import {useState} from 'react';
import {Link, useLocation} from 'react-router-dom';
import {useTranslation} from 'react-i18next';
import {useForm} from 'react-hook-form';
import {zodResolver} from '@hookform/resolvers/zod';
import {Loader2} from 'lucide-react';

import {Button} from '@/components/ui/button';
import {Input} from '@/components/ui/input';
import AuthLayout from '../components/AuthLayout.jsx';
import FeedbackAlert from '../components/FeedbackAlert.jsx';
import FormField from '../components/FormField.jsx';
import NewPasswordFields from '../components/NewPasswordFields.jsx';
import {confirmEmailSchema} from '../utils/validation.js';
import {clientFetch} from '../utils/api.js';

const post = (path, body) => clientFetch(`${import.meta.env.VITE_API_URL}${path}`, {
    method: 'POST',
    headers: {'Content-Type': 'application/json'},
    body: JSON.stringify(body),
});

const failureMessage = (t, response) => {
    if (response.status === 429) {
        const minutes = Math.ceil(Number(response.headers.get('Retry-After') ?? 900) / 60);
        return t('RESET_PASSWORD.ERROR_TOO_MANY', {minutes});
    }
    return t('RESET_PASSWORD.ERROR_GENERIC');
};

/**
 * Both ends of "forgot password". Without a fragment: ask for the mail. With the fragment of the mail link: choose
 * the new password. The token is in the fragment, so no server log sees it, and it is sent only on the click: a mail
 * scanner that opens the link must not use it up.
 */
export default function ResetPasswordPage() {
    const token = useLocation().hash.slice(1);
    // A new link in the same tab only changes the fragment: key restarts the state.
    return <ResetPassword key={token} token={token}/>;
}

function ResetPassword({token}) {
    const {t} = useTranslation();
    const [state, setState] = useState(token ? 'idle' : 'request');

    return (
        <AuthLayout title={t('RESET_PASSWORD.TITLE')}>
            {state === 'idle' && (
                <NewPasswordForm token={token} onDone={() => setState('done')} onInvalid={() => setState('invalid')}/>
            )}
            {state === 'done' && <>
                <FeedbackAlert message={t('RESET_PASSWORD.DONE')} isError={false}/>
                <Link to="/login" className="block text-center text-sm font-medium text-primary hover:underline">
                    {t('RESET_PASSWORD.TO_LOGIN')}
                </Link>
            </>}
            {state === 'invalid' && <FeedbackAlert message={t('RESET_PASSWORD.INVALID')} isError/>}
            {(state === 'request' || state === 'invalid') && <RequestForm/>}
        </AuthLayout>
    );
}

function RequestForm() {
    const {t} = useTranslation();
    const [email, setEmail] = useState('');
    const [isLoading, setIsLoading] = useState(false);
    const [feedback, setFeedback] = useState({message: '', isError: false});

    const send = async (event) => {
        event.preventDefault();
        setIsLoading(true);
        setFeedback({message: '', isError: false});
        try {
            const response = await post('/api/auth/password-reset', {email});
            setFeedback(response.ok
                ? {message: t('RESET_PASSWORD.SENT'), isError: false}
                : {message: failureMessage(t, response), isError: true});
        } catch (error) {
            console.error('Password reset API error:', error);
            setFeedback({message: t('INFO.ERROR.NETWORK_FAILURE'), isError: true});
        } finally {
            setIsLoading(false);
        }
    };

    return (
        <form onSubmit={send} className="space-y-3" noValidate>
            <FormField id="reset-email" label={t('RESET_PASSWORD.EMAIL')} t={t}>
                <Input id="reset-email" type="email" autoComplete="email" value={email}
                       onChange={(e) => setEmail(e.target.value)}/>
            </FormField>
            <Button type="submit" disabled={isLoading} className="w-full">
                {isLoading && <Loader2 className="animate-spin"/>}
                {t('RESET_PASSWORD.SEND')}
            </Button>
            <FeedbackAlert message={feedback.message} isError={feedback.isError}/>
        </form>
    );
}

function NewPasswordForm({token, onDone, onInvalid}) {
    const {t} = useTranslation();
    const [error, setError] = useState('');
    const {register, handleSubmit, formState: {errors, isSubmitting}} = useForm({
        resolver: zodResolver(confirmEmailSchema),
        defaultValues: {password: '', passwordConfirmation: ''},
    });

    const submit = async ({password}) => {
        setError('');
        try {
            const response = await post('/api/auth/password-reset/confirm', {token, password});
            if (response.ok) {
                onDone();
            } else if (response.status === 410 || response.status === 400) {
                onInvalid();
            } else {
                setError(failureMessage(t, response));
            }
        } catch (err) {
            console.error('Password reset confirm error:', err);
            setError(t('INFO.ERROR.NETWORK_FAILURE'));
        }
    };

    return (
        <form onSubmit={handleSubmit(submit)} className="space-y-4" noValidate>
            <p className="text-sm text-muted-foreground">{t('RESET_PASSWORD.INTRO')}</p>
            <NewPasswordFields register={register} errors={errors} t={t}/>
            <Button type="submit" disabled={isSubmitting} className="w-full">
                {isSubmitting && <Loader2 className="animate-spin"/>}
                {t('RESET_PASSWORD.SUBMIT')}
            </Button>
            <FeedbackAlert message={error} isError/>
        </form>
    );
}