import { useState, useRef, forwardRef, useEffect, KeyboardEvent, useCallback } from "react";
import Button from "../Button";
import { getIndex, getNearistIndex, parseSrt } from "../../subtitle";
import SubtitleDisplay from "./SubtitleDisplay";

type VideoPanelProps = {
    videoUrl: string | null;
    srtUrl: string | null;
};

const VideoPanel = forwardRef<HTMLVideoElement, VideoPanelProps>((
    { videoUrl, srtUrl }, videoRef
) => {
    videoRef = videoRef as React.RefObject<HTMLVideoElement>;
    const [isPlaying, setIsPlaying] = useState<boolean>(false);
    const [srtLength, setSrtLength] = useState<number>(0);
    const [progress, setProgress] = useState<number>(-1);
    const [autoPause, setAutoPause] = useState<boolean>(true);
    const [spanText, setSpanText] = useState<string>('');
    const [subtitle, setSubtitle] = useState<string>('');
    const parsedSrtRef = useRef<{ start: number; end: number; text: string; }[] | null>(null);
    const rafldRef = useRef<number>(0);
    const ready = useRef({
        'vid': false,
        'sub': false,
        'all': function () { return this.vid && this.sub }
    });

    const togglePlayPause = useCallback(() => {
        if (!videoUrl) return;

        const video = videoRef.current;
        if (!video) return;
        if (video.paused || video.currentTime === 0) {
            video.play();
        } else {
            video.pause();
        }
        setIsPlaying(!video.paused);
    }, [videoRef, videoUrl]);

    useEffect(() => {
        const cb = () => {
            if (ready.current.all()) {
                if (!parsedSrtRef.current) {
                    ;
                } else if (isPlaying) {
                    // 这里负责显示当前时间的字幕与自动暂停
                    const srt = parsedSrtRef.current;
                    const ct = videoRef.current?.currentTime as number;
                    const index = getIndex(srt, ct);
                    if (index !== null) {
                        setSubtitle(srt[index].text)
                        if (autoPause && ct >= (srt[index].end - 0.05) && ct < srt[index].end) {
                            videoRef.current!.currentTime = srt[index].start;
                            togglePlayPause();
                        }
                    } else {
                        setSubtitle('');
                    }
                } else {
                    ;
                }
            }
            rafldRef.current = requestAnimationFrame(cb);
        }
        rafldRef.current = requestAnimationFrame(cb);
        return () => {
            cancelAnimationFrame(rafldRef.current);
        }
    }, [autoPause, isPlaying, togglePlayPause, videoRef]);

    useEffect(() => {
        if (videoUrl && videoRef.current) {
            videoRef.current.src = videoUrl;
            videoRef.current.load();
            setIsPlaying(false);
            ready.current['vid'] = true;
        }
    }, [videoRef, videoUrl]);
    useEffect(() => {
        if (srtUrl) {
            fetch(srtUrl)
                .then(response => response.text())
                .then(data => {
                    parsedSrtRef.current = parseSrt(data);
                    setSrtLength(parsedSrtRef.current.length);
                    ready.current['sub'] = true;
                });
        }
    }, [srtUrl]);

    const timeUpdate = () => {
        if (!parsedSrtRef.current || !videoRef.current) return;
        const index = getIndex(parsedSrtRef.current, videoRef.current.currentTime);
        if (!index) return;
        setSpanText(`${index + 1}/${parsedSrtRef.current.length}`)
    }

    const handleSeek = (e: React.ChangeEvent<HTMLInputElement>) => {
        if (videoRef.current && parsedSrtRef.current) {
            const newProgress = parseInt(e.target.value);
            videoRef.current.currentTime = parsedSrtRef.current[newProgress]?.start || 0;
            setProgress(newProgress);
        }
    };

    const handleAutoPauseToggle = () => {
        setAutoPause(!autoPause);
    };

    const next = () => {
        if (!parsedSrtRef.current || !videoRef.current) return;
        const i = getNearistIndex(parsedSrtRef.current, videoRef.current.currentTime);
        if (i != null && i + 1 < parsedSrtRef.current.length) {
            videoRef.current.currentTime = parsedSrtRef.current[i + 1].start;
            videoRef.current.play();
            setIsPlaying(true);
        }
    }

    const previous = () => {
        if (!parsedSrtRef.current || !videoRef.current) return;
        const i = getNearistIndex(parsedSrtRef.current, videoRef.current.currentTime);
        if (i != null && i - 1 >= 0) {
            videoRef.current.currentTime = parsedSrtRef.current[i - 1].start;
            videoRef.current.play();
            setIsPlaying(true);
        }
    }

    const restart = () => {
        if (!parsedSrtRef.current || !videoRef.current) return;
        const i = getNearistIndex(parsedSrtRef.current, videoRef.current.currentTime);
        if (i != null && i >= 0) {
            videoRef.current.currentTime = parsedSrtRef.current[i].start;
            videoRef.current.play();
            setIsPlaying(true);
        }
    }

    const handleKeyDownEvent = (e: KeyboardEvent<HTMLDivElement>) => {
        if (e.key === 'n') {
            next();
        } else if (e.key === 'p') {
            previous();
        } else if (e.key === ' ') {
            togglePlayPause();
        } else if (e.key === 'r') {
            restart();
        } else if (e.key === 'a') {
            ; handleAutoPauseToggle();
        }
    }

    return (
        <div className="flex flex-col w-9/12" onKeyDown={handleKeyDownEvent}>
            <video className="max-h-80" ref={videoRef} onTimeUpdate={timeUpdate}></video>
            <SubtitleDisplay subtitle={subtitle}></SubtitleDisplay>
            <div className="buttons">
                <ul className="">
                    <Button label={isPlaying ? 'PAUSE' : 'PLAY'} onClick={togglePlayPause}></Button>
                    <Button label="NEXT" onClick={next}></Button>
                    <Button label="PREVIOUS" onClick={previous}></Button>
                    <Button label="RESTART" onClick={restart}></Button>
                    <Button label={`AUTOPAUSE(${autoPause ? 'Y' : 'N'})`} onClick={handleAutoPauseToggle}></Button>
                </ul>
            </div>
            <input className="seekbar" type="range" min={0} max={srtLength} onChange={handleSeek} step={1} value={progress}></input>
            <span>{spanText}</span>
        </div>
    );
});

VideoPanel.displayName = 'VideoPanel';

export default VideoPanel;