use ratatui::{buffer::Buffer, layout::Rect, style::{Color, Modifier, Style}, widgets::Widget};
use crate::{board::{GameBoard, Move, PieceType, Pos}, player::Highlights};
/// Columns between neighbouring points at scale 1. Twice `ROW_STEP`, since cells are about twice as tall as wide.
const COL_STEP: u16 = 4;
/// Rows between neighbouring points at scale 1.
const ROW_STEP: u16 = 2;
/// Columns taken by the rank labels on the left.
const LEFT: u16 = 3;
/// The spacing between points, in (columns, rows), at `scale`.
const fn steps(scale: u16) -> (u16, u16)
{
(COL_STEP * scale, ROW_STEP * scale)
}
/// How far a drawn piece reaches past its point, in (columns, rows), at `scale`:
/// `T` at scale 1, `[T]` at scale 2, and a 3x3 box from scale 3 up.
const fn reach(scale: u16) -> (u16, u16)
{
match scale
{
1 => (0, 0),
2 => (1, 0),
_ => (1, 1),
}
}
/// The board with its lines, rank labels down the left and file labels underneath.
/// It is drawn at the largest whole-number scale that fits its area; at scale 1 it looks like:
///
/// ```text
/// 5 T───·───·───·───T
/// │ ╲ │ ╱ │ ╲ │ ╱ │
/// 4 ·───·───·───·───·
/// …
/// 1 T───·───·───·───T
///
/// a b c d e
/// ```
pub struct BoardView
{
pub board: GameBoard,
pub highlights: Highlights,
pub last_move: Option<Move>,
}
impl BoardView
{
/// The (width, height) the board needs at `scale` (1 or more): the grid, the pieces sticking
/// out past its edge, then a blank row and the file labels.
pub const fn size(scale: u16) -> (u16, u16)
{
let (cs, rs) = steps(scale);
let (rx, ry) = reach(scale);
(LEFT + 4 * cs + 1 + rx, ry + 4 * rs + 1 + ry + 2)
}
/// The largest scale whose board fits in `width` by `height`; 1 if even that doesn't fit.
pub fn scale_to_fit(width: u16, height: u16) -> u16
{
let fits = |scale| { let (w, h) = BoardView::size(scale); w <= width && h <= height };
let mut scale = 1;
while fits(scale + 1)
{
scale += 1;
}
scale
}
/// The screen cell a point is drawn at at `scale`, relative to the widget's top-left.
/// The grid sits below a row for the top pieces' boxes once they are boxed.
fn cell((x, y): Pos, scale: u16) -> (u16, u16)
{
let (cs, rs) = steps(scale);
(LEFT + x as u16 * cs, reach(scale).1 + y as u16 * rs)
}
fn piece_style(&self, pos: Pos, piece: &PieceType) -> Style
{
let mut style = match piece
{
PieceType::Tiger => Style::new().fg(Color::Yellow).add_modifier(Modifier::BOLD),
PieceType::Sheep => Style::new().fg(Color::White).add_modifier(Modifier::BOLD),
PieceType::Empty => Style::new().fg(Color::DarkGray),
};
let (from, to) = match self.last_move
{
Some(Move::PlaceSheep { pos }) => (None, Some(pos)),
Some(Move::MoveSheep { from, to } | Move::MoveTiger { from, to }) => (Some(from), Some(to)),
None => (None, None),
};
if from == Some(pos) || to == Some(pos)
{
style = style.add_modifier(Modifier::UNDERLINED);
}
if self.highlights.targets.contains(&pos)
{
style = style.fg(Color::Green).add_modifier(Modifier::BOLD);
}
if self.highlights.selected == Some(pos)
{
style = style.add_modifier(Modifier::REVERSED);
}
style
}
}
impl Widget for &BoardView
{
fn render(self, area: Rect, buf: &mut Buffer)
{
let scale = BoardView::scale_to_fit(area.width, area.height);
let (cs, rs) = steps(scale);
let lines = Style::new().fg(Color::Gray);
let labels = Style::new().fg(Color::Cyan);
// Clip to the area so a small terminal doesn't index outside the buffer
let mut put = |cx: u16, cy: u16, s: &str, style: Style|
{
if cx < area.width && cy < area.height
{
buf.set_string(area.x + cx, area.y + cy, s, style);
}
};
// Lines first, so the pieces are drawn over them
for y in 0..5u8
{
for x in 0..5u8
{
let (cx, cy) = BoardView::cell((x, y), scale);
if x < 4
{
put(cx + 1, cy, &"─".repeat(cs as usize - 1), lines);
}
if y < 4
{
for k in 1..rs
{
put(cx, cy + k, "│", lines);
}
if x < 4
{
// Diagonals run through points where x + y is even (see `GameBoard::on_line`).
