"use client";

import React from 'react';
import { DashboardLayout } from "@/components/layout/dashboard-layout";

/**
 * Share (Invite) Page - Static UI with mocked data.
 * Sections: Invite Flow, My Invitation Code, Invite Records (with pagination)
 */

type InviteRecord = {
    id: string;
    invitedUsername: string;
    registeredAt: number; // epoch ms
    rewardA: string; // reward item 1 (content TBD)
    rewardB: string; // reward item 2 (content TBD)
};

const PAGE_SIZE = 10;

/**
 * Format epoch ms using browser preferred language.
 * @param {number} epochMs - timestamp in milliseconds
 * @returns {string} - localized date time string
 */
function formatLocalTime(epochMs: number): string {
    try {
        const locale = typeof navigator !== 'undefined' ? navigator.language : 'en-US';
        const dtf = new Intl.DateTimeFormat(locale, {
            dateStyle: 'medium',
            timeStyle: 'medium',
        });
        return dtf.format(new Date(epochMs));
    } catch {
        return new Date(epochMs).toLocaleString();
    }
}

/**
 * Generate mocked invite records for demo purpose only.
 * @param {number} count - number of items
 * @returns {InviteRecord[]} - mocked records
 */
function generateMockRecords(count: number): InviteRecord[] {
    const now = Date.now();
    return Array.from({ length: count }).map((_, index) => ({
        id: String(index + 1),
        invitedUsername: `user_${index + 1}`,
        registeredAt: now - index * 36_000, // different times
        rewardA: index % 3 === 0 ? '+100 points' : '—',
        rewardB: index % 5 === 0 ? '3-day membership' : '—',
    }));
}

export default function SharePage(): JSX.Element {
    // Mocked data (to be replaced by real API integration later)
    const [inviteCode] = React.useState<string>('VF-ABCD-1234');
    const [invitedCount] = React.useState<number>(37);
    const [copyState, setCopyState] = React.useState<'idle' | 'copied' | 'error'>('idle');

    const [records] = React.useState<InviteRecord[]>(() => generateMockRecords(47));
    const [pageIndex, setPageIndex] = React.useState<number>(0);

    const totalPages = Math.max(1, Math.ceil(records.length / PAGE_SIZE));
    const pagedRecords = React.useMemo(() => {
        const start = pageIndex * PAGE_SIZE;
        return records.slice(start, start + PAGE_SIZE);
    }, [records, pageIndex]);

    const handleCopy = React.useCallback(async () => {
        try {
            await navigator.clipboard.writeText(inviteCode);
            setCopyState('copied');
            window.setTimeout(() => setCopyState('idle'), 1600);
        } catch {
            setCopyState('error');
            window.setTimeout(() => setCopyState('idle'), 1600);
        }
    }, [inviteCode]);

    const canPrev = pageIndex > 0;
    const canNext = pageIndex < totalPages - 1;

    return (
        <DashboardLayout>
            <div data-alt="share-page" className="w-full h-full overflow-y-auto bg-black text-white">
                <div
                    data-alt="container"
                    className="w-full max-w-[95%] mx-auto px-4 py-10 sm:px-6 md:px-8 lg:px-12 xl:px-16 2xl:px-20"
                >
                    <header data-alt="page-header" className="mb-8 flex items-end justify-between">
                        <div data-alt="title-box">
                            <h1 data-alt="title" className="text-2xl font-semibold text-white">Invite Friends</h1>
                            <p data-alt="subtitle" className="mt-1 text-sm text-white/60">Invite friends to join and earn rewards.</p>
                        </div>
                    </header>

                {/* Section 1: Invite Flow */}
                <section data-alt="invite-flow" className="mb-8 rounded-lg border border-white/20 bg-black p-6 shadow-sm">
                    <h2 data-alt="section-title" className="text-lg font-medium text-white">Invitation Flow</h2>
                    <ol data-alt="steps" className="mt-4 grid gap-4 sm:grid-cols-3">
                        <li data-alt="step" className="rounded-md border border-white/20 p-4">
                            <div data-alt="step-header" className="flex items-center justify-between">
                                <span className="text-sm font-medium text-white/80">Step 1</span>
                                <span className="rounded bg-white/10 px-2 py-0.5 text-xs text-white">Share</span>
                            </div>
                            <p data-alt="step-desc" className="mt-2 text-sm text-white/70">Copy your invitation code and share it with friends.</p>
                        </li>
                        <li data-alt="step" className="rounded-md border border-white/20 p-4">
                            <div data-alt="step-header" className="flex items-center justify-between">
                                <span className="text-sm font-medium text-white/80">Step 2</span>
                                <span className="rounded bg-white/10 px-2 py-0.5 text-xs text-white">Register</span>
                            </div>
                            <p data-alt="step-desc" className="mt-2 text-sm text-white/70">Friends register and enter your invitation code.</p>
                        </li>
                        <li data-alt="step" className="rounded-md border border-white/20 p-4">
                            <div data-alt="step-header" className="flex items-center justify-between">
                                <span className="text-sm font-medium text-white/80">Step 3</span>
                                <span className="rounded bg-white/10 px-2 py-0.5 text-xs text-white">Reward</span>
                            </div>
                            <p data-alt="step-desc" className="mt-2 text-sm text-white/70">You both receive rewards after successful registration.</p>
                        </li>
                    </ol>
                </section>

