"use client";

import { useEffect, useMemo, useState } from "react";
import { useI18n } from "./I18nProvider";

type MonthView = {
  label: string;
  days: { label: string; date: string; blocked: boolean; isFiller: boolean }[];
};

function buildMonths(
  monthCount: number,
  blocked: Set<string>,
  startYear: number,
  startMonth: number,
): MonthView[] {
  const months: MonthView[] = [];
  const base = new Date(Date.UTC(startYear, startMonth, 1));

  for (let i = 0; i < monthCount; i += 1) {
    const monthDate = new Date(base);
    monthDate.setUTCMonth(base.getUTCMonth() + i);
    const year = monthDate.getUTCFullYear();
    const month = monthDate.getUTCMonth();
    const label = monthDate.toLocaleDateString(undefined, {
      month: "long",
      year: "numeric",
    });

    const firstDay = new Date(Date.UTC(year, month, 1));
    const startWeekday = firstDay.getUTCDay(); // 0=Sun
    const daysInMonth = new Date(Date.UTC(year, month + 1, 0)).getUTCDate();

    const days: MonthView["days"] = [];
    for (let f = 0; f < startWeekday; f += 1) {
      days.push({ label: "", date: "", blocked: false, isFiller: true });
    }
    for (let d = 1; d <= daysInMonth; d += 1) {
      const date = new Date(Date.UTC(year, month, d));
      const iso = date.toISOString().slice(0, 10);
      days.push({
        label: String(d),
        date: iso,
        blocked: blocked.has(iso),
        isFiller: false,
      });
    }

    months.push({ label, days });
  }

  return months;
}

type AvailabilityResponse = { blockedDates: string[] };

export default function AvailabilityCalendar({
  listingId,
  hasCalendar,
}: {
  listingId: string;
  hasCalendar: boolean;
}) {
  const { t, locale } = useI18n();
  const today = useMemo(() => new Date(), []);
  const [month, setMonth] = useState<number>(today.getUTCMonth());
  const [year, setYear] = useState<number>(today.getUTCFullYear());
  const [blockedDates, setBlockedDates] = useState<string[]>([]);
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const monthCount = 1;
  const blockedSet = useMemo(() => new Set(blockedDates), [blockedDates]);
  const monthViews = useMemo(
    () => buildMonths(monthCount, blockedSet, year, month),
    [monthCount, blockedSet, year, month],
  );

  useEffect(() => {
    if (!hasCalendar) return;
    setLoading(true);
    setError(null);
    const controller = new AbortController();
    const params = new URLSearchParams({
      month: String(month),
      year: String(year),
      months: String(monthCount),
      refresh: "1",
    });
    fetch(`/api/listings/${listingId}/availability?${params.toString()}`, {
      cache: "no-store",
      signal: controller.signal,
    })
      .then(async (res) => {
        const data: AvailabilityResponse = await res.json();
        if (!res.ok)
          throw new Error(
            (data as any)?.error || "Failed to load availability",
          );
        return data;
      })
      .then((data) => {
        setBlockedDates(
          Array.isArray(data.blockedDates) ? data.blockedDates : [],
        );
      })
      .catch((err) => {
        if (err.name === "AbortError") return;
        setError(err.message || "Failed to load availability");
      })
      .finally(() => setLoading(false));

    return () => controller.abort();
  }, [listingId, hasCalendar, month, year, monthCount]);

  function shiftMonth(delta: number) {
    const next = new Date(Date.UTC(year, month, 1));
    next.setUTCMonth(next.getUTCMonth() + delta);
    setMonth(next.getUTCMonth());
    setYear(next.getUTCFullYear());
  }

  const monthOptions = useMemo(
    () =>
      Array.from({ length: 12 }, (_, m) => ({
        value: m,
        label: new Date(Date.UTC(2020, m, 1)).toLocaleString(locale, {
          month: "long",
        }),
      })),
    [locale],
  );
  const yearOptions = useMemo(() => {
    const current = today.getUTCFullYear();
    return Array.from({ length: 5 }, (_, i) => current - 1 + i);
  }, [today]);

  return (
    <div style={{ display: "grid", gap: 12, opacity: hasCalendar ? 1 : 0.5 }}>
      <div
        style={{
          display: "flex",
          gap: 10,
          alignItems: "center",
          flexWrap: "wrap",
        }}
      >
        <div
          style={{
            display: "flex",
            gap: 8,
            alignItems: "center",
            flexWrap: "wrap",
          }}
        >
          <span style={{ fontWeight: 700 }}>{t("availabilityTitle")}</span>
        </div>
        <div
          style={{
            marginLeft: "auto",
            display: "flex",
            alignItems: "center",
            gap: 6,
            flexWrap: "wrap",
          }}
        >
          <span className="badge secondary">
            {t("availabilityLegendBooked")}
          </span>
          <button
            type="button"
            className="button secondary"
            onClick={() => shiftMonth(-1)}
            disabled={!hasCalendar || loading}
            style={{ padding: "6px 10px" }}
          >
            ←
          </button>
          <button
            type="button"
            className="button secondary"
            onClick={() => shiftMonth(1)}
            disabled={!hasCalendar || loading}
            style={{ padding: "6px 10px" }}
          >
            →
          </button>
        </div>
      </div>
      {error ? (
        <div style={{ color: "#f87171", fontSize: 13 }}>{error}</div>
      ) : null}
      {monthViews.map((monthView) => (
        <div key={monthView.label} className="panel" style={{ padding: 12 }}>
          <div
            style={{
              display: "flex",
              gap: 8,
              alignItems: "center",
              marginBottom: 8,
            }}
          >
            <select
              value={month}
              onChange={(e) => setMonth(Number(e.target.value))}
              disabled={!hasCalendar || loading}
              style={{ flex: 1 }}
            >
              {monthOptions.map((opt) => (
                <option key={opt.value} value={opt.value}>
                  {opt.label}
                </option>
              ))}
            </select>
            <select
              value={year}
              onChange={(e) => setYear(Number(e.target.value))}
              disabled={!hasCalendar || loading}
              style={{ width: 96 }}
            >
              {yearOptions.map((y) => (
                <option key={y} value={y}>
                  {y}
                </option>
              ))}
            </select>
          </div>
          <div
            style={{
              display: "grid",
              gridTemplateColumns: "repeat(7, 1fr)",
              gap: 6,
              fontSize: 12,
              textAlign: "center",
            }}
          >
            {["S", "M", "T", "W", "T", "F", "S"].map((d) => (
              <div key={d} style={{ color: "#94a3b8", fontWeight: 600 }}>
                {d}
              </div>
            ))}
            {monthView.days.map((day, idx) => (
              <div
                key={`${monthView.label}-${idx}`}
                style={{
                  height: 32,
                  borderRadius: 8,
                  background: day.isFiller
                    ? "transparent"
                    : day.blocked
                      ? "rgba(248,113,113,0.2)"
                      : "rgba(148,163,184,0.1)",
                  color: day.isFiller
                    ? "transparent"
                    : day.blocked
                      ? "#ef4444"
                      : "#e2e8f0",
                  display: "flex",
                  alignItems: "center",
                  justifyContent: "center",
                }}
                aria-label={
                  day.date
                    ? `${day.date}${day.blocked ? " (booked)" : ""}`
                    : undefined
                }
              >
                {day.label}
              </div>
            ))}
          </div>
        </div>
      ))}
    </div>
  );
}