// Each row down the diagonal moves cs / rs = 2 columns across.
let down_right = (x + y) % 2 == 0;
for k in 1..rs
{
let col = if down_right { cx + 2 * k } else { cx + cs - 2 * k };
put(col, cy + k, if down_right { "╲" } else { "╱" }, lines);
}
}
}
}
}
for y in 0..5u8
{
let (_, cy) = BoardView::cell((0, y), scale);
put(0, cy, &(5 - y).to_string(), labels);
for x in 0..5u8
{
let (cx, cy) = BoardView::cell((x, y), scale);
let piece = self.board.get((x, y));
let targeted = self.highlights.targets.contains(&(x, y));
let symbol = match piece
{
PieceType::Tiger => "T",
PieceType::Sheep => "S",
PieceType::Empty if targeted => "●",
PieceType::Empty => "·",
};
let style = self.piece_style((x, y), &piece);
// The last move's underline is only for the symbol, not the box around it
let frame = style.remove_modifier(Modifier::UNDERLINED);
let boxed = targeted || !matches!(piece, PieceType::Empty);
match scale
{
_ if !boxed => put(cx, cy, symbol, style),
1 => put(cx, cy, symbol, style),
2 =>
{
put(cx - 1, cy, "[", frame);
put(cx, cy, symbol, style);
put(cx + 1, cy, "]", frame);
}
_ =>
{
// Where a line meets the box, join it on
put(cx - 1, cy - 1, if y > 0 { "┌┴┐" } else { "┌─┐" }, frame);
put(cx - 1, cy, if x > 0 { "┤" } else { "│" }, frame);
put(cx, cy, symbol, style);
put(cx + 1, cy, if x < 4 { "├" } else { "│" }, frame);
put(cx - 1, cy + 1, if y < 4 { "└┬┘" } else { "└─┘" }, frame);
}
}
}
}
let files_row = BoardView::size(scale).1 - 1;
for x in 0..5u8
{
let (cx, _) = BoardView::cell((x, 0), scale);
put(cx, files_row, &((b'a' + x) as char).to_string(), labels);
}
}
}
/// The board point nearest a click at screen cell (`column`, `row`), for a `BoardView` drawn in `area`
/// (at the same scale `render` picks for it). Clicks on the lines between points go to the nearest
/// point; clicks off the grid give None.
