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 {settingsSchema} from '../utils/validation.js';
import {usePreferences} from '../context/PreferencesContext.jsx';

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

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

const inputClass =
    'w-full px-4 py-2 border border-slate-300 dark:border-slate-600 rounded-lg bg-slate-50 dark:bg-slate-700 text-slate-900 dark:text-white focus:ring-2 focus:ring-blue-500 focus:outline-none';
const inputErrorClass =
    'w-full px-4 py-2 border border-red-500 dark:border-red-500 rounded-lg bg-slate-50 dark:bg-slate-700 text-slate-900 dark:text-white focus:ring-2 focus:ring-red-500 focus:outline-none';
const readOnlyClass =
    'w-full px-4 py-2 border border-slate-200 dark:border-slate-700 rounded-lg bg-slate-100 dark:bg-slate-900 text-slate-500 dark:text-slate-400 cursor-not-allowed';

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 {isDarkMode, setDarkMode, setLanguage} = usePreferences();

    const [profile, setProfile] = useState(null);
    const [isLoading, setIsLoading] = useState(true);
    const [loadError, setLoadError] = useState(null);
    const [feedback, setFeedback] = useState({message: '', isError: false});

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

    useEffect(() => {
        const token = localStorage.getItem('tbp_jwt');
        if (!token) {
            navigate('/login');
            return;
        }

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

                if (response.status === 401) {
                    localStorage.removeItem('tbp_jwt');
                    navigate('/login');
                    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 ?? '',
                });
            } catch (err) {
                console.error('Settings load error:', err);
                setLoadError(t('INFO.ERROR.NETWORK_FAILURE'));
            } finally {
                setIsLoading(false);
            }
        };

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

    const persistSettings = async (payload) => {
        const token = localStorage.getItem('tbp_jwt');
        if (!token) {
            navigate('/login');
            return {ok: false};
        }

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

            if (response.status === 401) {
                localStorage.removeItem('tbp_jwt');
                navigate('/login');
                return {ok: false};
            }

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

            const data = await response.json();
            localStorage.setItem('tbp_jwt', data.token); // Core reads the steamId from the token
            setFeedback({message: t('SETTINGS.SAVED'), isError: false});
            return {ok: true};
        } catch (err) {
            console.error('Settings save error:', err);
            setFeedback({message: t('INFO.ERROR.NETWORK_FAILURE'), isError: true});
            return {ok: false};
        }
    };

    const handleDarkThemeToggle = async () => {
        const next = !isDarkMode;
        setDarkMode(next); // apply on the fly
        await persistSettings({
            useDarkTheme: next,
            language: i18n.language,
            steamId: profile?.steamId ?? null,
        });
    };

    const handleLanguageChange = async (event) => {
        const next = event.target.value;
        setLanguage(next); // apply on the fly
        await persistSettings({
            useDarkTheme: isDarkMode,
            language: next,
            steamId: profile?.steamId ?? null,
        });
    };

    const onSubmitSteamId = async (values) => {
        const result = await persistSettings({
            useDarkTheme: isDarkMode,
            language: i18n.language,
            steamId: values.steamId,
        });
        if (result.ok) {
            setProfile((p) => (p ? {...p, steamId: values.steamId} : p));
        }
    };

    const renderError = (field) =>
        errors[field] && (
            <p className="mt-1 text-sm text-red-600 dark:text-red-400">{t(errors[field].message)}</p>
        );

    if (isLoading) {
        return (
            <div className="flex min-h-screen items-center justify-center bg-slate-50 dark:bg-slate-900 text-slate-900 dark:text-white">
                {t('SETTINGS.LOADING')}
            </div>
        );
    }

    if (loadError) {
        return (
            <div className="flex min-h-screen items-center justify-center bg-slate-50 dark:bg-slate-900 text-red-500">
                {loadError}
            </div>
        );
    }

    return (
        <div className="min-h-screen bg-slate-50 dark:bg-slate-900 p-8">
            <div className="max-w-2xl mx-auto space-y-8">
                <div className="bg-white dark:bg-slate-800 rounded-xl shadow-lg p-8 border border-slate-200 dark:border-slate-700">
                    <h1 className="text-2xl font-bold text-slate-900 dark:text-white mb-6">
                        {t('SETTINGS.TITLE')}
                    </h1>

