commit 7bc10f34f251c9b915873790b4fb7ccdaf4747a2
Author: Lukas Wölfer <lukas.woelfer@rwth-aachen.de>
Date:   Thu Jan 22 22:48:24 2026 +0100

    Initial commit

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..5008cb7
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,312 @@
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diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..dfdd072
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "chkr"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+crossterm = "0.26"
+ratatui = { version = "0.20", features = ["crossterm"] }
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..3c28d33
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,112 @@
+use std::io::{self, Read, Stdout};
+use std::time::Duration;
+
+use crossterm::event::{self, Event, KeyCode};
+use crossterm::execute;
+use crossterm::terminal::{
+    EnterAlternateScreen, LeaveAlternateScreen, disable_raw_mode, enable_raw_mode,
+};
+use ratatui::backend::CrosstermBackend;
+use ratatui::layout::{Constraint, Direction, Layout};
+use ratatui::style::{Color, Modifier, Style};
+use ratatui::terminal::Terminal;
+use ratatui::widgets::{Block, Borders, List, ListItem, ListState};
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let mut input = String::new();
+    io::stdin().read_to_string(&mut input)?;
+
+    if input.trim().is_empty() {
+        eprintln!("Provide text via stdin (pipe or heredoc). Example: \n  cat file.txt | chkr");
+        return Ok(());
+    }
+
+    let lines: Vec<String> = input.lines().map(|s| s.to_string()).collect();
+    let mut marked = vec![false; lines.len()];
+
+    enable_raw_mode()?;
+    let mut stdout = std::io::stdout();
+    execute!(stdout, EnterAlternateScreen)?;
+    let backend = CrosstermBackend::new(stdout);
+    let mut terminal = Terminal::new(backend)?;
+
+    let mut state = ListState::default();
+    if !lines.is_empty() {
+        state.select(Some(0));
+    }
+
+    loop {
+        terminal.draw(|f| {
+            let size = f.size();
+            let chunks = Layout::default()
+                .direction(Direction::Vertical)
+                .constraints([Constraint::Min(0)].as_ref())
+                .split(size);
+
+            let items: Vec<ListItem> = lines
+                .iter()
+                .enumerate()
+                .map(|(i, l)| {
+                    let prefix = if marked[i] { "[x]" } else { "[ ]" };
+                    ListItem::new(format!("{} {}", prefix, l))
+                })
+                .collect();
+
+            let list = List::new(items)
+                .block(
+                    Block::default()
+                        .borders(Borders::ALL)
+                        .title("Lines (space to mark, q to quit)"),
+                )
+                .highlight_style(
+                    Style::default()
+                        .fg(Color::White)
+                        .bg(Color::Blue)
+                        .add_modifier(Modifier::BOLD),
+                );
+
+            f.render_stateful_widget(list, chunks[0], &mut state);
+        })?;
+
+        // Event handling
+        if event::poll(Duration::from_millis(100))?
+            && let Event::Key(key) = event::read()?
+        {
+            match key.code {
+                KeyCode::Char('q') => break,
+                KeyCode::Up => {
+                    if let Some(i) = state.selected()
+                        && i > 0
+                    {
+                        state.select(Some(i - 1));
+                    }
+                }
+                KeyCode::Down => {
+                    if let Some(i) = state.selected()
+                        && i + 1 < lines.len()
+                    {
+                        state.select(Some(i + 1));
+                    }
+                }
+                KeyCode::Char(' ') => {
+                    if let Some(i) = state.selected()
+                        && i < marked.len()
+                    {
+                        marked[i] = true;
+                        // move cursor down
+                        let next = if i + 1 < lines.len() { i + 1 } else { i };
+                        state.select(Some(next));
+                    }
+                }
+                _ => {}
+            }
+        }
+    }
+
+    disable_raw_mode()?;
+    let mut stdout: Stdout = std::io::stdout();
+    execute!(stdout, LeaveAlternateScreen)?;
+    terminal.show_cursor()?;
+
+    Ok(())
+}