import Link from "next/link";
import type { DayData } from "@/lib/db";

interface ParkMonthCalendarProps {
  parkId: string;
  year: number;
  month: number; // 1-indexed
  monthData: Record<string, DayData>; // 'YYYY-MM-DD' → DayData
  today: string; // YYYY-MM-DD
}

const DOW_LABELS = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"];
const MONTH_NAMES = [
  "January","February","March","April","May","June",
  "July","August","September","October","November","December",
];

function prevMonth(year: number, month: number) {
  if (month === 1) return { year: year - 1, month: 12 };
  return { year, month: month - 1 };
}

function nextMonth(year: number, month: number) {
  if (month === 12) return { year: year + 1, month: 1 };
  return { year, month: month + 1 };
}

function daysInMonth(year: number, month: number): number {
  return new Date(year, month, 0).getDate();
}

export function ParkMonthCalendar({ parkId, year, month, monthData, today }: ParkMonthCalendarProps) {
  const firstDow = new Date(year, month - 1, 1).getDay(); // 0=Sun
  const totalDays = daysInMonth(year, month);

  const prev = prevMonth(year, month);
  const next = nextMonth(year, month);
  const prevParam = `${prev.year}-${String(prev.month).padStart(2, "0")}`;
  const nextParam = `${next.year}-${String(next.month).padStart(2, "0")}`;

  // Build cells: leading empty + actual days
  const cells: Array<{ day: number | null; iso: string | null }> = [];
  for (let i = 0; i < firstDow; i++) cells.push({ day: null, iso: null });
  for (let d = 1; d <= totalDays; d++) {
    const iso = `${year}-${String(month).padStart(2, "0")}-${String(d).padStart(2, "0")}`;
    cells.push({ day: d, iso });
  }
  // Pad to complete last row
  while (cells.length % 7 !== 0) cells.push({ day: null, iso: null });

  const weeks: typeof cells[] = [];
  for (let i = 0; i < cells.length; i += 7) {
    weeks.push(cells.slice(i, i + 7));
  }

  return (
    <div>
      {/* Month nav */}
      <div style={{
        display: "flex",
        alignItems: "center",
        gap: 16,
        marginBottom: 16,
      }}>
        <Link
          href={`/park/${parkId}?month=${prevParam}`}
          style={navLinkStyle}
        >
          ←
        </Link>
        <span style={{
          fontSize: "1rem",
          fontWeight: 600,
          color: "var(--color-text)",
          minWidth: 160,
          textAlign: "center",
          letterSpacing: "-0.01em",
        }}>
          {MONTH_NAMES[month - 1]} {year}
        </span>
        <Link
          href={`/park/${parkId}?month=${nextParam}`}
          style={navLinkStyle}
        >
          →
        </Link>
      </div>

      {/* Calendar grid */}
      <div style={{
        border: "1px solid var(--color-border)",
        borderRadius: 10,
        overflow: "hidden",
        background: "var(--color-surface)",
      }}>
        {/* DOW header */}
        <div style={{
          display: "grid",
          gridTemplateColumns: "repeat(7, 1fr)",
          borderBottom: "1px solid var(--color-border)",
        }}>
          {DOW_LABELS.map((d, i) => (
            <div key={d} style={{
              padding: "8px 0",
              textAlign: "center",
              fontSize: "0.65rem",
              fontWeight: 700,
              letterSpacing: "0.06em",
              textTransform: "uppercase",
              color: i === 0 || i === 6 ? "var(--color-text-secondary)" : "var(--color-text-muted)",
              background: i === 0 || i === 6 ? "var(--color-weekend-header)" : "transparent",
            }}>
              {d}
            </div>
          ))}
        </div>

        {/* Weeks */}
        {weeks.map((week, wi) => (
          <div key={wi} style={{
            display: "grid",
            gridTemplateColumns: "repeat(7, 1fr)",
            borderBottom: wi < weeks.length - 1 ? "1px solid var(--color-border-subtle)" : "none",
          }}>
            {week.map((cell, ci) => {
              if (!cell.day || !cell.iso) {
                return (
                  <div key={ci} style={{
                    minHeight: 96,
                    background: ci === 0 || ci === 6 ? "var(--color-weekend-header)" : "transparent",
                    borderRight: ci < 6 ? "1px solid var(--color-border-subtle)" : "none",
                  }} />
                );
              }

              const dayData = monthData[cell.iso];
              const isToday = cell.iso === today;
              const isWeekend = ci === 0 || ci === 6;
              const isOpen = dayData?.isOpen && dayData?.hoursLabel;
              const isPH = dayData?.specialType === "passholder_preview";

              const bg = isToday
                ? "var(--color-today-bg)"
                : isWeekend
                ? "var(--color-weekend-header)"
                : "transparent";

              return (
                <div key={ci} style={{
                  minHeight: 96,
                  padding: "10px 12px",
                  background: bg,
                  borderRight: ci < 6 ? "1px solid var(--color-border-subtle)" : "none",
                  borderLeft: isToday ? "2px solid var(--color-today-border)" : "none",
                  display: "flex",
                  flexDirection: "column",
                  gap: 5,
                }}>
                  {/* Date number */}
                  <span style={{
                    fontSize: "0.95rem",
                    fontWeight: isToday ? 700 : isWeekend ? 600 : 400,
                    color: isToday
                      ? "var(--color-today-text)"
                      : isWeekend
                      ? "var(--color-text)"
                      : "var(--color-text-muted)",
                    lineHeight: 1,
                  }}>
                    {cell.day}
                  </span>

                  {/* Status */}
                  {!dayData ? (
                    <span style={{ fontSize: "0.75rem", color: "var(--color-text-dim)" }}>—</span>
                  ) : isPH && isOpen ? (
                    <div style={{
                      background: "var(--color-ph-bg)",
                      border: "1px solid var(--color-ph-border)",
                      borderRadius: 5,
                      padding: "3px 6px",
                    }}>
                      <div style={{ fontSize: "0.6rem", fontWeight: 700, color: "var(--color-ph-label)", textTransform: "uppercase", letterSpacing: "0.05em" }}>
                        Passholder
                      </div>
                      <div style={{ fontSize: "0.65rem", color: "var(--color-ph-hours)", marginTop: 2 }}>
                        {dayData.hoursLabel}
                      </div>
                    </div>
                  ) : isOpen ? (
                    <div style={{
                      background: "var(--color-open-bg)",
                      border: "1px solid var(--color-open-border)",
                      borderRadius: 5,
                      padding: "3px 6px",
                    }}>
                      <div style={{ fontSize: "0.65rem", color: "var(--color-open-hours)" }}>
                        {dayData.hoursLabel}
                      </div>
                    </div>
                  ) : (
                    <span style={{ fontSize: "1rem", color: "var(--color-text-dim)", lineHeight: 1 }}>·</span>
                  )}
                </div>
              );
            })}
          </div>
        ))}
      </div>
    </div>
  );
}

const navLinkStyle: React.CSSProperties = {
  display: "inline-flex",
  alignItems: "center",
  justifyContent: "center",
  padding: "6px 14px",
  borderRadius: 6,
  border: "1px solid var(--color-border)",
  background: "var(--color-surface)",
  color: "var(--color-text-muted)",
  fontSize: "1rem",
  lineHeight: 1,
  textDecoration: "none",
};