Almost done with list

2 files changed, 135 insertions, 103 deletions

diff --git a/src/list.rs b/src/list.rs
index e360182..a8e5225 100644
--- a/src/list.rs
+++ b/src/list.rs
@@ -59,9 +59,7 @@ fn handle_list(app_state: &mut AppState, stdout: &mut StdoutLock) -> Result<()>
 
                         list_state.message.push_str(message);
                     }
-                    KeyCode::Char('r') => {
-                        list_state.reset_selected()?;
-                    }
+                    KeyCode::Char('r') => list_state.reset_selected()?,
                     KeyCode::Char('c') => {
                         if list_state.selected_to_current_exercise()? {
                             return Ok(());
@@ -77,9 +75,7 @@ fn handle_list(app_state: &mut AppState, stdout: &mut StdoutLock) -> Result<()>
                 MouseEventKind::ScrollUp => list_state.select_previous(),
                 _ => continue,
             },
-            Event::Resize(width, height) => {
-                list_state.set_term_size(width, height);
-            }
+            Event::Resize(width, height) => list_state.set_term_size(width, height),
             // Ignore
             Event::FocusGained | Event::FocusLost => continue,
         }
diff --git a/src/list/state.rs b/src/list/state.rs
index cbca1d9..b8fdfcb 100644
--- a/src/list/state.rs
+++ b/src/list/state.rs
@@ -15,20 +15,21 @@ use crate::{app_state::AppState, exercise::Exercise, term::progress_bar, MAX_EXE
 // +1 for padding.
 const SPACE: &[u8] = &[b' '; MAX_EXERCISE_NAME_LEN + 1];
 
-fn next_ln<const CLEAR_LAST_CHAR: bool>(stdout: &mut StdoutLock) -> io::Result<()> {
-    if CLEAR_LAST_CHAR {
-        // Avoids having the last written char as the last displayed one when
-        // the written width is higher than the terminal width.
-        // Happens on the Gnome terminal for example.
-        stdout.write_all(b" ")?;
-    }
-
+fn next_ln(stdout: &mut StdoutLock) -> io::Result<()> {
     stdout
         .queue(Clear(ClearType::UntilNewLine))?
         .queue(MoveToNextLine(1))?;
     Ok(())
 }
 
+// Avoids having the last written char as the last displayed one when the
+// written width is higher than the terminal width.
+// Happens on the Gnome terminal for example.
+fn next_ln_overwrite(stdout: &mut StdoutLock) -> io::Result<()> {
+    stdout.write_all(b" ")?;
+    next_ln(stdout)
+}
+
 #[derive(Copy, Clone, PartialEq, Eq)]
 pub enum Filter {
     Done,
@@ -37,65 +38,111 @@ pub enum Filter {
 }
 
 pub struct ListState<'a> {
+    /// Footer message to be displayed if not empty.
     pub message: String,
-    filter: Filter,
     app_state: &'a mut AppState,
-    n_rows_with_filter: usize,
     name_col_width: usize,
-    offset: usize,
-    selected: Option<usize>,
+    filter: Filter,
+    n_rows_with_filter: usize,
+    /// Selected row out of the displayed ones.
+    selected_row: Option<usize>,
     term_width: u16,
     term_height: u16,
-    separator: Vec<u8>,
+    separator_line: Vec<u8>,
+    narrow_term: bool,
+    show_footer: bool,
+    max_n_rows_to_display: usize,
+    scroll_padding: usize,
+    row_offset: usize,
 }
 
 impl<'a> ListState<'a> {
     pub fn new(app_state: &'a mut AppState, stdout: &mut StdoutLock) -> io::Result<Self> {
-        let (term_width, term_height) = terminal::size()?;
         stdout.queue(Clear(ClearType::All))?;
 
+        let name_col_title_len = 4;
         let name_col_width = app_state
             .exercises()
             .iter()
             .map(|exercise| exercise.name.len())
             .max()
-            .map_or(4, |max| max.max(4));
+            .map_or(name_col_title_len, |max| max.max(name_col_title_len));
 
