"use client";

/**
 * Combobox — a shadcn-style single-select dropdown with optional search.
 *
 * Trigger button shows the selected label (or a placeholder); clicking it
 * opens a panel with an optional search box and a filtered, keyboard-
 * navigable list. Selecting an option calls `onChange(value)` and closes.
 *
 * Notes:
 *   • All state changes happen in event handlers (click / keydown / input)
 *     — never synchronously inside an effect — so opening can't trigger
 *     React's "cascading renders" warning. The only effect just wires the
 *     outside-pointerdown listener.
 *   • `value === ""` is a valid selectable value (e.g. a "Not specified"
 *     option), so the field can represent "cleared".
 *   • The panel is absolutely positioned within a relative wrapper, so the
 *     parent must not clip overflow (forms/cards here don't).
 */

import { useEffect, useMemo, useRef, useState } from "react";
import { Check, ChevronsUpDown, Search } from "lucide-react";
import { cn } from "@/lib/utils";

export type ComboboxOption = { value: string; label: string };

export function Combobox({
  options,
  value,
  onChange,
  placeholder = "Select…",
  searchPlaceholder = "Search…",
  emptyText = "No results.",
  searchable = true,
  disabled = false,
  id,
  ariaLabel,
}: {
  options: ComboboxOption[];
  value: string;
  onChange: (value: string) => void;
  placeholder?: string;
  searchPlaceholder?: string;
  emptyText?: string;
  searchable?: boolean;
  disabled?: boolean;
  id?: string;
  ariaLabel?: string;
}) {
  const [open, setOpen] = useState(false);
  const [query, setQuery] = useState("");
  const [activeIndex, setActiveIndex] = useState(0);
  const rootRef = useRef<HTMLDivElement>(null);
  const inputRef = useRef<HTMLInputElement>(null);

  const selected = options.find((o) => o.value === value) ?? null;

  const filtered = useMemo(() => {
    const q = query.trim().toLowerCase();
    if (!searchable || q === "") return options;
    return options.filter((o) => o.label.toLowerCase().includes(q));
  }, [options, query, searchable]);

  const active =
    filtered.length === 0 ? -1 : Math.min(activeIndex, filtered.length - 1);

  // Close on outside pointerdown. (Listener only — no setState in body.)
  useEffect(() => {
    if (!open) return;
    function onPointer(e: PointerEvent) {
      if (rootRef.current && !rootRef.current.contains(e.target as Node)) {
        setOpen(false);
      }
    }
    document.addEventListener("pointerdown", onPointer);
    return () => document.removeEventListener("pointerdown", onPointer);
  }, [open]);

  function openMenu() {
    setQuery("");
    const i = options.findIndex((o) => o.value === value);
    setActiveIndex(i < 0 ? 0 : i);
    setOpen(true);
    if (searchable) {
      requestAnimationFrame(() => inputRef.current?.focus());
    }
  }

  function toggle() {
    if (disabled) return;
    if (open) setOpen(false);
    else openMenu();
  }

  function select(v: string) {
    onChange(v);
    setOpen(false);
  }

  function onKeyDown(e: React.KeyboardEvent) {
    if (!open) return;
    if (e.key === "ArrowDown") {
      e.preventDefault();
      setActiveIndex((i) => Math.min(i + 1, filtered.length - 1));
    } else if (e.key === "ArrowUp") {
      e.preventDefault();
      setActiveIndex((i) => Math.max(i - 1, 0));
    } else if (e.key === "Enter") {
      e.preventDefault();
      if (active >= 0) select(filtered[active].value);
    } else if (e.key === "Escape") {
      e.preventDefault();
      setOpen(false);
    }
  }

  return (
    <div ref={rootRef} className="relative">
      <button
        type="button"
        id={id}
        aria-label={ariaLabel}
        aria-haspopup="listbox"
        aria-expanded={open}
        disabled={disabled}
        onClick={toggle}
        onKeyDown={onKeyDown}
        className={cn(
          "w-full h-10 flex items-center justify-between gap-2 rounded-md border border-border bg-background px-3 text-sm text-left",
          "outline-none focus-visible:ring-2 focus-visible:ring-primary/40 disabled:opacity-50",
        )}
      >
        <span className={cn("truncate", !selected && "text-muted-foreground")}>
          {selected ? selected.label : placeholder}
        </span>
        <ChevronsUpDown className="size-4 shrink-0 opacity-50" />
      </button>

      {open ? (
        <div className="absolute z-50 mt-1 w-full overflow-hidden rounded-md border border-border bg-card shadow-lg animate-in fade-in-0 zoom-in-95">
          {searchable ? (
            <div className="flex items-center gap-2 border-b border-border px-3">
              <Search className="size-4 shrink-0 text-muted-foreground" />
              <input
                ref={inputRef}
                value={query}
                onChange={(e) => {
                  setQuery(e.target.value);
                  setActiveIndex(0);
                }}
                onKeyDown={onKeyDown}
                placeholder={searchPlaceholder}
                className="w-full h-9 bg-transparent text-sm outline-none placeholder:text-muted-foreground"
              />
            </div>
          ) : null}
          <ul role="listbox" className="max-h-56 overflow-y-auto py-1">
            {filtered.length === 0 ? (
              <li className="px-3 py-2 text-sm text-muted-foreground">
                {emptyText}
              </li>
            ) : (
              filtered.map((o, i) => (
                <li
                  key={o.value || "__empty__"}
                  role="option"
                  aria-selected={o.value === value}
                  onMouseEnter={() => setActiveIndex(i)}
                  onClick={() => select(o.value)}
                  className={cn(
                    "flex items-center justify-between gap-2 px-3 py-2 text-sm cursor-pointer",
                    i === active ? "bg-muted" : "",
                  )}
                >
                  <span className="truncate">{o.label}</span>
                  {o.value === value ? (
                    <Check className="size-4 shrink-0 text-primary" />
                  ) : null}
                </li>
              ))
            )}
          </ul>
        </div>
      ) : null}
    </div>
  );
}