1 files changed, 108 insertions, 0 deletions
diff --git a/echo/src/main.rs b/echo/src/main.rs
new file mode 100644
index 0000000..381099c
--- /dev/null
+++ b/echo/src/main.rs
@@ -0,0 +1,108 @@
+use std::io;
+
+use common::{msg::*, send_msg, Handler};
+use serde::{Deserialize, Serialize};
+use serde_json::Deserializer;
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(tag = "type")]
+pub enum EchoBody {
+    #[serde(rename = "echo")]
+    Echo { msg_id: usize, echo: String },
+
+    #[serde(rename = "echo_ok")]
+    EchoOk {
+        msg_id: usize,
+        in_reply_to: usize,
+        echo: String,
+    },
+}
+fn main() {
+    let mut stdout = io::stdout();
+    let deser = Deserializer::from_reader(io::stdin());
+    let mut deser = deser.into_iter::<Message<()>>();
+    let Some(msg) = deser.next() else {
+        panic!("stream ended before init message");
+    };
+    let Ok(msg) = msg else {
+            panic!("{}", msg.unwrap_err());
+    };
+
+    let (node_id, node_ids, msg_id) = match msg.body {
+        MaelstromBodyOr::MaelstromBody {
+            inner:
+                MaelstromBody::Init {
+                    node_id,
+                    node_ids,
+                    msg_id,
+                },
+        } => (node_id, node_ids, msg_id),
+        _ => {
+            panic!("expected init message to be first message");
+        }
+    };
+
+    send_msg(
+        &mut stdout,
+        &Message {
+            header: msg.header.flip(),
+            body: MaelstromBodyOr::MaelstromBody::<()> {
+                inner: MaelstromBody::InitOk {
+                    msg_id: 0,
+                    in_reply_to: msg_id,
+                },
+            },
+        },
+    );
+
+    let mut handler = EchoHandler::init(node_id, node_ids, msg_id);
+
+    drop(deser);
+
+    let deser = Deserializer::from_reader(io::stdin());
+    for msg in deser.into_iter::<Message<EchoBody>>() {
+        let msg = msg.unwrap();
+        match msg.body {
+            MaelstromBodyOr::Other { inner } => {
+                if let Some(out) = handler.handle(msg.header, inner) {
+                    send_msg(&mut stdout, &out);
+                }
+            }
+            _ => todo!(),
+        };
+    }
+}
+
+pub struct EchoHandler {
+    next_msg_id: usize,
+}
+
+impl Handler for EchoHandler {
+    type Body = EchoBody;
+
+    fn init(_node_id: String, _node_ids: Vec<String>, _msg_id: usize) -> Self {
+        EchoHandler { next_msg_id: 1 }
+    }
+
+    fn handle(&mut self, header: MessageHeader, body: Self::Body) -> Option<Message<EchoBody>> {
+        match body {
+            EchoBody::Echo { msg_id, echo } => {
+                let msg = Message {
+                    header: header.flip(),
+                    body: MaelstromBodyOr::Other {
+                        inner: EchoBody::EchoOk {
+                            msg_id: self.next_msg_id,
+                            in_reply_to: msg_id,
+                            echo,
+                        },
+                    },
+                };
+
+                self.next_msg_id += 1;
+
+                Some(msg)
+            }
+            EchoBody::EchoOk { .. } => None,
+        }
+    }
+}