Nuxt and Zod validation

user.ts

import * as z from 'zod'
import { defineEventHandler, CompatibilityEvent, useQuery } from 'h3'

const userSchema = z
.object({
  name: z.string().min(4, { message: 'Must be 4 or more characters long' }),
  age: z.string().transform((age) => parseInt(age, 10))
})

type UnknownKeysParam = "passthrough" | "strict" | "strip";

export type ZodSchema<U extends UnknownKeysParam = any> =
  | z.ZodObject<any, U>
  | z.ZodUnion<[ZodSchema<U>, ...ZodSchema<U>[]]>
  | z.ZodIntersection<ZodSchema<U>, ZodSchema<U>>
  | z.ZodDiscriminatedUnion<string, z.Primitive, z.ZodObject<any, U>>;

type ValidationResult<IN extends ZodSchema> = Promise<z.SafeParseSuccess<z.output<IN>> | z.SafeParseError<z.inferFormattedError<IN>>>

async function validateQuery<Input extends ZodSchema>(event: CompatibilityEvent, schema: Input) {
  const query = useQuery(event)
  const parsed = schema.safeParseAsync(query);
  return parsed as ValidationResult<Input>
}

async function validateBody<Input extends ZodSchema>(event: CompatibilityEvent, schema: Input) {
  const body = await useBody(event)
  const parsed = schema.safeParseAsync(body);
  return parsed as ValidationResult<Input>
}

async function validateParams<Input extends ZodSchema>(event: CompatibilityEvent, schema: Input) {
  const { params } = event.context
  const parsed = schema.safeParseAsync(params);
  return parsed as ValidationResult<Input>
}

async function validateEvent<
  QueryInput extends ZodSchema,
  BodyInput extends ZodSchema,
  ParamsInput extends ZodSchema
>(event: CompatibilityEvent, fields: {
  query?: QueryInput
  body?: BodyInput
  params?: ParamsInput
}) {
  const queryResult = fields.query ? await validateQuery(event, fields.query) : null
  const bodyResult = fields.body ? await validateBody(event, fields.body) : null
  const paramsResult = fields.params ? await validateParams(event, fields.params) : null

  return {
    query: queryResult,
    body: bodyResult,
    params: paramsResult
  }
}

export default defineEventHandler(async(event) => {
  const result = await validateEvent(event, {
    query: userSchema
  })
})