import { useEffect, useRef, useState } from "react";
import { api, CardRef, Deck } from "./api";
import { DialogFrame, useClickPreview } from "./components";

// Kept in step with App.tsx's Tab union by hand — it isn't exported.
type Tab = "add" | "library" | "search" | "decks" | "game" | "news" | "info";

interface PaletteItem {
  key: string;
  label: string;
  hint?: string;
  run: () => void;
}

/** Simple, dependency-free case-insensitive subsequence match — e.g. "gtd"
 * matches "Go to Decks". Good enough for the small static command list and
 * the deck list; card search still defers to the server-side fuzzy matcher
 * via `api.searchCards`. */
function subsequenceMatch(query: string, text: string): boolean {
  if (!query) return true;
  const q = query.toLowerCase();
  const t = text.toLowerCase();
  let qi = 0;
  for (let ti = 0; ti < t.length && qi < q.length; ti++) {
    if (t[ti] === q[qi]) qi++;
  }
  return qi === q.length;
}

/**
 * Alt+/ opens a fuzzy-searchable palette of navigation commands, decks, and
 * cards. Selecting a deck switches to the Decks tab with it pre-selected;
 * selecting a card opens the existing click-to-zoom preview modal without
 * changing tabs. When an undoable action's grace window hasn't lapsed yet,
 * an "Undo: …" entry is listed first, so Alt+/ then Enter is a fast way to
 * undo without hunting for the floating snackbar's button.
 */
export function CommandPalette({
  onNavigate,
  onUpdateCardData,
  onSyncNow,
  undo,
  onRunUndo,
}: {
  onNavigate: (tab: Tab) => void;
  onUpdateCardData: () => void;
  onSyncNow: () => void;
  /** The most recent undoable action, if its window hasn't lapsed yet. */
  undo: { message: string; run: () => void | Promise<void> } | null;
  onRunUndo: () => void;
}) {
  const [open, setOpen] = useState(false);
  const [query, setQuery] = useState("");
  const [decks, setDecks] = useState<Deck[]>([]);
  const [cardResults, setCardResults] = useState<CardRef[]>([]);
  const [sel, setSel] = useState(0);
  const inputRef = useRef<HTMLInputElement>(null);
  const { open: openCardPreview } = useClickPreview();

  useEffect(() => {
    function onKey(e: KeyboardEvent) {
      if (e.altKey && e.key === "/") {
        e.preventDefault();
        setOpen((o) => !o);
      }
    }
    window.addEventListener("keydown", onKey);
    return () => window.removeEventListener("keydown", onKey);
  }, []);

  useEffect(() => {
    if (!open) return;
    setQuery("");
    setCardResults([]);
    api.listDecks().then(setDecks);
    setTimeout(() => inputRef.current?.focus(), 0);
  }, [open]);

  useEffect(() => {
    if (!open) return;
    const q = query.trim();
    if (!q) return setCardResults([]);
    const t = setTimeout(() => api.searchCards(q, 8).then(setCardResults), 80);
    return () => clearTimeout(t);
  }, [query, open]);

  function close() {
    setOpen(false);
  }

  const staticCommands: PaletteItem[] = [
    ...(undo ? [{ key: "undo", label: `Undo: ${undo.message}`, run: onRunUndo }] : []),
    { key: "nav-add", label: "Go to Add Cards", run: () => onNavigate("add") },
    { key: "nav-library", label: "Go to Library", run: () => onNavigate("library") },
    { key: "nav-search", label: "Go to Card Search", run: () => onNavigate("search") },
    { key: "nav-decks", label: "Go to Decks", run: () => onNavigate("decks") },
    { key: "nav-game", label: "Go to Game night (life counter, dice)", run: () => onNavigate("game") },
    { key: "nav-news", label: "Go to News", run: () => onNavigate("news") },
    { key: "update-card-data", label: "Update card data", run: onUpdateCardData },
    { key: "sync-now", label: "Sync library now", run: onSyncNow },
    { key: "nav-sync", label: "Sync settings", run: () => onNavigate("info") },
  ];

  const items: PaletteItem[] = [
    ...staticCommands.filter((c) => subsequenceMatch(query, c.label)),
    ...decks
      .filter((d) => subsequenceMatch(query, d.name))
      .map((d) => ({
        key: `deck-${d.id}`,
        label: d.name,
        hint: "Deck",
        run: () => {
          // DeckView reads its initial selection from this same
          // localStorage key on mount (usePersistedState("deck-selected"),
          // src/views/DeckView.tsx). App.tsx unmounts/remounts DeckView on
          // tab switch, so writing here before navigating is enough for it
          // to pick up the selection on its next mount.
          localStorage.setItem("deck-selected", JSON.stringify(d.id));
          onNavigate("decks");
        },
      })),
    ...cardResults.map((c) => ({
      key: `card-${c.oracle_id}`,
      label: c.name,
      hint: c.type_line,
      run: () => openCardPreview(c),
    })),
  ].slice(0, 20);

  useEffect(() => setSel(0), [items.length, query]);

  function pick(item: PaletteItem) {
    item.run();
    close();
  }

  function onKeyDown(e: React.KeyboardEvent) {
    if (e.key === "ArrowDown") {
      e.preventDefault();
      setSel((s) => Math.min(s + 1, items.length - 1));
    } else if (e.key === "ArrowUp") {
      e.preventDefault();
      setSel((s) => Math.max(s - 1, 0));
    } else if (e.key === "Enter" && items[sel]) {
      e.preventDefault();
      pick(items[sel]);
    }
  }

  if (!open) return null;

  return (
    <DialogFrame title="Command palette" onCancel={close} wide>
      <input
        ref={inputRef}
        autoFocus
        style={{ width: "100%", marginBottom: 8 }}
        placeholder="Type a command, deck, or card name…"
        value={query}
        onChange={(e) => setQuery(e.target.value)}
        onKeyDown={onKeyDown}
      />
      {items.length > 0 && (
        <ul className="result-list" style={{ marginBottom: 0 }}>
          {items.map((item, i) => (
            <li
              key={item.key}
              style={i === sel ? { background: "var(--accent-subtle)" } : undefined}
              onMouseEnter={() => setSel(i)}
              onClick={() => pick(item)}
            >
              <span className="card-name">{item.label}</span>
              {item.hint && <span className="card-type">{item.hint}</span>}
            </li>
          ))}
        </ul>
      )}
    </DialogFrame>
  );
}