railway.ts

export class ErrorResult {
    readonly IsSuccess = false;
    constructor(readonly message: string, readonly error: any = undefined) {}
}

export class SuccessResult<T> {
    readonly IsSuccess = true;
    constructor(readonly value: T) {}
}

export type Result<T> = SuccessResult<T> | ErrorResult;
export type PromiseResult<T> = Promise<Result<T>>;
export type TrainBuilder<T> = Result<T> | (() => Result<T>);
export type TrainRelayAction<T1, T2> = (i: T1) => Result<T2>;
export type TrainRelayActionAsync<T1, T2> = (i: T1) => PromiseResult<T2>;

export function keptPromise<T>(
    callback: (
        success: (result: T) => void,
        failure: (message: string, error?: any) => void
    ) => void
): PromiseResult<T> {
    return new Promise(res => {
        callback(
            r => res(new SuccessResult(r)),
            (m, e) => res(new ErrorResult(m, e))
        );
    });
}

export function buildTrain<T1, T2, T3>(
    a: TrainBuilder<T1>,
    b: TrainBuilder<T2>,
    c: TrainBuilder<T3>
): Result<[T1, T2, T3]>;
export function buildTrain<T1, T2, T3, T4>(
    a: TrainBuilder<T1>,
    b: TrainBuilder<T2>,
    c: TrainBuilder<T3>,
    d: TrainBuilder<T4>
): Result<[T1, T2, T3, T4]>;
export function buildTrain<T1, T2, T3, T4, T5>(
    a: TrainBuilder<T1>,
    b: TrainBuilder<T2>,
    c: TrainBuilder<T3>,
    d: TrainBuilder<T4>,
    e: TrainBuilder<T5>
): Result<[T1, T2, T3, T4, T5]>;
export function buildTrain<T1, T2, T3, T4, T5, T6>(
    a: TrainBuilder<T1>,
    b: TrainBuilder<T2>,
    c: TrainBuilder<T3>,
    d: TrainBuilder<T4>,
    e: TrainBuilder<T5>,
    f: TrainBuilder<T6>
): Result<[T1, T2, T3, T4, T5, T6]>;
export function buildTrain(...builders: TrainBuilder<any>[]): Result<any> {
    const train: any[] = [];
    for (const b of builders) {
        const r = typeof b === "function" ? b() : b;
        if (!r.IsSuccess) {
            return r;
        }
        train.push(r.value);
    }
    return new SuccessResult(train);
}

export function relayTrain<T1, T2, T3>(
    a: TrainRelayAction<void, T1>,
    b: TrainRelayAction<T1, T2>,
    c: TrainRelayAction<T2, T3>
): Result<T3>;
export function relayTrain<T1, T2, T3, T4>(
    a: TrainRelayAction<void, T1>,
    b: TrainRelayAction<T1, T2>,
    c: TrainRelayAction<T2, T3>,
    d: TrainRelayAction<T3, T4>
): Result<T4>;
export function relayTrain<T1, T2, T3, T4, T5>(
    a: TrainRelayAction<void, T1>,
    b: TrainRelayAction<T1, T2>,
    c: TrainRelayAction<T2, T3>,
    d: TrainRelayAction<T3, T4>,
    e: TrainRelayAction<T4, T5>
): Result<T5>;
export function relayTrain<T1, T2, T3, T4, T5, T6>(
    a: TrainRelayAction<void, T1>,
    b: TrainRelayAction<T1, T2>,
    c: TrainRelayAction<T2, T3>,
    d: TrainRelayAction<T3, T4>,
    e: TrainRelayAction<T4, T5>,
    f: TrainRelayAction<T5, T6>
): Result<T6>;
export function relayTrain<T1, T2, T3, T4, T5, T6, T7>(
    a: TrainRelayAction<void, T1>,
    b: TrainRelayAction<T1, T2>,
    c: TrainRelayAction<T2, T3>,
    d: TrainRelayAction<T3, T4>,
    e: TrainRelayAction<T4, T5>,
    f: TrainRelayAction<T5, T6>,
    g: TrainRelayAction<T6, T7>
): Result<T7>;
export function relayTrain<T1, T2, T3, T4, T5, T6, T7, T8>(
    a: TrainRelayAction<void, T1>,
    b: TrainRelayAction<T1, T2>,
    c: TrainRelayAction<T2, T3>,
    d: TrainRelayAction<T3, T4>,
    e: TrainRelayAction<T4, T5>,
    f: TrainRelayAction<T5, T6>,
    g: TrainRelayAction<T6, T7>,
    h: TrainRelayAction<T7, T8>
): Result<T8>;
export function relayTrain<T1, T2, T3, T4, T5, T6, T7, T8, T9>(
    a: TrainRelayAction<void, T1>,
    b: TrainRelayAction<T1, T2>,
    c: TrainRelayAction<T2, T3>,
    d: TrainRelayAction<T3, T4>,
    e: TrainRelayAction<T4, T5>,
    f: TrainRelayAction<T5, T6>,
    g: TrainRelayAction<T6, T7>,
    h: TrainRelayAction<T7, T8>,
    i: TrainRelayAction<T8, T9>
): Result<T9>;
export function relayTrain(
    ...actions: TrainRelayAction<any, any>[]
): Result<any> {
    let result: Result<any> | undefined = undefined;
    for (const a of actions) {
        result = a(result && result.IsSuccess ? result.value : undefined);
        if (!result.IsSuccess) {
            return result;
        }
    }
    return result !== undefined
        ? result
        : new ErrorResult("No actions provided.");
}

