import React, {useEffect, useState} from 'react';
import {useHotkeys} from 'react-hotkeys-hook';
import {deleteFileGroups, downloadVideoMetadata, tagFileGroup, untagFileGroup} from "../api";
import {Link, useNavigate, useParams} from "react-router";
import _ from "lodash";
import {
    APIButton,
    BackButton,
    DirectoryLink,
    encodeMediaPath,
    humanFileSize,
    humanNumber,
    isoDatetimeToAgoPopup,
    MultilineText,
    PageContainer,
    PreviewPath,
    useMediaSession,
    useTitle
} from "./Common";
import {VideoPlaceholder} from "./Placeholder";
import {useChannel, useVideoCaptions, useVideoExtras} from "../hooks/customHooks";
import {Button, Grid, Header, Icon, Label, Loading, Panel, Tabs, TextInput} from "./ui";
import {VideoCard} from "./Videos";
import {TagsSelector} from "../Tags";
import {AddToPlaylistButton} from "./AddToPlaylist";
import {TaggedDeleteConfirmModal} from "./TaggedDeleteConfirmModal";
import {IconPlayerPause, IconPlayerPlay} from "@tabler/icons-react";

const MEDIA_PATH = '/media';



// YouTube auto-generated captions (downloaded via yt-dlp) stamp every cue with `align:start position:0%`,
// which pins the text to the bottom-left of the player and makes it hard to read.  Detect that signature and
// reset those cues to the browser's centered default.  This mutates only the in-memory VTTCue objects the
// browser parsed; the .vtt file on disk is never modified.  Cues that were deliberately positioned (anything
// other than the auto-caption signature) are left untouched.  YouTube auto-captions never set `line`, so we
// require `line === 'auto'` too; that leaves a deliberately placed cue (e.g. `line:0` for top-edge) alone even
// if it happens to also be `align:start position:0%`.
export function centerAutoCaptions(track) {
    if (!track || !track.cues) {
        return 0;
    }
    let changed = 0;
    for (const cue of track.cues) {
        if (cue.align === 'start' && cue.position === 0 && cue.line === 'auto') {
            cue.align = 'center';
            cue.position = 'auto';
            changed++;
        }
    }
    return changed;
}

function handleCaptionTrackLoad(event) {
    const track = event.target.track;
    if (!track) {
        return;
    }
    if (track.cues && track.cues.length > 0) {
        centerAutoCaptions(track);
    } else {
        // A non-default track has mode 'disabled' at load time, so its cues are not parsed yet.  Normalize
        // them once the browser populates the cue list (when the user selects the track and playback advances
        // into a cue).  Only detach after cues actually exist, in case a cuechange fires before they load.
        const onCueChange = () => {
            if (track.cues && track.cues.length > 0) {
                centerAutoCaptions(track);
                track.removeEventListener('cuechange', onCueChange);
            }
        };
        track.addEventListener('cuechange', onCueChange);
    }
}

export function CaptionTrack({src, ...props}) {
    // Center YouTube auto-generated captions once the browser parses the cues (see centerAutoCaptions).
    props = {onLoad: handleCaptionTrackLoad, ...props};
    if (src.endsWith('.de.vtt')) {
        return <track kind="captions" label="German" src={src} srcLang="de" {...props}/>
    } else if (src.endsWith('.es.vtt')) {
        return <track kind="captions" label="Spanish" src={src} srcLang="es" {...props}/>
    } else if (src.endsWith('.fr.vtt')) {
        return <track kind="captions" label="French" src={src} srcLang="fr" {...props}/>
    } else if (src.endsWith('.id.vtt')) {
        return <track kind="captions" label="Indonesian" src={src} srcLang="id" {...props}/>
    } else if (src.endsWith('.it.vtt')) {
        return <track kind="captions" label="Italian" src={src} srcLang="it" {...props}/>
    } else if (src.endsWith('.ja.vtt')) {
        return <track kind="captions" label="Japanese" src={src} srcLang="ja" {...props}/>
    } else if (src.endsWith('.pl.vtt')) {
        return <track kind="captions" label="Polish" src={src} srcLang="pl" {...props}/>
    } else if (src.endsWith('.pt.vtt')) {
        return <track kind="captions" label="Portuguese" src={src} srcLang="pt" {...props}/>
    } else if (src.endsWith('.ro.vtt')) {
        return <track kind="captions" label="Romanian" src={src} srcLang="ro" {...props}/>
    } else if (src.endsWith('.ru.vtt')) {
        return <track kind="captions" label="Russian" src={src} srcLang="ru" {...props}/>
    } else if (src.endsWith('.th.vtt')) {
        return <track kind="captions" label="Thai" src={src} srcLang="th" {...props}/>
    }
    return <track kind="captions" label="English" src={src} srcLang="en" default {...props}/>
}

