Validator for taking camelcase or snake case inputs and converting them to a consistent type checked value.

parser.ts

import * as z from "zod";

const camelToSnakeCase = (str: string) =>
  str.replace(/[A-Z]/g, (letter) => `_${letter.toLowerCase()}`);

const validActions = ["HELLO_THERE"] as const;
const ValidActionsSchema = z.enum(validActions);

const ParseableSchema = z.object({
  action: z.string().transform((value, ctx) => {
    const transformed = value.includes("_") ? value: camelToSnakeCase(value).toUpperCase();
    const result = ValidActionsSchema.safeParse(transformed);
    if (!result.success) {
      result.error.issues.forEach((issue) => {
        ctx.addIssue(issue);
      });

      return z.NEVER;
    }
    return result.data;
  }),
});

export function parseAction(action: { action: string }) {
  return ParseableSchema.parse(action);
}