interface IPipeReturn { slice(skip: number, limit: number): IPipeReturn; sortByField(fieldName: keyof D, direction?: 1 | -1, fallback?: Array): IPipeReturn; sortByField(fieldName: Array, direction?: 1 | -1, fallback?: Array): IPipeReturn; apply(): D[]; pipe(p: IPipeReturn): IPipeReturn; } interface IPipeReturnNoInitialData { slice(skip: number, limit: number): IPipeReturnNoInitialData; sortByField(fieldName: keyof D, direction?: 1 | -1, fallback?: Array): IPipeReturnNoInitialData; sortByField(fieldName: Array, direction?: 1 | -1): IPipeReturnNoInitialData; apply(arg: D[]): D[]; pipe(p: IPipeReturnNoInitialData): IPipeReturnNoInitialData; } type PipeFunction = (arg: D[]) => D[]; const merge = (fn: PipeFunction, inner: PipeFunction): PipeFunction => (args) => fn(inner(args)); export function pipe(): IPipeReturnNoInitialData; export function pipe(initialData: D[]): IPipeReturn; export function pipe(initialData: D[], acc: PipeFunction): IPipeReturn; export function pipe( initialData?: any, acc: PipeFunction = (arg) => [...arg], ): typeof initialData extends undefined ? IPipeReturnNoInitialData : IPipeReturn { return { slice(skip = 0, limit: number) { return pipe( initialData, merge((arr: D[]) => arr.slice(skip, skip + limit), acc), ); }, sortByField(fieldName: keyof D | Array, direction: 1 | -1 = 1, fallback: Array = []) { if (Array.isArray(fieldName)) { return this.sortByField(fieldName[0], direction, fieldName.slice(1)); } const sort = (fieldName: keyof D, direction: 1 | -1, fallback: Array) => { return (a: D, b: D): number => { const aValue = a[fieldName]; const bValue = b[fieldName]; if (aValue === undefined && bValue === undefined && fallback.length > 0) { const [field, ...rest] = fallback; return sort(field, direction, rest)(a, b); } if (aValue === undefined) { return 1; } if (bValue === undefined) { return -1; } if (aValue instanceof Date && bValue instanceof Date) { return direction * (aValue.getTime() - bValue.getTime()); } if (typeof aValue === 'string' && typeof bValue === 'string') { return direction * aValue.localeCompare(bValue); } if (typeof aValue === 'number' && typeof bValue === 'number') { return direction * (aValue - bValue); } return 0; }; }; return pipe( initialData, merge((arr: D[]) => [...arr].sort(sort(fieldName, direction, fallback)), acc), ); }, apply: (arg: D[]) => { return acc(initialData ?? arg); }, pipe(p: IPipeReturn) { return pipe(initialData, merge(p.apply, acc)); }, }; }