/**
 * Protobuf does not allow "required" objects in messages. As a result, all TS interfaces generated from protobuf messages
 * have all fields pointing to objects as potentially undefined. This is a problem for us because we need to add
 * unnecessary checks for undefined fields in our code. Those transformers cast the generated interfaces to interfaces
 * with object fields being required.
 */

type NonUndefined<T> = T extends undefined ? never : T;
export type NonUndefinedFields<T> = {
    [K in keyof T]: NonUndefined<T[K]>;
};

export type RequiredFields<T, K extends keyof T> = Omit<T, K> & NonUndefinedFields<Pick<T, K>>;

export function noUndefinedForKeys<T, K extends keyof T>(message: T, fields: K[]): RequiredFields<T, K> {
    for (const field of fields) {
        if (message[field] === undefined) {
            throw new Error(`${String(field)} is required`);
        }
    }
    return message as RequiredFields<T, K>;
}

/**
 * Checks that all fields of the message are not undefined and casts the message to a type where all fields are required.
 */
export function noUndefined<T>(message: T): NonUndefinedFields<T> {
    for (const key in message) {
        if (message[key] === undefined) {
            throw new Error(`${key} is required`);
        }
    }
    return message as NonUndefinedFields<T>;
}