interface PaginationProps {
    page: number;
    totalPages: number;
    totalElements: number;
    pageSize: number;
    onPageChange: (page: number) => void;
}

/**
 * 표시할 페이지 번호 목록 생성 (Truncated Page Number)
 * - 총 7슬롯 이하면 전부 표시
 * - 7슬롯 초과면 현재 페이지 기준 양쪽 1개 + 처음/끝 + ellipsis
 */
function getPageNumbers(current: number, total: number): (number | 'ellipsis')[] {
    if (total <= 7) {
        return Array.from({ length: total }, (_, i) => i);
    }

    const pages: (number | 'ellipsis')[] = [];
    const SIBLING = 1;

    const leftSibling = Math.max(current - SIBLING, 0);
    const rightSibling = Math.min(current + SIBLING, total - 1);

    const showLeftEllipsis = leftSibling > 1;
    const showRightEllipsis = rightSibling < total - 2;

    pages.push(0);

    if (showLeftEllipsis) {
        pages.push('ellipsis');
    } else {
        for (let i = 1; i < leftSibling; i++) {
            pages.push(i);
        }
    }

    for (let i = leftSibling; i <= rightSibling; i++) {
        if (i !== 0 && i !== total - 1) {
            pages.push(i);
        }
    }

    if (showRightEllipsis) {
        pages.push('ellipsis');
    } else {
        for (let i = rightSibling + 1; i < total - 1; i++) {
            pages.push(i);
        }
    }

    if (total > 1) {
        pages.push(total - 1);
    }

    return pages;
}

export default function Pagination({
    page,
    totalPages,
    totalElements,
    pageSize,
    onPageChange,
}: PaginationProps) {
    if (totalPages <= 1) return null;

    const start = page * pageSize + 1;
    const end = Math.min((page + 1) * pageSize, totalElements);
    const pages = getPageNumbers(page, totalPages);

    const btnBase =
        'inline-flex items-center justify-center w-7 h-7 text-xs rounded transition-colors';
    const btnEnabled = 'hover:bg-wing-hover text-wing-muted';
    const btnDisabled = 'opacity-30 cursor-not-allowed text-wing-muted';

    return (
        <div className="flex items-center justify-between mt-2 text-xs text-wing-muted">
            <span>
                {totalElements.toLocaleString()}건 중 {start.toLocaleString()}~
                {end.toLocaleString()}
            </span>
            <div className="flex items-center gap-0.5">
                {/* First */}
                <button
                    onClick={() => onPageChange(0)}
                    disabled={page === 0}
                    className={`${btnBase} ${page === 0 ? btnDisabled : btnEnabled}`}
                    title="처음"
                >
                    &laquo;
                </button>
                {/* Prev */}
                <button
                    onClick={() => onPageChange(page - 1)}
                    disabled={page === 0}
                    className={`${btnBase} ${page === 0 ? btnDisabled : btnEnabled}`}
                    title="이전"
                >
                    &lsaquo;
                </button>

                {/* Page Numbers */}
                {pages.map((p, idx) =>
                    p === 'ellipsis' ? (
                        <span key={`e-${idx}`} className="w-7 h-7 inline-flex items-center justify-center text-wing-muted">
                            &hellip;
                        </span>
                    ) : (
                        <button
                            key={p}
                            onClick={() => onPageChange(p)}
                            className={`${btnBase} ${
                                p === page
                                    ? 'bg-wing-accent text-white font-semibold'
                                    : btnEnabled
                            }`}
                        >
                            {p + 1}
                        </button>
                    ),
                )}

                {/* Next */}
                <button
                    onClick={() => onPageChange(page + 1)}
                    disabled={page >= totalPages - 1}
                    className={`${btnBase} ${page >= totalPages - 1 ? btnDisabled : btnEnabled}`}
                    title="다음"
                >
                    &rsaquo;
                </button>
                {/* Last */}
                <button
                    onClick={() => onPageChange(totalPages - 1)}
                    disabled={page >= totalPages - 1}
                    className={`${btnBase} ${page >= totalPages - 1 ? btnDisabled : btnEnabled}`}
                    title="마지막"
                >
                    &raquo;
                </button>
            </div>
        </div>
    );
}