export function relayTrainAsync<T1, T2, T3>(
    a: TrainRelayActionAsync<void, T1>,
    b: TrainRelayActionAsync<T1, T2>,
    c: TrainRelayActionAsync<T2, T3>
): PromiseResult<T3>;
export function relayTrainAsync<T1, T2, T3, T4>(
    a: TrainRelayActionAsync<void, T1>,
    b: TrainRelayActionAsync<T1, T2>,
    c: TrainRelayActionAsync<T2, T3>,
    d: TrainRelayActionAsync<T3, T4>
): PromiseResult<T4>;
export function relayTrainAsync<T1, T2, T3, T4, T5>(
    a: TrainRelayActionAsync<void, T1>,
    b: TrainRelayActionAsync<T1, T2>,
    c: TrainRelayActionAsync<T2, T3>,
    d: TrainRelayActionAsync<T3, T4>,
    e: TrainRelayActionAsync<T4, T5>
): PromiseResult<T5>;
export function relayTrainAsync<T1, T2, T3, T4, T5, T6>(
    a: TrainRelayActionAsync<void, T1>,
    b: TrainRelayActionAsync<T1, T2>,
    c: TrainRelayActionAsync<T2, T3>,
    d: TrainRelayActionAsync<T3, T4>,
    e: TrainRelayActionAsync<T4, T5>,
    f: TrainRelayActionAsync<T5, T6>
): PromiseResult<T6>;
export function relayTrainAsync<T1, T2, T3, T4, T5, T6, T7>(
    a: TrainRelayActionAsync<void, T1>,
    b: TrainRelayActionAsync<T1, T2>,
    c: TrainRelayActionAsync<T2, T3>,
    d: TrainRelayActionAsync<T3, T4>,
    e: TrainRelayActionAsync<T4, T5>,
    f: TrainRelayActionAsync<T5, T6>,
    g: TrainRelayActionAsync<T6, T7>
): PromiseResult<T7>;
export function relayTrainAsync<T1, T2, T3, T4, T5, T6, T7, T8>(
    a: TrainRelayActionAsync<void, T1>,
    b: TrainRelayActionAsync<T1, T2>,
    c: TrainRelayActionAsync<T2, T3>,
    d: TrainRelayActionAsync<T3, T4>,
    e: TrainRelayActionAsync<T4, T5>,
    f: TrainRelayActionAsync<T5, T6>,
    g: TrainRelayActionAsync<T6, T7>,
    h: TrainRelayActionAsync<T7, T8>
): PromiseResult<T8>;
export function relayTrainAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9>(
    a: TrainRelayActionAsync<void, T1>,
    b: TrainRelayActionAsync<T1, T2>,
    c: TrainRelayActionAsync<T2, T3>,
    d: TrainRelayActionAsync<T3, T4>,
    e: TrainRelayActionAsync<T4, T5>,
    f: TrainRelayActionAsync<T5, T6>,
    g: TrainRelayActionAsync<T6, T7>,
    h: TrainRelayActionAsync<T7, T8>,
    i: TrainRelayActionAsync<T8, T9>
): PromiseResult<T9>;
export async function relayTrainAsync(
    ...actions: TrainRelayActionAsync<any, any>[]
): PromiseResult<any> {
    let result: Result<any> | undefined = undefined;
    for (const a of actions) {
        result = await a(result && result.IsSuccess ? result.value : undefined);
        if (!result.IsSuccess) {
            return result;
        }
    }
    return result !== undefined
        ? result
        : new ErrorResult("No actions provided.");
}