import { branch } from "https://deno.land/x/domain_functions@v2.6.0/src/domain-functions.ts";
Use it to add conditional logic to your domain functions' compositions.
It receives a domain function and a predicate function that should return the next domain function to be executed based on the previous domain function's output, like pipe. If the predicate returns null the result of the previous domain function will be returned and it won't be piped.
Examples
import { mdf, branch } from 'domain-functions'
import { mdf, branch } from 'domain-functions'
const getIdOrEmail = mdf(z.object({ id: z.number().optional(), email: z.string().optional() }))((data) => data.id ?? data.email) const findUserById = mdf(z.number())((id) => db.users.find({ id })) const findUserByEmail = mdf(z.string().email())((email) => db.users.find({ email })) const findUserByIdOrEmail = branch( getIdOrEmail, (output) => (typeof output === "number" ? findUserById : findUserByEmail) ) // ^? DomainFunction
const getStock = mdf(z.any(), z.object({ id: z.number() }))(, ({ id }) => db.stocks.find({ id })) const getExtraStock = mdf(z.any(), z.object({ id: z.number() }))(, ({ id }) => db.stockes.find({ id, extra: true }))
const getStockOrExtraStock = branch( getStock, ({ items }) => (items.length >= 0 ? null : getExtraStock) ) // ^? DomainFunction<{ items: Item[] }>