import {useEffect, useState} from 'react';
import {useNavigate} from 'react-router-dom';
import {useTranslation} from 'react-i18next';
import {useForm} from 'react-hook-form';
import {zodResolver} from '@hookform/resolvers/zod';

import {Copy, Gamepad2, ImageOff, Loader2, Palette, RotateCcw, Save, SlidersHorizontal, UserRound} from 'lucide-react';
import {toast} from 'sonner';

import {Button} from '@/components/ui/button';
import {Card, CardContent, CardHeader, CardTitle} from '@/components/ui/card';
import {Input} from '@/components/ui/input';
import {Label} from '@/components/ui/label';
import {Select, SelectContent, SelectItem, SelectTrigger, SelectValue} from '@/components/ui/select';
import {Skeleton} from '@/components/ui/skeleton';
import {Switch} from '@/components/ui/switch';
import FormField from '../components/FormField.jsx';
import {settingsSchema} from '../utils/validation.js';
import {usePreferences} from '../context/PreferencesContext.jsx';
import useSessionExpired from '../hooks/useSessionExpired.js';
import useSaveAppearance from '../hooks/useSaveAppearance.js';
import {ACCENTS, CORNERS} from '../utils/appearance.js';
import {coverUrl} from '../utils/games.js';
import {cn} from '@/lib/utils';
import {apiFetch} from '../utils/api.js';
import {hasSession, markSession} from '../utils/auth.js';

const BACKEND_ERROR_KEY = {
    STEAM_ID_ALREADY_IN_USE: 'REGISTRATION.ERROR_STEAM_ID_IN_USE',
    DISPLAY_NAME_ALREADY_IN_USE: 'SETTINGS.ERROR_DISPLAY_NAME_IN_USE',
};

const SUPPORTED_LANGUAGES = ['en', 'de'];

const formatDate = (value, locale) => {
    if (!value) return '—';
    try {
        return new Date(value).toLocaleString(locale);
    } catch {
        return value;
    }
};

export default function SettingsPage() {
    const {t, i18n} = useTranslation();
    const navigate = useNavigate();
    const expireSession = useSessionExpired();
    const {isDarkMode, setDarkMode, setLanguage, appearance} = usePreferences();
    const saveAppearance = useSaveAppearance();

    const [profile, setProfile] = useState(null);
    const [isLoading, setIsLoading] = useState(true);
    const [loadError, setLoadError] = useState(null);

    const {
        register,
        handleSubmit,
        reset,
        formState: {errors, isSubmitting},
    } = useForm({
        resolver: zodResolver(settingsSchema),
        defaultValues: {useDarkTheme: true, language: 'en', steamId: '', displayName: ''},
    });

    useEffect(() => {
        if (!hasSession()) {
            navigate('/login');
            return;
        }

        const load = async () => {
            try {
                const response = await apiFetch(`${import.meta.env.VITE_API_URL}/api/users/me?v=1`, {
                    method: 'GET',
                    headers: {
                        'Content-Type': 'application/json',
                    },
                });

                if (response.status === 401) {
                    expireSession();
                    return;
                }

                if (!response.ok) {
                    setLoadError(t('INFO.ERROR.LOAD_PROFILE'));
                    return;
                }

                const data = await response.json();
                setProfile(data);
                reset({
                    useDarkTheme: !!data.settings?.useDarkTheme,
                    language: data.settings?.language || 'en',
                    steamId: data.steamId ?? '',
                    displayName: data.displayName ?? '',
                });
            } catch (err) {
                console.error('Settings load error:', err);
                setLoadError(t('INFO.ERROR.NETWORK_FAILURE'));
            } finally {
                setIsLoading(false);
            }
        };

        load();
    }, [navigate, expireSession, reset, t]);

    const persistSettings = async (payload) => {
        if (!hasSession()) {
            navigate('/login');
            return {ok: false};
        }

        try {
            const response = await apiFetch(`${import.meta.env.VITE_API_URL}/api/users/settings`, {
                method: 'PUT',
                headers: {
                    'Content-Type': 'application/json',
                },
                body: JSON.stringify(payload),
            });

            if (response.status === 401) {
                expireSession();
                return {ok: false};
            }

            if (!response.ok) {
                const data = await response.json().catch(() => ({}));
                const mappedKey = BACKEND_ERROR_KEY[data.code];
                toast.error(mappedKey ? t(mappedKey) : data.message || t('SETTINGS.ERROR_SAVE'));
                return {ok: false};
            }