                {/* Section 2: My Invitation Code */}
                <section data-alt="my-invite-code" className="mb-8 rounded-lg border border-white/20 bg-black p-6 shadow-sm">
                    <div data-alt="code-panel" className="mt-4 grid gap-6 sm:grid-cols-3">
                        <div data-alt="code-box" className="sm:col-span-2">
                            <h2 data-alt="section-title" className="text-lg font-medium text-white">My Invitation Code</h2>
                            <div className="flex items-center gap-3">
                                <div data-alt="code" className="rounded-md border border-white/20 bg-white/10 px-4 py-2 text-lg font-semibold tracking-wider text-white">
                                    {inviteCode}
                                </div>
                                <button
                                    data-alt="copy-button"
                                    className="inline-flex h-9 items-center justify-center rounded-full bg-gradient-to-r from-custom-blue to-custom-purple px-3 text-sm font-medium text-black/90 hover:opacity-90 active:translate-y-px"
                                    onClick={handleCopy}
                                    type="button"
                                    aria-label="Copy invitation code"
                                >
                                    {copyState === 'copied' ? 'Copied' : copyState === 'error' ? 'Failed' : 'Copy'}
                                </button>
                            </div>
                            <p data-alt="hint" className="mt-2 text-xs text-white/60">Share this code. Your friends can enter it during registration.</p>
                        </div>
                        <div data-alt="invited-count" className="flex flex-col items-start justify-center rounded-md border border-white/20 bg-white/5 p-4">
                            <span className="text-sm text-white/70">Invited Friends</span>
                            <span className="mt-1 text-2xl font-semibold text-white">{invitedCount}</span>
                            <span className="mt-2 text-xs text-white/60">Points detail will be available soon.</span>
                        </div>
                    </div>
                </section>

                {/* Section 3: Invite Records */}
                <section data-alt="invite-records" className="rounded-lg border border-white/20 bg-black p-6 shadow-sm">
                    <div data-alt="section-header" className="mb-4 flex items-center justify-between">
                        <h2 data-alt="section-title" className="text-lg font-medium text-white">Invite Records</h2>
                        <div data-alt="pagination" className="flex items-center gap-2">
                            <button
                                data-alt="prev-page"
                                className="inline-flex h-8 items-center justify-center rounded border border-gray-300 bg-white px-2 text-sm text-gray-700 hover:bg-gray-50 disabled:cursor-not-allowed disabled:opacity-50"
                                type="button"
                                onClick={() => setPageIndex((p) => Math.max(0, p - 1))}
                                disabled={!canPrev}
                                aria-label="Previous page"
                            >
                                Prev
                            </button>
                            <span data-alt="page-info" className="text-sm text-white/70">
                                {pageIndex + 1} / {totalPages}
                            </span>
                            <button
                                data-alt="next-page"
                                className="inline-flex h-8 items-center justify-center rounded border border-gray-300 bg-white px-2 text-sm text-gray-700 hover:bg-gray-50 disabled:cursor-not-allowed disabled:opacity-50"
                                type="button"
                                onClick={() => setPageIndex((p) => Math.min(totalPages - 1, p + 1))}
                                disabled={!canNext}
                                aria-label="Next page"
                            >
                                Next
                            </button>
                        </div>
                    </div>

                    <div data-alt="table-wrapper" className="overflow-x-auto">
                        <table data-alt="records-table" className="min-w-full divide-y divide-white/10">
                            <thead data-alt="table-head" className="bg-black">
                                <tr data-alt="table-head-row">
                                    <th className="px-4 py-3 text-left text-xs font-medium uppercase tracking-wider text-white/60">Invited Username</th>
                                    <th className="px-4 py-3 text-left text-xs font-medium uppercase tracking-wider text-white/60">Registered At</th>
                                    <th className="px-4 py-3 text-left text-xs font-medium uppercase tracking-wider text-white/60">Registration Reward</th>
                                    <th className="px-4 py-3 text-left text-xs font-medium uppercase tracking-wider text-white/60">First Payment Reward</th>
                                </tr>
                            </thead>
                            <tbody data-alt="table-body" className="divide-y divide-white/10 bg-black">
                                {pagedRecords.map((r) => (
                                    <tr key={r.id} data-alt="table-row" className="hover:bg-white/5">
                                        <td className="px-4 py-3 text-sm text-white">{r.invitedUsername}</td>
                                        <td className="px-4 py-3 text-sm text-white/80">{formatLocalTime(r.registeredAt)}</td>
                                        <td className="px-4 py-3 text-sm text-white/90">{r.rewardA}</td>
                                        <td className="px-4 py-3 text-sm text-white/90">{r.rewardB}</td>
                                    </tr>
                                ))}
                            </tbody>
                        </table>
                    </div>
                </section>
                </div>
            </div>
        </DashboardLayout>
    );
}