misskey/src/server/api/endpoints/drive.ts

import DriveFile from '../../../models/drive-file';
import { ILocalUser } from '../../../models/user';

/**
 * Get drive information
 */
module.exports = (params: any, user: ILocalUser) => new Promise(async (res, rej) => {
	// Calculate drive usage
	const usage = await DriveFile
		.aggregate([{
			$match: {
				'metadata.userId': user._id,
				'metadata.deletedAt': { $exists: false }
			}
		}, {
			$project: {
				length: true
			}
		}, {
			$group: {
				_id: null,
				usage: { $sum: '$length' }
			}
		}])
		.then((aggregates: any[]) => {
			if (aggregates.length > 0) {
				return aggregates[0].usage;
			}
			return 0;
		});

	res({
		capacity: user.driveCapacity,
		usage: usage
	});
});