split code into sensible modules

src/main.rs

@@ -1,24 +1,24 @@
 //! A simple CLI app for displaying rich 24 hour time information for multiple
-//! people and/or time zones.
+//! locations.
 
 mod config;
+mod message;
+mod model;
+mod update;
+mod view;
 
 use std::{ffi::OsString, io, time::Duration};
 
-use chrono::{NaiveTime, TimeDelta, Timelike, Utc, offset::LocalResult};
-use chrono_tz::Tz;
 use clap::Parser;
-use crossterm::event::{self, Event, KeyCode, KeyEvent, KeyEventKind, KeyModifiers};
-use ratatui::{
-    DefaultTerminal,
-    prelude::*,
-    symbols::border,
-    widgets::{Block, BorderType::Rounded, Cell, Padding, Row, Table, TableState},
-};
-use ratatui_textarea::{Input, TextArea};
-use unidecode::unidecode;
+use crossterm::event::{self, Event, KeyCode, KeyEventKind, KeyModifiers};
+use ratatui::DefaultTerminal;
 
-use crate::config::{Config, Location};
+use crate::{
+    config::Config,
+    message::Message,
+    model::{FocusState, Model, RunningState},
+    view::view,
+};
 
 /// A simple CLI app for displaying rich 24 hour time information for multiple
 /// people and/or time zones.
@@ -40,70 +40,42 @@ fn main() -> color_eyre::Result<()> {
 /// TUI render loop.
 fn run(terminal: &mut DefaultTerminal, config: Config) -> color_eyre::Result<()> {
     let mut model = Model::from_config(config);
-
     while model.running_state != RunningState::Done {
-        terminal.draw(|f| view(&mut model, f))?;
-
-        // Handle events and map to a Message
-        let mut current_msg = handle_event(&model)?;
-
+        model.update_loop(Some(Message::TimeProgressed))?;
+        terminal.draw(|frame| view(&mut model, frame))?;
         // Process updates as long as they return a non-None message
-        while current_msg.is_some() {
-            current_msg = update(&mut model, current_msg.unwrap());
+        model.update_loop(handle_event(&model)?)?;
     }
-    }
-
     Ok(())
 }
 