            // Auth set a new access cookie for the new Steam ID; the new stamp makes the header load it again.
            markSession();
            toast.success(t('SETTINGS.SAVED'));
            return {ok: true};
        } catch (err) {
            console.error('Settings save error:', err);
            toast.error(t('INFO.ERROR.NETWORK_FAILURE'));
            return {ok: false};
        }
    };

    // The backend replaces all settings, so every save sends the saved values of the fields it does not change.
    const savedSettings = () => ({
        useDarkTheme: isDarkMode,
        language: i18n.language,
        steamId: profile?.steamId ?? null,
        displayName: profile?.displayName ?? null,
        publicProfile: !!profile?.settings?.publicProfile,
    });

    const handleDarkThemeToggle = async () => {
        const next = !isDarkMode;
        setDarkMode(next); // apply on the fly
        await persistSettings({...savedSettings(), useDarkTheme: next});
    };

    const handleLanguageChange = async (next) => {
        setLanguage(next); // apply on the fly
        await persistSettings({...savedSettings(), language: next});
    };

    const handlePublicProfileToggle = async () => {
        const next = !profile?.settings?.publicProfile;
        const result = await persistSettings({...savedSettings(), publicProfile: next});
        if (result.ok) {
            setProfile((p) => ({...p, settings: {...p.settings, publicProfile: next}}));
        }
    };

    const copyProfileLink = async (link) => {
        try {
            await navigator.clipboard.writeText(link);
            toast.success(t('SETTINGS.PUBLIC_PROFILE_COPIED'));
        } catch {
            toast.error(link);
        }
    };

    const onSubmitProfile = async (values) => {
        // Without a name the profile has no link, so removing the name also makes it private.
        const publicProfile = savedSettings().publicProfile && !!values.displayName;
        const result = await persistSettings({
            ...savedSettings(),
            steamId: values.steamId,
            displayName: values.displayName,
            publicProfile,
        });
        if (result.ok) {
            setProfile((p) => (p ? {
                ...p, steamId: values.steamId, displayName: values.displayName, settings: {...p.settings, publicProfile},
            } : p));
        }
    };

    if (isLoading) {
        return (
            <div className="w-full max-w-2xl mx-auto p-4 md:p-8 space-y-6">
                <Skeleton className="h-9 w-48"/>
                <Skeleton className="h-56 rounded-xl"/>
                <Skeleton className="h-40 rounded-xl"/>
                <Skeleton className="h-44 rounded-xl"/>
            </div>
        );
    }

    if (loadError) {
        return <div className="py-24 text-center text-destructive">{loadError}</div>;
    }

    const publicProfile = !!profile?.settings?.publicProfile;
    const profileLink = profile?.displayName
        ? `${window.location.origin}/u/${encodeURIComponent(profile.displayName)}`
        : null;

    const accountRows = [
        [t('SETTINGS.EMAIL'), profile?.email],
        [t('SETTINGS.ROLE'), profile?.role],
        [t('SETTINGS.CREATED_DATE'), formatDate(profile?.createdDate, i18n.language)],
        [t('SETTINGS.LAST_LOGIN'), formatDate(profile?.lastLogin, i18n.language)],
    ];

    return (
        <div className="w-full max-w-2xl mx-auto p-4 md:p-8 space-y-6">
            <h1 className="text-3xl font-bold tracking-tight">{t('SETTINGS.TITLE')}</h1>

            <Card>
                <CardHeader>
                    <CardTitle className="flex items-center gap-2"><UserRound className="size-4 text-primary"/>{t('SETTINGS.ACCOUNT')}</CardTitle>
                </CardHeader>
                <CardContent>
                    <dl className="divide-y">
                        {accountRows.map(([label, value]) => (
                            <div key={label} className="flex flex-col gap-1 py-3 first:pt-0 last:pb-0 sm:flex-row sm:items-center sm:justify-between">
                                <dt className="text-sm text-muted-foreground">{label}</dt>
                                <dd className="text-sm font-medium break-all">{value || '—'}</dd>
                            </div>
                        ))}
                    </dl>
                </CardContent>
            </Card>

