import { useState, useEffect } from "react";
import { get } from "../api/client";
import type { FormDescriptor } from "../api/types";

// Module-level cache to avoid refetching across mounts.
let cached: FormDescriptor | null = null;

export function useFormDescriptor(schemaName = "kindred-rd") {
  const [descriptor, setDescriptor] = useState<FormDescriptor | null>(cached);
  const [loading, setLoading] = useState(cached === null);

  useEffect(() => {
    if (cached) return;
    get<FormDescriptor>(`/api/schemas/${encodeURIComponent(schemaName)}/form`)
      .then((desc) => {
        cached = desc;
        setDescriptor(desc);
      })
      .catch(() => {})
      .finally(() => setLoading(false));
  }, [schemaName]);

  // Derive flat categories map from the category_picker stages
  const categories: Record<string, string> = {};
  if (descriptor?.category_picker) {
    const subcatStage = descriptor.category_picker.stages.find(
      (s) => s.values_by_domain,
    );
    if (subcatStage?.values_by_domain) {
      for (const domainVals of Object.values(subcatStage.values_by_domain)) {
        Object.assign(categories, domainVals);
      }
    }
  }

  return { descriptor, categories, loading };
}