unique ids challenge

1 files changed, 83 insertions, 0 deletions

diff --git a/unique_ids/src/main.rs b/unique_ids/src/main.rs
new file mode 100644
index 0000000..3787033
--- /dev/null
+++ b/unique_ids/src/main.rs
@@ -0,0 +1,83 @@
+use std::{
+    io,
+    time::{SystemTime, UNIX_EPOCH},
+};
+
+use common::{run_with, Handler};
+use rand::{rngs::StdRng, Rng, SeedableRng};
+use serde::{Deserialize, Serialize};
+
+fn main() {
+    run_with::<UniqueIdsHandler>(io::stdin(), io::stdout())
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(tag = "type")]
+enum UniqueIdsBody {
+    #[serde(rename = "generate")]
+    Generate { msg_id: usize },
+
+    #[serde(rename = "generate_ok")]
+    GenerateOk {
+        msg_id: usize,
+        in_reply_to: usize,
+        id: u128,
+    },
+}
+
+type RngMethod = StdRng;
+
+struct UniqueIdsHandler {
+    rng: RngMethod,
+    next_msg_id: usize,
+}
+
+impl Handler for UniqueIdsHandler {
+    type Body = UniqueIdsBody;
+
+    fn init(_node_id: String, _node_ids: Vec<String>, _msg_id: usize) -> Self {
+        Self {
+            rng: RngMethod::from_entropy(), // TODO: This could be seeded from the node ID
+            next_msg_id: 1,
+        }
+    }
+
+    fn handle(
+        &mut self,
+        header: common::msg::MessageHeader,
+        body: Self::Body,
+        writer: &mut common::MsgWriter<impl std::io::Write>,
+    ) -> () {
+        match body {
+            UniqueIdsBody::Generate { msg_id } => {
+                let id = self.gen_id();
+                writer.write(
+                    header.src,
+                    &UniqueIdsBody::GenerateOk {
+                        msg_id: self.next_msg_id,
+                        in_reply_to: msg_id,
+                        id,
+                    },
+                );
+
+                self.next_msg_id += 1;
+            }
+            UniqueIdsBody::GenerateOk { .. } => (),
+        };
+    }
+}
+
+impl UniqueIdsHandler {
+    fn gen_id(&mut self) -> u128 {
+        // Time since UNIX epoch in milliseconds
+        let now = SystemTime::now();
+        let time_millis: u128 = now.duration_since(UNIX_EPOCH).unwrap().as_millis();
+
+        // 80 bits of randomness
+        let rand1: u16 = self.rng.gen();
+        let rand2: u64 = self.rng.gen();
+        let rand: u128 = rand1 as u128 | ((rand2 as u128) << 64);
+
+        (time_millis << 80) | rand
+    }
+}