packages/pi-tui/src/layout-node.ts

import type { Component } from "./tui.ts";

export const LAYOUT_NODE = Symbol.for("@earendil-works/pi-tui/layout-node");

export interface LayoutViewport {
	width: number;
	height: number;
}

export interface StackLayoutEntry {
	component: Component;
	basis?: number | "auto";
	grow?: number;
	shrink?: number;
	minSize?: number;
	maxSize?: number;
	visible?: (viewport: LayoutViewport) => boolean;
}

export interface StackLayoutNode {
	type: "vstack" | "hstack";
	entries: readonly StackLayoutEntry[];
	gap: number;
	align: "stretch" | "start" | "center" | "end";
}

export interface ScrollLayoutState {
	readonly scrollTop: number;
	readonly primary: boolean;
	readonly overscroll: "chain" | "contain";
	readonly viewportHeight: number;
	getContentWidth(width: number): number;
	updateLayout(contentHeight: number, viewportHeight: number, requestRender: () => void): void;
}

export interface ScrollLayoutNode {
	type: "scroll";
	component: Component;
	state: ScrollLayoutState;
}

export type LayoutNode = StackLayoutNode | ScrollLayoutNode;

export interface LayoutComponent extends Component {
	[LAYOUT_NODE](): LayoutNode;
}

export function getLayoutNode(component: Component): LayoutNode | undefined {
	const candidate = component as Partial<LayoutComponent>;
	return typeof candidate[LAYOUT_NODE] === "function" ? candidate[LAYOUT_NODE]() : undefined;
}