Add stdout/stderr printing support to UIThread

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

src/helpers/ui_thread.rs

@@ -1,14 +1,26 @@
 use std::io::{self, BufRead, Write};
 
+use bytes::Bytes;
 use tokio::sync::mpsc;
 use tokio::task::spawn_blocking;
 
 use crate::BinstallError;
 
+pub(super) enum UIRequest {
+    /// Request user confirmation
+    Confirm,
+    /// Print to stdout
+    PrintToStdout(Bytes),
+    /// Print to stderr
+    PrintToStderr(Bytes),
+    /// Flush stdout
+    FlushStdout,
+}
+
 #[derive(Debug)]
 struct UIThreadInner {
     /// Request for confirmation
-    request_tx: mpsc::Sender<()>,
+    request_tx: mpsc::Sender<UIRequest>,
 
     /// Confirmation
     confirm_rx: mpsc::Receiver<Result<(), BinstallError>>,
@@ -23,17 +35,13 @@ impl UIThreadInner {
             // This task should be the only one able to
             // access stdin
             let mut stdin = io::stdin().lock();
+            let mut stdout = io::stdout().lock();
+            let mut stderr = io::stderr().lock();
             let mut input = String::with_capacity(16);
 
             loop {
-                if request_rx.blocking_recv().is_none() {
+                match request_rx.blocking_recv() {
-                    break;
+                    Some(UIRequest::Confirm) => {
-                }
-
-                // Lock stdout so that nobody can interfere
-                // with confirmation.
-                let mut stdout = io::stdout().lock();
-
                         let res = loop {
                             writeln!(&mut stdout, "Do you wish to continue? yes/[no]").unwrap();
                             write!(&mut stdout, "? ").unwrap();
@@ -44,14 +52,22 @@ impl UIThreadInner {
 
                             match input.as_str().trim() {
                                 "yes" | "y" | "YES" | "Y" => break Ok(()),
-                        "no" | "n" | "NO" | "N" | "" => break Err(BinstallError::UserAbort),
+                                "no" | "n" | "NO" | "N" | "" => {
+                                    break Err(BinstallError::UserAbort)
+                                }
                                 _ => continue,
                             }
                         };
 
                         confirm_tx
                             .blocking_send(res)
-                    .expect("entry exits when confirming request");
+                            .expect("entry exits when confirming request")
+                    }
+                    Some(UIRequest::PrintToStdout(output)) => stdout.write_all(&output).unwrap(),
+                    Some(UIRequest::PrintToStderr(output)) => stderr.write_all(&output).unwrap(),
+                    Some(UIRequest::FlushStdout) => stdout.flush().unwrap(),
+                    None => break,
+                }
             }
         });
 
@@ -63,7 +79,7 @@ impl UIThreadInner {
 
     async fn confirm(&mut self) -> Result<(), BinstallError> {
         self.request_tx
-            .send(())
+            .send(UIRequest::Confirm)
             .await
             .map_err(|_| BinstallError::UserAbort)?;