add first ratatui frame with dummy prompt

Cargo.toml

@@ -64,6 +64,7 @@ once_cell = "1.16"
 petgraph = "0.6"
 pimalaya-tui = { version = "=0.1.0", default-features = false, features = ["email", "path", "cli", "config", "tracing"] }
 process-lib = { version = "=0.4.2", features = ["derive"] }
+ratatui = "=0.28.1"
 secret-lib = { version = "=0.4.6", default-features = false, features = ["command", "derive"], optional = true }
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"

src/main.rs

@@ -1,3 +1,116 @@
-fn main() {
-    println!("Hello, world!");
+use color_eyre::Result;
+use ratatui::{
+    crossterm::event::{self, Event, KeyCode, KeyModifiers},
+    layout::{Constraint, Layout, Position},
+    style::Stylize,
+    text::Text,
+    DefaultTerminal, Frame,
+};
+
+fn main() -> Result<()> {
+    color_eyre::install()?;
+    let terminal = ratatui::init();
+    let app_result = App::new().run(terminal);
+    ratatui::restore();
+    app_result
+}
+
+struct App {
+    input: String,
+    character_index: usize,
+}
+
+impl App {
+    const fn new() -> Self {
+        Self {
+            input: String::new(),
+            character_index: 0,
+        }
+    }
+
+    fn move_cursor_left(&mut self) {
+        let cursor_moved_left = self.character_index.saturating_sub(1);
+        self.character_index = self.clamp_cursor(cursor_moved_left);
+    }
+
+    fn move_cursor_right(&mut self) {
+        let cursor_moved_right = self.character_index.saturating_add(1);
+        self.character_index = self.clamp_cursor(cursor_moved_right);
+    }
+
+    fn enter_char(&mut self, new_char: char) {
+        let index = self.byte_index();
+        self.input.insert(index, new_char);
+        self.move_cursor_right();
+    }
+
+    fn byte_index(&self) -> usize {
+        self.input
+            .char_indices()
+            .map(|(i, _)| i)
+            .nth(self.character_index)
+            .unwrap_or(self.input.len())
+    }
+
+    fn delete_char(&mut self) {
+        let is_not_cursor_leftmost = self.character_index != 0;
+        if is_not_cursor_leftmost {
+            let current_index = self.character_index;
+            let from_left_to_current_index = current_index - 1;
+
+            let before_char_to_delete = self.input.chars().take(from_left_to_current_index);
+            let after_char_to_delete = self.input.chars().skip(current_index);
+            self.input = before_char_to_delete.chain(after_char_to_delete).collect();
+            self.move_cursor_left();
+        }
+    }
+
+    fn clamp_cursor(&self, new_cursor_pos: usize) -> usize {
+        new_cursor_pos.clamp(0, self.input.chars().count())
+    }
+
+    fn reset_cursor(&mut self) {
+        self.character_index = 0;
+    }
+
+    fn submit_message(&mut self) {
+        self.input.clear();
+        self.reset_cursor();
+    }
+
+    fn run(mut self, mut terminal: DefaultTerminal) -> Result<()> {
+        loop {
+            terminal.draw(|frame| self.draw(frame))?;
+
+            if let Event::Key(key) = event::read()? {
+                match key.code {
+                    KeyCode::Enter => self.submit_message(),
+                    KeyCode::Char('c') if key.modifiers.contains(KeyModifiers::CONTROL) => {
+                        return Ok(());
+                    }
+                    KeyCode::Char(c) => self.enter_char(c),
+                    KeyCode::Backspace => self.delete_char(),
+                    KeyCode::Left => self.move_cursor_left(),
+                    KeyCode::Right => self.move_cursor_right(),
+                    _ => {}
+                }
+            }
+        }
+    }
+
+    fn draw(&self, frame: &mut Frame) {
+        let prompt = "himalaya > ";
+
+        let layout =
+            Layout::horizontal([Constraint::Length(prompt.len() as u16), Constraint::Fill(1)]);
+        let [prompt_area, input_area] = layout.areas(frame.area());
+
+        frame.render_widget(Text::raw(prompt).blue(), prompt_area);
+        frame.render_widget(&self.input, input_area);
+
+        frame.set_cursor_position(Position::new(
+            input_area.x + self.character_index as u16,
+            input_area.y,
+        ))
+    }
 }