export type DefaultOrFunc<T> = T | (() => T)

/** Get `T` in `DefaultOrFunc<T>` */
export function getDefault<T>(defv: DefaultOrFunc<T>): T {
    if (typeof defv === 'function') return (defv as any)()
    return defv
}

/** Identity function */
export function identity<T>(val: T): T {
    return val
}

/** Guard value type */
export function guard<T>(val: T): T {
    return val
}

/** Do nothing */
export function empty(): void { }

/** `throw 'todo'` */
export function TODO(reason: any = 'todo'): never {
    throw reason ?? 'todo'
}

/** throw but expression */
export function raise(err: any): never {
    throw err
}

/** Promise that will never continue */
export function abort(): Promise<never> {
    return new Promise(empty)
}

/** Yield time slice */
export function Yield(): Promise<void> {
    return Promise.resolve()
}

/** build tuple */
export function tuple<T extends unknown[]>(...vals: T): T {
    return vals
}