const NoComments = ({video}) => {
    const videoUrl = video.url;

    const handleRefresh = async () => {
        await downloadVideoMetadata(videoUrl);
    };

    if (videoUrl) {
        return <React.Fragment>
            <p>No comments have been been downloaded. Refresh the video?</p>

            <APIButton
                role='primary'
                size='large'
                onClick={handleRefresh}
            >Refresh</APIButton>
        </React.Fragment>
    } else {
        return <React.Fragment>
            <p>No comment have been downloaded. WROLPi does not know the URL of this video, so it cannot download
                the comments.</p>

            <big>Try finding and downloading the video again.</big>
        </React.Fragment>
    }
}

// Semantic's <Comment>/<CommentGroup> have no equivalent in the token library -- this is a nested
// comment thread, not a reusable widget, so it is built here from plain elements and tokens.
const VideoComment = ({comment, children}) => {
    const {is_favorited, like_count, author, timestamp, text, author_is_uploader} = comment;

    // Author comments and favorited comments are important.
    let specialIcon = null;
    if (author_is_uploader) {
        specialIcon = <Icon name='star' label='Uploader' style={{color: 'var(--green)'}}/>;
    } else if (is_favorited) {
        specialIcon = <Icon name='heart' label='Favorited' style={{color: 'var(--red)'}}/>;
    }

    return <div style={{marginBottom: '1.2em'}}>
        <div style={{fontWeight: 600, display: 'flex', alignItems: 'center', gap: '0.3em'}}>
            {specialIcon}<span>{author}</span>
        </div>
        <div style={{display: 'flex', gap: '1em', fontSize: '0.85em', color: 'var(--muted)'}}>
            <div>{isoDatetimeToAgoPopup(timestamp * 1000)}</div>
            {like_count ? <div>
                <Icon name='thumbs up' size={14}/> {humanNumber(comment['like_count'])}
            </div> : null}
        </div>
        <div>
            <MultilineText text={text} style={{marginLeft: '0.5em'}}/>
        </div>
        {children && !_.isEmpty(children) &&
            <div style={{
                marginLeft: '1.5em',
                marginTop: '0.7em',
                paddingLeft: '1em',
                borderLeft: '1px solid var(--border)',
            }}>
                {children.map((i, key) => <VideoComment key={key} comment={i}/>)}
            </div>
        }
    </div>
}


const Comments = ({comments, video}) => {
    if (!comments || _.isEmpty(comments)) {
        return <NoComments video={video}/>
    }

    comments.sort((a, b) => {
        // Treat undefined like_count as 0
        const likeA = a.like_count ?? 0;
        const likeB = b.like_count ?? 0;

        // For descending order
        return likeB - likeA;
    });

    const rootComments = comments.filter(i => i['parent'] === 'root');

    // Comments are in an array, convert it to a dict, grouped by their parent.
    const groupedByParent = {};
    comments.forEach(obj => {
        if (!groupedByParent[obj.parent]) {
            groupedByParent[obj.parent] = [];
        }
        groupedByParent[obj.parent].push(obj);
    })
    // Sort replies to each parent by the time they were created.
    comments.forEach(obj => {
        const children = groupedByParent[obj.parent];
        groupedByParent[obj.parent] = _.sortBy(children, ['timestamp']);
    })

    return <div>
        {rootComments.map((i, key) => <VideoComment key={key} comment={i} children={groupedByParent[i.id]}/>)}
    </div>
}

// Generate a video page URL for a file object.
function getVideoLink(file) {
    if (!file || !file.video) return null;
    return `/videos/${file.id}`;
}

function VideoPage({videoFile, prevFile, nextFile, fetchVideo, ...props}) {
    const navigate = useNavigate();
    const videoRef = React.useRef();
    const [taggedFileGroups, setTaggedFileGroups] = useState(null);
    const [activeTab, setActiveTab] = useState('comments');

    useTitle(videoFile ? videoFile.title ? videoFile.title : videoFile.name : null);
    let video;
    if (videoFile) {
        video = videoFile.video;
    }