-/// App-wide Elm model.
-#[derive(Debug)]
-struct Model<'a> {
-    config: Config,
-    table_state: TableState,
-    running_state: RunningState,
-    focus_state: FocusState,
-    filter_textarea: TextArea<'a>,
-}
-
-impl<'a> Model<'a> {
-    fn from_config(config: Config) -> Self {
-        Self {
-            config,
-            table_state: Default::default(),
-            running_state: Default::default(),
-            focus_state: Default::default(),
-            filter_textarea: Default::default(),
-        }
-    }
-}
-
-#[derive(Debug, Default, Eq, PartialEq)]
-enum RunningState {
-    #[default]
-    Running,
-    Done,
-}
-
-#[derive(Debug, Default, Eq, PartialEq)]
-enum FocusState {
-    #[default]
-    Table,
-    Filter,
-}
-
-enum Message {
-    Quit,
-    FilterOpened,
-    FilterCancelled,
-    FilterUpdated(Input),
-}
-
+/// Momentarily block until a crossterm event is detected or the internal
+/// timeout expires.
 fn handle_event(model: &Model) -> io::Result<Option<Message>> {
     Ok(if event::poll(Duration::from_secs(5))? {
         match event::read()? {
             Event::Key(key_event) if key_event.kind == KeyEventKind::Press => {
-                handle_key_event(model, key_event)
+                match (&model.focus_state, key_event.code) {
+                    (_, KeyCode::Char('c'))
+                        if key_event.modifiers.contains(KeyModifiers::CONTROL) =>
+                    {
+                        Some(Message::Quit)
+                    }
+                    (FocusState::Table, KeyCode::Char('q')) => Some(Message::Quit),
+                    (FocusState::Table, KeyCode::Char('/')) => Some(Message::FilterOpened),
+                    (FocusState::Filter, KeyCode::Esc) => Some(Message::FilterCancelled),
+                    // Ignore input that creates newlines: START
+                    (FocusState::Filter, KeyCode::Enter) => None,
+                    (FocusState::Filter, KeyCode::Char('m'))
+                        if key_event.modifiers.contains(KeyModifiers::CONTROL)
+                            && !key_event.modifiers.contains(KeyModifiers::ALT) =>
+                    {
+                        None
+                    }
+                    // Ignore input that creates newlines: END
+                    (FocusState::Filter, _) => Some(Message::FilterUpdated(key_event.into())),
+                    _ => None,
+                }
             }
             _ => None,
         }
@@ -113,177 +85,3 @@ fn handle_event(model: &Model) -> io::Result<Option<Message>> {
         None
     })
 }
-
-fn handle_key_event(model: &Model, key_event: KeyEvent) -> Option<Message> {
-    match (&model.focus_state, key_event.code) {
-        (_, KeyCode::Char('c')) if key_event.modifiers.contains(KeyModifiers::CONTROL) => {
-            Some(Message::Quit)
-        }
-        (FocusState::Table, KeyCode::Char('q')) => Some(Message::Quit),
-        (FocusState::Table, KeyCode::Char('/')) => Some(Message::FilterOpened),
-        (FocusState::Filter, KeyCode::Esc) | (FocusState::Filter, KeyCode::Enter) => {
-            Some(Message::FilterCancelled)
-        }
-        // Ignore input that creates newlines.
-        (FocusState::Filter, KeyCode::Char('m'))
-            if key_event.modifiers.contains(KeyModifiers::CONTROL)
-                && !key_event.modifiers.contains(KeyModifiers::ALT) =>
-        {
-            None
-        }
-        (FocusState::Filter, _) => Some(Message::FilterUpdated(key_event.into())),
-        _ => None,
-    }
-}
-
-/// Elm update function.
-fn update(model: &mut Model, msg: Message) -> Option<Message> {
-    match msg {
-        Message::Quit => model.running_state = RunningState::Done,
-        Message::FilterOpened => model.focus_state = FocusState::Filter,
-        Message::FilterCancelled => {
-            model.focus_state = FocusState::Table;
-            model.filter_textarea.clear();
-        }
-        Message::FilterUpdated(input) => {
-            model.filter_textarea.input(input);
-        }
-    }
-    None
-}
-
-/// Elm render function.
-fn view(model: &mut Model, frame: &mut Frame) {
-    let title = Line::from(" Team Time Zones ".bold());
-    let instructions = Line::from(vec![
-        " Filter ".into(),
-        "/".blue().bold(),
-        "  Quit ".into(),
