/**
 * @file articleSearchAutomat.js
 * @description In-memory article search and pagination state for the `/artikel`
 * overview and search pages, querying against the derived `articleIndexAutomat`.
 *
 * Upstream Triggers:
 * - UI / Search input / FillSpace: Components call `actions.search({ target, filter, offset, pageSize })`.
 * - Reads data from `articleIndexAutomat`: Derives and slices matching records
 *   synchronously, updating continuously as category views load during launch.
 * - `categoryAutomat`: Provides category hierarchy metadata for faceted counts.
 */

import { Automat } from 'react-automat';
import articleIndexAutomat from './articleIndexAutomat';
import categoryAutomat from './categoryAutomat';
import { parseFilter } from '../components/article/searchFormat';

/**
 * @typedef {Object} ArticleSearchResult
 * @property {Record<string,object>} categoryFacets Facet counts per category id.
 * @property {number} totalCount Number of matching records.
 * @property {Array<object>} recordset Sliced matching article index records for the current page.
 * @property {number} offset Current 0-based offset.
 * @property {number|null} pageSize Current page size.
 * @property {number} pageCount Total number of pages.
 * @property {number} currentPage Current 1-based page number.
 * @property {Error|null} error Search failure, or `null`.
 */

/**
 * @typedef {Object} ArticleSearchState
 * @property {ArticleSearchResult} result Latest search outcome.
 * @property {string} target Active search term.
 * @property {string} filter Active category filter string.
 * @property {number} offset Current 0-based offset.
 * @property {number|null} pageSize Current page size.
 * @property {boolean} loading Whether a search or index load is in flight.
 */

/** @type {ArticleSearchResult} */
const emptyResult = {
  categoryFacets: {},
  totalCount: 0,
  recordset: [],
  offset: 0,
  pageSize: null,
  pageCount: 1,
  currentPage: 1,
  error: null,
};

/** @type {ArticleSearchState} */
const initialState = {
  result: emptyResult,
  target: '',
  filter: '',
  offset: 0,
  pageSize: null,
  loading: false,
};

let articleSearchAutomat;

/**
 * Matches one index record against a search query (checks tokens in name, sku, brand, eans).
 *
 * @param {object} row Article index record.
 * @param {string} query Lowercased search term.
 * @returns {boolean} Whether the record matches.
 */
function matches(row, query) {
  if (!query) return true;
  const tokens = query.split(/\s+/).filter(Boolean);
  if (tokens.length === 0) return true;
  const name = String(row.name ?? '').toLowerCase();
  const sku = String(row.sku ?? '').toLowerCase();
  const brand = String(row.brand?.name || row.brandName || '').toLowerCase();
  const eans = (row.eans ?? []).map((e) => String(e).toLowerCase());
  return tokens.every(
    (token) =>
      name.includes(token) ||
      sku.includes(token) ||
      brand.includes(token) ||
      eans.some((ean) => ean.includes(token)),
  );
}

/**
 * Calculates a search relevance score for an article record against a query.
 *
 * @param {object} article Article index record.
 * @param {string} query Lowercased search term.
 * @returns {number} Higher score indicates a better match.
 */
export function getArticleRelevanceScore(article, query) {
  if (!query) return 0;
  const q = String(query).trim().toLowerCase();
  const sku = String(article.sku ?? '').toLowerCase();
  const name = String(article.name ?? '').toLowerCase();
  const brand = String(article.brand?.name || article.brandName || '').toLowerCase();
  const eans = (article.eans ?? []).map((e) => String(e).toLowerCase());

  // 1. Exact SKU match
  if (sku === q) return 10000;
  // 2. SKU starts with query
  if (sku.startsWith(q)) return 5000;
  // 3. Exact Name match
  if (name === q) return 4000;
  // 4. Name starts with query
  if (name.startsWith(q)) return 3000;
  // 5. SKU contains query
  if (sku.includes(q)) return 2000;
  // 6. Word in name starts with query
  const words = name.split(/\s+/);
  if (words.some((w) => w.startsWith(q))) return 1500;
  // 7. Name contains query
  if (name.includes(q)) return 1000;
  // 8. Exact EAN match
  if (eans.includes(q)) return 800;
  // 9. EAN starts with query
  if (eans.some((e) => e.startsWith(q))) return 600;
  // 10. Brand starts with query
  if (brand.startsWith(q)) return 400;
  // 11. Brand contains query
  if (brand.includes(q)) return 200;

  return 10;
}

/**
 * Sorts articles by relevance to the query, breaking ties alphabetically by name and SKU.
 *
 * @param {Array<object>} articles List of articles to sort.
 * @param {string} query Search term.
 * @returns {Array<object>} Sorted articles.
 */
export function sortArticlesByRelevance(articles, query) {
  const q = String(query ?? '').trim().toLowerCase();
  return [...articles].sort((a, b) => {
    if (q) {
      const scoreA = getArticleRelevanceScore(a, q);
      const scoreB = getArticleRelevanceScore(b, q);
      if (scoreA !== scoreB) {
        return scoreB - scoreA;
      }
    }
    const nameA = String(a.name ?? '');
    const nameB = String(b.name ?? '');
    const comp = nameA.localeCompare(nameB, 'de', { sensitivity: 'base' });
    if (comp !== 0) return comp;
    return String(a.sku ?? '').localeCompare(String(b.sku ?? ''), 'de');
  });
}