    // Seeks to the `seconds` on video player.
    const setVideoTime = (seconds) => {
        videoRef.current.currentTime = seconds;
    }

    // Get the Video's channel, fallback to the URL's channel id.
    const {channelId} = useParams();
    const {channel} = useChannel(video && video.channel_id ? video.channel_id : channelId);
    const {comments} = useVideoExtras(videoFile?.id);
    const {captions, captionsLoading, fetchCaptions} = useVideoCaptions(videoFile?.id);

    const mediaTitle = videoFile ? (videoFile.title || videoFile.stem || videoFile.name) : null;
    const mediaArtworkUrl = video && video.poster_path ? `${MEDIA_PATH}/${encodeMediaPath(video.poster_path)}` : null;
    useMediaSession(mediaTitle, channel ? channel.name : null, mediaArtworkUrl);

    // Keyboard shortcuts for video player controls
    // k: Play/pause
    useHotkeys('k', () => {
        if (videoRef.current) {
            if (videoRef.current.paused) {
                videoRef.current.play();
            } else {
                videoRef.current.pause();
            }
        }
    }, {enableOnFormTags: false});

    // j: Jump back 15 seconds
    useHotkeys('j', () => {
        if (videoRef.current) {
            videoRef.current.currentTime = Math.max(0, videoRef.current.currentTime - 15);
        }
    }, {enableOnFormTags: false});

    // l: Jump forward 30 seconds
    useHotkeys('l', () => {
        if (videoRef.current) {
            videoRef.current.currentTime = Math.min(
                videoRef.current.duration || Infinity,
                videoRef.current.currentTime + 30
            );
        }
    }, {enableOnFormTags: false});

    // n: Navigate to newer video
    useHotkeys('n', () => {
        const link = getVideoLink(nextFile);
        if (link) {
            navigate(link);
        }
    }, {enableOnFormTags: false}, [nextFile, navigate]);

    // p: Navigate to older video
    useHotkeys('p', () => {
        const link = getVideoLink(prevFile);
        if (link) {
            navigate(link);
        }
    }, {enableOnFormTags: false}, [prevFile, navigate]);

    // f: Toggle fullscreen
    useHotkeys('f', () => {
        if (videoRef.current) {
            if (document.fullscreenElement) {
                document.exitFullscreen();
            } else {
                videoRef.current.requestFullscreen();
            }
        }
    }, {enableOnFormTags: false});

    const isAudioFile = videoFile?.mimetype?.startsWith('audio/');
    const [showAudioOverlay, setShowAudioOverlay] = useState(!!isAudioFile);
    const [audioPosterHover, setAudioPosterHover] = useState(false);
    const [audioPlaying, setAudioPlaying] = useState(false);
    useEffect(() => {
        if (!isAudioFile) return;
        setShowAudioOverlay(true);
        const timer = setTimeout(() => setShowAudioOverlay(false), 3000);
        return () => clearTimeout(timer);
    }, [isAudioFile]);
    useEffect(() => {
        const el = videoRef.current;
        if (!isAudioFile || !el) return;
        const onPlay = () => setAudioPlaying(true);
        const onPause = () => setAudioPlaying(false);
        el.addEventListener('play', onPlay);
        el.addEventListener('pause', onPause);
        return () => { el.removeEventListener('play', onPlay); el.removeEventListener('pause', onPause); };
    }, [isAudioFile]);

    if (videoFile === null) {
        return <VideoPlaceholder/>;
    }
    if (videoFile === undefined) {
        return <PageContainer><Header as='h4'>Could not find video</Header></PageContainer>;
    }

    const handleDeleteVideo = async (fileGroupId, force = false) => {
        const result = await deleteFileGroups([fileGroupId], force);
        if (result && result.tagged) {
            setTaggedFileGroups(result.file_groups);
            return;
        }
        navigate(-1);
    }

    const handleRefresh = async () => {
        await downloadVideoMetadata(videoFile.url);
    };

