"use client";

import { useState, useRef, useEffect, useMemo, useLayoutEffect } from "react";
import { createPortal } from "react-dom";
import { useRouter } from "next/navigation";
import { Loader2, AlertCircle, ChevronDown, Check, Search, X } from "lucide-react";

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

// A searchable replacement for the native <select> of 44 machines.
//
// A native select cannot be filtered, so finding "TLB07" meant scrolling a list that
// repeats two dozen near-identical "CASE TLB" entries. This filters as you type, on
// either the code or the name, and still behaves like a select: opening it, arrowing,
// Enter to choose, Escape to cancel, and a clear option.
//
// Keyboard and touch are both first-class — arrows move the highlighted row, the list
// scrolls, and every row is a 44px target so it is usable on a phone.
export function MachineCombobox({
  lineId,
  value,
  machines,
  lineCode,
  lineDescription,
}: {
  lineId: string;
  value: string;
  machines: Machine[];
  // The invoice's own words for this line. The register rarely uses them: an invoice
  // says "CB22 2.2 TON Roller Vibration" where the asset is filed as "CAT 2,4TON RV",
  // so searching on the register alone would never connect the two.
  lineCode?: string;
  lineDescription?: string;
}) {
  const router = useRouter();
  const [query, setQuery] = useState("");
  const [open, setOpen] = useState(false);
  const [busy, setBusy] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const [highlight, setHighlight] = useState(0);
  const boxRef = useRef<HTMLDivElement>(null);
  const menuRef = useRef<HTMLDivElement>(null);
  const inputRef = useRef<HTMLInputElement>(null);
  const listRef = useRef<HTMLUListElement>(null);
  // The line table lives inside an overflow-x-auto scroll container, which CLIPS any
  // absolutely-positioned child — an in-place dropdown is cut off by the table edge and
  // by the card. Rendering into <body> with viewport coordinates is the only way out.
  const [anchor, setAnchor] = useState<{ top: number; left: number; width: number } | null>(null);

  const selected = machines.find((m) => m.id === value) || null;

  useLayoutEffect(() => {
    if (!open || !inputRef.current) {
      setAnchor(null);
      return;
    }
    const measure = () => {
      const r = inputRef.current?.getBoundingClientRect();
      if (r) setAnchor({ top: r.bottom, left: r.left, width: r.width });
    };
    measure();
    // Follow the page: the table scrolls, and so does the window.
    window.addEventListener("scroll", measure, true);
    window.addEventListener("resize", measure);
    return () => {
      window.removeEventListener("scroll", measure, true);
      window.removeEventListener("resize", measure);
    };
  }, [open]);

  // Flattened, filtered list — the flat order is what the keyboard walks.
  const groups = useMemo(() => {
    const q = query.trim().toLowerCase();
    // Anything the invoice calls this line is searchable too, so "skidsteer" or
    // "CB22" finds the machine even though neither word is in the register's name.
    const extra = [lineCode, lineDescription].filter(Boolean).join(" ").toLowerCase();
    const hit = (m: Machine) => {
      if (!q) return true;
      if (m.code.toLowerCase().includes(q) || m.name.toLowerCase().includes(q) || m.category.toLowerCase().includes(q))
        return true;
      return extra.length > 0 && extra.includes(q);
    };
    const matched = machines.filter(hit);
    const byCategory = new Map<string, Machine[]>();
    for (const m of matched) {
      if (!byCategory.has(m.category)) byCategory.set(m.category, []);
      byCategory.get(m.category)!.push(m);
    }
    return {
      list: Array.from(byCategory.entries())
        .sort((a, b) => a[0].localeCompare(b[0]))
        .map(([category, items]) => ({
          category,
          items: items.sort((a, b) => a.code.localeCompare(b.code)),
        })),
      flat: Array.from(byCategory.values())
        .flat()
        .sort((a, b) => a.code.localeCompare(b.code)),
    };
  }, [machines, query, lineCode, lineDescription]);

  const menuWidth = 300;
  // ~16px count strip + a "Not booked" row (if any) + 12px per row, capped.
  const menuHeight = useMemo(() => {
    const rows = groups.flat.length;
    return 44 + (value ? 44 : 0) + 24 + Math.min(rows, 8) * 44 + 8;
  }, [groups.flat.length, value]);

  const flipUp = useMemo(() => {
    if (typeof window === "undefined" || !anchor) return false;
    return anchor.top + menuHeight + 8 > window.innerHeight && anchor.top - menuHeight - 8 > 8;
  }, [anchor, menuHeight]);