                    {/* Read-only account info */}
                    <section className="space-y-4 mb-8">
                        <h2 className="text-lg font-semibold text-slate-700 dark:text-slate-200">
                            {t('SETTINGS.ACCOUNT')}
                        </h2>
                        <div>
                            <label className="block text-sm font-medium text-slate-700 dark:text-slate-300 mb-1">
                                {t('SETTINGS.EMAIL')}
                            </label>
                            <input type="text" value={profile?.email ?? ''} readOnly className={readOnlyClass}/>
                        </div>
                        <div className="grid grid-cols-1 md:grid-cols-2 gap-4">
                            <div>
                                <label className="block text-sm font-medium text-slate-700 dark:text-slate-300 mb-1">
                                    {t('SETTINGS.ROLE')}
                                </label>
                                <input type="text" value={profile?.role ?? ''} readOnly className={readOnlyClass}/>
                            </div>
                            <div>
                                <label className="block text-sm font-medium text-slate-700 dark:text-slate-300 mb-1">
                                    {t('SETTINGS.CREATED_DATE')}
                                </label>
                                <input
                                    type="text"
                                    value={formatDate(profile?.createdDate, i18n.language)}
                                    readOnly
                                    className={readOnlyClass}
                                />
                            </div>
                        </div>
                        <div>
                            <label className="block text-sm font-medium text-slate-700 dark:text-slate-300 mb-1">
                                {t('SETTINGS.LAST_LOGIN')}
                            </label>
                            <input
                                type="text"
                                value={formatDate(profile?.lastLogin, i18n.language)}
                                readOnly
                                className={readOnlyClass}
                            />
                        </div>
                    </section>

                    {/* Preferences — live */}
                    <section className="space-y-4 mb-8">
                        <h2 className="text-lg font-semibold text-slate-700 dark:text-slate-200">
                            {t('SETTINGS.PREFERENCES')}
                        </h2>

                        <div className="flex items-center justify-between">
                            <label htmlFor="useDarkTheme" className="text-sm font-medium text-slate-700 dark:text-slate-300">
                                {t('SETTINGS.DARK_THEME')}
                            </label>
                            <button
                                id="useDarkTheme"
                                type="button"
                                role="switch"
                                aria-checked={isDarkMode}
                                onClick={handleDarkThemeToggle}
                                className={`relative inline-flex h-6 w-11 items-center rounded-full transition-colors ${
                                    isDarkMode ? 'bg-blue-600' : 'bg-slate-300 dark:bg-slate-600'
                                }`}
                            >
                                <span
                                    className={`inline-block h-4 w-4 transform rounded-full bg-white transition-transform ${
                                        isDarkMode ? 'translate-x-6' : 'translate-x-1'
                                    }`}
                                />
                            </button>
                        </div>

                        <div>
                            <label htmlFor="language" className="block text-sm font-medium text-slate-700 dark:text-slate-300 mb-1">
                                {t('SETTINGS.LANGUAGE')}
                            </label>
                            <select
                                id="language"
                                value={i18n.language}
                                onChange={handleLanguageChange}
                                className={inputClass}
                            >
                                {SUPPORTED_LANGUAGES.map((lang) => (
                                    <option key={lang} value={lang}>
                                        {t(`SETTINGS.LANGUAGE_OPTIONS.${lang.toUpperCase()}`)}
                                    </option>
                                ))}
                            </select>
                        </div>
                    </section>

                    {/* Steam ID — explicit save */}
                    <section>
                        <h2 className="text-lg font-semibold text-slate-700 dark:text-slate-200 mb-4">
                            {t('SETTINGS.STEAM')}
                        </h2>
                        <form onSubmit={handleSubmit(onSubmitSteamId)} className="space-y-4" noValidate>
                            <div>
                                <label htmlFor="steamId" className="block text-sm font-medium text-slate-700 dark:text-slate-300 mb-1">
                                    {t('SETTINGS.STEAM_ID')}
                                </label>
                                <input
                                    id="steamId"
                                    type="text"
                                    inputMode="numeric"
                                    className={errors.steamId ? inputErrorClass : inputClass}
                                    {...register('steamId')}
                                />
                                {renderError('steamId')}
                            </div>
                            <button
                                type="submit"
                                disabled={isSubmitting}
                                className="w-full py-2 px-4 bg-blue-600 hover:bg-blue-700 disabled:bg-blue-400 text-white font-semibold rounded-lg transition-colors duration-200"
                            >
                                {isSubmitting ? '...' : t('SETTINGS.SAVE_STEAM_ID')}
                            </button>
                        </form>
                    </section>

                    {feedback.message && (
                        <div
                            className={`mt-6 p-4 rounded-lg text-sm text-center ${
                                feedback.isError
                                    ? 'bg-red-100 text-red-700 dark:bg-red-900/30 dark:text-red-400'
                                    : 'bg-green-100 text-green-700 dark:bg-green-900/30 dark:text-green-400'
                            }`}
                        >
                            {feedback.message}
                        </div>
                    )}
                </div>
            </div>
        </div>
    );
}