/**
 * Pure category tree helper functions.
 * These operate on plain category maps and have no side-effects.
 */

export const ROOT_CATEGORY_NAME = 'Home';

/**
 * @param {object} item
 * @returns {object}
 */
export function normalizeCategoryNode(item) {
  return {
    ...item,
    id: item.id,
    parentId: item.parentId,
    name: item.name == null ? null : String(item.name).trim() || null,
    posterminalIds: Array.isArray(item.posterminalIds) ? item.posterminalIds : [],
  };
}

/**
 * Parse the raw GET /api/category/tree response body into normalized state.
 * @param {object} data
 * @param {number|string|null} companyRootCategoryId
 */
export function parseCategoryTreeResponse(data, companyRootCategoryId) {
  const list = Array.isArray(data.tree) ? data.tree : [];
  const rootCategoryId = data.rootCategoryId != null ? data.rootCategoryId : companyRootCategoryId;

  const categories = Object.fromEntries(
    list.map((item) => [String(item.id), normalizeCategoryNode(item)]),
  );

  return {
    rootCategoryId,
    categories,
    languageId: data.languageId,
  };
}

/**
 * Display name for a category node (root → "Home").
 */
export function categoryDisplayName(name, categoryId, rootCategoryId) {
  if (rootCategoryId != null && String(categoryId) === String(rootCategoryId)) {
    return ROOT_CATEGORY_NAME;
  }
  return name?.trim() || '';
}

/**
 * URL slug for a category node (root → "Home").
 */
export function categorySlug(node, rootCategoryId) {
  if (rootCategoryId != null && String(node.id) === String(rootCategoryId)) {
    return ROOT_CATEGORY_NAME;
  }
  return node.slug || null;
}

/**
 * Direct children of `parentId`, sorted by `sort` then `id`.
 */
export function getCategoryChildren(categories, parentId) {
  if (!categories) return [];
  const parentKey = String(parentId);
  return Object.values(categories)
    .filter((item) => item.parentId != null && String(item.parentId) === parentKey)
    .sort((a, b) => (a.sort ?? 0) - (b.sort ?? 0) || a.id - b.id);
}

/**
 * Breadcrumb trail from root to `currentCategoryId`.
 */
export function getCategoryBreadcrumbs(categories, currentCategoryId, rootCategoryId) {
  if (!categories || currentCategoryId == null) return [];

  const crumbs = [];
  const seen = new Set();
  let id = currentCategoryId;

  while (id != null && !seen.has(String(id))) {
    seen.add(String(id));
    const node = categories[String(id)];
    if (!node) break;

    crumbs.unshift({
      id: node.id,
      name: categoryDisplayName(node.name, node.id, rootCategoryId),
      slug: categorySlug(node, rootCategoryId),
    });

    const parentId = node.parentId;
    if (parentId == null || parentId === 0) break;
    if (String(parentId) === String(id)) break;
    id = parentId;
  }

  return crumbs;
}

/**
 * Map of category.id → category node from a raw tree response.
 * @param {object} data
 * @param {number|string|null} companyRootCategoryId
 */
export function normalizeCategoryMap(data, companyRootCategoryId) {
  return parseCategoryTreeResponse(data, companyRootCategoryId).categories;
}

/**
 * Returns an array containing the category id and all of its recursive descendant ids.
 * Useful for preventing cyclic moves.
 * @param {object} categories - id -> node map
 * @param {number|string} categoryId - Target category id
 * @returns {number[]} Array of category ids
 */
export function getCategoryDescendantIds(categories, categoryId) {
  const result = [];
  if (!categories || categoryId == null) return result;
  const numId = Number(categoryId);
  result.push(numId);
  const queue = [numId];
  while (queue.length > 0) {
    const currentId = queue.shift();
    const children = getCategoryChildren(categories, currentId);
    for (const child of children) {
      result.push(Number(child.id));
      queue.push(Number(child.id));
    }
  }
  return result;
}

/**
 * Normalizes a category slug path by stripping leading/trailing slashes.
 * @param {string|null|undefined} slugPath
 * @returns {string}
 */
export function cleanCategorySlugPath(slugPath) {
  return (slugPath ?? '').replace(/^\/+|\/+$/g, '');
}

/**
 * Resolves a numeric/string category ID from a URL slug path using the category tree.
 * @param {object} categories - id -> node map
 * @param {number|string|null} rootCategoryId
 * @param {string|null|undefined} slugPath
 * @returns {number|string|null}
 */
export function resolveCategoryIdFromSlugPath(categories, rootCategoryId, slugPath) {
  if (!categories || rootCategoryId == null) return null;

  let segments = (slugPath ?? '')
    .split('/')
    .filter(Boolean)
    .map((segment) => decodeURIComponent(segment));

  if (segments[0] === ROOT_CATEGORY_NAME) {
    segments = segments.slice(1);
  }

  if (segments.length === 0) {
    return rootCategoryId;
  }

  let currentId = rootCategoryId;
  for (const slug of segments) {
    const children = getCategoryChildren(categories, currentId);
    const match = children.find(
      (child) => categorySlug(child, rootCategoryId) === slug,
    );
    if (!match) return null;
    currentId = match.id;
  }

  return currentId;
}