revite/src/lib/TextAreaAutoSize.tsx

import styled from "styled-components";

import { useEffect, useLayoutEffect, useRef } from "preact/hooks";

import TextArea, { TextAreaProps } from "../components/ui/TextArea";

import { internalSubscribe } from "./eventEmitter";
import { isTouchscreenDevice } from "./isTouchscreenDevice";
import { RefObject } from "preact";

type TextAreaAutoSizeProps = Omit<
    JSX.HTMLAttributes<HTMLTextAreaElement>,
    "style" | "value" | "onChange"
> &
    TextAreaProps & {
        forceFocus?: boolean;
        autoFocus?: boolean;
        minHeight?: number;
        maxRows?: number;
        value: string;

        id?: string;

        onChange?: (ev: JSX.TargetedEvent<HTMLTextAreaElement, Event>) => void;
    };

const Container = styled.div`
    flex-grow: 1;
    display: flex;
    flex-direction: column;
`;

const Ghost = styled.div<{ lineHeight: string, maxRows: number }>`
    flex: 0;
    width: 100%;
    overflow: hidden;
    visibility: hidden;
    position: relative;

    > div {
        width: 100%;
        white-space: pre-wrap;
        word-break: break-all;
        
        top: 0;
        position: absolute;
        font-size: var(--text-size);
        line-height: ${(props) => props.lineHeight};

        max-height: calc(calc( ${(props) => props.lineHeight} * ${ (props) => props.maxRows } ));
    }
`;

export default function TextAreaAutoSize(props: TextAreaAutoSizeProps) {
    const {
        autoFocus,
        minHeight,
        maxRows,
        value,
        padding,
        lineHeight,
        hideBorder,
        forceFocus,
        children,
        as,
        onChange,
        ...textAreaProps
    } = props;

    const ref = useRef<HTMLTextAreaElement>() as RefObject<HTMLTextAreaElement>;
    const ghost = useRef<HTMLDivElement>() as RefObject<HTMLDivElement>;

    useLayoutEffect(() => {
        if (ref.current && ghost.current) {
            ref.current.style.height = ghost.current.clientHeight + 'px';
        }
    }, [ghost, props.value]);

    useEffect(() => {
        if (isTouchscreenDevice) return;
        autoFocus && ref.current && ref.current.focus();
    }, [value]);

    const inputSelected = () =>
        ["TEXTAREA", "INPUT"].includes(document.activeElement?.nodeName ?? "");

    useEffect(() => {
        if (!ref.current) return;
        if (forceFocus) {
            ref.current.focus();
        }

        if (isTouchscreenDevice) return;
        if (autoFocus && !inputSelected()) {
            ref.current.focus();
        }

        // ? if you are wondering what this is
        // ? it is a quick and dirty hack to fix
        // ? value not setting correctly
        // ? I have no clue what's going on
        ref.current.value = value;

        if (!autoFocus) return;
        function keyDown(e: KeyboardEvent) {
            if ((e.ctrlKey && e.key !== "v") || e.altKey || e.metaKey) return;
            if (e.key.length !== 1) return;
            if (ref && !inputSelected()) {
                ref.current!.focus();
            }
        }

        document.body.addEventListener("keydown", keyDown);
        return () => document.body.removeEventListener("keydown", keyDown);
    }, [ref]);

    useEffect(() => {
        if (!ref.current) return;
        function focus(id: string) {
            if (id === props.id) {
                ref.current!.focus();
            }
        }

        return internalSubscribe("TextArea", "focus", focus);
    }, [ref]);

    return (
        <Container>
            <TextArea
                ref={ref}
                value={value}
                padding={padding}
                style={{ minHeight }}
                hideBorder={hideBorder}
                lineHeight={lineHeight}
                onChange={(ev) => {
                    onChange && onChange(ev);
                }}
                {...textAreaProps}
            />
            <Ghost lineHeight={lineHeight ?? 'var(--textarea-line-height)'} maxRows={maxRows ?? 5}>
                <div ref={ghost} style={{ padding }}>
                    {props.value
                        ? props.value
                              .split("\n")
                              .map((x) => `\u200e${x}`)
                              .join("\n")
                        : undefined ?? "‎\n"}
                </div>
            </Ghost>
        </Container>
    );
}