1 files changed, 85 insertions, 0 deletions
diff --git a/src/main/rust/ui.rs b/src/main/rust/ui.rs
new file mode 100644
index 0000000..2f69cea
--- /dev/null
+++ b/src/main/rust/ui.rs
@@ -0,0 +1,85 @@
+use crate::{app::App, ui};
+use ratatui::{
+    Frame,
+    buffer::Buffer,
+    layout::Rect,
+    style::Stylize,
+    symbols::border,
+    text::{Line, Text},
+    widgets::{Block, Paragraph, Widget},
+};
+
+/// Explicitly declare lifetime as App is a reference;
+/// Runtime is only instantiated for render
+struct Runtime<'a> {
+    app: &'a App,
+}
+
+pub fn draw(frame: &mut Frame, app: &App) {
+    let run = ui::Runtime { app };
+    frame.render_widget(&run, frame.area());
+}
+
+impl<'a> Widget for &Runtime<'a> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        let title = Line::from(" Counter App Tutorial ".bold());
+        let instructions = Line::from(vec![
+            " Decrement ".into(),
+            "<Left>".blue().bold(),
+            " Increment ".into(),
+            "<Right>".blue().bold(),
+            " Quit ".into(),
+            "<Q> ".blue().bold(),
+        ]);
+        let block = Block::bordered()
+            .title(title.centered())
+            .title_bottom(instructions.centered())
+            .border_set(border::THICK);
+
+        let counter_text = Text::from(vec![Line::from(vec![
+            "Value: ".into(),
+            self.app.display_counter().yellow(),
+        ])]);
+
+        Paragraph::new(counter_text)
+            .centered()
+            .block(block)
+            .render(area, buf);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+
+    use super::*;
+    use ratatui::style::Style;
+
+    #[test]
+    fn render() {
+        let mut app = App::default();
+        assert!(app.init_context().is_ok());
+        let runtime = Runtime { app: &app };
+
+        let mut buf = Buffer::empty(Rect::new(0, 0, 50, 4));
+
+        runtime.render(buf.area, &mut buf);
+
+        let mut expected = Buffer::with_lines(vec![
+            "┏━━━━━━━━━━━━━ Counter App Tutorial ━━━━━━━━━━━━━┓",
+            "┃                    Value: 0                    ┃",
+            "┃                                                ┃",
+            "┗━ Decrement <Left> Increment <Right> Quit <Q> ━━┛",
+        ]);
+        let title_style = Style::new().bold();
+        let counter_style = Style::new().yellow();
+        let key_style = Style::new().blue().bold();
+
+        expected.set_style(Rect::new(14, 0, 22, 1), title_style);
+        expected.set_style(Rect::new(28, 1, 1, 1), counter_style);
+        expected.set_style(Rect::new(13, 3, 6, 1), key_style);
+        expected.set_style(Rect::new(30, 3, 7, 1), key_style);
+        expected.set_style(Rect::new(43, 3, 4, 1), key_style);
+
+        assert_eq!(buf, expected);
+    }
+}