import {useEffect, useState} from 'react';
import {useTranslation} from 'react-i18next';
import {Link} from 'react-router-dom';
import {ChevronDown, Loader2} from 'lucide-react';

import {Card, CardContent, CardHeader, CardTitle} from '@/components/ui/card';
import {cn} from '@/lib/utils';
import PageContainer from '../components/PageContainer.jsx';
import {formatDate} from '../utils/format.js';
import {profileGameHref, profileHref} from '../utils/people.js';
import {digestParts, fetchInbox, fetchInboxDetails, groupDetails, markInboxRead} from '../utils/inbox.js';

const PSN_KINDS = ['PSN_EXPIRING', 'PSN_EXPIRED'];
const ACHIEVEMENTS_SHOWN = 5;

/**
 * The newest notes about the people the user follows and about the PlayStation link. Opening the page marks them read.
 */
export default function InboxPage() {
    const {t, i18n} = useTranslation();
    const [notes, setNotes] = useState([]);
    const [status, setStatus] = useState('loading');
    const [open, setOpen] = useState(null);
    // note id -> {status: 'loading' | 'error' | 'ready', results}
    const [details, setDetails] = useState({});
    const [showAll, setShowAll] = useState({});

    useEffect(() => {
        (async () => {
            const {ok, status: code, data} = await fetchInbox();
            if (code === 401) return;
            if (!ok) {
                setStatus('error');
                return;
            }
            setNotes(data.results);
            setStatus('ready');
            // A failed mark is silent: the notes show as unread again on the next visit.
            if (data.unread > 0) markInboxRead();
        })();
    }, []);

    const text = (note) => {
        if (PSN_KINDS.includes(note.kind)) return t(`INBOX.${note.kind}`);
        const name = note.displayName ?? t('FOLLOW.PRIVATE_USER');
        if (note.kind === 'VISIBILITY') return t('INBOX.VISIBILITY', {name});
        return t('INBOX.DIGEST', {name, parts: partsText(note)});
    };

    const partsText = (note) => digestParts(note).map(({key, count}) => t(`INBOX.PART_${key}`, {count})).join(', ');

    // A link in a button is invalid, so the profile link sits next to the toggle button.
    const noteLine = (note) => {
        const linked = note.kind === 'DIGEST' && note.profileName;
        const label = linked ? t('INBOX.DIGEST_PARTS', {parts: partsText(note)}) : text(note);
        const line = note.kind === 'DIGEST' && note.details ? (
            <button type="button" aria-expanded={open === note.id}
                    className="inline-flex cursor-pointer items-center gap-1 break-words text-left hover:underline"
                    onClick={() => toggle(note.id)}>
                {label}
                <ChevronDown className={cn('size-4 shrink-0 transition-transform', open === note.id && 'rotate-180')}/>
            </button>
        ) : label;
        if (!linked) return line;
        return <><Link to={profileHref(note.profileName)} className="underline">{note.displayName}</Link>: {line}</>;
    };

    const toggle = async (id) => {
        if (open === id) {
            setOpen(null);
            return;
        }
        setOpen(id);
        if (details[id]) return;
        setDetails((current) => ({...current, [id]: {status: 'loading', results: []}}));
        const {ok, status, data} = await fetchInboxDetails(id);
        setDetails((current) => ({...current, [id]: ok || status === 404 ? {status: 'ready', results: data?.results ?? []} : {status: 'error', results: []}}));
    };

    const gameLabel = (note, {gameName, appid}) => (
        <>
            {appid == null ? gameName : <Link to={`/library/${appid}`} className="hover:underline">{gameName}</Link>}
            {appid != null && note.profileName && (
                <Link to={profileGameHref(note.profileName, appid)}
                      className="ml-2 text-xs text-muted-foreground underline">{t('INBOX.ON_PROFILE')}</Link>
            )}
        </>
    );

    const gameLines = (group, gameGroup, note) => {
        const {gameName, items} = gameGroup;
        if (group.kind === 'STATUS') {
            return items.map((item, i) => (
                <li key={`${gameName}-${i}`}>
                    {gameLabel(note, gameGroup)}: {t(`BACKLOG.STATUS.${item.fromStatus}`)} → {t(`BACKLOG.STATUS.${item.toStatus}`)}
                </li>
            ));
        }
        if (group.kind !== 'ACHIEVEMENT') return <li key={gameName}>{gameLabel(note, gameGroup)}</li>;
        const key = `${note.id}:${gameName}`;
        const shown = showAll[key] ? items : items.slice(0, ACHIEVEMENTS_SHOWN);
        return (
            <li key={gameName}>
                {gameLabel(note, gameGroup)}
                <ul className="ml-4 list-disc">
                    {shown.map((item, i) => <li key={i}>{item.itemName}</li>)}
                </ul>
                {!showAll[key] && items.length > ACHIEVEMENTS_SHOWN && (
                    <button type="button" className="ml-4 underline"
                            onClick={() => setShowAll((current) => ({...current, [key]: true}))}>
                        {t('INBOX.SHOW_ALL', {count: items.length})}
                    </button>
                )}
            </li>
        );
    };

    const detailBlock = (note) => {
        const entry = details[note.id];
        if (!entry || entry.status === 'loading') return <Loader2 className="size-4 animate-spin text-muted-foreground"/>;
        if (entry.status === 'error') return <p className="text-xs text-destructive">{t('INBOX.DETAILS_ERROR')}</p>;
        const groups = groupDetails(entry.results);
        if (groups.length === 0) return <p className="text-xs text-muted-foreground">{t('INBOX.DETAILS_GONE')}</p>;
        return groups.map((group) => (
            <div key={group.kind} className="space-y-1">
                <h3 className="text-xs font-semibold uppercase text-muted-foreground">{t(`INBOX.DETAIL_${group.kind}`)}</h3>
                <ul className="space-y-0.5 text-sm">{group.games.map((gameGroup) => gameLines(group, gameGroup, note))}</ul>
            </div>
        ));
    };

    return (
        <PageContainer className="space-y-4 px-4 py-6 md:px-8">
            <Card>
                <CardHeader>
                    <CardTitle>{t('INBOX.TITLE')}</CardTitle>
                </CardHeader>
                <CardContent>
                    {status === 'loading' && <Loader2 className="size-5 animate-spin text-muted-foreground"/>}
                    {status === 'error' && <p className="text-sm text-destructive">{t('INBOX.LOAD_ERROR')}</p>}
                    {status === 'ready' && notes.length === 0 && <p className="text-sm text-muted-foreground">{t('INBOX.EMPTY')}</p>}
                    {status === 'ready' && notes.length > 0 && (
                        <ul className="divide-y">
                            {notes.map((note) => (
                                <li key={note.id} className="space-y-1 py-3">
                                    <p className="text-xs text-muted-foreground">
                                        {formatDate(note.createdAt, i18n.language, {dateStyle: 'medium'})}
                                    </p>
                                    <p className={cn('break-words text-sm', !note.read && 'font-semibold')}>
                                        {noteLine(note)}
                                        {PSN_KINDS.includes(note.kind) && (
                                            <> <Link to="/settings" className="underline">{t('INBOX.OPEN_SETTINGS')}</Link></>
                                        )}
                                    </p>
                                    {open === note.id && <div className="space-y-2 pt-1">{detailBlock(note)}</div>}
                                </li>
                            ))}
                        </ul>
                    )}
                </CardContent>
            </Card>
        </PageContainer>
    );
}