function createHeadDoc(options: { workspaceId: string }) {
	const { workspaceId } = options;

	/**
	 * Get the current epoch number.
	 *
	 * Computes the maximum of all client-proposed epochs.
	 * This ensures concurrent bumps converge to the same version.
	 *
	 * @returns The current epoch (0 if no bumps have occurred)
	 */
	function getEpoch(): number {
		let max = 0;
		for (const value of epochsMap.values()) {
			max = Math.max(max, value);
		}
		return max;
	}

	return {
		workspaceId,
		getEpoch, // JSDoc is NOT visible when hovering on returned object!

		bumpEpoch(): number {
			const next = getEpoch() + 1; // Calling internal helper
			return next;
		},
	};
}

function createHeadDoc(options: { workspaceId: string }) {
	const { workspaceId } = options;

	return {
		workspaceId,

		/**
		 * Get the current epoch number.
		 *
		 * Computes the maximum of all client-proposed epochs.
		 * This ensures concurrent bumps converge to the same version.
		 *
		 * @returns The current epoch (0 if no bumps have occurred)
		 */
		getEpoch(): number {
			let max = 0;
			for (const value of epochsMap.values()) {
				max = Math.max(max, value);
			}
			return max;
		},

		bumpEpoch(): number {
			const next = this.getEpoch() + 1; // Use this.methodName()
			return next;
		},
	};
}

// BAD: Helper defined separately, JSDoc lost on return
function createService(client) {
  /** Fetches user data with caching. */
  function fetchUser(id: string) { ... }

  return {
    fetchUser,  // JSDoc not visible to consumers!
    getProfile(id: string) {
      return fetchUser(id);  // Works, but consumers can't see docs
    },
  };
}

// GOOD: Method shorthand, JSDoc preserved
function createService(client) {
  return {
    /** Fetches user data with caching. */
    fetchUser(id: string) { ... },

    getProfile(id: string) {
      return this.fetchUser(id);  // Use this.method()
    },
  };
}

// BAD: Arrow function, this is undefined
return {
  getEpoch: () => { ... },
  bumpEpoch: () => {
    this.getEpoch();  // ERROR: this is undefined!
  },
};

// GOOD: Method shorthand has correct this binding
return {
  getEpoch() { ... },
  bumpEpoch() {
    this.getEpoch();  // Works!
  },
};

export function createHeadDoc(options: { workspaceId: string; ydoc?: Y.Doc }) {
	const { workspaceId } = options;
	const ydoc = options.ydoc ?? new Y.Doc({ guid: workspaceId });
	const epochsMap = ydoc.getMap<number>('epochs');

	return {
		ydoc,
		workspaceId,

		/**
		 * Get the current epoch number.
		 *
		 * Computes the maximum of all client-proposed epochs.
		 * This ensures concurrent bumps converge to the same version
		 * without skipping epoch numbers.
		 *
		 * @returns The current epoch (0 if no bumps have occurred)
		 */
		getEpoch(): number {
			let max = 0;
			for (const value of epochsMap.values()) {
				max = Math.max(max, value);
			}
			return max;
		},

		/**
		 * Bump the epoch to the next version.
		 *
		 * @returns The new epoch number after bumping
		 */
		bumpEpoch(): number {
			const next = this.getEpoch() + 1;
			epochsMap.set(ydoc.clientID.toString(), next);
			return next;
		},

		// ... other methods using this.getEpoch()
	};
}