lib: Add scrollable paragraph widget

src/flux/ui/widget.rs

@@ -1,5 +1,6 @@
 pub mod container;
 pub mod input;
+pub mod text;
 
 use std::cmp;
 use std::fmt::Debug;

src/flux/ui/widget/text.rs

@@ -0,0 +1,137 @@
+use tokio::sync::mpsc::UnboundedSender;
+
+use termion::event::Key;
+
+use ratatui::backend::Backend;
+use ratatui::layout::{Constraint, Layout, Rect};
+use ratatui::text::Text;
+use ratatui::widgets::{Block, BorderType, Borders};
+
+use crate::flux::ui::theme::style;
+
+use super::{Render, Widget};
+
+pub struct ParagraphProps<'a> {
+    pub content: Text<'a>,
+    pub focus: bool,
+    pub has_header: bool,
+    pub has_footer: bool,
+}
+
+pub struct Paragraph<A> {
+    /// Sending actions to the state store
+    pub action_tx: UnboundedSender<A>,
+    /// Internal offset
+    offset: usize,
+    /// Internal progress
+    progress: usize,
+}
+
+impl<A> Paragraph<A> {
+    pub fn scroll(&self) -> (u16, u16) {
+        (self.offset as u16, 0)
+    }
+
+    pub fn prev(&mut self, len: usize, page_size: usize) -> (u16, u16) {
+        self.offset = self.offset.saturating_sub(1);
+        self.progress = Self::scroll_percent(self.offset, len, page_size);
+        self.scroll()
+    }
+
+    pub fn next(&mut self, len: usize, page_size: usize) -> (u16, u16) {
+        if self.progress < 100 {
+            self.offset = self.offset.saturating_add(1);
+            self.progress = Self::scroll_percent(self.offset, len, page_size);
+        }
+
+        self.scroll()
+    }
+
+    pub fn prev_page(&mut self, len: usize, page_size: usize) -> (u16, u16) {
+        self.offset = self.offset.saturating_sub(page_size);
+        self.progress = Self::scroll_percent(self.offset, len, page_size);
+        self.scroll()
+    }
+
+    pub fn next_page(&mut self, len: usize, page_size: usize) -> (u16, u16) {
+        let end = len.saturating_sub(page_size);
+
+        self.offset = std::cmp::min(self.offset.saturating_add(page_size), end);
+        self.progress = Self::scroll_percent(self.offset, len, page_size);
+        self.scroll()
+    }
+
+    pub fn begin(&mut self, len: usize, page_size: usize) -> (u16, u16) {
+        self.offset = 0;
+        self.progress = Self::scroll_percent(self.offset, len, page_size);
+        self.scroll()
+    }
+
+    pub fn end(&mut self, len: usize, page_size: usize) -> (u16, u16) {
+        self.offset = len.saturating_sub(page_size);
+        self.progress = Self::scroll_percent(self.offset, len, page_size);
+        self.scroll()
+    }
+
+    pub fn progress(&self) -> usize {
+        self.progress
+    }
+
+    fn scroll_percent(offset: usize, len: usize, height: usize) -> usize {
+        if height >= len {
+            100
+        } else {
+            let y = offset as f64;
+            let h = height as f64;
+            let t = len.saturating_sub(1) as f64;
+            let v = y / (t - h) * 100_f64;
+
+            std::cmp::max(0, std::cmp::min(100, v as usize))
+        }
+    }
+}
+
+impl<S, A> Widget<S, A> for Paragraph<A> {
+    fn new(state: &S, action_tx: UnboundedSender<A>) -> Self
+    where
+        Self: Sized,
+    {
+        Self {
+            action_tx: action_tx.clone(),
+            offset: 0,
+            progress: 0,
+        }
+        .move_with_state(state)
+    }
+
+    fn move_with_state(self, _state: &S) -> Self
+    where
+        Self: Sized,
+    {
+        Self { ..self }
+    }
+
+    fn name(&self) -> &str {
+        "paragraph"
+    }
+
+    fn handle_key_event(&mut self, _key: Key) {}
+}
+
+impl<'a, A> Render<ParagraphProps<'a>> for Paragraph<A> {
+    fn render<B: Backend>(&self, frame: &mut ratatui::Frame, area: Rect, props: ParagraphProps) {
+        let block = Block::default()
+            .borders(Borders::LEFT | Borders::RIGHT)
+            .border_type(BorderType::Rounded)
+            .border_style(style::border(props.focus));
+        frame.render_widget(block, area);
+
+        let [content_area] = Layout::horizontal([Constraint::Min(1)])
+            .horizontal_margin(2)
+            .areas(area);
+        let content =
+            ratatui::widgets::Paragraph::new(props.content.clone()).scroll((self.offset as u16, 0));
+
+        frame.render_widget(content, content_area);
+    }
+}