-        "Q ".blue().bold(),
-    ]);
-    let block = Block::bordered()
-        .title(title.centered().fg(Color::Reset))
-        .title_bottom(instructions.centered().fg(Color::Reset))
-        .border_set(border::PLAIN)
-        .border_style(Style::new().fg(Color::DarkGray))
-        .border_type(Rounded)
-        .padding(Padding::horizontal(2));
-
-    let visible_locations: Vec<&Location> = if model.focus_state == FocusState::Filter {
-        let filter_terms: Vec<String> = model
-            .filter_textarea
-            .clone()
-            .into_lines()
-            .into_iter()
-            .next()
-            .unwrap_or_default()
-            .split('|')
-            .map(|value| value.trim().to_owned())
-            .collect();
-        model
-            .config
-            .locations
-            .iter()
-            .enumerate()
-            .filter(|(i, location)| {
-                *i == 0
-                    || filter_terms.iter().any(|filter_term| {
-                        unidecode(&location.name.to_ascii_lowercase())
-                            .contains(&unidecode(&filter_term.to_ascii_lowercase()))
-                    })
-            })
-            .map(|(_, value)| value)
-            .collect()
-    } else {
-        model.config.locations.iter().collect()
-    };
-
-    let header = Row::new(
-        visible_locations
-            .iter()
-            .map(|location| location.name.as_str())
-            .collect::<Vec<&str>>(),
-    )
-    .cyan()
-    .bold();
-    let col_widths: Vec<Constraint> = visible_locations
-        .iter()
-        .map(|location| Constraint::Length(clamp_u16(location.name.len(), 5, 32)))
-        .collect();
-
-    let mut rows: Vec<Row> = Vec::with_capacity(24);
-    let home_tz = visible_locations
-        .first()
-        .expect("should always be at least one location loaded and visible")
-        .tz;
-    let now = Utc::now();
-    let mut home_datetime = match now
-        .with_timezone(&home_tz)
-        .with_time(NaiveTime::from_hms_opt(0, 0, 0).expect("00:00:00 is a valid time"))
-    {
-        LocalResult::Single(datetime) | LocalResult::Ambiguous(datetime, _) => datetime,
-        LocalResult::None => {
-            // TODO: display error
-            return;
-        }
-    };
-    for _ in 0..24 {
-        let is_current_time = now.with_timezone(&Tz::UTC) - home_datetime > TimeDelta::zero()
-            && now.with_timezone(&Tz::UTC) - home_datetime < TimeDelta::minutes(60);
-        rows.push(
-            Row::new(visible_locations.iter().map(|Location { tz, .. }| {
-                let col_datetime = home_datetime.with_timezone(tz);
-                let is_daylight = col_datetime.hour() >= 9 && col_datetime.hour() <= 16;
-                Cell::new(col_datetime.format("%H:%M").to_string()).style(
-                    if is_current_time || is_daylight {
-                        Style::new()
-                    } else {
-                        Style::new().fg(Color::DarkGray)
-                    },
-                )
-            }))
-            .style(if is_current_time {
-                Style::new().red()
-            } else {
-                Style::new()
-            }),
-        );
-        home_datetime += TimeDelta::hours(1);
-    }
-
-    let table = Table::new(rows, col_widths)
-        .header(header)
-        .block(block)
-        .column_spacing(4);
-
-    let layout = Layout::vertical([
-        Constraint::Fill(1),
-        Constraint::Length(if model.focus_state == FocusState::Filter {
-            1
-        } else {
-            0
-        }),
-    ]);
-    let [table_area, filter_area] = layout.areas(frame.area());
-    if model.focus_state == FocusState::Filter {
-        frame.render_widget(&model.filter_textarea, filter_area);
-    }
-    frame.render_stateful_widget(table, table_area, &mut model.table_state);
-}
-
-/// Clip a [`usize`]-like value to between two [`u16`]s (inclusive).
-fn clamp_u16<T>(value: T, min: u16, max: u16) -> u16
-where
-    T: Into<usize>,
-{
-    let value: usize = value.into();
-    if value <= min.into() {
-        min
-    } else if value >= max.into() {
-        max
-    } else {
-        value
-            .try_into()
-            .expect("value is known to be unsigned and less than some valid u16")
-    }
-}

