/**
 * MessageBridge — postMessage protocol between the PDF viewer iframe
 * and the parent Leptos application.
 *
 * Inbound  (parent → iframe): "pdf.page.next" | "pdf.page.prev"
 * Outbound (iframe → parent): { type: "brittle:keydown", key, ctrlKey, ... }
 */
export class MessageBridge {
  /**
   * @param {Function} onPageNext - () => void
   * @param {Function} onPagePrev - () => void
   */
  constructor(onPageNext, onPagePrev) {
    this._handler = ev => {
      if (ev.data === "pdf.page.next") onPageNext();
      if (ev.data === "pdf.page.prev") onPagePrev();
    };
    window.addEventListener("message", this._handler);
  }

  /** Send the current viewer state (zoom + scroll) to the parent window. */
  postViewerState(refId, zoom, scrollTop) {
    if (window.parent === window) return;
    window.parent.postMessage({
      type: "brittle:viewer-state",
      refId,
      zoom,
      scrollTop,
    }, "*");
  }

  /** Forward a keydown event to the parent window for global keybindings. */
  forwardKeydown(ev) {
    if (window.parent === window) return;
    window.parent.postMessage({
      type:     "brittle:keydown",
      key:      ev.key,
      ctrlKey:  ev.ctrlKey,
      shiftKey: ev.shiftKey,
      altKey:   ev.altKey,
      metaKey:  ev.metaKey,
    }, "*");
  }

  disconnect() {
    window.removeEventListener("message", this._handler);
  }
}