"use client";

import { useState, useMemo } from "react";
import { useRouter } from "next/navigation";
import { Loader2, AlertCircle } from "lucide-react";

type AssetOption = { id: string; code: string; name: string; category: string };

// Books one invoice line to a plant item from the register.
//
// Saves immediately on change — there is no separate "save" button to miss on a phone.
// On success it refreshes the router so the server-rendered header, banner and totals
// re-read from PocketBase rather than showing stale booking state.
export function BookingSelect({
  lineId,
  value,
  assets,
}: {
  lineId: string;
  value: string;
  assets: AssetOption[];
}) {
  const router = useRouter();
  const [current, setCurrent] = useState(value);
  const [saving, setSaving] = useState(false);
  const [error, setError] = useState<string | null>(null);

  // 44 plant items flat in one dropdown is unusable — group them by category.
  const groups = useMemo(() => {
    const byCategory = new Map<string, AssetOption[]>();
    for (const a of assets) {
      const key = a.category || "Other";
      if (!byCategory.has(key)) byCategory.set(key, []);
      byCategory.get(key)!.push(a);
    }
    return Array.from(byCategory.entries())
      .map(([category, items]) => ({ category, items: items.sort((x, y) => x.code.localeCompare(y.code)) }))
      .sort((a, b) => a.category.localeCompare(b.category));
  }, [assets]);

  async function book(assetId: string) {
    const previous = current;
    setSaving(true);
    setError(null);
    setCurrent(assetId); // optimistic
    try {
      const res = await fetch(`/api/invoice-lines/${lineId}/book`, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ assetId }),
      });
      const data = await res.json().catch(() => ({ ok: false, error: "Unexpected response" }));
      if (!data.ok) {
        setCurrent(previous); // roll back so the UI never claims a booking that failed
        setError(data.error || "Booking failed");
      } else {
        router.refresh(); // re-read server-rendered banner/totals
      }
    } catch {
      setCurrent(previous);
      setError("Could not reach the server");
    } finally {
      setSaving(false);
    }
  }

  return (
    <div>
      <div className="flex items-center gap-2">
        <label className="sr-only" htmlFor={`book-${lineId}`}>
          Book this line to a plant item
        </label>
        <select
          id={`book-${lineId}`}
          value={current}
          disabled={saving}
          onChange={(e) => book(e.target.value)}
          className={`min-h-[44px] w-full rounded-lg border px-2 text-sm transition focus:outline-none focus:border-[#30638E] disabled:opacity-60 ${
            current
              ? "border-[#00798C]/30 bg-[#00798C]/5 text-[#003D5B] dark:text-white"
              : "border-[#D1495B]/40 bg-[#D1495B]/5 text-[#D1495B]"
          }`}
        >
          <option value="">— Not booked —</option>
          {groups.map((g) => (
            <optgroup key={g.category} label={g.category}>
              {g.items.map((a) => (
                <option key={a.id} value={a.id}>
                  {a.code} · {a.name}
                </option>
              ))}
            </optgroup>
          ))}
        </select>
        {saving && <Loader2 className="w-4 h-4 animate-spin text-[#00798C] shrink-0" aria-label="Saving" />}
      </div>
      {error && (
        <p className="flex items-start gap-1 text-sm text-[#D1495B] mt-1">
          <AlertCircle className="w-3.5 h-3.5 mt-0.5 shrink-0" />
          {error}
        </p>
      )}
    </div>
  );
}