index.tsx

import * as React from 'react';
import * as ReactDOM from 'react-dom';

// Internally, the portalNode must be for either HTML or SVG elements
const ELEMENT_TYPE_HTML = 'html';
const ELEMENT_TYPE_SVG  = 'svg';

type BaseOptions = {
    attributes?: { [key: string]: string };
};

type HtmlOptions = BaseOptions & {
    containerElement?: keyof HTMLElementTagNameMap;
};

type SvgOptions = BaseOptions & {
    containerElement?: keyof SVGElementTagNameMap;
};

type Options = HtmlOptions | SvgOptions;

// ReactDOM can handle several different namespaces, but they're not exported publicly
// https://github.com/facebook/react/blob/b87aabdfe1b7461e7331abb3601d9e6bb27544bc/packages/react-dom/src/shared/DOMNamespaces.js#L8-L10
const SVG_NAMESPACE = 'http://www.w3.org/2000/svg';

type Component<P> = React.Component<P> | React.ComponentType<P>;

type ComponentProps<C extends Component<any>> = C extends Component<infer P> ? P : never;

interface PortalNodeBase<C extends Component<any>> {
    // Used by the out portal to send props back to the real element
    // Hooked by InPortal to become a state update (and thus rerender)
    setPortalProps(p: ComponentProps<C>): void;
    // Used to track props set before the InPortal hooks setPortalProps
    getInitialPortalProps(): ComponentProps<C>;
    // Move the node from wherever it is, to this parent, replacing the placeholder
    mount(newParent: Node, placeholder: Node): void;
    // If mounted, unmount the node and put the initial placeholder back
    // If an expected placeholder is provided, only unmount if that's still that was the
    // latest placeholder we replaced. This avoids some race conditions.
    unmount(expectedPlaceholder?: Node): void;
}
export interface HtmlPortalNode<C extends Component<any> = Component<any>> extends PortalNodeBase<C> {
    element: HTMLElement;
    elementType: typeof ELEMENT_TYPE_HTML;
}
export interface SvgPortalNode<C extends Component<any> = Component<any>> extends PortalNodeBase<C> {
    element: SVGElement;
    elementType: typeof ELEMENT_TYPE_SVG;
}
type AnyPortalNode<C extends Component<any> = Component<any>> = HtmlPortalNode<C> | SvgPortalNode<C>;


const validateElementType = (domElement: Element, elementType: typeof ELEMENT_TYPE_HTML | typeof ELEMENT_TYPE_SVG) => {
    const ownerDocument = (domElement.ownerDocument ?? document) as any;
    // Cast document to `any` because Typescript doesn't know about the legacy `Document.parentWindow` field, and also
    // doesn't believe `Window.HTMLElement`/`Window.SVGElement` can be used in instanceof tests.
    const ownerWindow = ownerDocument.defaultView ?? ownerDocument.parentWindow ?? window; // `parentWindow` for IE8 and earlier

    switch (elementType) {
        case ELEMENT_TYPE_HTML:
            return domElement instanceof ownerWindow.HTMLElement;
        case ELEMENT_TYPE_SVG:
            return domElement instanceof ownerWindow.SVGElement;
        default:
            throw new Error(`Unrecognized element type "${elementType}" for validateElementType.`);
    }
};

// This is the internal implementation: the public entry points set elementType to an appropriate value
const createPortalNode = <C extends Component<any>>(
    elementType: typeof ELEMENT_TYPE_HTML | typeof ELEMENT_TYPE_SVG,
    options?: Options
): AnyPortalNode<C> => {
    let initialProps = {} as ComponentProps<C>;

    let parent: Node | undefined;
    let lastPlaceholder: Node | undefined;

    let element;

    switch (elementType) {
        case ELEMENT_TYPE_HTML:
            element = document.createElement(options?.containerElement ?? 'div');
            break;
        case ELEMENT_TYPE_SVG:
            element = document.createElementNS(SVG_NAMESPACE, options?.containerElement ?? 'g');
            break;
        default:
            throw new Error(`Invalid element type "${elementType}" for createPortalNode: must be "html" or "svg".`);
    }

    if (options && typeof options === "object" && options.attributes) {
        for (const [key, value] of Object.entries(options.attributes)) {
            element.setAttribute(key, value);
        }
    }

    const portalNode: AnyPortalNode<C> = {
        element,
        elementType,
        setPortalProps: (props: ComponentProps<C>) => {
            initialProps = props;
        },
        getInitialPortalProps: () => {
            return initialProps;
        },
        mount: (newParent: HTMLElement, newPlaceholder: HTMLElement) => {
            if (newPlaceholder === lastPlaceholder) {
                // Already mounted - noop.
                return;
            }
            portalNode.unmount();

