feat(ui/ux): Show navigation help when h is pressed

app/src/screen/asset/controller.rs

@@ -18,6 +18,10 @@ pub enum InputEvent {
     #[description = "Quit application"]
     Quit,
 
+    #[key = 'h']
+    #[description = "Open/close navigation help"]
+    NavigationHelp,
+
     #[key = 'b']
     #[description = "Return one screen back"]
     Back,
@@ -60,6 +64,10 @@ pub(super) fn process_input<L: LedgerApiT, C: CoinPriceApiT, M: BlockchainMonito
 
     match event {
         InputEvent::Quit => Some(OutgoingMessage::Exit),
+        InputEvent::NavigationHelp => {
+            model.show_navigation_help ^= true;
+            None
+        }
         InputEvent::Back => Some(OutgoingMessage::Back),
         InputEvent::OpenDepositScreen => Some(OutgoingMessage::SwitchScreen(ScreenName::Deposit)),
         InputEvent::SelectTimeInterval(event) => {

app/src/screen/asset/mod.rs

@@ -23,6 +23,7 @@ pub struct Model<L: LedgerApiT, C: CoinPriceApiT, M: BlockchainMonitoringApiT> {
     coin_price_history: Option<Vec<PriceHistoryPoint>>,
     transactions: Option<Vec<(TransactionUid, TransactionInfo)>>,
     selected_time_period: TimePeriod,
+    show_navigation_help: bool,
 
     state: StateRegistry,
     apis: ApiRegistry<L, C, M>,
@@ -98,6 +99,7 @@ impl<L: LedgerApiT, C: CoinPriceApiT, M: BlockchainMonitoringApiT> ScreenT<L, C,
             coin_price_history: Default::default(),
             transactions: Default::default(),
             selected_time_period: DEFAULT_SELECTED_TIME_PERIOD,
+            show_navigation_help: false,
 
             state,
             apis: api_registry,

app/src/screen/asset/view.rs

@@ -1,7 +1,8 @@
+use input_mapping_common::InputMappingT;
 use ratatui::{
     layout::{Alignment, Constraint, Direction, Layout, Rect},
     style::{Style, Stylize},
-    symbols,
+    symbols::{self},
     text::{Line, Span, Text},
     widgets::{
         Axis, Block, Borders, Chart, Dataset, GraphType, HighlightSpacing, Padding, Row, Table,
@@ -21,7 +22,7 @@ use crate::{
         ledger::LedgerApiT,
     },
     screen::{
-        common::{format_address, network_symbol, render_centered_text, BackgroundWidget},
+        common::{self, format_address, network_symbol, render_centered_text, BackgroundWidget},
         resources::Resources,
     },
 };
@@ -103,6 +104,11 @@ pub(super) fn render<L: LedgerApiT, C: CoinPriceApiT, M: BlockchainMonitoringApi
             render_tx_list_placeholder(frame, inner_txs_list_area);
         }
     }
+
+    if model.show_navigation_help {
+        let mapping = super::controller::InputEvent::get_mapping();
+        common::render_navigation_help(mapping, frame, resources);
+    }
 }
 
 fn render_price_chart(

app/src/screen/common/background_widget.rs

@@ -0,0 +1,29 @@
+use ratatui::{
+    buffer::Buffer,
+    layout::Rect,
+    style::{Color, Stylize},
+    text::Line,
+    widgets::Widget,
+};
+
+pub struct BackgroundWidget {
+    color: Color,
+}
+
+impl BackgroundWidget {
+    pub fn new(color: Color) -> Self {
+        Self { color }
+    }
+}
+
+impl Widget for BackgroundWidget {
+    fn render(self, area: Rect, buf: &mut Buffer)
+    where
+        Self: Sized,
+    {
+        let line = Line::raw(" ".repeat(area.width as usize)).bg(self.color);
+        for y in area.y..area.y + area.height {
+            buf.set_line(area.x, y, &line, area.width);
+        }
+    }
+}

