@data-client/rest/src/OptionsToFunction.ts

Quickly define typed REST resources and endpoints

import type { FetchFunction, ResolveType } from '@data-client/endpoint';

import { PathArgs } from './pathTypes.js';
import { PartialRestGenerics, RestFetch } from './RestEndpoint.js';

export type OptionsToFunction<
  O extends PartialRestGenerics,
  E extends { body?: any; path?: string; method?: string },
  F extends FetchFunction,
> =
  'path' extends keyof O ?
    RestFetch<
      'searchParams' extends keyof O ?
        O['searchParams'] & PathArgs<Exclude<O['path'], undefined>>
      : PathArgs<Exclude<O['path'], undefined>>,
      OptionsToBodyArgument<
        'body' extends keyof O ? O : E,
        'method' extends keyof O ? O['method'] : E['method']
      >,
      O['process'] extends {} ? ReturnType<O['process']> : ResolveType<F>
    >
  : 'body' extends keyof O ?
    RestFetch<
      'searchParams' extends keyof O ?
        O['searchParams'] & PathArgs<Exclude<E['path'], undefined>>
      : PathArgs<Exclude<E['path'], undefined>>,
      OptionsToBodyArgument<
        O,
        'method' extends keyof O ? O['method'] : E['method']
      >,
      O['process'] extends {} ? ReturnType<O['process']> : ResolveType<F>
    >
  : 'searchParams' extends keyof O ?
    RestFetch<
      O['searchParams'] & PathArgs<Exclude<E['path'], undefined>>,
      OptionsToBodyArgument<
        E,
        'method' extends keyof O ? O['method'] : E['method']
      >,
      O['process'] extends {} ? ReturnType<O['process']> : ResolveType<F>
    >
  : (
      this: ThisParameterType<F>,
      ...args: Parameters<F>
    ) => Promise<
      O['process'] extends {} ? ReturnType<O['process']> : ResolveType<F>
    >;

export type OptionsToBodyArgument<
  O extends { body?: any },
  Method extends string | undefined,
> =
  Method extends 'POST' | 'PUT' | 'PATCH' | 'DELETE' ?
    'body' extends keyof O ?
      O['body']
    : any
  : undefined;