import type { RpcClient } from "@neoinkjs/rpc";
import type { Nvim } from "./index";
import { subscribeNotification } from "./notify";

/**
 * The RPC method name the `VimResized` autocmd fires via `rpcnotify`, and the
 * method the host filters for. Single source of truth so the autocmd command
 * and the subscriber (`render.ts`) can never drift apart — mirrors
 * `NEOINK_INPUT_METHOD` in `input.ts`.
 */
export const NEOINK_RESIZE_METHOD = "neoink_resize";

/**
 * The Ex command a `VimResized` autocmd runs: notifies the host with the
 * NEW width. `&columns` is read at the moment the autocmd fires — i.e.
 * already the post-resize value — so the host never needs a follow-up
 * request to learn the new width; it arrives as the notification's only
 * argument.
 */
function buildAutocmdCommand(channelId: number): string {
  return `call rpcnotify(${channelId}, '${NEOINK_RESIZE_METHOD}', &columns)`;
}

/**
 * Registers the `VimResized` autocmd that reports terminal/UI width changes
 * to the host — Ink parity: Ink listens for its stdout's `'resize'` event;
 * neoink has no such stream, so it listens for Neovim's own resize signal
 * instead. Returns the autocmd id, which `uninstallResizeAutocmd` accepts to
 * tear it back down (`render.ts` does this on unmount).
 */
export async function installResizeAutocmd(nvim: Nvim, channelId: number): Promise<number> {
  return nvim.createAutocmd("VimResized", buildAutocmdCommand(channelId));
}

/** Removes a resize autocmd previously installed by `installResizeAutocmd`. */
export async function uninstallResizeAutocmd(nvim: Nvim, autocmdId: number): Promise<void> {
  await nvim.deleteAutocmd(autocmdId);
}

/**
 * Routes `neoink_resize` notifications on `client` to `handler` with just the
 * new width. Returns an unsubscribe function. Mirrors `subscribeInput`.
 */
export function subscribeResize(client: RpcClient, handler: (columns: number) => void): () => void {
  return subscribeNotification(
    client,
    NEOINK_RESIZE_METHOD,
    (value): value is number => typeof value === "number",
    handler,
  );
}