gw/web/src/pages/Home/index.tsx

import { useEffect, useState } from 'preact/hooks';

type EntryBody = {
    err: boolean;
    referral: string;
    key: string;
}

export const Home = () => {
    const [referral, setReferral] = useState('');
    const [entryBody, setEntryBody] = useState<EntryBody | null>({
        err: true,
        referral: '',
        key: ''
    });

	const [timeLeft, setTimeLeft] = useState<string>('...');

    useEffect(() => {
        console.log('Referral:', referral);
    }, [referral]);

    const entry = async () => {
        let res = await fetch("http://localhost:8080/entry", { 
            method: 'GET',
            headers: { referral }
        })
        
        if (!res.ok) {
            console.error('Error:', res.status);
            return
        }

        let body: EntryBody = await res.json();

        if (body.err) {
            console.error('Error:', body.referral);
            window.location.href = '/error';

            return
        }

        console.log('Entry:', body);
        
        setEntryBody(body);

        setReferral('');
    }
    
    const eventDateCET = new Date('2025-01-01T00:00:00Z');
    const userTime = new Intl.DateTimeFormat(undefined, {
        year: 'numeric',
        month: 'long',
        day: 'numeric',
        hour: '2-digit',
        minute: '2-digit',
        timeZoneName: 'short'
    }).format(eventDateCET);

	const getTimeLeft = (date: Date) => {
		const now = new Date();
		const diff = date.getTime() - now.getTime();
		const days = Math.floor(diff / (1000 * 60 * 60 * 24));
		const hours = Math.floor(diff / (1000 * 60 * 60) % 24);
		const minutes = Math.floor(diff / (1000 * 60) % 60);
		const seconds = Math.floor(diff / 1000 % 60);
		
		let s = "";
		if (days > 0) s += days + "d ";
		if (hours > 0) s += hours + "h ";
		if (minutes > 0) s += minutes + "m ";
		if (seconds > 0) s += seconds + "s";
		
		if (s === "") s = "the time is upon us.";
		else s += " remaining.";
		return s;
	}

	useEffect(() => {
		const interval = setInterval(() => {
			setTimeLeft(getTimeLeft(eventDateCET));
		}, 1000);

		return () => clearInterval(interval);
	}, []);

    return (
        <div class="flex flex-col gap-6 w-full h-full justify-center items-center">
            <h1 class="text-6xl font-bold animate-pulse">???</h1>
			<p>{timeLeft}</p>
            
                <span>
                    <p class="opacity-100 hover:opacity-75 transition-opacity">
                        Referral:
                    </p>
                    
                
                    <div class="flex gap-2">
                        <input
                            type="text"
                            value={referral}
                            onInput={(e) => setReferral(e.currentTarget.value)}

                            class="bg-black text-green-500 border-green-500 border-2 px-2 hover:bg-green-500 hover:text-black active:bg-green-500 active:text-black transition-colors"
                        />

                        <button
                            onClick={async () => await entry()}
                            class="bg-green-500 text-black hover:bg-black hover:text-green-500 transition-colors px-4"
                        >
                            Submit
                        </button>
                    </div>
                </span>

                {
                    !entryBody.err ? (
                        <div class="flex flex-col gap-1.5 mt-3 justify-center items-center">
                            <p class="text-green-700">tip: click to copy.</p>
                            <h2 onClick={() => navigator.clipboard.writeText(entryBody?.key)}>Key: <code class="cursor-pointer bg-green-800 hover:bg-green-900 active:bg-green-700 transition-colors py-1 px-2 rounded-lg text-white">{entryBody?.key}</code></h2>
                            <h2 onClick={() => navigator.clipboard.writeText(entryBody?.referral)}>Referral: <code class="cursor-pointer bg-green-800 hover:bg-green-900 active:bg-green-700 transition-colors py-1 px-2 rounded-lg text-white">{entryBody?.referral}</code></h2>
                            <p class="text-green-700">good luck. keep note of these, if you lose them, you can't reroll.</p>
                        </div>
                    ) : (
                        <div class="w-2/3 text-center flex flex-col gap-2">
                            <div>
                                <b>What is this?</b>
                                <p>At exactly {userTime} (00:00 CET on 1 Jan), the system will choose a random entry. Their referral key shall be publicly
                                    displayed on this page. The person associated with this referral key shall contact us with their private key.
                                    They shall win a little prize. To have one's entry weigh more than the rest, one shall have to spread their
                                    referral key amongst people. Every referral shall increase their chance of getting selected.
                                </p>
                            </div>

                            <div>
                                <b>How does one enter?</b>
                                <p>One needs a referral key to enter.</p>
                            </div>
                        </div>
                    )
                }
		</div>
    )
};