            <Card>
                <CardHeader>
                    <CardTitle className="flex items-center gap-2"><SlidersHorizontal className="size-4 text-primary"/>{t('SETTINGS.PREFERENCES')}</CardTitle>
                </CardHeader>
                <CardContent className="space-y-6">
                    <div className="flex items-center justify-between gap-4">
                        <Label htmlFor="useDarkTheme">{t('SETTINGS.DARK_THEME')}</Label>
                        <Switch id="useDarkTheme" checked={isDarkMode} onCheckedChange={handleDarkThemeToggle}/>
                    </div>
                    <div className="flex items-center justify-between gap-4">
                        <Label htmlFor="language">{t('SETTINGS.LANGUAGE')}</Label>
                        <Select value={i18n.language} onValueChange={handleLanguageChange}>
                            <SelectTrigger id="language" className="w-40">
                                <SelectValue/>
                            </SelectTrigger>
                            <SelectContent>
                                {SUPPORTED_LANGUAGES.map((lang) => (
                                    <SelectItem key={lang} value={lang}>
                                        {t(`SETTINGS.LANGUAGE_OPTIONS.${lang.toUpperCase()}`)}
                                    </SelectItem>
                                ))}
                            </SelectContent>
                        </Select>
                    </div>
                </CardContent>
            </Card>

            <Card>
                <CardHeader>
                    <CardTitle className="flex items-center gap-2"><Palette className="size-4 text-primary"/>{t('SETTINGS.APPEARANCE')}</CardTitle>
                </CardHeader>
                <CardContent className="space-y-6">
                    <div className="flex flex-col gap-3 sm:flex-row sm:items-center sm:justify-between">
                        <Label id="accent-label">{t('SETTINGS.ACCENT')}</Label>
                        <div role="group" aria-labelledby="accent-label" className="flex flex-wrap gap-2">
                            {ACCENTS.map((accent) => (
                                <button key={accent} type="button" data-accent={accent}
                                        aria-label={t(`SETTINGS.ACCENT_OPTIONS.${accent.toUpperCase()}`)}
                                        title={t(`SETTINGS.ACCENT_OPTIONS.${accent.toUpperCase()}`)}
                                        aria-pressed={appearance.accent === accent}
                                        onClick={() => saveAppearance({accent})}
                                        className={cn('size-8 rounded-full bg-primary ring-offset-2 ring-offset-background transition hover:scale-110',
                                            appearance.accent === accent && 'ring-2 ring-foreground')}/>
                            ))}
                        </div>
                    </div>
                    <div className="flex flex-col gap-3 sm:flex-row sm:items-center sm:justify-between">
                        <Label id="corners-label">{t('SETTINGS.CORNERS')}</Label>
                        <div role="group" aria-labelledby="corners-label" className="flex gap-2">
                            {CORNERS.map((corners) => (
                                <Button key={corners} type="button" size="sm" data-corners={corners}
                                        variant={appearance.corners === corners ? 'default' : 'outline'}
                                        aria-pressed={appearance.corners === corners}
                                        onClick={() => saveAppearance({corners})}>
                                    {t(`SETTINGS.CORNER_OPTIONS.${corners.toUpperCase()}`)}
                                </Button>
                            ))}
                        </div>
                    </div>
                    <div className="flex items-center justify-between gap-4">
                        <div className="space-y-1">
                            <Label htmlFor="wideLayout">{t('SETTINGS.WIDE_LAYOUT')}</Label>
                            <p className="text-xs text-muted-foreground">{t('SETTINGS.WIDE_LAYOUT_HINT')}</p>
                        </div>
                        <Switch id="wideLayout" checked={appearance.wideLayout}
                                onCheckedChange={(wideLayout) => saveAppearance({wideLayout})}/>
                    </div>
                    <div className="flex items-center justify-between gap-4">
                        <div className="space-y-1">
                            <Label id="background-label">{t('SETTINGS.BACKGROUND')}</Label>
                            {!appearance.backgroundAppid && (
                                <p className="text-xs text-muted-foreground">{t('SETTINGS.BACKGROUND_HINT')}</p>
                            )}
                        </div>
                        {appearance.backgroundAppid && (
                            <div className="flex items-center gap-2">
                                <img src={coverUrl(appearance.backgroundAppid)} alt=""
                                     onError={(event) => { event.currentTarget.hidden = true; }}
                                     className="h-10 w-20 rounded-md object-cover"/>
                                <Button type="button" variant="outline" size="sm"
                                        aria-describedby="background-label"
                                        onClick={() => saveAppearance({backgroundAppid: null})}>
                                    <ImageOff/>{t('SETTINGS.BACKGROUND_REMOVE')}
                                </Button>
                            </div>
                        )}
                    </div>
                    <div className="space-y-3">
                        <div className="flex items-center justify-between gap-4">
                            <div className="space-y-1">
                                <Label id="banner-label" htmlFor="showBanner">{t('SETTINGS.BANNER')}</Label>
                                {appearance.showBanner && !appearance.bannerAppid && (
                                    <p className="text-xs text-muted-foreground">{t('SETTINGS.BANNER_HINT')}</p>
                                )}
                            </div>
                            <Switch id="showBanner" checked={appearance.showBanner}
                                    onCheckedChange={(showBanner) => saveAppearance({showBanner})}/>
                        </div>
                        {appearance.showBanner && appearance.bannerAppid && (
                            <div className="flex items-center justify-end gap-2">
                                <img src={coverUrl(appearance.bannerAppid)} alt=""
                                     onError={(event) => { event.currentTarget.hidden = true; }}
                                     className="h-10 w-20 rounded-md object-cover"/>
                                <Button type="button" variant="outline" size="sm"
                                        aria-describedby="banner-label"
                                        onClick={() => saveAppearance({bannerAppid: null})}>
                                    <RotateCcw/>{t('SETTINGS.BANNER_AUTO')}
                                </Button>
                            </div>
                        )}
                    </div>
                </CardContent>
            </Card>