+        let filter = Filter::None;
         let n_rows_with_filter = app_state.exercises().len();
-        let selected = app_state.current_exercise_ind();
+        let selected = Some(app_state.current_exercise_ind());
 
         let mut slf = Self {
             message: String::with_capacity(128),
-            filter: Filter::None,
             app_state,
-            n_rows_with_filter,
             name_col_width,
-            offset: selected.saturating_sub(10),
-            selected: Some(selected),
-            term_width,
-            term_height,
-            separator: "─".as_bytes().repeat(term_width as usize),
+            filter,
+            n_rows_with_filter,
+            selected_row: selected,
+            // Set by `set_term_size`
+            term_width: 0,
+            term_height: 0,
+            separator_line: Vec::new(),
+            narrow_term: false,
+            show_footer: true,
+            max_n_rows_to_display: 0,
+            scroll_padding: 0,
+            // Updated by `draw`
+            row_offset: 0,
         };
 
+        let (width, height) = terminal::size()?;
+        slf.set_term_size(width, height);
         slf.draw(stdout)?;
 
         Ok(slf)
     }
 
+    pub fn set_term_size(&mut self, width: u16, height: u16) {
+        self.term_width = width;
+        self.term_height = height;
+
+        self.separator_line = "─".as_bytes().repeat(width as usize);
+
+        self.narrow_term = width < 95 && self.selected_row.is_some();
+        self.show_footer = height > 6;
+        self.max_n_rows_to_display =
+            (height - 1 - u16::from(self.show_footer) * (4 + u16::from(self.narrow_term))) as usize;
+        self.scroll_padding = (self.max_n_rows_to_display / 4).min(5);
+    }
+
+    fn update_offset(&mut self) {
+        let Some(selected) = self.selected_row else {
+            return;
+        };
+
+        let min_offset = (selected + self.scroll_padding)
+            .saturating_sub(self.max_n_rows_to_display.saturating_sub(1));
+        let max_offset = selected.saturating_sub(self.scroll_padding);
+        let global_max_offset = self
+            .n_rows_with_filter
+            .saturating_sub(self.max_n_rows_to_display);
+
+        self.row_offset = self
+            .row_offset
+            .max(min_offset)
+            .min(max_offset)
+            .min(global_max_offset);
+    }
+
     fn draw_rows(
         &self,
         stdout: &mut StdoutLock,
-        max_n_rows_to_display: usize,
         filtered_exercises: impl Iterator<Item = (usize, &'a Exercise)>,
     ) -> io::Result<usize> {
         let current_exercise_ind = self.app_state.current_exercise_ind();
         let mut n_displayed_rows = 0;
 
         for (exercise_ind, exercise) in filtered_exercises
-            .skip(self.offset)
-            .take(max_n_rows_to_display)
+            .skip(self.row_offset)
+            .take(self.max_n_rows_to_display)
         {
-            if self.selected == Some(n_displayed_rows) {
+            if self.selected_row == Some(self.row_offset + n_displayed_rows) {
                 stdout.queue(SetBackgroundColor(Color::Rgb {
                     r: 50,
                     g: 50,
@@ -128,7 +175,7 @@ impl<'a> ListState<'a> {
 
             stdout.write_all(exercise.path.as_bytes())?;
 
-            next_ln::<true>(stdout)?;
+            next_ln_overwrite(stdout)?;
             stdout.queue(ResetColor)?;
             n_displayed_rows += 1;
         }
@@ -147,36 +194,27 @@ impl<'a> ListState<'a> {
         stdout.write_all(b"  Current  State    Name")?;
         stdout.write_all(&SPACE[..self.name_col_width - 2])?;
         stdout.write_all(b"Path")?;
-        next_ln::<true>(stdout)?;
+        next_ln_overwrite(stdout)?;
 