  // Click away closes.
  //
  // The menu is PORTALED into <body>, so it is not a DOM descendant of boxRef. Testing
  // `boxRef.contains(target)` alone therefore reported every option as an outside
  // click: mousedown closed the menu, React unmounted the button, and the click that
  // would have booked it never landed. Selecting a machine silently did nothing. The
  // menu has to be treated as part of the control.
  useEffect(() => {
    if (!open) return;
    const onDown = (e: MouseEvent) => {
      const t = e.target as Node;
      if (boxRef.current?.contains(t)) return;
      if (menuRef.current?.contains(t)) return;
      setOpen(false);
    };
    document.addEventListener("mousedown", onDown);
    return () => document.removeEventListener("mousedown", onDown);
  }, [open]);

  // Keep the highlighted row inside the results after each keystroke.
  useEffect(() => {
    setHighlight((h) => Math.min(h, Math.max(0, groups.flat.length - 1)));
  }, [groups.flat.length]);

  // Scroll the highlighted row into view.
  useEffect(() => {
    if (!open || !listRef.current) return;
    const el = listRef.current.querySelector<HTMLElement>(`[data-idx="${highlight}"]`);
    el?.scrollIntoView({ block: "nearest" });
  }, [highlight, open]);

  async function book(id: string) {
    setBusy(true);
    setError(null);
    try {
      const res = await fetch(`/api/invoice-lines/${lineId}/book`, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ assetId: id }),
      });
      const data = await res.json().catch(() => ({ ok: false, error: "Unexpected response" }));
      if (!data.ok) setError(data.error || "Could not book it");
      else {
        setOpen(false);
        setQuery("");
        router.refresh();
      }
    } catch {
      setError("Could not reach the server");
    } finally {
      setBusy(false);
    }
  }

  function onKeyDown(e: React.KeyboardEvent) {
    if (e.key === "Escape") {
      setOpen(false);
      setQuery("");
      return;
    }
    if (e.key === "Enter") {
      e.preventDefault();
      const pick = groups.flat[highlight];
      if (pick) book(pick.id);
      return;
    }
    if (e.key === "ArrowDown" || e.key === "ArrowUp") {
      e.preventDefault();
      if (!open) {
        setOpen(true);
        return;
      }
      const n = groups.flat.length;
      if (!n) return;
      setHighlight((h) => (e.key === "ArrowDown" ? (h + 1) % n : (h - 1 + n) % n));
    }
  }

  return (
    <div ref={boxRef} className="relative min-w-[200px]">
      <div className="flex items-center gap-2">
        <div className="relative flex-1">
          <Search className="w-3.5 h-3.5 absolute left-2.5 top-1/2 -translate-y-1/2 text-gray-400 pointer-events-none" />
          <input
            ref={inputRef}
            type="text"
            role="combobox"
            aria-expanded={open}
            aria-autocomplete="list"
            aria-controls={`machine-list-${lineId}`}
            value={open ? query : selected ? `${selected.code} · ${selected.name}` : ""}
            placeholder="Search machines…"
            onFocus={() => setOpen(true)}
            onChange={(e) => {
              setQuery(e.target.value);
              setOpen(true);
              setHighlight(0);
            }}
            onKeyDown={onKeyDown}
            className={`min-h-[44px] w-full pl-8 pr-8 rounded-lg border text-sm transition focus:outline-none focus:border-[#30638E] ${
              selected
                ? "border-[#00798C]/30 bg-[#00798C]/5 text-[#003D5B] dark:text-white font-medium"
                : "border-[#D1495B]/40 bg-[#D1495B]/5 text-[#D1495B]"
            }`}
          />
          {busy ? (
            <Loader2 className="w-4 h-4 animate-spin text-[#00798C] absolute right-2.5 top-1/2 -translate-y-1/2" />
          ) : (
            <ChevronDown
              className={`w-4 h-4 absolute right-2.5 top-1/2 -translate-y-1/2 text-gray-400 transition-transform pointer-events-none ${
                open ? "rotate-180" : ""
              }`}
            />
          )}
        </div>
        {selected && !busy && (
          <button
            type="button"
            onClick={() => book("")}
            aria-label="Clear the machine booking"
            className="grid place-items-center w-11 h-11 rounded-lg text-gray-500 hover:bg-gray-100 dark:hover:bg-white/5 transition shrink-0"
          >
            <X className="w-4 h-4" />
          </button>
        )}
      </div>