app/src/screen/common/mod.rs

@@ -0,0 +1,127 @@
+use input_mapping_common::InputMapping;
+use ratatui::{
+    layout::{Alignment, Constraint, Flex, Layout, Margin, Rect},
+    style::Stylize,
+    text::Text,
+    widgets::{Block, BorderType, Borders, Padding},
+    Frame,
+};
+
+use crate::api::common_types::Network;
+
+mod background_widget;
+pub use background_widget::*;
+
+mod navigation_help_widget;
+pub use navigation_help_widget::*;
+
+use super::resources::Resources;
+
+pub fn network_symbol(network: Network) -> String {
+    match network {
+        Network::Bitcoin => "₿",
+        Network::Ethereum => "⟠",
+    }
+    .to_string()
+}
+
+pub fn render_centered_text(frame: &mut Frame, area: Rect, text: Text) {
+    let [area] = Layout::horizontal([Constraint::Length(text.width() as u16)])
+        .flex(Flex::Center)
+        .areas(area);
+    let [area] = Layout::vertical([Constraint::Length(text.height() as u16)])
+        .flex(Flex::Center)
+        .areas(area);
+
+    frame.render_widget(text, area);
+}
+
+pub fn format_address(address: &str, max_symbols: usize) -> String {
+    if max_symbols <= 3 {
+        return "".to_string();
+    }
+
+    if max_symbols <= 8 {
+        return "...".to_string();
+    }
+
+    let part_size = (max_symbols - 3) / 2;
+    let part_size = part_size.min(8);
+
+    if address.len() <= part_size * 2 {
+        return address.to_string();
+    }
+
+    format!(
+        "{}...{}",
+        &address[..part_size],
+        &address[(address.len() - part_size)..]
+    )
+}
+
+pub fn render_navigation_help(
+    input_mapping: InputMapping,
+    frame: &mut Frame<'_>,
+    resources: &Resources,
+) {
+    let area = frame.size();
+
+    let bindings = input_mapping
+        .mapping
+        .into_iter()
+        .map(|map| (map.key, map.description))
+        .collect();
+
+    let widget = NavigationHelpWidget::new(bindings);
+
+    let block_area = area.inner(Margin::new(8, 4));
+
+    let width = widget.min_width().max(block_area.width as usize / 2);
+    let height = widget.height();
+
+    let block = Block::new()
+        .border_type(BorderType::Double)
+        .borders(Borders::all())
+        .border_style(resources.main_color)
+        .padding(Padding::proportional(1))
+        .title("Help")
+        .title_alignment(Alignment::Center)
+        .reset()
+        .bg(resources.background_color)
+        .fg(resources.main_color);
+
+    let block_inner = block.inner(block_area);
+
+    let [widget_area] = Layout::horizontal([Constraint::Length(width as u16)])
+        .flex(Flex::Center)
+        .areas(block_inner);
+    let [widget_area] = Layout::vertical([Constraint::Length(height as u16)])
+        .flex(Flex::Center)
+        .areas(widget_area);
+
+    frame.render_widget(
+        BackgroundWidget::new(resources.background_color),
+        block_area,
+    );
+    frame.render_widget(block, block_area);
+
+    frame.render_widget(widget, widget_area);
+}
+
+#[cfg(test)]
+mod tests {
+    use itertools::Itertools;
+
+    use super::format_address;
+
+    #[test]
+    fn test_format_address() {
+        let address_lengths = [0, 2, 8, 10, 100].into_iter();
+        let max_lengths = [0, 3, 5, 6, 8, 10, 100].into_iter();
+
+        for (addr_len, max_len) in address_lengths.cartesian_product(max_lengths) {
+            let address = "0".repeat(addr_len);
+            assert!(format_address(&address, max_len).len() <= max_len);
+        }
+    }
+}

app/src/screen/common/navigation_help_widget.rs

@@ -0,0 +1,73 @@
+use ratatui::{
+    buffer::Buffer,
+    crossterm::event::KeyCode,
+    layout::{Alignment, Rect},
+    text::Text,
+    widgets::Widget,
+};
+
+pub struct NavigationHelpWidget {
+    key_bindings: Vec<(KeyCode, String)>,
+}
+
+impl NavigationHelpWidget {
+    pub fn new(key_bindings: Vec<(KeyCode, String)>) -> Self {
+        Self { key_bindings }
+    }
+
+    pub fn height(&self) -> usize {
+        self.key_bindings.len()
+    }
+
+    pub fn min_width(&self) -> usize {
+        self.key_bindings
+            .iter()
+            .map(|(key, description)| min_line_length(description, &key_name(key)))
+            .max()
+            .unwrap_or_default()
+    }
+}
+
+impl Widget for NavigationHelpWidget {
+    fn render(self, area: Rect, buf: &mut Buffer)
+    where
+        Self: Sized,
+    {
+        let width = area.width as usize;
+
+        let text: String = self
+            .key_bindings
+            .iter()
+            .map(|(key, description)| {
+                let key_name = key_name(key);
+                let line_len = min_line_length(description, &key_name);
+
+                let padding = width - line_len.min(width);
+                let padding_str: String = vec![".".to_string(); padding + 1].into_iter().collect();
+
+                format!("[{}]{}{}", key_name, padding_str, description)
+            })
+            .intersperse("\n".to_string())
+            .collect();
+
+        let text = Text::raw(text).alignment(Alignment::Center);
+        text.render(area, buf);
+    }
+}
+
+fn key_name(key: &KeyCode) -> String {
+    match key {
+        KeyCode::Char(ch) => ch.to_string(),
+        KeyCode::Up => "↑".to_string(),
+        KeyCode::Down => "↓".to_string(),
+        KeyCode::Enter => "⏎".to_string(),
+        _ => unimplemented!(),
+    }
+}
+
+fn min_line_length(description: &str, key_name: &str) -> usize {
+    const BRACKETS_LEN: usize = 2;
+    const MINIMAL_SPACING: usize = 1;
+
+    Text::raw(description).width() + Text::raw(key_name).width() + BRACKETS_LEN + MINIMAL_SPACING
+}