implement client ping (#108)

src/bin/cli.rs

@@ -26,6 +26,10 @@ struct Cli {
 
 #[derive(Subcommand, Debug)]
 enum Command {
+    Ping {
+        /// Message to ping
+        msg: Option<String>,
+    },
     /// Get the value of key.
     Get {
         /// Name of key to get
@@ -85,6 +89,14 @@ async fn main() -> mini_redis::Result<()> {
 
     // Process the requested command
     match cli.command {
+        Command::Ping { msg } => {
+            let value = client.ping(msg).await?;
+            if let Ok(string) = str::from_utf8(&value) {
+                println!("\"{}\"", string);
+            } else {
+                println!("{:?}", value);
+            }
+        }
         Command::Get { key } => {
             if let Some(value) = client.get(&key).await? {
                 if let Ok(string) = str::from_utf8(&value) {

src/client.rs

@@ -2,7 +2,7 @@
 //!
 //! Provides an async connect and methods for issuing the supported commands.
 
-use crate::cmd::{Get, Publish, Set, Subscribe, Unsubscribe};
+use crate::cmd::{Get, Ping, Publish, Set, Subscribe, Unsubscribe};
 use crate::{Connection, Frame};
 
 use async_stream::try_stream;
@@ -87,6 +87,42 @@ pub async fn connect<T: ToSocketAddrs>(addr: T) -> crate::Result<Client> {
 }
 
 impl Client {
+    /// Ping to the server.
+    ///
+    /// Returns PONG if no argument is provided, otherwise
+    /// return a copy of the argument as a bulk.
+    ///
+    /// This command is often used to test if a connection
+    /// is still alive, or to measure latency.
+    ///
+    /// # Examples
+    ///
+    /// Demonstrates basic usage.
+    /// ```no_run
+    /// use mini_redis::client;
+    ///
+    /// #[tokio::main]
+    /// async fn main() {
+    ///     let mut client = client::connect("localhost:6379").await.unwrap();
+    ///
+    ///     let pong = client.ping(None).await.unwrap();
+    ///     assert_eq!(b"PONG", &pong[..]);
+    /// }
+    /// ```
+    #[instrument(skip(self))]
+    pub async fn ping(&mut self, msg: Option<String>) -> crate::Result<Bytes> {
+        let frame = Ping::new(msg).into_frame();
+        debug!(request = ?frame);
+
+        self.connection.write_frame(&frame).await?;
+
+        match self.read_response().await? {
+            Frame::Simple(value) => Ok(value.into()),
+            Frame::Bulk(value) => Ok(value),
+            frame => Err(frame.to_error()),
+        }
+    }
+
     /// Get the value of key.
     ///
     /// If the key does not exist the special value `None` is returned.

src/cmd/ping.rs

@@ -63,4 +63,17 @@ impl Ping {
 
         Ok(())
     }
+
+    /// Converts the command into an equivalent `Frame`.
+    ///
+    /// This is called by the client when encoding a `Ping` command to send
+    /// to the server.
+    pub(crate) fn into_frame(self) -> Frame {
+        let mut frame = Frame::array();
+        frame.push_bulk(Bytes::from("ping".as_bytes()));
+        if let Some(msg) = self.msg {
+            frame.push_bulk(Bytes::from(msg));
+        }
+        frame
+    }
 }