-        let narrow = self.term_width < 95;
-        let show_footer = self.term_height > 6;
-        let max_n_rows_to_display =
-            (self.term_height - 1 - u16::from(show_footer) * (4 + u16::from(narrow))) as usize;
+        self.update_offset();
 
         // Rows
         let iter = self.app_state.exercises().iter().enumerate();
         let n_displayed_rows = match self.filter {
-            Filter::Done => self.draw_rows(
-                stdout,
-                max_n_rows_to_display,
-                iter.filter(|(_, exercise)| exercise.done),
-            )?,
-            Filter::Pending => self.draw_rows(
-                stdout,
-                max_n_rows_to_display,
-                iter.filter(|(_, exercise)| !exercise.done),
-            )?,
-            Filter::None => self.draw_rows(stdout, max_n_rows_to_display, iter)?,
+            Filter::Done => self.draw_rows(stdout, iter.filter(|(_, exercise)| exercise.done))?,
+            Filter::Pending => {
+                self.draw_rows(stdout, iter.filter(|(_, exercise)| !exercise.done))?
+            }
+            Filter::None => self.draw_rows(stdout, iter)?,
         };
 
-        for _ in 0..max_n_rows_to_display - n_displayed_rows {
-            next_ln::<false>(stdout)?;
+        for _ in 0..self.max_n_rows_to_display - n_displayed_rows {
+            next_ln(stdout)?;
         }
 
-        if show_footer {
-            stdout.write_all(&self.separator)?;
-            next_ln::<false>(stdout)?;
+        if self.show_footer {
+            stdout.write_all(&self.separator_line)?;
+            next_ln(stdout)?;
 
             progress_bar(
                 stdout,
@@ -184,21 +222,25 @@ impl<'a> ListState<'a> {
                 self.app_state.exercises().len() as u16,
                 self.term_width,
             )?;
-            next_ln::<false>(stdout)?;
+            next_ln(stdout)?;
 
-            stdout.write_all(&self.separator)?;
-            next_ln::<false>(stdout)?;
+            stdout.write_all(&self.separator_line)?;
+            next_ln(stdout)?;
 
             if self.message.is_empty() {
                 // Help footer
-                stdout.write_all(
-                    "↓/j ↑/k home/g end/G │ <c>ontinue at │ <r>eset exercise │".as_bytes(),
-                )?;
-                if narrow {
-                    next_ln::<true>(stdout)?;
-                    stdout.write_all(b"filter ")?;
+                if self.selected_row.is_some() {
+                    stdout.write_all(
+                        "↓/j ↑/k home/g end/G | <c>ontinue at | <r>eset exercise".as_bytes(),
+                    )?;
+                    if self.narrow_term {
+                        next_ln_overwrite(stdout)?;
+                        stdout.write_all(b"filter ")?;
+                    } else {
+                        stdout.write_all(b" | filter ")?;
+                    }
                 } else {
-                    stdout.write_all(b" filter ")?;
+                    stdout.write_all(b"filter ")?;
                 }
 
                 match self.filter {
@@ -220,19 +262,19 @@ impl<'a> ListState<'a> {
                     }
                     Filter::None => stdout.write_all(b"<d>one/<p>ending")?,
                 }
-                stdout.write_all(" │ <q>uit list".as_bytes())?;
-                if narrow {
-                    next_ln::<true>(stdout)?;
+                stdout.write_all(b" | <q>uit list")?;
+                if self.narrow_term {
+                    next_ln_overwrite(stdout)?;
                 } else {
-                    next_ln::<false>(stdout)?;
+                    next_ln(stdout)?;
                 }
             } else {
                 stdout.queue(SetForegroundColor(Color::Magenta))?;
                 stdout.write_all(self.message.as_bytes())?;
                 stdout.queue(ResetColor)?;
-                next_ln::<true>(stdout)?;
-                if narrow {
-                    next_ln::<false>(stdout)?;
+                next_ln_overwrite(stdout)?;
+                if self.narrow_term {
+                    next_ln(stdout)?;
                 }
             }
         }
@@ -240,20 +282,8 @@ impl<'a> ListState<'a> {
         stdout.queue(EndSynchronizedUpdate)?.flush()
     }
 
