seyfert/packages/core/src/structures/special/permissions.ts

import { BitwisePermissionFlags } from '@biscuitland/api-types';

export type PermissionString = keyof typeof BitwisePermissionFlags;
export type PermissionResolvable =
	| bigint
	| PermissionString
	| PermissionString[]
	| BitwisePermissionFlags;

export class Permissions {
	static Flags = BitwisePermissionFlags;
	bitfield: bigint;

	constructor(bitfield: PermissionResolvable) {
		this.bitfield = Permissions.resolve(bitfield);
	}

	has(bit: PermissionResolvable): boolean {
		if (this.bitfield & BigInt(Permissions.Flags.ADMINISTRATOR)) {
			return true;
		}

		return !!(this.bitfield & Permissions.resolve(bit));
	}

	static resolve(bit: PermissionResolvable): bigint {
		switch (typeof bit) {
			case 'bigint':
				return bit;
			case 'number':
				return BigInt(bit);
			case 'string':
				return BigInt(Permissions.Flags[bit]);
			case 'object':
				return Permissions.resolve(
					bit
						.map(p => BigInt(Permissions.Flags[p]))
						.reduce((acc, cur) => acc | cur, 0n)
				);
			default:
				throw new TypeError(`Cannot resolve permission: ${bit}`);
		}
	}

    toJSON(): { fields: string[] } {
        const fields = Object.keys(Permissions.Flags).filter((bit) => typeof bit !== 'string' && this.has(bit));

        return { fields };
    }
}