Rename Confirmer to UIThread

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

src/helpers/ui_thread.rs

@@ -0,0 +1,97 @@
+use std::io::{self, BufRead, Write};
+
+use tokio::sync::mpsc;
+use tokio::task::spawn_blocking;
+
+use crate::BinstallError;
+
+#[derive(Debug)]
+struct UIThreadInner {
+    /// Request for confirmation
+    request_tx: mpsc::Sender<()>,
+
+    /// Confirmation
+    confirm_rx: mpsc::Receiver<Result<(), BinstallError>>,
+}
+
+impl UIThreadInner {
+    fn new() -> Self {
+        let (request_tx, mut request_rx) = mpsc::channel(1);
+        let (confirm_tx, confirm_rx) = mpsc::channel(10);
+
+        spawn_blocking(move || {
+            // This task should be the only one able to
+            // access stdin
+            let mut stdin = io::stdin().lock();
+            let mut input = String::with_capacity(16);
+
+            loop {
+                if request_rx.blocking_recv().is_none() {
+                    break;
+                }
+
+                // 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();
+                    stdout.flush().unwrap();
+
+                    input.clear();
+                    stdin.read_line(&mut input).unwrap();
+
+                    match input.as_str().trim() {
+                        "yes" | "y" | "YES" | "Y" => break Ok(()),
+                        "no" | "n" | "NO" | "N" | "" => break Err(BinstallError::UserAbort),
+                        _ => continue,
+                    }
+                };
+
+                confirm_tx
+                    .blocking_send(res)
+                    .expect("entry exits when confirming request");
+            }
+        });
+
+        Self {
+            request_tx,
+            confirm_rx,
+        }
+    }
+
+    async fn confirm(&mut self) -> Result<(), BinstallError> {
+        self.request_tx
+            .send(())
+            .await
+            .map_err(|_| BinstallError::UserAbort)?;
+
+        self.confirm_rx
+            .recv()
+            .await
+            .unwrap_or(Err(BinstallError::UserAbort))
+    }
+}
+
+#[derive(Debug)]
+pub struct UIThread(Option<UIThreadInner>);
+
+impl UIThread {
+    ///  * `enable` - `true` to enable confirmation, `false` to disable it.
+    pub fn new(enable: bool) -> Self {
+        Self(if enable {
+            Some(UIThreadInner::new())
+        } else {
+            None
+        })
+    }
+
+    pub async fn confirm(&mut self) -> Result<(), BinstallError> {
+        if let Some(inner) = self.0.as_mut() {
+            inner.confirm().await
+        } else {
+            Ok(())
+        }
+    }
+}