pipeline.ts

export type Pipeline = (env: PipelineEnv, next: () => Promise<void>) => Promise<void>;

const runPipeline = (pipelines: Pipeline[]) => {
    return (env: PipelineEnv, next?: Pipeline): Promise<void> => {
        let index = -1;
        const dispatch = (i: number): Promise<void> => {
            if (i <= index) return Promise.reject(new Error('next() called multiple times'));
            index = i;
            let fn = pipelines[i];
            if (i === pipelines.length) fn = next;
            if (!fn) return Promise.resolve();
            try {
                return Promise.resolve(fn(env, () => dispatch(i + 1)));
            } catch (err) {
                return Promise.reject(err);
            }
        };
        return dispatch(0);
    };
};