ruin/lib/ui/src/tree.rs

use crate::scene::Color;
use crate::text::{TextSpan, TextStyle, TextWrap};

#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub struct ElementId(u64);

impl ElementId {
    pub const fn new(raw: u64) -> Self {
        Self(raw)
    }

    pub const fn raw(self) -> u64 {
        self.0
    }
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum FlexDirection {
    Row,
    Column,
}

#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub enum CursorIcon {
    Default,
    Pointer,
    Text,
}

#[derive(Clone, Copy, Debug, PartialEq)]
pub struct Edges {
    pub top: f32,
    pub right: f32,
    pub bottom: f32,
    pub left: f32,
}

impl Edges {
    pub const ZERO: Self = Self {
        top: 0.0,
        right: 0.0,
        bottom: 0.0,
        left: 0.0,
    };

    pub const fn all(value: f32) -> Self {
        Self {
            top: value,
            right: value,
            bottom: value,
            left: value,
        }
    }

    pub const fn symmetric(horizontal: f32, vertical: f32) -> Self {
        Self {
            top: vertical,
            right: horizontal,
            bottom: vertical,
            left: horizontal,
        }
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct Style {
    pub direction: FlexDirection,
    pub width: Option<f32>,
    pub height: Option<f32>,
    pub flex_grow: f32,
    pub gap: f32,
    pub padding: Edges,
    pub background: Option<Color>,
    pub pointer_events: bool,
    pub focusable: bool,
    pub cursor: Option<CursorIcon>,
}

impl Default for Style {
    fn default() -> Self {
        Self {
            direction: FlexDirection::Column,
            width: None,
            height: None,
            flex_grow: 0.0,
            gap: 0.0,
            padding: Edges::ZERO,
            background: None,
            pointer_events: true,
            focusable: false,
            cursor: None,
        }
    }
}

#[derive(Clone, Debug, PartialEq)]
enum ElementContent {
    Container,
    Text(TextNode),
}

#[derive(Clone, Debug, PartialEq)]
pub(crate) struct TextNode {
    pub spans: Vec<TextSpan>,
    pub style: TextStyle,
}

#[derive(Clone, Debug, PartialEq)]
pub struct Element {
    pub id: Option<ElementId>,
    pub style: Style,
    pub children: Vec<Element>,
    content: ElementContent,
}

impl Element {
    pub fn new() -> Self {
        Self {
            id: None,
            style: Style::default(),
            children: Vec::new(),
            content: ElementContent::Container,
        }
    }

    pub fn text(text: impl Into<String>, style: TextStyle) -> Self {
        Self::spans([TextSpan::new(text)], style)
    }

    pub fn spans(spans: impl IntoIterator<Item = TextSpan>, style: TextStyle) -> Self {
        Self {
            id: None,
            style: Style::default(),
            children: Vec::new(),
            content: ElementContent::Text(TextNode {
                spans: spans.into_iter().collect(),
                style,
            }),
        }
    }

    pub fn paragraph(text: impl Into<String>, style: TextStyle) -> Self {
        Self::text(text, style.with_wrap(TextWrap::Word))
    }

    pub fn rich_paragraph(spans: impl IntoIterator<Item = TextSpan>, style: TextStyle) -> Self {
        Self::spans(spans, style.with_wrap(TextWrap::Word))
    }

    pub fn row() -> Self {
        Self::new().direction(FlexDirection::Row)
    }

    pub fn column() -> Self {
        Self::new().direction(FlexDirection::Column)
    }

    pub fn direction(mut self, direction: FlexDirection) -> Self {
        self.style.direction = direction;
        self
    }

    pub fn width(mut self, width: f32) -> Self {
        self.style.width = Some(width);
        self
    }

    pub fn height(mut self, height: f32) -> Self {
        self.style.height = Some(height);
        self
    }

    pub fn flex(mut self, flex_grow: f32) -> Self {
        self.style.flex_grow = flex_grow.max(0.0);
        self
    }

    pub fn gap(mut self, gap: f32) -> Self {
        self.style.gap = gap.max(0.0);
        self
    }

    pub fn padding(mut self, padding: Edges) -> Self {
        self.style.padding = padding;
        self
    }

    pub fn background(mut self, color: Color) -> Self {
        self.style.background = Some(color);
        self
    }

    pub fn id(mut self, id: ElementId) -> Self {
        self.id = Some(id);
        self
    }

    pub fn pointer_events(mut self, pointer_events: bool) -> Self {
        self.style.pointer_events = pointer_events;
        self
    }

    pub fn focusable(mut self, focusable: bool) -> Self {
        self.style.focusable = focusable;
        self
    }

    pub fn cursor(mut self, cursor: CursorIcon) -> Self {
        self.style.cursor = Some(cursor);
        self
    }

    pub fn child(mut self, child: Element) -> Self {
        self.assert_container();
        self.children.push(child);
        self
    }

    pub fn children(mut self, children: impl IntoIterator<Item = Element>) -> Self {
        self.assert_container();
        self.children.extend(children);
        self
    }

    pub(crate) fn text_node(&self) -> Option<&TextNode> {
        match &self.content {
            ElementContent::Text(text) => Some(text),
            ElementContent::Container => None,
        }
    }

    fn assert_container(&self) {
        assert!(
            matches!(self.content, ElementContent::Container),
            "text elements cannot contain children"
        );
    }
}

impl Default for Element {
    fn default() -> Self {
        Self::new()
    }
}