src/message.rs

@@ -0,0 +1,10 @@
+use ratatui_textarea::Input;
+
+/// Elm message type.
+pub(crate) enum Message {
+    Quit,
+    FilterOpened,
+    FilterCancelled,
+    FilterUpdated(Input),
+    TimeProgressed,
+}

src/model.rs

@@ -0,0 +1,101 @@
+use chrono::NaiveDateTime;
+use color_eyre::Result;
+use ratatui::widgets::TableState;
+use ratatui_textarea::TextArea;
+use unidecode::unidecode;
+
+use crate::{
+    config::{Config, Location},
+    message::Message,
+    update::update,
+};
+
+/// App-wide Elm model.
+#[derive(Debug)]
+pub(crate) struct Model<'a> {
+    pub(crate) config: Config,
+    pub(crate) table_state: TableState,
+    pub(crate) table_rows: Vec<Vec<CellData>>,
+    pub(crate) running_state: RunningState,
+    pub(crate) focus_state: FocusState,
+    pub(crate) filter_textarea: TextArea<'a>,
+}
+
+impl<'a> Model<'a> {
+    /// Create new model from parsed runtime config.
+    pub(crate) fn from_config(config: Config) -> Self {
+        Self {
+            config,
+            table_state: Default::default(),
+            table_rows: Default::default(),
+            running_state: Default::default(),
+            focus_state: Default::default(),
+            filter_textarea: Default::default(),
+        }
+    }
+
+    /// Run Elm updates until they produce no further recursive messages.
+    pub(crate) fn update_loop(&mut self, msg: Option<Message>) -> Result<()> {
+        let mut maybe_msg = msg;
+        while let Some(msg) = maybe_msg {
+            maybe_msg = update(self, msg)?;
+        }
+        Ok(())
+    }
+
+    /// Compute list of visible locations based on filter value.
+    pub(crate) fn get_visible_locations(&self) -> Vec<Location> {
+        if self.focus_state == FocusState::Filter {
+            let filter_terms = self.get_filter_terms();
+            self.config
+                .locations
+                .iter()
+                .enumerate()
+                .filter(|(i, location)| {
+                    *i == 0
+                        || filter_terms.iter().any(|filter_term| {
+                            unidecode(&location.name.to_ascii_lowercase())
+                                .contains(&unidecode(&filter_term.to_ascii_lowercase()))
+                        })
+                })
+                .map(|(_, value)| value.clone())
+                .collect()
+        } else {
+            self.config.locations.to_vec()
+        }
+    }
+
+    fn get_filter_terms(&self) -> Vec<String> {
+        self.filter_textarea
+            .clone()
+            .into_lines()
+            .into_iter()
+            .next()
+            .unwrap_or_default()
+            .split('|')
+            .map(|value| value.trim().to_owned())
+            .collect()
+    }
+}
+
+#[derive(Debug, Default, Eq, PartialEq)]
+pub(crate) enum RunningState {
+    #[default]
+    Running,
+    Done,
+}
+
+#[derive(Debug, Default, Eq, PartialEq)]
+pub(crate) enum FocusState {
+    #[default]
+    Table,
+    Filter,
+}
+
+/// Computed data required to render a timetable cell.
+#[derive(Debug)]
+pub(crate) struct CellData {
+    pub(crate) is_daylight: bool,
+    pub(crate) is_current_time: bool,
+    pub(crate) datetime: NaiveDateTime,
+}

src/update.rs

@@ -0,0 +1,69 @@
+use chrono::{NaiveTime, TimeDelta, Timelike as _, Utc, offset::LocalResult};
+use chrono_tz::Tz;
+use color_eyre::{Result, eyre::eyre};
+
+use crate::{
+    config::Location,
+    message::Message,
+    model::{CellData, FocusState, Model, RunningState},
+};
+
+/// Elm update function.
+pub(crate) fn update(model: &mut Model, msg: Message) -> Result<Option<Message>> {
+    match msg {
+        Message::Quit => model.running_state = RunningState::Done,
+        Message::FilterOpened => model.focus_state = FocusState::Filter,
+        Message::FilterCancelled => {
+            model.focus_state = FocusState::Table;
+            model.filter_textarea.clear();
+        }
+        Message::FilterUpdated(input) => {
+            model.filter_textarea.input(input);
+        }
+        Message::TimeProgressed => {
+            model.table_rows = compute_rows(&model.get_visible_locations())?;
+        }
+    }
+    Ok(None)
+}
+
+/// Compute timetable data based on the model state and current system time.
+fn compute_rows(visible_locations: &[Location]) -> Result<Vec<Vec<CellData>>> {
+    let mut rows: Vec<Vec<CellData>> = Vec::with_capacity(24);
+    let home_tz = visible_locations
+        .first()
+        .expect("should always be at least one location loaded and visible")
+        .tz;
+    let now = Utc::now();
+    let mut home_datetime = match now
+        .with_timezone(&home_tz)
+        .with_time(NaiveTime::from_hms_opt(0, 0, 0).expect("00:00:00 is a valid time"))
+    {
+        LocalResult::Single(datetime) | LocalResult::Ambiguous(datetime, _) => datetime,
+        LocalResult::None => {
+            return Err(eyre!(
+                "Unable to compute: home time zone has no midnight. Date math is hard!"
+            ));
+        }
+    };
+    for _ in 0..24 {
+        let is_current_time = now.with_timezone(&Tz::UTC) - home_datetime > TimeDelta::zero()
+            && now.with_timezone(&Tz::UTC) - home_datetime < TimeDelta::minutes(60);
+
+        rows.push(
+            visible_locations
+                .iter()
+                .map(|Location { tz, .. }| {
+                    let cell_datetime = home_datetime.with_timezone(tz).naive_local();
+                    CellData {
+                        is_current_time,
+                        is_daylight: cell_datetime.hour() >= 9 && cell_datetime.hour() <= 16,
+                        datetime: cell_datetime,
+                    }
+                })
+                .collect(),
+        );
+        home_datetime += TimeDelta::hours(1);
+    }
+    Ok(rows)
+}

