graphql-typed-client/src/client/applyTypeMapperToResponse.ts

A tool that generates a strongly typed client library for any GraphQL endpoint. The client allows writing GraphQL queries as plain JS objects (with type safety, awesome code completion experience, custom scalar type mapping, type guards and more)

import { ExecutionResult } from 'graphql'
import { getFieldFromPath } from './getFieldFromPath'
import { LinkedType } from './linkTypeMap'

export interface TypeMapper {
  [type: string]:
    | {
        serialize: (input: any) => any
        deserialize: (output: any) => any
      }
    | undefined
}

const applyRecursively = (root: LinkedType, data: any, typeMapper: TypeMapper, path: string[]): any => {
  if (data === null || data === undefined) return data
  else if (Array.isArray(data)) return data.map(i => applyRecursively(root, i, typeMapper, path))
  else if (typeof data === 'object')
    return Object.keys(data).reduce<any>((r, k) => {
      r[k] = applyRecursively(root, data[k], typeMapper, [...path, k])
      return r
    }, {})
  else {
    const field = getFieldFromPath(root, path)
    const specificMapper = typeMapper[field.type.name]
    if (specificMapper !== undefined) return specificMapper.deserialize(data)
    else return data
  }
}

export const applyTypeMapperToResponse = <T>(
  root: LinkedType,
  result: ExecutionResult<T>,
  mapper: TypeMapper,
): ExecutionResult<T> => ({
  data: applyRecursively(root, result.data, mapper, []),
  errors: result.errors,
})