@assistant-ui/react/dist/utils/smooth/useSmooth.js

TypeScript/React library for AI Chat

"use client";
import { useEffect, useMemo, useRef, useState } from "react";
import { useAssistantState } from "../../context/index.js";
import { useCallbackRef } from "@radix-ui/react-use-callback-ref";
import { useSmoothStatusStore } from "./SmoothContext.js";
import { writableStore } from "../../context/ReadonlyStore.js";
class TextStreamAnimator {
    currentText;
    setText;
    animationFrameId = null;
    lastUpdateTime = Date.now();
    targetText = "";
    constructor(currentText, setText) {
        this.currentText = currentText;
        this.setText = setText;
    }
    start() {
        if (this.animationFrameId !== null)
            return;
        this.lastUpdateTime = Date.now();
        this.animate();
    }
    stop() {
        if (this.animationFrameId !== null) {
            cancelAnimationFrame(this.animationFrameId);
            this.animationFrameId = null;
        }
    }
    animate = () => {
        const currentTime = Date.now();
        const deltaTime = currentTime - this.lastUpdateTime;
        let timeToConsume = deltaTime;
        const remainingChars = this.targetText.length - this.currentText.length;
        const baseTimePerChar = Math.min(5, 250 / remainingChars);
        let charsToAdd = 0;
        while (timeToConsume >= baseTimePerChar && charsToAdd < remainingChars) {
            charsToAdd++;
            timeToConsume -= baseTimePerChar;
        }
        if (charsToAdd !== remainingChars) {
            this.animationFrameId = requestAnimationFrame(this.animate);
        }
        else {
            this.animationFrameId = null;
        }
        if (charsToAdd === 0)
            return;
        this.currentText = this.targetText.slice(0, this.currentText.length + charsToAdd);
        this.lastUpdateTime = currentTime - timeToConsume;
        this.setText(this.currentText);
    };
}
const SMOOTH_STATUS = Object.freeze({
    type: "running",
});
export const useSmooth = (state, smooth = false) => {
    const { text } = state;
    const id = useAssistantState(({ message }) => message.id);
    const idRef = useRef(id);
    const [displayedText, setDisplayedText] = useState(text);
    const smoothStatusStore = useSmoothStatusStore({ optional: true });
    const setText = useCallbackRef((text) => {
        setDisplayedText(text);
        if (smoothStatusStore) {
            const target = displayedText !== text || state.status.type === "running"
                ? SMOOTH_STATUS
                : state.status;
            writableStore(smoothStatusStore).setState(target, true);
        }
    });
    // TODO this is hacky
    useEffect(() => {
        if (smoothStatusStore) {
            const target = smooth && (displayedText !== text || state.status.type === "running")
                ? SMOOTH_STATUS
                : state.status;
            writableStore(smoothStatusStore).setState(target, true);
        }
    }, [smoothStatusStore, smooth, text, displayedText, state.status]);
    const [animatorRef] = useState(new TextStreamAnimator(text, setText));
    useEffect(() => {
        if (!smooth) {
            animatorRef.stop();
            return;
        }
        if (idRef.current !== id || !text.startsWith(animatorRef.targetText)) {
            idRef.current = id;
            setText(text);
            animatorRef.currentText = text;
            animatorRef.targetText = text;
            animatorRef.stop();
            return;
        }
        animatorRef.targetText = text;
        animatorRef.start();
    }, [setText, animatorRef, id, smooth, text]);
    useEffect(() => {
        return () => {
            animatorRef.stop();
        };
    }, [animatorRef]);
    return useMemo(() => smooth
        ? {
            type: "text",
            text: displayedText,
            status: text === displayedText ? state.status : SMOOTH_STATUS,
        }
        : state, [smooth, displayedText, state, text]);
};
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