    let videoUrl = `${MEDIA_PATH}/${encodeMediaPath(video.video_path)}`;
    let downloadUrl = `/download/${encodeMediaPath(video.video_path)}`;

    let posterUrl = video.poster_path ? `${MEDIA_PATH}/${encodeMediaPath(video.poster_path)}` : null;
    const {caption_files} = video;
    const captionUrls = caption_files && caption_files.length > 0 ?
        caption_files.filter(i => i['mimetype'] === 'text/vtt').map(i => `${MEDIA_PATH}/${encodeMediaPath(i['path'])}`)
        : [];

    let description = 'No description available.';
    if (video && video['description']) {
        // Only replace empty description if there is one available.
        description = video['description'];
        description = formatVideoDescription(description, setVideoTime)
    }

    const getFile = (suffix) => videoFile.files.find(i => i.path.toLowerCase().endsWith(suffix));
    const fileSize = (file) => file && file.size
        ? <span style={{marginLeft: '1em', color: 'var(--muted)'}}>({humanFileSize(file.size)})</span>
        : null;

    const {poster_file, info_json_file} = video;
    const videoPathFile = videoFile.files.find(i => i.path === video['video_path']);
    const ffprobeJsonFile = getFile('.ffprobe.json');
    const tableStyle = {width: '100%', borderCollapse: 'separate', borderSpacing: '0 0.7em'};
    const labelStyle = {whiteSpace: 'nowrap', paddingRight: '1.5em', verticalAlign: 'top'};

    const localAddTag = async (name) => {
        await tagFileGroup(videoFile, name);
        await fetchVideo();
    }

    const localRemoveTag = async (name) => {
        await untagFileGroup(videoFile, name);
        await fetchVideo();
    }

    let videoSource = <source src={videoUrl}/>;
    const isAudio = videoFile.mimetype && videoFile.mimetype.startsWith('audio/');

    let prevNextVideosPanel = <Panel><p>No related videos found.</p></Panel>;
    if (prevFile || nextFile) {
        prevNextVideosPanel = <Panel>
            <Grid>
                <Grid.Col span={{base: 12, sm: 6}}>
                    {prevFile && <><Header as='h3'>Older</Header><VideoCard file={prevFile}/></>}
                </Grid.Col>
                <Grid.Col span={{base: 12, sm: 6}}>
                    {nextFile && <><Header as='h3'>Newer</Header><VideoCard file={nextFile}/></>}
                </Grid.Col>
            </Grid>
        </Panel>
    }

    let title = video.video_path;
    if (videoFile.title) {
        title = hashtagLinks(videoFile.title);
    } else if (videoFile.stem) {
        title = videoFile.stem;
    }

    const audioPlayPauseLabel = audioPlaying ? 'Pause' : 'Play';

    return <>
        <div className='wrolpi-button-row' style={{margin: '1em'}}>
            <BackButton/>
        </div>

        {isAudio ? <>
            {posterUrl && <div
                // A wrapper whose custom play/pause/volume glyphs are drawn over the poster image: the whole
                // composite must be tinted as one unit in night mode, so it carries `.media` even though the
                // <img/> inside is already a filtered leaf on its own.
                className='audio-poster-container media'
                role='button'
                tabIndex={0}
                aria-label={audioPlaying ? 'Pause audio' : 'Play audio'}
                onClick={() => {
                    if (videoRef.current) {
                        videoRef.current.paused ? videoRef.current.play() : videoRef.current.pause();
                    }
                }}
                onKeyDown={(e) => {
                    if (e.key === 'Enter' || e.key === ' ') {
                        e.preventDefault();
                        if (videoRef.current) {
                            videoRef.current.paused ? videoRef.current.play() : videoRef.current.pause();
                        }
                    }
                }}
                onMouseEnter={() => setAudioPosterHover(true)}
                onMouseLeave={() => setAudioPosterHover(false)}
            >
                <img
                    src={posterUrl}
                    alt={mediaTitle || 'Audio thumbnail'}
                    style={{maxWidth: '100%', maxHeight: '400px', cursor: 'pointer'}}
                />
                <div
                    className='audio-poster-overlay'
                    aria-hidden='true'
                    style={{opacity: showAudioOverlay ? 1 : 0, transition: 'opacity 500ms ease'}}
                >
                    <Icon name='volume up' size={64}/>
                </div>
                <div
                    className='audio-poster-overlay'
                    aria-hidden='true'
                    style={{
                        opacity: (audioPosterHover && !showAudioOverlay) ? 1 : 0,
                        transition: 'opacity 200ms ease',
                    }}
                >
                    <Icon component={audioPlaying ? IconPlayerPause : IconPlayerPlay} size={64}
                          label={audioPlayPauseLabel}/>
                </div>
            </div>}
            <audio controls
                   autoPlay={props.autoplay !== undefined ? props.autoplay : true}
                   id="player"
                   style={{width: '100%', marginTop: posterUrl ? '0.5em' : 0}}
                   ref={videoRef}
            >
                {videoSource}
            </audio>
        </> : <video controls
               className='video-player'
               autoPlay={props.autoplay !== undefined ? props.autoplay : true}
               poster={posterUrl}
               id="player"
               playsInline={true}
               style={{maxWidth: '100%'}}
               ref={videoRef}
        >
            {videoSource}
            {/* Only WebVTT captions can be displayed. */}
            {captionUrls.map(i => <CaptionTrack key={i} src={i}/>)}
        </video>}

