broken :(

src/controller/mod.rs

@@ -10,7 +10,7 @@ use std::collections::HashMap;
 use std::io::{ErrorKind, Write};
 use std::process::{Command, Stdio};
 use std::sync::{mpsc, Arc, Mutex};
-use std::time::Duration;
+use std::time::{Duration, Instant};
 use std::{io, thread};
 use tracing::{error, info};
 use tui::backend::Backend;
@@ -27,9 +27,7 @@ pub fn run_app<B: Backend>(terminal: &mut Terminal<B>, mut app: App) -> SmResult
     loop {
         terminal.draw(|f| view::render_ui(f, &mut app))?;
 
-        app.recv_stdouts();
-
-        if event::poll(Duration::from_millis(10))? {
+        if event::poll(Duration::from_secs(0))? {
             if let Event::Key(key) = event::read()? {
                 match key.code {
                     KeyCode::Char('q') => match app.selected {
@@ -40,14 +38,22 @@ pub fn run_app<B: Backend>(terminal: &mut Terminal<B>, mut app: App) -> SmResult
                     },
                     KeyCode::Char('r') => app.run_service()?,
                     KeyCode::Char('k') => app.kill_service()?,
-                    KeyCode::Down => app.next(),
-                    KeyCode::Up => app.previous(),
+                    KeyCode::Down => match app.selected {
+                        Some(_) => app.scroll_down(),
+                        None => app.next(),
+                    },
+                    KeyCode::Up => match app.selected {
+                        Some(_) => app.scroll_up(),
+                        None => app.previous(),
+                    },
                     KeyCode::Enter => app.select_service(),
                     KeyCode::Esc => app.leave_service(),
                     _ => {}
                 }
             }
         }
+
+        app.recv_stdouts(Duration::from_millis(10));
     }
 
     // terminate the child processes
@@ -80,6 +86,7 @@ impl App {
                             env: service.env.unwrap_or_else(HashMap::new),
                             status: Arc::new(Mutex::new(ServiceStatus::NotStarted)),
                             std_io_buf: Vec::new(),
+                            std_io_line_cache: Vec::new(),
                             stdout: StdIoStream {
                                 recv: stdout_recv,
                                 send: stdout_send,
@@ -89,6 +96,7 @@ impl App {
                     .collect::<io::Result<_>>()?,
             },
             selected: None,
+            scroll_pos: None,
             thread_terminates: HashMap::new(),
         })
     }
@@ -97,13 +105,30 @@ impl App {
         self.selected.is_none()
     }
 
-    fn recv_stdouts(&mut self) {
+    fn recv_stdouts(&mut self, duration: Duration) {
         for service in self.table.services.iter_mut() {
-            while let Ok((buf, n)) = service.stdout.recv.try_recv() {
-                service.std_io_buf.extend(&buf[0..n]);
+            let start = Instant::now();
+            let buf = &mut service.std_io_buf;
 
-                if service.std_io_buf.len() > 2_000_000 {
-                    service.std_io_buf.clear(); // todo don't
+            while let Ok((new_buf, n)) = service.stdout.recv.try_recv() {
+                let len_before = buf.len();
+                buf.extend(&new_buf[0..n]);
+
+                let new_newline_positions = new_buf
+                    .iter()
+                    .enumerate()
+                    .filter(|(_, &byte)| byte == b'\n')
+                    .map(|(position, _)| position + len_before);
+
+                service.std_io_line_cache.extend(new_newline_positions);
+
+                if buf.len() > 2_000_000 {
+                    buf.clear(); // todo don't
+                    service.std_io_line_cache.clear();
+                }
+
+                if start.elapsed() > duration {
+                    break;
                 }
             }
         }
@@ -149,6 +174,14 @@ impl App {
         self.table.table_state.select(Some(i));
     }
 
+    fn scroll_up(&mut self) {
+        self.scroll_pos = self.scroll_pos.map(|pos| pos + 1);
+    }
+
+    fn scroll_down(&mut self) {
+        self.scroll_pos = self.scroll_pos.map(|pos| pos - 1);
+    }
+
     fn run_service(&mut self) -> SmResult {
         let index = self.selected.or_else(|| self.table.table_state.selected());
 

src/model.rs

@@ -10,6 +10,7 @@ pub use error::{SmError, SmResult};
 pub struct App {
     pub table: AppState,
     pub selected: Option<usize>,
+    pub scroll_pos: Option<usize>,
     pub thread_terminates: HashMap<usize, mpsc::Sender<()>>,
 }
 
@@ -27,6 +28,8 @@ pub struct Service {
     pub env: HashMap<String, String>,
     pub status: Arc<Mutex<ServiceStatus>>,
     pub std_io_buf: Vec<u8>,
+    /// The start position of every line number
+    pub std_io_line_cache: Vec<usize>,
     pub stdout: StdIoStream,
 }
 

src/view.rs

@@ -41,12 +41,21 @@ fn render_full_view<B: Backend>(f: &mut Frame<B>, state: &mut AppState, index: u
         .borders(Borders::ALL)
         .title("service".as_ref());
 
-    let len = service.std_io_buf.len();
-    let stdout = if len > 10000 {
-        String::from_utf8_lossy(&service.std_io_buf[len - 10000..len])
-    } else {
-        String::from_utf8_lossy(&service.std_io_buf)
-    };
+    let height = area.height - 2; // the block takes up 2 lines
+    let buf_len = service.std_io_buf.len();
+
+    let display_start_pos = service
+        .std_io_line_cache
+        .get(
+            service
+                .std_io_line_cache
+                .len()
+                .saturating_sub(usize::from(height)),
+        )
+        .cloned()
+        .unwrap_or(0);
+
+    let stdout = String::from_utf8_lossy(&service.std_io_buf[display_start_pos..buf_len]);
 
     let paragraph = Paragraph::new(stdout.as_ref()).block(block.clone());