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import type { PromType, λ } from "./types.ts";
/** * Given a list of functions that accept the same parameters, returns a function * that given these arguments returns the result of the first function whose * result is not nullish. * * This is equivalent to chaining together invocations of the passed in * functions with the given arguments with nullish coalescing _(`??`)_ operators. * * @example * ``` * const isAdult   = (age: number) => { if (n >= 18) return 'adult' } * const isToddler = (age: number) => { if (n <= 3) return 'toddler' } * * const ageGroup = nullishChain(isAdult, isToddler, () => 'child') * * // this is functionally equivalent to: * const ageGroup = age => isAdult(age) ?? isToddler(age) ?? 'child' * * ageGroup(1)  // prints: 'toddler' * ageGroup(10) // prints: 'child' * ageGroup(50) // prints: 'adult' * ``` */export const nullishChain = <FF extends λ, FR extends λ<Parameters<FF>>[]>(  ...[fun, ...rest]: [FF, ...FR] | []) =>(...args: Parameters<FF>): ReturnType<FF | FR[number]> | undefined =>  !fun ? undefined : fun(...args) ?? nullishChain(...(rest as any))(...args);
/** * Same as {@link nullishChain} but accept asynchronous functions too. * * @example * ``` * const readFromCache = (id: string): Resource => { if (id in cache) return cache[id] } * const readFromFile  = (id: string): Resource => { if (fileExists(id)) return readFile(id) } * const fetchFromNet  = async (id: string): Promise<Resource> => await fetch(`someURL/${id}`) * * // async (id: string) => Promise<Resource> * const getResource = asyncNullishChain(readFromCache, readFromFile, fetchFromNet) * ``` */export const asyncNullishChain = <FF extends λ, FR extends λ<Parameters<FF>>[]>(  ...[fun, ...rest]: [FF, ...FR] | []) =>async (  ...args: Parameters<FF>): Promise<PromType<ReturnType<FF | FR[number]>> | undefined> =>  !fun ? undefined : (await fun(...args)) ??    (await asyncNullishChain(...(rest as any))(...args));