import { useEffect, useMemo, useRef, useState } from "react";
import { createPortal } from "react-dom";
import { useTranslation } from "react-i18next";
import Icon from "./Icon";
import IconChip from "./IconChip";

// Auf-/zuklappbares Kategorie-Dropdown (Gruppe -> Kategorien als Baum) mit
// Suchfeld. Ersetzt das native <select> mit optgroup, das die oberste Gruppe
// abgesetzt wirken ließ. Das Panel wird per Portal mit fester Position gerendert,
// damit es in scrollbaren Tabellen (Import-Prüfansicht) nicht abgeschnitten wird.
export default function CategorySelect({
  groups = [],
  value,
  onChange,
  allowNone = false,
  noneLabel = "—",
  placeholder = "—",
  minWidth = 0,
  disabled = false,
}) {
  const { t } = useTranslation();
  const selectedId = value === "" || value == null ? null : Number(value);

  const [open, setOpen] = useState(false);
  const [q, setQ] = useState("");
  const [collapsed, setCollapsed] = useState(() => new Set());
  const [pos, setPos] = useState(null);

  const btnRef = useRef(null);
  const panelRef = useRef(null);
  const searchRef = useRef(null);

  const byId = useMemo(() => {
    const m = {};
    for (const g of groups) for (const c of g.categories) m[c.id] = c;
    return m;
  }, [groups]);
  const sel = selectedId != null ? byId[selectedId] : null;

  function computePos() {
    const el = btnRef.current;
    if (!el) return;
    const r = el.getBoundingClientRect();
    const width = Math.max(r.width, 260);
    const spaceBelow = window.innerHeight - r.bottom;
    const spaceAbove = r.top;
    const desired = 340;
    let top;
    let maxHeight;
    if (spaceBelow >= 220 || spaceBelow >= spaceAbove) {
      maxHeight = Math.min(desired, spaceBelow - 10);
      top = r.bottom + 4;
    } else {
      maxHeight = Math.min(desired, spaceAbove - 10);
      top = r.top - 4 - maxHeight;
    }
    let left = r.left;
    if (left + width > window.innerWidth - 8) left = window.innerWidth - 8 - width;
    if (left < 8) left = 8;
    setPos({ left, top, width, maxHeight });
  }

  function openPanel() {
    if (disabled) return;
    computePos();
    setQ("");
    setOpen(true);
  }

  useEffect(() => {
    if (!open) return undefined;
    searchRef.current?.focus();
    const onDown = (e) => {
      if (panelRef.current?.contains(e.target) || btnRef.current?.contains(e.target)) return;
      setOpen(false);
    };
    const onKey = (e) => e.key === "Escape" && setOpen(false);
    const onScrollResize = () => setOpen(false);
    document.addEventListener("mousedown", onDown);
    document.addEventListener("keydown", onKey);
    // capture=true: fängt auch das Scrollen innerhalb der Tabelle ab.
    window.addEventListener("scroll", onScrollResize, true);
    window.addEventListener("resize", onScrollResize);
    return () => {
      document.removeEventListener("mousedown", onDown);
      document.removeEventListener("keydown", onKey);
      window.removeEventListener("scroll", onScrollResize, true);
      window.removeEventListener("resize", onScrollResize);
    };
  }, [open]);

  function choose(id) {
    onChange(id);
    setOpen(false);
  }
  function toggleGroup(id) {
    setCollapsed((prev) => {
      const next = new Set(prev);
      next.has(id) ? next.delete(id) : next.add(id);
      return next;
    });
  }

  const ql = q.trim().toLowerCase();

  return (
    <div className="catsel" style={{ minWidth }}>
      <button
        type="button"
        ref={btnRef}
        className={`catsel-btn${open ? " open" : ""}`}
        onClick={() => (open ? setOpen(false) : openPanel())}
        disabled={disabled}
      >
        {sel ? (
          <span className="catsel-value">
            <IconChip name={sel.icon} color={sel.color} size={22} />
            <span className="ellipsis">{sel.name}</span>
          </span>
        ) : (
          <span className="catsel-value muted ellipsis">{placeholder}</span>
        )}
        <Icon name="chevron-down" size={15} className="catsel-caret" />
      </button>

      {open &&
        pos &&
        createPortal(
          <div
            ref={panelRef}
            className="catsel-panel"
            style={{ left: pos.left, top: pos.top, width: pos.width, maxHeight: pos.maxHeight }}
          >
            <div className="catsel-search">
              <Icon name="search" size={14} />
              <input
                ref={searchRef}
                value={q}
                onChange={(e) => setQ(e.target.value)}
                placeholder={t("categories.searchPlaceholder")}
              />
            </div>
            <div className="catsel-list">
              {allowNone && (
                <button
                  type="button"
                  className={`catsel-opt${selectedId == null ? " selected" : ""}`}
                  onClick={() => choose(null)}
                >
                  <span className="muted ellipsis">{noneLabel}</span>
                  {selectedId == null && <Icon name="check" size={15} className="catsel-check" />}
                </button>
              )}
              {groups.map((g) => {
                const cats = ql
                  ? g.categories.filter((c) => c.name.toLowerCase().includes(ql))
                  : g.categories;
                if (ql && cats.length === 0) return null;
                const isCollapsed = !ql && collapsed.has(g.id);
                return (
                  <div className="catsel-group" key={g.id}>
                    <button
                      type="button"
                      className="catsel-group-head"
                      onClick={() => toggleGroup(g.id)}
                    >
                      <Icon
                        name="chevron-down"
                        size={14}
                        className={`catsel-gchev${isCollapsed ? " collapsed" : ""}`}
                      />
                      <IconChip name={g.icon} color={g.color} size={18} />
                      <span className="ellipsis">{g.name}</span>
                    </button>
                    {!isCollapsed &&
                      cats.map((c) => (
                        <button
                          type="button"
                          key={c.id}
                          className={`catsel-opt${selectedId === c.id ? " selected" : ""}`}
                          onClick={() => choose(c.id)}
                        >
                          <IconChip name={c.icon} color={c.color} size={20} />
                          <span className="ellipsis">{c.name}</span>
                          {selectedId === c.id && <Icon name="check" size={15} className="catsel-check" />}
                        </button>
                      ))}
                  </div>
                );
              })}
              {groups.length === 0 && <div className="catsel-empty muted small">{t("categories.emptyGroup")}</div>}
            </div>
          </div>,
          document.body
        )}
    </div>
  );
}