ttl command

src/client.rs

@@ -144,6 +144,32 @@ impl Client {
         Ok(r.try_get_u8()? == 1)
     }
 
+    pub async fn ttl(&mut self, key: &str) -> Result<Option<u64>> {
+        let mut bytes = BytesMut::new();
+        bytes.put_u16(3);
+        bytes.put_slice(b"ttl");
+
+        let key_length: u16 = key
+            .len()
+            .try_into()
+            .map_err(|_| AppError::KeyLength(key.len()))?;
+
+        bytes.put_u16(key_length);
+        bytes.put_slice(key.as_bytes());
+
+        self.connection.write(bytes.into()).await?;
+
+        let mut r = self.get_response().await?;
+
+        let ttl = match r.try_get_u8()? {
+            1 => Some(r.try_get_u64()?),
+            0 => None,
+            _ => return Err(AppError::InvalidCommandResponse),
+        };
+
+        Ok(ttl)
+    }
+
     async fn get_response(&mut self) -> Result<Bytes> {
         self.connection
             .read_bytes()

src/commands/mod.rs

@@ -1,7 +1,8 @@
-pub mod delete;
+mod delete;
 mod get;
-pub mod has;
-pub mod set;
+mod has;
+mod set;
+mod ttl;
 
 use std::io::Cursor;
 
@@ -10,6 +11,7 @@ use delete::Delete;
 use get::Get;
 use has::Has;
 use set::Set;
+use ttl::Ttl;
 
 use crate::{Result, connection::Connection, database::Database, errors::AppError};
 
@@ -19,6 +21,7 @@ pub enum Command {
     Set(Set),
     Delete(Delete),
     Has(Has),
+    Ttl(Ttl),
 }
 
 impl Command {
@@ -28,6 +31,7 @@ impl Command {
             Command::Set(set) => set.execute(db, connection).await,
             Command::Delete(delete) => delete.execute(db, connection).await,
             Command::Has(has) => has.execute(db, connection).await,
+            Command::Ttl(ttl) => ttl.execute(db, connection).await,
         }
     }
 
@@ -51,6 +55,7 @@ impl Command {
             "set" => Self::Set(Set::parse(bytes)?),
             "delete" => Self::Delete(Delete::parse(bytes)?),
             "has" => Self::Has(Has::parse(bytes)?),
+            "ttl" => Self::Ttl(Ttl::parse(bytes)?),
             _ => return Err(AppError::UnknownCommand(command_name)),
         };
 

src/commands/ttl.rs

@@ -0,0 +1,42 @@
+use std::io::Cursor;
+
+use bytes::{Buf as _, BufMut, Bytes, BytesMut};
+
+use crate::{Result, connection::Connection, database::Database, errors::AppError};
+
+#[derive(Debug, Clone)]
+pub struct Ttl {
+    key: String,
+}
+
+impl Ttl {
+    pub async fn execute(self, db: &Database, connection: &mut Connection) -> Result<()> {
+        let ttl = db.ttl(&self.key).await;
+
+        let Some(ttl) = ttl else {
+            connection.write(Bytes::from_static(&[0])).await?;
+            return Ok(());
+        };
+
+        let mut buf = BytesMut::new();
+
+        buf.put_u8(1);
+        buf.put_u64(ttl);
+
+        connection.write(buf.into()).await?;
+
+        Ok(())
+    }
+
+    pub fn parse(bytes: &mut Cursor<&[u8]>) -> Result<Self> {
+        let key_length = bytes.try_get_u16()? as usize;
+
+        if bytes.remaining() < key_length {
+            return Err(AppError::IncompleteCommandBuffer);
+        }
+
+        let key = String::from_utf8(bytes.copy_to_bytes(key_length).to_vec())?;
+
+        Ok(Self { key })
+    }
+}

src/database.rs

@@ -128,6 +128,16 @@ impl Database {
         state.entries.contains_key(key)
     }
 
+    pub async fn ttl(&self, key: &str) -> Option<u64> {
+        self.state
+            .lock()
+            .await
+            .entries
+            .get(key)
+            .map(|v| v.expiration.map(|e| (e - Instant::now()).as_secs()))
+            .flatten()
+    }
+
     pub async fn shutdown(&mut self) {
         self.state.lock().await.shutdown = true;
         self.notify.notify_one();

src/tests.rs

@@ -15,12 +15,18 @@ async fn expiration() -> Result<(), Box<dyn std::error::Error>> {
     let mut client = client("127.0.0.1:6171").await?;
 
     client
-        .set("test-key", "test-value".as_bytes(), Some(2))
+        .set("test-key", "test-value".as_bytes(), Some(3))
         .await
         .unwrap();
+
     assert!(client.has("test-key").await.unwrap());
+    assert_eq!(client.ttl("test-key").await.unwrap(), Some(2));
+
     tokio::time::sleep(Duration::from_secs(1)).await;
+
     assert!(client.has("test-key").await.unwrap());
+    assert_eq!(client.ttl("test-key").await.unwrap(), Some(1));
+
     tokio::time::sleep(Duration::from_secs(2)).await;
     assert!(!client.has("test-key").await.unwrap());