pub fn pos_at(area: Rect, column: u16, row: u16) -> Option<Pos>
{
let scale = BoardView::scale_to_fit(area.width, area.height);
let (cs, rs) = steps(scale);
let (rx, ry) = reach(scale);
// Offsets from the top-left point, letting clicks land on the edge pieces' boxes
let cx = column.checked_sub(area.x + LEFT - rx)?;
let cy = row.checked_sub(area.y)?;
if cx > 4 * cs + 1 + rx || cy > 4 * rs + 2 * ry
{
return None;
}
// Shifted by the reach, so (cx, cy) are offsets from one column/row before the first point
let x = ((cx + cs / 2 - rx) / cs).min(4);
let y = ((cy + rs / 2 - ry) / rs).min(4);
Some((x as u8, y as u8))
}
#[cfg(test)]
mod tests
{
use super::*;
fn rendered(view: &BoardView, area: Rect) -> Buffer
{
let mut buf = Buffer::empty(Rect::new(0, 0, area.right() + 2, area.bottom() + 2));
view.render(area, &mut buf);
buf
}
fn symbol(buf: &Buffer, x: u16, y: u16) -> &str
{
buf[(x, y)].symbol()
}
#[test]
fn renders_default_board_with_labels()
{
let area = Rect::new(1, 1, BoardView::size(1).0, BoardView::size(1).1);
let view = BoardView { board: GameBoard::default(), highlights: Highlights::default(), last_move: None };
let buf = rendered(&view, area);
for (pos, s) in [((0, 0), "T"), ((4, 0), "T"), ((0, 4), "T"), ((4, 4), "T"), ((2, 2), "·")]
{
let (cx, cy) = BoardView::cell(pos, 1);
assert_eq!(symbol(&buf, area.x + cx, area.y + cy), s, "{pos:?}");
}
assert_eq!(symbol(&buf, area.x, area.y), "5");
assert_eq!(symbol(&buf, area.x, area.y + 8), "1");
assert_eq!(symbol(&buf, area.x + LEFT, area.y + BoardView::size(1).1 - 1), "a");
assert_eq!(symbol(&buf, area.x + LEFT + 16, area.y + BoardView::size(1).1 - 1), "e");
// (0, 0) has an even sum, so its diagonal runs down-right
assert_eq!(symbol(&buf, area.x + LEFT + 2, area.y + 1), "╲");
assert_eq!(symbol(&buf, area.x + LEFT + 6, area.y + 1), "╱");
}
#[test]
fn renders_target_highlights()
{
let area = Rect::new(0, 0, BoardView::size(1).0, BoardView::size(1).1);
let highlights = Highlights { selected: Some((0, 0)), targets: vec![(1, 1)] };
let view = BoardView { board: GameBoard::default(), highlights, last_move: None };
let buf = rendered(&view, area);
let (cx, cy) = BoardView::cell((1, 1), 1);
assert_eq!(symbol(&buf, cx, cy), "●");
let (cx, cy) = BoardView::cell((0, 0), 1);
assert!(buf[(cx, cy)].modifier.contains(Modifier::REVERSED));
}
#[test]
fn renders_into_a_small_area_without_panicking()
{
let view = BoardView { board: GameBoard::default(), highlights: Highlights::default(), last_move: None };
rendered(&view, Rect::new(0, 0, 5, 3));
}
#[test]
fn scale_to_fit_picks_the_largest_board_that_fits()
{
for scale in 1..5
{
let (w, h) = BoardView::size(scale);
assert_eq!(BoardView::scale_to_fit(w, h), scale);
assert_eq!(BoardView::scale_to_fit(w + 5, h + 5), scale);
assert_eq!(BoardView::scale_to_fit(w - 1, h), (scale - 1).max(1));
assert_eq!(BoardView::scale_to_fit(w, h - 1), (scale - 1).max(1));
}
assert_eq!(BoardView::scale_to_fit(0, 0), 1);
}
#[test]
fn renders_bigger_when_there_is_room()
{
let (w, h) = BoardView::size(2);
let area = Rect::new(0, 0, w, h);
let view = BoardView { board: GameBoard::default(), highlights: Highlights::default(), last_move: None };
let buf = rendered(&view, area);
let (cx, cy) = BoardView::cell((4, 4), 2);
assert_eq!((cx, cy), (LEFT + 32, 16));
assert_eq!(symbol(&buf, cx, cy), "T");
