import { meshkeeGet, tenantPath } from "@/lib/meshkee";
import { detailPath, slugifyForUrl } from "@/lib/seo-slug";

export type ApiCategory = {
  id: string;
  parentId?: string | null;
  name?: string | null;
  nameFa?: string | null;
  slug?: string | null;
  description?: string | null;
  sortOrder?: number | null;
  isActive?: boolean;
};

export type NavCategory = {
  id: string;
  title: string;
  href: string;
  image?: string;
  children: NavCategory[];
};

function titleOf(category: Pick<ApiCategory, "nameFa" | "name" | "id">) {
  return category.nameFa?.trim() || category.name?.trim() || String(category.id);
}

/** Public category URL: /products/category/{id}/{nameFaSlug} */
export function categoryHref(category: Pick<ApiCategory, "id" | "nameFa" | "name">) {
  return detailPath("/products/category", category.id, titleOf(category));
}

export function categoryNameSlug(title: string) {
  return slugifyForUrl(title);
}

export async function fetchProductCategories() {
  const data = await meshkeeGet<{ items?: ApiCategory[] }>(tenantPath("/categories?entityType=product"), {
    items: [],
  });
  return (data.items ?? []).filter((category) => category.isActive !== false);
}

export async function fetchCategoryById(categoryId: string) {
  const data = await meshkeeGet<{ category?: ApiCategory }>(
    tenantPath(`/categories/by-id/${encodeURIComponent(categoryId)}`),
    {},
  );
  return data.category ?? null;
}

export function buildCategoryTree(flat: ApiCategory[]): NavCategory[] {
  const byId = new Map(flat.map((category) => [String(category.id), category]));
  const children = new Map<string, ApiCategory[]>();

  for (const category of flat) {
    const parentId = category.parentId ? String(category.parentId) : "";
    const key = parentId && byId.has(parentId) ? parentId : "root";
    const list = children.get(key) ?? [];
    list.push(category);
    children.set(key, list);
  }

  const sort = (list: ApiCategory[]) =>
    [...list].sort((a, b) => (a.sortOrder ?? 0) - (b.sortOrder ?? 0) || titleOf(a).localeCompare(titleOf(b), "fa"));

  const build = (category: ApiCategory): NavCategory => ({
    id: String(category.id),
    title: titleOf(category),
    href: categoryHref(category),
    children: sort(children.get(String(category.id)) ?? []).map(build),
  });

  return sort(children.get("root") ?? []).map(build);
}

/** Skip single-child wrapper roots (e.g. کالاها → لوازم…) so mega menu starts at useful columns. */
export function unwrapNavRoots(nodes: NavCategory[]): NavCategory[] {
  let current = nodes;
  while (current.length === 1 && current[0].children.length > 0) {
    current = current[0].children;
  }
  return current;
}

export function flattenNavCategories(nodes: NavCategory[]): NavCategory[] {
  const result: NavCategory[] = [];
  const walk = (list: NavCategory[]) => {
    for (const node of list) {
      result.push(node);
      if (node.children.length) walk(node.children);
    }
  };
  walk(nodes);
  return result;
}

export function findNavCategory(nodes: NavCategory[], id?: string | null) {
  if (!id) return undefined;
  return flattenNavCategories(nodes).find((item) => item.id === id);
}

/**
 * Flatten one level for the mega menu: nested groups become sibling sections
 * so CSS columns can pack them evenly.
 */
export function toMegaSections(categories: NavCategory[]): NavCategory[] {
  const sections: NavCategory[] = [];

  for (const category of categories) {
    const leaves = category.children.filter((child) => child.children.length === 0);
    const branches = category.children.filter((child) => child.children.length > 0);

    if (!branches.length) {
      sections.push(category);
      continue;
    }

    if (leaves.length) {
      sections.push({ ...category, children: leaves });
    }

    for (const branch of branches) {
      sections.push(branch);
    }
  }

  return sections;
}

export async function getNavCategories() {
  return unwrapNavRoots(buildCategoryTree(await fetchProductCategories()));
}