      {open && anchor && createPortal(
        <div
          ref={menuRef}
          style={{
            position: "fixed",
            top: flipUp ? Math.max(8, anchor.top - menuHeight - 6) : anchor.top + 4,
            left: Math.min(anchor.left, window.innerWidth - menuWidth - 8),
            width: Math.max(anchor.width, menuWidth),
            zIndex: 1300,
          }}
          className="rounded-xl bg-white dark:bg-surface border border-gray-200 dark:border-white/10 shadow-2xl overflow-hidden"
        >
          <div className="px-3 py-2 text-xs text-gray-500 dark:text-gray-400 border-b border-gray-100 dark:border-white/5">
            {groups.flat.length} of {machines.length} machines
            {!selected && " · search a code, name or the invoice description"}
          </div>

          {value && (
            <ul>
              <li>
                <button
                  type="button"
                  onClick={() => book("")}
                  className="w-full min-h-[44px] px-3 py-2 text-left text-sm text-gray-500 dark:text-gray-400 hover:bg-gray-50 dark:hover:bg-white/5 flex items-center gap-2"
                >
                  <X className="w-3.5 h-3.5" />
                  Not booked
                </button>
              </li>
            </ul>
          )}

          {groups.flat.length === 0 ? (
            <p className="px-3 py-4 text-sm text-gray-500 dark:text-gray-400">
              No machine matches “{query}”.
            </p>
          ) : (
            <ul ref={listRef} id={`machine-list-${lineId}`} className="max-h-64 overflow-y-auto py-1">
              {groups.list.map((g) => (
                <li key={g.category}>
                  <div className="px-3 pt-2 pb-1 text-xs font-semibold uppercase tracking-wider text-gray-400 dark:text-gray-500">
                    {g.category}
                  </div>
                  <ul>
                    {g.items.map((m) => {
                      const idx = groups.flat.indexOf(m);
                      const isSel = m.id === value;
                      return (
                        <li key={m.id}>
                          <button
                            type="button"
                            data-idx={idx}
                            onMouseEnter={() => setHighlight(idx)}
                            onClick={() => book(m.id)}
                            className={`w-full min-h-[44px] px-3 py-2 text-left text-sm flex items-center gap-2 transition ${
                              idx === highlight
                                ? "bg-[#00798C]/10 text-[#003D5B] dark:text-white"
                                : "text-gray-600 dark:text-gray-300"
                            }`}
                          >
                            <span className="font-mono text-xs font-semibold text-[#00798C] w-16 shrink-0">
                              {m.code || "—"}
                            </span>
                            <span className="truncate">{m.name}</span>
                            {isSel && <Check className="w-4 h-4 text-[#00798C] ml-auto shrink-0" />}
                          </button>
                        </li>
                      );
                    })}
                  </ul>
                </li>
              ))}
            </ul>
          )}
        </div>,
        document.body,
      )}

      {error && (
        <p className="mt-1 flex items-start gap-1 text-sm text-[#D1495B]">
          <AlertCircle className="w-3.5 h-3.5 mt-0.5 shrink-0" />
          {error}
        </p>
      )}
    </div>
  );
}