import type { Unsubscribe } from "./shell/workbench.ts";

/**
 * The file access the stock views need. It stands in for the kernel's filesystem and the Loro docs
 * behind it (D16); views keep no state of their own beyond what is on screen (D11).
 */
export interface Files {
  list(): string[];
  read(path: string): string | undefined;
  write(path: string, text: string): void;
  /** Calls `listener` with the path of every write. */
  watch(listener: (path: string) => void): Unsubscribe;
}

export function memoryFiles(initial: Record<string, string>): Files {
  const files = new Map(Object.entries(initial));
  const listeners = new Set<(path: string) => void>();
  return {
    list: () => [...files.keys()].sort(),
    read: (path) => files.get(path),
    write(path, text) {
      files.set(path, text);
      for (const listener of listeners) listener(path);
    },
    watch(listener) {
      listeners.add(listener);
      return () => listeners.delete(listener);
    },
  };
}