        {/* `wrolpi-stack`: everything below the player is stacked in here rather than in the
            page, so this is what spaces it. */}
        <div className='wrolpi-stack wrolpi-page-inset' style={{marginTop: '1em'}}>
            <Panel>

                <Header as='h2'>{title}</Header>
                {videoFile.published_datetime && <h3>{isoDatetimeToAgoPopup(videoFile.published_datetime)}</h3>}
                <h3>
                    {channel && <Link to={`/videos/channel/${channel.id}/video`}>
                        {channel.name}
                    </Link>}
                </h3>

                <div className='wrolpi-button-row'>
                    <Button component='a' href={downloadUrl} icon='download'>
                        Download
                    </Button>
                    <APIButton
                        role='danger'
                        confirmContent='Are you sure you want to delete this video?  All files related to this video will be deleted. It will not be downloaded again!'
                        confirmButton='Delete'
                        onClick={async () => await handleDeleteVideo(videoFile.id)}
                        obeyWROLMode={true}
                    >Delete</APIButton>
                    <APIButton
                        role='primary'
                        onClick={handleRefresh}
                        obeyWROLMode={true}
                        disabled={!videoFile.url}
                    >Refresh</APIButton>
                    <AddToPlaylistButton fileGroupId={videoFile.id}/>
                </div>
            </Panel>

            <Panel>
                <TagsSelector selectedTagNames={videoFile['tags']} onAdd={localAddTag} onRemove={localRemoveTag}/>
            </Panel>

            <Panel>
                <Header as='h2'>About Video</Header>

                <Grid>
                    <Grid.Col span={6}>
                        <h3>Size</h3>
                        <p>{videoFile.size ? humanFileSize(videoFile.size) : 'Unknown'}</p>
                    </Grid.Col>
                    <Grid.Col span={6}>
                        <h3>View Count</h3>
                        <p>{video.view_count ? humanNumber(video.view_count) : 'N/A'}</p>
                    </Grid.Col>
                    <Grid.Col span={6}>
                        <h3>Codec Names</h3>
                        <>{video.codec_names ? video.codec_names.map(i => <Label key={i}>{i}</Label>) : 'N/A'}</>
                    </Grid.Col>
                    <Grid.Col span={6}>
                        <h3>Censored</h3>
                        <p>{videoFile.censored ? 'Yes' : 'No'}</p>
                    </Grid.Col>
                    <Grid.Col span={12}>
                        <h3>Source URL</h3>
                        <p>{videoFile.url ? <a href={videoFile.url}>{videoFile.url}</a> : 'N/A'}</p>
                    </Grid.Col>
                </Grid>
            </Panel>

            <Tabs value={activeTab} onChange={setActiveTab} keepMounted={false}>
                <Tabs.List>
                    <Tabs.Tab value='comments'>Comments</Tabs.Tab>
                    <Tabs.Tab value='description'>Description</Tabs.Tab>
                    <Tabs.Tab value='files'>Files</Tabs.Tab>
                    <Tabs.Tab value='captions'>Captions</Tabs.Tab>
                </Tabs.List>

