import { toJSONSchema, type z } from "zod";

/**
 * Serialises a Zod schema into a string the LLM can read in the prompt.
 *
 * Implementation: defers to Zod 4's built-in `z.toJSONSchema()`. The output
 * is standard JSON Schema, which LLMs handle natively AND carries the Zod
 * constraints (`minimum`, `maximum`, `default`, `enum`) that an LLM benefits
 * from seeing — e.g. the model picks `hours: 6` rather than `hours: 999`
 * when it sees `"maximum": 168` in the schema.
 *
 * The wrapper is the formatter. If Zod's JSON Schema output ever shifts
 * shape between releases, the change is contained here; the public API
 * (`printSchema(schema): string`) and the LLM-facing prompt format stay
 * stable unless we deliberately change them.
 */
export function printSchema(schema: z.ZodType): string {
  return JSON.stringify(toJSONSchema(schema), null, 2);
}