.de>
Date: Tue, 25 Jun 2019 18:55:52 +0200
Subject: Add minimal required interfaces

---
 src/id.rs         | 18 ++++++++++++++++++
 src/lib.rs        | 16 +++++++++-------
 src/node.rs       | 39 +++++++++++++++++++++++++++++++++++++++
 src/repository.rs | 27 +++++++++++++++++++++++++++
 4 files changed, 93 insertions(+), 7 deletions(-)
 create mode 100644 src/id.rs
 create mode 100644 src/node.rs
 create mode 100644 src/repository.rs

diff --git a/src/id.rs b/src/id.rs
new file mode 100644
index 0000000..018ae60
--- /dev/null
+++ b/src/id.rs
@@ -0,0 +1,18 @@
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+//
+
+use std::fmt::Debug;
+
+/// An "ID" is an object that can be used to uniquely identify a node in the DAG.
+///
+/// In git-speak, this would be a SHA1 hash.
+///
+pub trait Id : Clone + Debug + PartialEq + Eq {
+
+    /* empty */
+
+}
+
diff --git a/src/lib.rs b/src/lib.rs
index 31e1bb2..bda0996 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,7 +1,9 @@
-#[cfg(test)]
-mod tests {
-    #[test]
-    fn it_works() {
-        assert_eq!(2 + 2, 4);
-    }
-}
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+//
+
+pub mod id;
+pub mod node;
+pub mod repository;
diff --git a/src/node.rs b/src/node.rs
new file mode 100644
index 0000000..b6a088b
--- /dev/null
+++ b/src/node.rs
@@ -0,0 +1,39 @@
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+//
+
+use std::fmt::Debug;
+
+use crate::id::Id;
+
+use futures::future::Future;
+use futures::stream::Stream;
+
+/// A "Node" is an object of the (DA)Graph
+///
+/// In git-speak, this would be an "Object".
+///
+///
+/// # Equality
+///
+/// A node might be compared to another node. In git, for example, equality would be the equality
+/// of the nodes ids, because objects are non-mutable.
+///
+pub trait Node: Debug + PartialEq + Eq {
+    type Id: Id;
+    type NodePayload: Debug;
+    type Error: Debug;
+    type Payload: Future<Item = Self::NodePayload, Error = Self::Error>;
+
+    /// It should be trivial to get the Id of a Node.
+    fn id(&self) -> Self::Id;
+
+    /// Fetch the payload of the node.
+    fn payload(&self) -> Self::Payload;
+
+    /// Fetch the Ids of the parents of this node
+    fn parent_ids(&self) -> Stream<Item = Self::Id, Error = Self::Error>;
+}
+
diff --git a/src/repository.rs b/src/repository.rs
new file mode 100644
index 0000000..b4ab3a4
--- /dev/null
+++ b/src/repository.rs
@@ -0,0 +1,27 @@
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+//
+
+use std::fmt::Debug;
+
+use crate::node::Node;
+use crate::id::Id;
+
+use futures::future::Future;
+
+///
+pub trait Repository: Debug {
+    type Id: Id;
+    type Error: Debug;
+    type Node: Node<Id = Self::Id, Error = Self::Error>;
+
+    type Get: Future<Item = Self::Node, Error = Self::Error>;
+
+    /// It should be trivial to get the Id of a Node.
+    fn get<ID>(id: ID) -> Result<Self::Get, Self::Error>
+        where ID: Id;
+
+}
+
-- 
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