assert_eq!(symbol(&buf, 0, 16), "1");
assert_eq!(symbol(&buf, cx, h - 1), "e");
// Lines fill the gaps: three rows of │ between points, a diagonal two columns per row
for k in 1..4
{
assert_eq!(symbol(&buf, LEFT, k), "│");
assert_eq!(symbol(&buf, LEFT + 2 * k, k), "╲");
}
assert_eq!(symbol(&buf, LEFT + 7, 0), "─");
}
fn row(buf: &Buffer, y: u16) -> String
{
(0..buf.area.width).map(|x| buf[(x, y)].symbol()).collect()
}
#[test]
fn pieces_get_brackets_at_scale_2()
{
let (w, h) = BoardView::size(2);
let highlights = Highlights { selected: None, targets: vec![(1, 1)] };
let view = BoardView { board: GameBoard::default(), highlights, last_move: None };
let buf = rendered(&view, Rect::new(0, 0, w, h));
assert!(row(&buf, 0).starts_with("5 [T]──────·"), "{}", row(&buf, 0));
assert!(row(&buf, 4).starts_with("4 ·──────[●]──────·"), "{}", row(&buf, 4));
}
#[test]
fn pieces_get_boxes_from_scale_3()
{
let (w, h) = BoardView::size(3);
let mut board = GameBoard::default();
board.make_move(Move::PlaceSheep { pos: (2, 2) }).unwrap();
let view = BoardView { board, highlights: Highlights::default(), last_move: None };
let buf = rendered(&view, Rect::new(0, 0, w, h));
// Corner tiger: lines only join on the sides that have them
assert!(row(&buf, 0).starts_with(" ┌─┐"), "{}", row(&buf, 0));
assert!(row(&buf, 1).starts_with("5 │T├───"), "{}", row(&buf, 1));
assert!(row(&buf, 2).starts_with(" └┬┘"), "{}", row(&buf, 2));
// Centre sheep: lines join on all four sides
let (cx, cy) = BoardView::cell((2, 2), 3);
let around = |dy: u16| (cx - 1..=cx + 1).map(|x| buf[(x, cy + dy - 1)].symbol()).collect::<String>();
assert_eq!([around(0), around(1), around(2)], ["┌┴┐", "┤S├", "└┬┘"]);
assert_eq!(symbol(&buf, cx, h - 1), "c");
}
#[test]
fn pos_at_takes_clicks_on_a_piece_box()
{
let (w, h) = BoardView::size(3);
let area = Rect::new(4, 3, w, h);
for pos in [(0, 0), (4, 4), (2, 2), (4, 0)]
{
let (cx, cy) = BoardView::cell(pos, 3);
for (dx, dy) in [(-1, -1), (1, 1), (-1, 1), (1, -1)]
{
let column = (area.x + cx).checked_add_signed(dx).unwrap();
let row = (area.y + cy).checked_add_signed(dy).unwrap();
assert_eq!(pos_at(area, column, row), Some(pos), "{pos:?} {dx},{dy}");
}
}
assert_eq!(pos_at(area, area.x + 1, area.y), None);
assert_eq!(pos_at(area, area.x + LEFT, area.y + h - 1), None); // file labels
}
#[test]
fn pos_at_finds_every_drawn_point()
{
for scale in 1..6
{
let (w, h) = BoardView::size(scale);
let area = Rect::new(3, 2, w, h);
for y in 0..5
{
for x in 0..5
{
let (cx, cy) = BoardView::cell((x, y), scale);
assert_eq!(pos_at(area, area.x + cx, area.y + cy), Some((x, y)), "scale {scale}");
}
}
}
}
#[test]
fn pos_at_snaps_line_clicks_to_nearest_point()
{
let area = Rect::new(0, 0, BoardView::size(1).0, BoardView::size(1).1);
assert_eq!(pos_at(area, LEFT + 1, 0), Some((0, 0)));
assert_eq!(pos_at(area, LEFT + 3, 0), Some((1, 0)));
assert_eq!(pos_at(area, LEFT + 16, 1), Some((4, 1)));
}
#[test]
fn pos_at_rejects_clicks_off_the_grid()
{
let area = Rect::new(2, 2, BoardView::size(1).0, BoardView::size(1).1);
assert_eq!(pos_at(area, 0, 0), None);
assert_eq!(pos_at(area, area.x, area.y), None); // rank label
assert_eq!(pos_at(area, area.x + LEFT, area.y + 9), None); // below the last rank
assert_eq!(pos_at(area, area.x + LEFT + 18, area.y), None);
}
}