            <Card>
                <CardHeader>
                    <CardTitle className="flex items-center gap-2"><Gamepad2 className="size-4 text-primary"/>{t('SETTINGS.PROFILE')}</CardTitle>
                </CardHeader>
                <CardContent>
                    <form onSubmit={handleSubmit(onSubmitProfile)} className="space-y-4" noValidate>
                        <FormField id="displayName" label={t('SETTINGS.DISPLAY_NAME')} error={errors.displayName} t={t}>
                            <Input
                                id="displayName"
                                type="text"
                                maxLength={24}
                                placeholder={t('SETTINGS.DISPLAY_NAME_PLACEHOLDER')}
                                aria-invalid={!!errors.displayName}
                                {...register('displayName')}
                            />
                            <p className="text-xs text-muted-foreground">{t('SETTINGS.DISPLAY_NAME_HINT')}</p>
                        </FormField>
                        <FormField id="steamId" label={t('SETTINGS.STEAM_ID')} error={errors.steamId} t={t}>
                            <Input
                                id="steamId"
                                type="text"
                                inputMode="numeric"
                                className="font-mono"
                                aria-invalid={!!errors.steamId}
                                {...register('steamId')}
                            />
                        </FormField>
                        <Button type="submit" disabled={isSubmitting}>
                            {isSubmitting ? <Loader2 className="animate-spin"/> : <Save/>}
                            {t('SETTINGS.SAVE_PROFILE')}
                        </Button>
                    </form>

                    <div className="mt-6 space-y-3 border-t pt-6">
                        <div className="flex items-center justify-between gap-4">
                            <div className="space-y-1">
                                <Label htmlFor="publicProfile">{t('SETTINGS.PUBLIC_PROFILE')}</Label>
                                <p className="text-xs text-muted-foreground">
                                    {profileLink ? t('SETTINGS.PUBLIC_PROFILE_HINT') : t('SETTINGS.PUBLIC_PROFILE_NEEDS_NAME')}
                                </p>
                            </div>
                            <Switch id="publicProfile" checked={publicProfile} disabled={!profileLink}
                                    onCheckedChange={handlePublicProfileToggle}/>
                        </div>
                        {publicProfile && profileLink && (
                            <div className="flex items-center gap-2 rounded-md bg-muted px-3 py-2 text-sm">
                                <a href={profileLink} target="_blank" rel="noopener noreferrer"
                                   className="min-w-0 flex-1 truncate font-mono text-primary hover:underline">{profileLink}</a>
                                <Button type="button" variant="ghost" size="icon" className="size-7"
                                        aria-label={t('SETTINGS.PUBLIC_PROFILE_COPY')} onClick={() => copyProfileLink(profileLink)}>
                                    <Copy/>
                                </Button>
                            </div>
                        )}
                    </div>
                </CardContent>
            </Card>
        </div>
    );
}