src/view.rs

@@ -0,0 +1,119 @@
+use ratatui::widgets::BorderType::Rounded;
+use ratatui::widgets::{Cell, Padding, Row, Table};
+use ratatui::{prelude::*, symbols::border, widgets::Block};
+
+use crate::model::{CellData, FocusState, Model};
+
+/// Elm render function.
+pub(crate) fn view(model: &mut Model, frame: &mut Frame) {
+    let title = Line::from(" Team Time Zones ".bold());
+    let instructions = Line::from(match model.focus_state {
+        FocusState::Table => vec![
+            " Filter ".into(),
+            "/".blue().bold(),
+            "  Quit ".into(),
+            "Q ".blue().bold(),
+        ],
+        FocusState::Filter => vec![" Reset ".into(), "<Esc>".blue().bold(), " ".into()],
+    });
+    let main_block = Block::bordered()
+        .title(title.centered().fg(Color::Reset))
+        .title_bottom(instructions.centered().fg(Color::Reset))
+        .border_set(border::PLAIN)
+        .border_style(Style::new().fg(Color::DarkGray))
+        .border_type(Rounded);
+    frame.render_widget(&main_block, frame.area());
+
+    let visible_locations = model.get_visible_locations();
+    let header = Row::new(
+        visible_locations
+            .iter()
+            .map(|location| location.name.as_str())
+            .collect::<Vec<&str>>(),
+    )
+    .cyan()
+    .bold();
+    let col_widths: Vec<Constraint> = visible_locations
+        .iter()
+        .map(|location| Constraint::Length(clamp_u16(location.name.len(), 5, 32)))
+        .collect();
+
+    // TODO: Figure out a good way to refactor this into a distinct view
+    // function without offending the borrow checker.
+    let table = Table::new(
+        model
+            .table_rows
+            .iter()
+            .map(|row| {
+                Row::new(
+                    row.iter()
+                        .map(
+                            |&CellData {
+                                 is_current_time,
+                                 is_daylight,
+                                 datetime,
+                             }| {
+                                Cell::new(datetime.format("%H:%M").to_string()).style(
+                                    if is_current_time {
+                                        Style::new().red()
+                                    } else if !is_daylight {
+                                        Style::new().fg(Color::DarkGray)
+                                    } else {
+                                        Style::new()
+                                    },
+                                )
+                            },
+                        )
+                        .collect::<Vec<Cell>>(),
+                )
+            })
+            .collect::<Vec<Row>>(),
+        col_widths,
+    )
+    .header(header)
+    .column_spacing(4)
+    .block(Block::new().padding(Padding::horizontal(2)));
+
+    let [table_area, filter_area] = Layout::vertical([
+        Constraint::Fill(1),
+        Constraint::Length(if model.focus_state == FocusState::Filter {
+            1
+        } else {
+            0
+        }),
+    ])
+    .areas(main_block.inner(frame.area()));
+    if model.focus_state == FocusState::Filter {
+        const FILTER_LABEL_TEXT: &str = "Filter: ";
+        let [filter_label_area, filter_input_area] = Layout::horizontal([
+            Constraint::Length(
+                FILTER_LABEL_TEXT
+                    .len()
+                    .try_into()
+                    .expect("filter label is of static, reasonable length"),
+            ),
+            Constraint::Fill(1),
+        ])
+        .areas(filter_area);
+        frame.render_widget(FILTER_LABEL_TEXT.dim(), filter_label_area);
+        frame.render_widget(&model.filter_textarea, filter_input_area);
+    }
+    frame.render_stateful_widget(table, table_area, &mut model.table_state);
+}
+
+/// Clip a [`usize`]-like value to between two [`u16`]s (inclusive).
+fn clamp_u16<T>(value: T, min: u16, max: u16) -> u16
+where
+    T: Into<usize>,
+{
+    let value: usize = value.into();
+    if value <= min.into() {
+        min
+    } else if value >= max.into() {
+        max
+    } else {
+        value
+            .try_into()
+            .expect("value is known to be unsigned and less than some valid u16")
+    }
+}