daton/lib/src/support/timeout.ts

export interface TimeoutSubscriber<T> {
    on_time: (handler: (arg: T) => any) => TimeoutSubscriber<T>,
    late: (handler: (arg: T) => any) => TimeoutSubscriber<T>,
    timeout: (handler: () => any) => TimeoutSubscriber<T>,
    run: () => Promise<T>,
}

export function withTimeout<T>(timeout: number, promise: Promise<T>) {
    let on_time_handler: (arg: T) => any = (arg) => {}
    let late_handler: (arg: T) => any = (arg) => {}
    let timeout_handler: () => any = () => {}

    const sub = {
        on_time: handler => {
            on_time_handler = handler
            return sub
        },
        late: handler => {
            late_handler = handler
            return sub
        },
        timeout: handler => {
            timeout_handler = handler
            return sub
        },
        run: async () => {
            let expired = false
            let resolved = false
            setTimeout(() => {
                expired = true
                if ( !resolved ) timeout_handler()
            }, timeout)

            const result: T = await promise
            resolved = true

            if ( !expired ) {
                await on_time_handler(result)
            } else {
                await late_handler(result)
            }

            return result
        }
    } as TimeoutSubscriber<T>

    return sub
}