-    pub fn set_term_size(&mut self, width: u16, height: u16) {
-        self.term_width = width;
-        self.term_height = height;
-        self.separator = "─".as_bytes().repeat(width as usize);
-    }
-
-    #[inline]
-    pub fn filter(&self) -> Filter {
-        self.filter
-    }
-
-    pub fn set_filter(&mut self, filter: Filter) {
-        self.filter = filter;
-        self.n_rows_with_filter = match filter {
+    fn update_rows(&mut self) {
+        self.n_rows_with_filter = match self.filter {
             Filter::Done => self
                 .app_state
                 .exercises()
@@ -270,42 +300,46 @@ impl<'a> ListState<'a> {
         };
 
         if self.n_rows_with_filter == 0 {
-            self.selected = None;
+            self.selected_row = None;
         } else {
-            self.selected = Some(
-                self.selected
+            self.selected_row = Some(
+                self.selected_row
                     .map_or(0, |selected| selected.min(self.n_rows_with_filter - 1)),
             );
         }
     }
 
+    #[inline]
+    pub fn filter(&self) -> Filter {
+        self.filter
+    }
+
+    pub fn set_filter(&mut self, filter: Filter) {
+        self.filter = filter;
+        self.update_rows();
+    }
+
     pub fn select_next(&mut self) {
-        if self.n_rows_with_filter > 0 {
-            let next = self.selected.map_or(0, |selected| {
-                (selected + 1).min(self.n_rows_with_filter - 1)
-            });
-            self.selected = Some(next);
+        if let Some(selected) = self.selected_row {
+            self.selected_row = Some((selected + 1).min(self.n_rows_with_filter - 1));
         }
     }
 
     pub fn select_previous(&mut self) {
-        if self.n_rows_with_filter > 0 {
-            let previous = self
-                .selected
-                .map_or(0, |selected| selected.saturating_sub(1));
-            self.selected = Some(previous);
+        if let Some(selected) = self.selected_row {
+            self.selected_row = Some(selected.saturating_sub(1));
         }
     }
 
     pub fn select_first(&mut self) {
         if self.n_rows_with_filter > 0 {
-            self.selected = Some(0);
+            self.selected_row = Some(0);
         }
     }
 
     pub fn select_last(&mut self) {
         if self.n_rows_with_filter > 0 {
-            self.selected = Some(self.n_rows_with_filter - 1);
+            self.selected_row = Some(self.n_rows_with_filter - 1);
         }
     }
 
@@ -334,13 +368,14 @@ impl<'a> ListState<'a> {
     }
 
     pub fn reset_selected(&mut self) -> Result<()> {
-        let Some(selected) = self.selected else {
+        let Some(selected) = self.selected_row else {
             self.message.push_str("Nothing selected to reset!");
             return Ok(());
         };
 
         let exercise_ind = self.selected_to_exercise_ind(selected)?;
         let exercise_path = self.app_state.reset_exercise_by_ind(exercise_ind)?;
+        self.update_rows();
         write!(self.message, "The exercise {exercise_path} has been reset")?;
 
         Ok(())
@@ -348,13 +383,14 @@ impl<'a> ListState<'a> {
 
     // Return `true` if there was something to select.
     pub fn selected_to_current_exercise(&mut self) -> Result<bool> {
-        let Some(selected) = self.selected else {
+        let Some(selected) = self.selected_row else {
             self.message.push_str("Nothing selected to continue at!");
             return Ok(false);
         };
 
         let exercise_ind = self.selected_to_exercise_ind(selected)?;
         self.app_state.set_current_exercise_ind(exercise_ind)?;
+
         Ok(true)
     }
 }