                <Tabs.Panel value='comments' style={{paddingTop: '1em'}}>
                    <Header as='h3'>Top Comments</Header>
                    <Comments comments={comments} video={videoFile}/>
                </Tabs.Panel>

                <Tabs.Panel value='description' style={{paddingTop: '1em'}}>
                    <pre className="wrap-text">
                        {description}
                    </pre>
                </Tabs.Panel>

                <Tabs.Panel value='files' style={{paddingTop: '1em'}}>
                    <table style={tableStyle}>
                        <tbody>
                        <tr>
                            <td style={labelStyle}><strong>{isAudio ? 'Audio File' : 'Video File'}</strong></td>
                            <td>
                                {video['video_path']
                                    ? <><PreviewPath path={video['video_path']} mimetype={isAudio ? 'audio/*' : 'video/*'} taggable={false}>
                                        {video['video_path']}
                                    </PreviewPath>{fileSize(videoPathFile)}</>
                                    : 'Unknown'}
                            </td>
                        </tr>

                        <tr>
                            <td style={labelStyle}><strong>Caption Files</strong></td>
                            <td>
                                {caption_files
                                    ? caption_files.map(i => <div key={i['path']} style={{marginBottom: '0.3em'}}>
                                        <PreviewPath {...i} taggable={false}>{i['path']}</PreviewPath>
                                        {fileSize(i)}
                                    </div>)
                                    : 'No caption files'}
                            </td>
                        </tr>

                        <tr>
                            <td style={labelStyle}><strong>Poster File</strong></td>
                            <td>
                                {poster_file
                                    ? <><PreviewPath path={poster_file['path']} mimetype={poster_file['mimetype']}
                                                     taggable={false}>
                                        {poster_file['path']}
                                    </PreviewPath>{fileSize(poster_file)}</>
                                    : 'No poster file'}
                            </td>
                        </tr>

                        <tr>
                            <td style={labelStyle}><strong>Info JSON File</strong></td>
                            <td>
                                {info_json_file
                                    ? <><PreviewPath path={info_json_file['path']} mimetype={info_json_file['mimetype']}
                                                     taggable={false}>
                                        {info_json_file['path']}
                                    </PreviewPath>{fileSize(info_json_file)}</>
                                    : 'No yt-dlp info json file'}
                            </td>
                        </tr>

                        <tr>
                            <td style={labelStyle}><strong>ffprobe JSON File</strong></td>
                            <td>
                                {ffprobeJsonFile
                                    ? <><PreviewPath path={ffprobeJsonFile['path']} mimetype={ffprobeJsonFile['mimetype']}
                                                     taggable={false}>
                                        {ffprobeJsonFile['path']}
                                    </PreviewPath>{fileSize(ffprobeJsonFile)}</>
                                    : 'No ffprobe json file'}
                            </td>
                        </tr>

                        <tr>
                            <td style={labelStyle}><strong>Directory</strong></td>
                            <td><DirectoryLink path={videoFile['directory']}/></td>
                        </tr>
                        </tbody>
                    </table>
                </Tabs.Panel>

                <Tabs.Panel value='captions' style={{paddingTop: '1em'}}>
                    <CaptionsPane
                        captions={captions}
                        captionsLoading={captionsLoading}
                        fetchCaptions={fetchCaptions}
                        setVideoTime={setVideoTime}
                    />
                </Tabs.Panel>
            </Tabs>

            {prevNextVideosPanel}
        </div>
        <TaggedDeleteConfirmModal
            open={taggedFileGroups !== null}
            taggedFileGroups={taggedFileGroups}
            onCancel={() => setTaggedFileGroups(null)}
            onConfirm={async () => {
                setTaggedFileGroups(null);
                await handleDeleteVideo(videoFile.id, true);
            }}
        />
    </>
}

function formatCaptionTimestamp(totalSeconds) {
    totalSeconds = Math.floor(totalSeconds);
    const hours = Math.floor(totalSeconds / 3600);
    const minutes = Math.floor((totalSeconds % 3600) / 60);
    const seconds = totalSeconds % 60;
    const pad2 = (n) => String(n).padStart(2, '0');
    if (hours > 0) {
        return `${hours}:${pad2(minutes)}:${pad2(seconds)}`;
    }
    return `${minutes}:${pad2(seconds)}`;
}

function CaptionsPane({captions, captionsLoading, fetchCaptions, setVideoTime}) {
    const [filter, setFilter] = useState('');

