"use client";

import { useRouter } from "next/navigation";
import { useEffect, useMemo, useTransition } from "react";
import { Card } from "@/components/ui/card";
import { useMonthPeriod } from "@/hooks/use-month-period";
import LoadingSpinner from "./loading-spinner";
import NavigationButton from "./nav-button";
import ReturnButton from "./return-button";

export default function MonthNavigation() {
	const {
		monthNames,
		currentMonth,
		currentYear,
		defaultMonth,
		defaultYear,
		buildHref,
	} = useMonthPeriod();

	const router = useRouter();
	const [isPending, startTransition] = useTransition();

	const currentMonthLabel = useMemo(
		() => currentMonth.charAt(0).toUpperCase() + currentMonth.slice(1),
		[currentMonth],
	);

	const currentMonthIndex = useMemo(
		() => monthNames.indexOf(currentMonth),
		[monthNames, currentMonth],
	);

	const prevTarget = useMemo(() => {
		let idx = currentMonthIndex - 1;
		let year = currentYear;
		if (idx < 0) {
			idx = monthNames.length - 1;
			year = (parseInt(currentYear, 10) - 1).toString();
		}
		return buildHref(monthNames[idx], year);
	}, [currentMonthIndex, currentYear, monthNames, buildHref]);

	const nextTarget = useMemo(() => {
		let idx = currentMonthIndex + 1;
		let year = currentYear;
		if (idx >= monthNames.length) {
			idx = 0;
			year = (parseInt(currentYear, 10) + 1).toString();
		}
		return buildHref(monthNames[idx], year);
	}, [currentMonthIndex, currentYear, monthNames, buildHref]);

	const returnTarget = useMemo(
		() => buildHref(defaultMonth, defaultYear),
		[buildHref, defaultMonth, defaultYear],
	);

	const isDifferentFromCurrent =
		currentMonth !== defaultMonth || currentYear !== defaultYear.toString();

	// Prefetch otimizado: apenas meses adjacentes (M-1, M+1) e mês atual
	// Isso melhora a performance da navegação sem sobrecarregar o cliente
	useEffect(() => {
		// Prefetch do mês anterior e próximo para navegação instantânea
		router.prefetch(prevTarget);
		router.prefetch(nextTarget);

		// Prefetch do mês atual se não estivermos nele
		if (isDifferentFromCurrent) {
			router.prefetch(returnTarget);
		}
	}, [router, prevTarget, nextTarget, returnTarget, isDifferentFromCurrent]);

	const handleNavigate = (href: string) => {
		startTransition(() => {
			router.replace(href, { scroll: false });
		});
	};

	return (
		<Card className="sticky top-0 z-30 w-full flex-row bg-month-picker text-month-picker-foreground p-4">
			<div className="flex items-center gap-1">
				<NavigationButton
					direction="left"
					disabled={isPending}
					onClick={() => handleNavigate(prevTarget)}
				/>

				<div className="flex items-center">
					<div
						className="mx-1 space-x-1 capitalize font-bold"
						aria-current={!isDifferentFromCurrent ? "date" : undefined}
						aria-label={`Período selecionado: ${currentMonthLabel} de ${currentYear}`}
					>
						<span>{currentMonthLabel}</span>
						<span>{currentYear}</span>
					</div>

					{isPending && <LoadingSpinner />}
				</div>

				<NavigationButton
					direction="right"
					disabled={isPending}
					onClick={() => handleNavigate(nextTarget)}
				/>
			</div>

			{isDifferentFromCurrent && (
				<ReturnButton
					disabled={isPending}
					onClick={() => handleNavigate(returnTarget)}
				/>
			)}
		</Card>
	);
}
