/** Keyboard-shortcut overlay (`?`), the web counterpart of the TUI's help
 *  overlay. One registry drives both the rendering and what we claim is bound,
 *  so a binding added to `main.ts` without an entry here reads as missing. */

export interface Shortcut {
  /** Keycaps, rendered left to right as separate <kbd>. */
  keys: string[];
  description: string;
}

export interface ShortcutGroup {
  title: string;
  items: Shortcut[];
}

export const SHORTCUTS: ShortcutGroup[] = [
  {
    title: "Sessions",
    items: [
      { keys: ["n"], description: "Open the spawn form" },
      { keys: ["N"], description: "Spawn a session with every default resolved" },
    ],
  },
  {
    title: "Session list",
    items: [
      {
        keys: ["Ctrl", "Shift", "H"],
        description: "Move the keyboard between the session list and the pane",
      },
      { keys: ["j"], description: "Highlight the next session" },
      { keys: ["k"], description: "Highlight the previous session" },
      { keys: ["Enter"], description: "Open the highlighted session, or expand a folder" },
      { keys: ["c"], description: "Collapse or expand the highlighted folder" },
      { keys: ["r"], description: "Rename the highlighted session" },
      { keys: ["x"], description: "Kill the highlighted session" },
      { keys: ["Tab"], description: "Send the keyboard to the pane" },
      { keys: ["Esc"], description: "Hand the keyboard back to the session list, from the pane" },
    ],
  },
  {
    title: "Help",
    items: [
      { keys: ["?"], description: "Show or hide this help" },
      { keys: ["Esc"], description: "Close the help overlay or an open menu" },
    ],
  },
  {
    title: "Debug",
    items: [{ keys: ["Ctrl", "Shift", "D"], description: "Toggle the debug HUD" }],
  },
];

/** True when the event target swallows plain keystrokes — a form field, or the
 *  hidden textarea xterm types into. Shared with `main.ts` so every global
 *  single-key binding is deaf in the same places. */
export function isTypingTarget(target: EventTarget | null): boolean {
  const el = target as HTMLElement | null;
  if (!el || typeof el.tagName !== "string") return false;
  return (
    el.tagName === "INPUT" ||
    el.tagName === "TEXTAREA" ||
    el.tagName === "SELECT" ||
    el.isContentEditable
  );
}

let open: { el: HTMLElement; dispose: () => void } | null = null;

export function isHelpOpen(): boolean {
  return open !== null;
}

export function closeHelp(): void {
  open?.dispose();
}

export function toggleHelp(): void {
  if (open) closeHelp();
  else openHelp();
}

/** Mount the overlay. Opening while already open is a no-op re-render, so a
 *  stray second call can never stack two dialogs. */
export function openHelp(): HTMLElement {
  closeHelp();

  const el = document.createElement("div");
  el.className = "help-overlay";
  el.setAttribute("role", "dialog");
  el.setAttribute("aria-modal", "true");
  el.setAttribute("aria-label", "Keyboard shortcuts");

  const panel = document.createElement("div");
  panel.className = "help-panel";

  const head = document.createElement("header");
  head.className = "help-head";
  const title = document.createElement("h2");
  title.className = "help-title";
  title.textContent = "Keyboard shortcuts";
  const close = document.createElement("button");
  close.type = "button";
  close.className = "help-close";
  close.setAttribute("aria-label", "Close");
  close.textContent = "✕";
  close.addEventListener("click", closeHelp);
  head.append(title, close);
  panel.appendChild(head);

  for (const group of SHORTCUTS) {
    const section = document.createElement("section");
    section.className = "help-group";
    const heading = document.createElement("h3");
    heading.className = "help-group-title";
    heading.textContent = group.title;
    const list = document.createElement("dl");
    list.className = "help-list";
    for (const item of group.items) {
      const row = document.createElement("div");
      row.className = "help-row";
      const keys = document.createElement("dt");
      keys.className = "help-keys";
      for (const key of item.keys) {
        const cap = document.createElement("kbd");
        cap.textContent = key;
        keys.appendChild(cap);
      }
      const desc = document.createElement("dd");
      desc.className = "help-desc";
      desc.textContent = item.description;
      row.append(keys, desc);
      list.appendChild(row);
    }
    section.append(heading, list);
    panel.appendChild(section);
  }

  // A press on the scrim closes; one inside the panel is left alone.
  el.addEventListener("click", (ev) => {
    if (!panel.contains(ev.target as Node)) closeHelp();
  });
  el.appendChild(panel);
  document.body.appendChild(el);

  const dispose = () => {
    if (open?.el !== el) return;
    open = null;
    el.remove();
  };
  open = { el, dispose };
  close.focus();
  return el;
}

let installed = false;

/** Global keybind: `?` toggles the overlay, Escape closes it. Idempotent, so a
 *  second call during a hot reload doesn't double-toggle. */
export function installHelpKeybind(): void {
  if (installed) return;
  installed = true;
  window.addEventListener("keydown", (e) => {
    if (e.key === "Escape" && open) {
      e.preventDefault();
      closeHelp();
      return;
    }
    // Shift is how `?` is typed on most layouts; the others would be a
    // different binding entirely.
    if (e.key !== "?" || e.ctrlKey || e.altKey || e.metaKey) return;
    if (isTypingTarget(e.target)) return;
    e.preventDefault();
    toggleHelp();
  });
}