2 files changed, 91 insertions, 0 deletions
diff --git a/common/src/lib.rs b/common/src/lib.rs
new file mode 100644
index 0000000..d0db5d1
--- /dev/null
+++ b/common/src/lib.rs
@@ -0,0 +1,41 @@
+use std::io::{Stdout, Write};
+
+use msg::{MaelstromBodyOr, Message, MessageHeader};
+use serde::{Deserialize, Serialize};
+
+pub mod msg;
+
+pub trait Handler {
+    type Body: Serialize + for<'a> Deserialize<'a>;
+
+    fn init(node_id: String, node_ids: Vec<String>, msg_id: usize) -> Self;
+    fn handle(
+        &mut self,
+        header: MessageHeader,
+        body: Self::Body,
+        writer: &mut MsgWriter<Self::Body>,
+    ) -> ();
+}
+
+pub struct MsgWriter<W> {
+    node_id: String,
+    writer: W,
+}
+
+impl<W: Write> MsgWriter<W> {
+    pub fn new(node_id: String, writer: W) -> Self {
+        Self { node_id, writer }
+    }
+
+    pub fn write<T: Serialize>(&mut self, dst: String, msg: &T) {
+        let msg = Message {
+            header: MessageHeader {
+                src: self.node_id.clone(),
+                dst,
+            },
+            body: MaelstromBodyOr::Other { inner: msg },
+        };
+        serde_json::to_writer(&mut self.writer, &msg).unwrap();
+        self.writer.write(&[b'\n']).unwrap();
+    }
+}
diff --git a/common/src/msg.rs b/common/src/msg.rs
new file mode 100644
index 0000000..23db171
--- /dev/null
+++ b/common/src/msg.rs
@@ -0,0 +1,50 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct Message<B> {
+    #[serde(flatten)]
+    pub header: MessageHeader,
+    pub body: MaelstromBodyOr<B>,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct MessageHeader {
+    pub src: String,
+    #[serde(rename = "dest")]
+    pub dst: String,
+}
+
+impl MessageHeader {
+    pub fn flip(self) -> Self {
+        Self {
+            src: self.dst,
+            dst: self.src,
+        }
+    }
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(untagged)]
+pub enum MaelstromBodyOr<B> {
+    MaelstromBody {
+        #[serde(flatten)]
+        inner: MaelstromBody,
+    },
+    Other {
+        #[serde(flatten)]
+        inner: B,
+    },
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(tag = "type")]
+pub enum MaelstromBody {
+    #[serde(rename = "init")]
+    Init {
+        node_id: String,
+        node_ids: Vec<String>,
+        msg_id: usize,
+    },
+    #[serde(rename = "init_ok")]
+    InitOk { msg_id: usize, in_reply_to: usize },
+}