    // Trigger fetch on first render of this pane.
    React.useEffect(() => {
        fetchCaptions();
    }, []);

    if (captionsLoading) {
        return <Loading/>;
    }

    if (!captions || captions.length === 0) {
        return <div>No captions available.</div>;
    }

    let filtered = captions;
    if (filter.trim()) {
        const words = filter.toLowerCase().split(/\s+/).filter(Boolean);
        filtered = captions.filter(chunk => {
            const text = chunk.text.toLowerCase();
            return words.every(word => text.includes(word));
        });
    }

    return <>
        <TextInput
            leftSection={<Icon name='filter' size={14}/>}
            placeholder='Filter captions...'
            value={filter}
            onChange={(e) => setFilter(e.currentTarget.value)}
            style={{marginBottom: '1em', width: '100%'}}
        />
        <div style={{maxHeight: '400px', overflowY: 'auto'}}>
            {filtered.map((chunk, idx) => (
                <div key={idx} style={{display: 'flex', gap: '1em', marginBottom: '0.4em'}}>
                    <a href='#'
                       onClick={(e) => {
                           e.preventDefault();
                           setVideoTime(chunk.start_seconds);
                       }}
                       style={{whiteSpace: 'nowrap', fontFamily: 'var(--font-mono)'}}
                    >
                        {formatCaptionTimestamp(chunk.start_seconds)}
                    </a>
                    <span>{chunk.text}</span>
                </div>
            ))}
        </div>
    </>;
}

export default VideoPage;

const chapterRegex = new RegExp('^(\\(?(?:((\\d?\\d):)?(?:(\\d?\\d):(\\d\\d)))\\)?)\.?\\s+(.*)$', 'i');

function formatVideoDescription(description, setVideoTime) {
    // Convert timestamps to links which change the video's playback location.  Change hashtags to search links.
    if (description && description.length > 0) {
        try {
            const lines = _.split(description, '\n');
            let newLines = [];
            for (let i = 0; i <= lines.length; i++) {
                const line = lines[i];
                const match = line ? line.match(chapterRegex) : null;
                let link;
                if (match) {
                    // This line in the description starts with a chapter timestamp, parse it and create a link.
                    try {
                        const timestamp = match[1];
                        const title = match[6];
                        // Assume 0 if no part of timestamp could be found.
                        const [hour, minute, second] = match.slice(3, 6).map(i => parseInt(i) || 0);
                        // Convert timestamp to seconds.
                        const seconds = (((hour * 60) + minute) * 60) + second;
                        link = <>
                            <a href='#' onClick={() => setVideoTime(seconds)}>{timestamp}</a>
                            &nbsp;{title}
                        </>;
                    } catch (e) {
                        // Report an error while creating timestamp link.
                        console.error(e);
                    }

                    // Use the link if we could create it, otherwise fallback to the original `line`.
                    newLines = [...newLines, link || hashtagLinks(line)];
                } else if (line !== undefined) {
                    // Line does not start with a timestamp.
                    newLines = [...newLines, hashtagLinks(line)];
                }
            }
            // Map all lines and links with a break between.
            return <>
                {newLines.map((i, idx) => <div key={idx}>{i}<br/></div>)}
            </>;
        } catch (e) {
            // Some error happened while parsing description.  Report it but don't fail.
            console.error(e);
        }
    }
    // Error occurred, or no description, don't fail.
    return description;

}

const hashtagRegex = /(#+[_a-zA-Z0-9]+)/ig;


function hashtagLinks(text) {
    // Converts a string into a div which has hashtags converted to search links.
    // Example: Some text <a href="/search?q=#hashtag">#hashtag</a> the rest of the text
    if (text && text.length > 0) {
        const parts = text.split(hashtagRegex);
        let newParts = '';
        for (let i = 0; i < parts.length; i++) {
            let part = parts[i];
            part = part.startsWith('#') ?
                // Part is a hashtag.
                <a key={i} href={`/search?q=${encodeURIComponent(part)}`} target="_self">{part}</a>
                // Part is not a hashtag.
                : <span key={i}>{part}</span>;
            newParts = [...newParts, part];
        }
        return <React.Fragment>{newParts}</React.Fragment>;
    }
    return text;
}