            // To support SVG and other non-html elements, the portalNode's elementType needs to match
            // the elementType it's being rendered into
            if (newParent !== parent) {
                if (!validateElementType(newParent, elementType)) {
                    throw new Error(`Invalid element type for portal: "${elementType}" portalNodes must be used with ${elementType} elements, but OutPortal is within <${newParent.tagName}>.`);
                }
            }

            newParent.replaceChild(
                portalNode.element,
                newPlaceholder,
            );

            parent = newParent;
            lastPlaceholder = newPlaceholder;
        },
        unmount: (expectedPlaceholder?: Node) => {
            if (expectedPlaceholder && expectedPlaceholder !== lastPlaceholder) {
                // Skip unmounts for placeholders that aren't currently mounted
                // They will have been automatically unmounted already by a subsequent mount()
                return;
            }

            if (parent && lastPlaceholder) {
                parent.replaceChild(
                    lastPlaceholder,
                    portalNode.element,
                );

                parent = undefined;
                lastPlaceholder = undefined;
            }
        }
    } as AnyPortalNode<C>;

    return portalNode;
};

interface InPortalProps {
    node: AnyPortalNode;
    children: React.ReactNode;
}

class InPortal extends React.PureComponent<InPortalProps, { nodeProps: {} }> {

    constructor(props: InPortalProps) {
        super(props);
        this.state = {
            nodeProps: this.props.node.getInitialPortalProps(),
        };
    }

    addPropsChannel = () => {
        Object.assign(this.props.node, {
            setPortalProps: (props: {}) => {
                // Rerender the child node here if/when the out portal props change
                this.setState({ nodeProps: props });
            }
        });
    };

    componentDidMount() {
        this.addPropsChannel();
    }

    componentDidUpdate() {
        this.addPropsChannel();
    }

    render() {
        const { children, node } = this.props;

        return ReactDOM.createPortal(
            React.Children.map(children, (child) => {
                if (!React.isValidElement(child)) return child;
                return React.cloneElement(child, this.state.nodeProps)
            }),
            node.element
        );
    }
}

type OutPortalProps<C extends Component<any>> = {
    node: AnyPortalNode<C>
} & Partial<ComponentProps<C>>;

class OutPortal<C extends Component<any>> extends React.PureComponent<OutPortalProps<C>> {

    private placeholderNode = React.createRef<HTMLElement>();
    private currentPortalNode?: AnyPortalNode<C>;

    constructor(props: OutPortalProps<C>) {
        super(props);
        this.passPropsThroughPortal();
    }

    passPropsThroughPortal() {
        const propsForTarget = Object.assign({}, this.props, { node: undefined });
        this.props.node.setPortalProps(propsForTarget);
    }

    componentDidMount() {
        const node = this.props.node as AnyPortalNode<C>;
        this.currentPortalNode = node;

        const placeholder = this.placeholderNode.current!;
        const parent = placeholder.parentNode!;
        node.mount(parent, placeholder);
        this.passPropsThroughPortal();
    }

    componentDidUpdate() {
        // We re-mount on update, just in case we were unmounted (e.g. by
        // a second OutPortal, which has now been removed)
        const node = this.props.node as AnyPortalNode<C>;

        // If we're switching portal nodes, we need to clean up the current one first.
        if (this.currentPortalNode && node !== this.currentPortalNode) {
            this.currentPortalNode.unmount(this.placeholderNode.current!);
            this.currentPortalNode.setPortalProps({} as ComponentProps<C>);
            this.currentPortalNode = node;
        }

        const placeholder = this.placeholderNode.current!;
        const parent = placeholder.parentNode!;
        node.mount(parent, placeholder);
        this.passPropsThroughPortal();
    }

    componentWillUnmount() {
        const node = this.props.node as AnyPortalNode<C>;
        node.unmount(this.placeholderNode.current!);
        node.setPortalProps({} as ComponentProps<C>);
    }

    render() {
        // Render a placeholder to the DOM, so we can get a reference into
        // our location in the DOM, and swap it out for the portaled node.
        const tagName = this.props.node.element.tagName;

        // SVG tagName is lowercase and case sensitive, HTML is uppercase and case insensitive.
        // React.createElement expects lowercase first letter to treat as non-component element.
        // (Passing uppercase type won't break anything, but React warns otherwise:)
        // https://github.com/facebook/react/blob/8039f1b2a05d00437cd29707761aeae098c80adc/CHANGELOG.md?plain=1#L1984
        const type = this.props.node.elementType === ELEMENT_TYPE_HTML
            ? tagName.toLowerCase()
            : tagName;

        return React.createElement(type, { ref: this.placeholderNode });
    }
}

const createHtmlPortalNode = createPortalNode.bind(null, ELEMENT_TYPE_HTML) as
    <C extends Component<any> = Component<any>>(options?: HtmlOptions) => HtmlPortalNode<C>;
const createSvgPortalNode  = createPortalNode.bind(null, ELEMENT_TYPE_SVG) as
    <C extends Component<any> = Component<any>>(options?: SvgOptions) => SvgPortalNode<C>;

export {
    createHtmlPortalNode,
    createSvgPortalNode,
    InPortal,
    OutPortal,
}