k-frame/crates/client-domain/tests/layout_engine_tests.rs

use client_domain::{BoundingBox, LayoutEngine, RenderTree};
use domain::{ContainerNode, Direction, LayoutChild, LayoutNode, Sizing};

fn screen() -> BoundingBox {
    BoundingBox::screen(240, 320)
}

fn leaf(id: u16) -> LayoutChild {
    LayoutChild {
        sizing: Sizing::Flex(1),
        node: LayoutNode::Leaf(id),
    }
}

fn leaf_fixed(id: u16, size: u16) -> LayoutChild {
    LayoutChild {
        sizing: Sizing::Fixed(size),
        node: LayoutNode::Leaf(id),
    }
}

fn row(children: Vec<LayoutChild>) -> LayoutNode {
    LayoutNode::Container(ContainerNode {
        direction: Direction::Row,
        gap: 0,
        padding: 0,
        children,
    })
}

fn column(children: Vec<LayoutChild>) -> LayoutNode {
    LayoutNode::Container(ContainerNode {
        direction: Direction::Column,
        gap: 0,
        padding: 0,
        children,
    })
}

fn row_with_gap(gap: u8, children: Vec<LayoutChild>) -> LayoutNode {
    LayoutNode::Container(ContainerNode {
        direction: Direction::Row,
        gap,
        padding: 0,
        children,
    })
}

fn row_with_padding(padding: u8, children: Vec<LayoutChild>) -> LayoutNode {
    LayoutNode::Container(ContainerNode {
        direction: Direction::Row,
        gap: 0,
        padding,
        children,
    })
}

#[test]
fn single_leaf_fills_screen() {
    let layout = LayoutNode::Leaf(1);
    let tree = LayoutEngine::compute(&layout, screen());

    assert_eq!(
        tree.get_widget_bounds(1),
        Some(&BoundingBox::new(0, 0, 240, 320))
    );
}

#[test]
fn row_splits_width_among_equal_flex_children() {
    let layout = row(vec![leaf(1), leaf(2), leaf(3)]);
    let tree = LayoutEngine::compute(&layout, screen());

    assert_eq!(
        tree.get_widget_bounds(1),
        Some(&BoundingBox::new(0, 0, 80, 320))
    );
    assert_eq!(
        tree.get_widget_bounds(2),
        Some(&BoundingBox::new(80, 0, 80, 320))
    );
    assert_eq!(
        tree.get_widget_bounds(3),
        Some(&BoundingBox::new(160, 0, 80, 320))
    );
}

#[test]
fn column_splits_height_among_equal_flex_children() {
    let layout = column(vec![leaf(1), leaf(2)]);
    let tree = LayoutEngine::compute(&layout, screen());

    assert_eq!(
        tree.get_widget_bounds(1),
        Some(&BoundingBox::new(0, 0, 240, 160))
    );
    assert_eq!(
        tree.get_widget_bounds(2),
        Some(&BoundingBox::new(0, 160, 240, 160))
    );
}

#[test]
fn fixed_and_flex_children_coexist() {
    let layout = row(vec![leaf_fixed(1, 40), leaf(2)]);
    let tree = LayoutEngine::compute(&layout, screen());

    assert_eq!(
        tree.get_widget_bounds(1),
        Some(&BoundingBox::new(0, 0, 40, 320))
    );
    assert_eq!(
        tree.get_widget_bounds(2),
        Some(&BoundingBox::new(40, 0, 200, 320))
    );
}

#[test]
fn gap_is_subtracted_before_distributing_space() {
    // 240px wide, 2 children, gap=10 → 230px available, 115px each
    let layout = row_with_gap(10, vec![leaf(1), leaf(2)]);
    let tree = LayoutEngine::compute(&layout, screen());

    assert_eq!(
        tree.get_widget_bounds(1),
        Some(&BoundingBox::new(0, 0, 115, 320))
    );
    assert_eq!(
        tree.get_widget_bounds(2),
        Some(&BoundingBox::new(125, 0, 115, 320))
    );
}

#[test]
fn padding_insets_available_area() {
    // padding=10 → inner area starts at (10,10), size (220,300)
    let layout = row_with_padding(10, vec![leaf(1)]);
    let tree = LayoutEngine::compute(&layout, screen());

    assert_eq!(
        tree.get_widget_bounds(1),
        Some(&BoundingBox::new(10, 10, 220, 300))
    );
}

#[test]
fn nested_containers_compute_correctly() {
    // Row with [leaf(1), column([leaf(2), leaf(3)])]
    let inner_col = LayoutChild {
        sizing: Sizing::Flex(1),
        node: column(vec![leaf(2), leaf(3)]),
    };
    let layout = row(vec![leaf(1), inner_col]);
    let tree = LayoutEngine::compute(&layout, screen());

    assert_eq!(
        tree.get_widget_bounds(1),
        Some(&BoundingBox::new(0, 0, 120, 320))
    );
    assert_eq!(
        tree.get_widget_bounds(2),
        Some(&BoundingBox::new(120, 0, 120, 160))
    );
    assert_eq!(
        tree.get_widget_bounds(3),
        Some(&BoundingBox::new(120, 160, 120, 160))
    );
}

#[test]
fn weighted_flex_distributes_proportionally() {
    // weights [1, 2, 1] → 25%, 50%, 25% of 240 = 60, 120, 60
    let layout = LayoutNode::Container(ContainerNode {
        direction: Direction::Row,
        gap: 0,
        padding: 0,
        children: vec![
            LayoutChild {
                sizing: Sizing::Flex(1),
                node: LayoutNode::Leaf(1),
            },
            LayoutChild {
                sizing: Sizing::Flex(2),
                node: LayoutNode::Leaf(2),
            },
            LayoutChild {
                sizing: Sizing::Flex(1),
                node: LayoutNode::Leaf(3),
            },
        ],
    });
    let tree = LayoutEngine::compute(&layout, screen());

    assert_eq!(
        tree.get_widget_bounds(1),
        Some(&BoundingBox::new(0, 0, 60, 320))
    );
    assert_eq!(
        tree.get_widget_bounds(2),
        Some(&BoundingBox::new(60, 0, 120, 320))
    );
    assert_eq!(
        tree.get_widget_bounds(3),
        Some(&BoundingBox::new(180, 0, 60, 320))
    );
}