import { error } from '@sveltejs/kit';
import type { ZodSchema } from 'zod';

// Shared error body shape for SvelteKit `error()` calls. `issues` is set
// when validateBody fails so the client can show a precise validation
// hint; everywhere else only `message` is used.
export type ErrorResponse = {
  message: string;
  issues?: unknown;
};

/**
 * Parse a route param (or query param) as a positive integer (>=1).
 * Throws SvelteKit `error(400)` with `Missing <field>` when null/undefined,
 * or `Invalid <field>` when the value is not an integer >= 1.
 */
export function parsePositiveIntParam(
  raw: string | undefined | null,
  field: string
): number {
  if (raw == null) error(400, { message: `Missing ${field}` });
  const n = Number(raw);
  if (!Number.isInteger(n) || n <= 0) error(400, { message: `Invalid ${field}` });
  return n;
}

/**
 * Validate an unknown body against a Zod schema. Throws SvelteKit
 * `error(400, { message: 'Invalid body', issues })` on mismatch and returns
 * the typed parse result on success. Accepts `null` (the typical result of
 * `await request.json().catch(() => null)`).
 */
export function validateBody<T>(body: unknown, schema: ZodSchema<T>): T {
  const parsed = schema.safeParse(body);
  if (!parsed.success) {
    error(400, { message: 'Invalid body', issues: parsed.error.issues });
  }
  return parsed.data;
}