hikari-components 0.3.12

// hi-components/src/data/virtual_scroll.rs
// Virtual scroll component for large tree data sets

use hikari_palette::classes::{ClassesBuilder, VirtualScrollClass};

use crate::{prelude::*, styled::StyledComponent};

pub struct VirtualScrollComponent;

#[derive(Clone, PartialEq, Debug, Default)]
pub struct VirtualTreeNodeData {
    pub id: String,

    pub title: String,

    pub children: Vec<VirtualTreeNodeData>,

    pub disabled: bool,
}

#[define_props]
pub struct VirtualTreeProps {
    pub data: Vec<VirtualTreeNodeData>,

    #[default("400px".to_string())]
    pub height: String,

    #[default(32)]
    pub item_height: u32,

    #[default(5)]
    pub overscan: u32,

    pub class: String,

    pub on_scroll: Option<EventHandler<f64>>,
}

#[component]
pub fn VirtualTree(props: VirtualTreeProps) -> Element {
    let scroll_position = use_signal(|| 0.0);
    let container_height = props.height.parse::<f64>().unwrap_or(400.0);

    // Flatten tree data for virtual scrolling
    let flattened_items = use_memo(move || {
        let mut result = Vec::new();
        fn flatten(
            node: &VirtualTreeNodeData,
            depth: usize,
            result: &mut Vec<(VirtualTreeNodeData, usize)>,
        ) {
            result.push((node.clone(), depth));
            for child in &node.children {
                flatten(child, depth + 1, result);
            }
        }
        for node in &props.data {
            flatten(node, 0, &mut result);
        }
        result
    });

    let total_height = flattened_items.read().len() as f64 * props.item_height as f64;

    // Calculate visible range
    let flattened_for_range = flattened_items.clone();
    let scroll_for_range = scroll_position.clone();
    let range = use_memo(move || {
        let scroll = scroll_for_range.get();
        let start = (scroll / props.item_height as f64).floor() as usize;
        let visible_count = (container_height / props.item_height as f64).ceil() as usize;
        let end =
            (start + visible_count + props.overscan as usize).min(flattened_for_range.read().len());
        let start = start.saturating_sub(props.overscan as usize);
        (start, end)
    });

    let flattened_for_visible = flattened_items.clone();
    let visible_items = use_memo(move || {
        let (start, end) = range.read();
        flattened_for_visible.read()[start..end].to_vec()
    });

    // Pre-compute items_data outside rsx!
    let flattened_for_items = flattened_items.clone();
    let items_data: Vec<_> = visible_items
        .read()
        .iter()
        .map(|(item, depth)| {
            let idx = {
                let items = flattened_for_items.read();
                items.iter().position(|(n, _)| n.id == item.id).unwrap_or(0)
            };
            (
                item.id.clone(),
                item.title.clone(),
                item.disabled,
                idx,
                *depth,
            )
        })
        .collect();

    // Pre-build item elements outside rsx!
    let item_elements: Vec<Element> = items_data.into_iter().map(|(id, title, disabled, idx, depth)| {
        let node_classes = ClassesBuilder::new()
            .add(VirtualScrollClass::VirtualTree)
            .add_if(VirtualScrollClass::NodeDisabled, || disabled)
            .build();

        let item_height = props.item_height;
        rsx! {
            div {
                class: node_classes,
                style: "position: absolute; top: {(idx as f64 * item_height as f64)}px; left: 0; right: 0; height: {item_height}px; padding-left: {(depth * 24)}px; display: flex; align-items: center;",
                "data-key": id,

                span {
                    class: "hi-tree-node-content",
                    style: "display: flex; align-items: center; gap: 8px;",
                    "{title}"
                }
            }
        }
    }).collect();

    // Clone for onscroll handler
    let scroll_position_for_onscroll = scroll_position.clone();
    let on_scroll_handler = props.on_scroll.clone();

    rsx! {
        div {
            class: format!("hi-virtual-tree {}", props.class),
            style: "position: relative; overflow: hidden; height: {props.height};",

            div { style: "position: absolute; top: 0; left: 0; right: 0; height: {total_height}px; pointer-events: none;" }

            div {
                class: "hi-virtual-tree-viewport",
                style: "position: absolute; top: 0; left: 0; right: 0; bottom: 0; overflow-y: auto;",
                onscroll: move |_e: Event| {
                    #[cfg(all(target_arch = "wasm32", target_os = "unknown"))]
                    {
                        use crate::platform::get_scroll_top_by_selector;
                        let scroll_top = get_scroll_top_by_selector(".hi-virtual-tree-viewport");
                        scroll_position_for_onscroll.set(scroll_top);

                        if let Some(handler) = on_scroll_handler.as_ref() {
                            handler.call(scroll_top);
                        }
                    }
                },

                div {
                    style: "position: relative; height: {total_height}px;",
                    ..item_elements,
                }
            }
        }
    }
}

impl StyledComponent for VirtualScrollComponent {
    fn styles() -> &'static str {
        include_str!(concat!(env!("OUT_DIR"), "/styles/virtual-scroll.css"))
    }

    fn name() -> &'static str {
        "virtual-scroll"
    }
}