honojs-middleware/packages/zod-validator/src/index.ts

import type { Context, MiddlewareHandler, Env } from 'hono'
import { validator } from 'hono/validator'
import type { z } from 'zod'
import type { ZodSchema, ZodError } from 'zod'

type ValidationTargets = 'json' | 'form' | 'query' | 'queries'
type Hook<T> = (
  result: { success: true; data: T } | { success: false; error: ZodError },
  c: Context
) => Response | Promise<Response> | void

export const zValidator = <
  T extends ZodSchema,
  Target extends ValidationTargets,
  E extends Env,
  P extends string
>(
  target: Target,
  schema: T,
  hook?: Hook<z.infer<T>>
): MiddlewareHandler<
  E,
  P,
  { in: { [K in Target]: z.input<T> }; out: { [K in Target]: z.output<T> } }
> =>
  validator(target, (value, c) => {
    const result = schema.safeParse(value)

    if (hook) {
      const hookResult = hook(result, c)
      if (hookResult instanceof Response || hookResult instanceof Promise<Response>) {
        return hookResult
      }
    }

    if (!result.success) {
      return c.json(result, 400)
    }

    const data = result.data as z.infer<T>
    return data
  })