/**
 * Synchronously searches the article index using the search automat token matching and relevance order.
 *
 * @param {string} query Search input string.
 * @param {object} [options]
 * @param {Array<string>} [options.excludeSkus] SKUs to exclude from results.
 * @param {boolean} [options.allowParent=false] Whether to include parent articles.
 * @param {Array<string>} [options.categories] Category IDs to filter by.
 * @param {number} [options.offset=0] Pagination offset.
 * @param {number} [options.pageSize=10] Results per page.
 * @param {number} [options.limit] Alternative to pageSize.
 * @returns {Array<object>} Array of matching article index records with attached pagination metadata.
 */
export function searchArticlesIndex(query, options = {}) {
  const {
    excludeSkus = [],
    allowParent = false,
    categories = [],
    offset = 0,
    pageSize = 10,
    limit,
  } = options;

  if (articleIndexAutomat.state.status === 'idle') {
    void articleIndexAutomat.actions.ensureLoaded().catch(() => {});
  }

  const articles = articleIndexAutomat.state.items ?? [];
  const q = String(query ?? '').trim().toLowerCase();

  const excludedSet = new Set((excludeSkus ?? []).map((s) => String(s).toLowerCase()));

  let pool = articles;
  if (!allowParent) {
    pool = pool.filter((a) => !a.isParent && !a.is_parent);
  }
  if (excludedSet.size > 0) {
    pool = pool.filter((a) => a.sku && !excludedSet.has(String(a.sku).toLowerCase()));
  }

  let matchesList = q ? pool.filter((row) => matches(row, q)) : pool;

  if (categories && categories.length > 0) {
    const categoriesMap = categoryAutomat.state?.categories ?? {};
    const expandedIds = getCategoryAndDescendantIds(categories, categoriesMap);
    matchesList = matchesList.filter((row) => matchesCategory(row, expandedIds));
  }

  const sorted = sortArticlesByRelevance(matchesList, q);
  const totalCount = sorted.length;
  const safePageSize = limit != null ? limit : (pageSize != null && pageSize > 0 ? pageSize : 10);
  const safeOffset = Math.max(0, offset || 0);
  const pageCount = Math.max(1, Math.ceil(totalCount / safePageSize));
  const currentPage = Math.floor(safeOffset / safePageSize) + 1;
  const recordset = sorted.slice(safeOffset, safeOffset + safePageSize);

  Object.assign(recordset, {
    recordset,
    totalCount,
    pageCount,
    currentPage,
    offset: safeOffset,
    pageSize: safePageSize,
  });

  return recordset;
}

/**
 * Determines whether a category ID or name represents the root category.
 *
 * @param {string|number} id Category ID.
 * @param {string|number|null} [rootCategoryId] Configured root category ID.
 * @param {string} [metaName] Optional category display name.
 * @returns {boolean}
 */
function isRootCategory(id, rootCategoryId, metaName) {
  if (String(id) === '1') return true;
  if (rootCategoryId != null && String(id) === String(rootCategoryId)) return true;
  if (metaName) {
    const lower = String(metaName).trim().toLowerCase();
    if (lower === 'home' || lower === 'kategorie 1' || lower === 'category 1') return true;
  }
  return false;
}

/**
 * Recursively collects categoryId and all its descendant category IDs.
 *
 * @param {Array<string|number>} selectedCategories Array of category ID strings.
 * @param {Record<string, object>} categoriesMap Map of id -> categoryNode.
 * @param {Record<string, object>} [facets] Optional fallback facet map.
 * @returns {Set<string>} Set of category ID strings including selected and all descendants.
 */
export function getCategoryAndDescendantIds(selectedCategories, categoriesMap, facets) {
  const allIds = new Set();
  const queue = [];

  for (const id of selectedCategories ?? []) {
    const sId = String(id).trim();
    if (sId && !allIds.has(sId)) {
      allIds.add(sId);
      queue.push(sId);
    }
  }

  if (queue.length === 0) return allIds;

  if (categoriesMap && Object.keys(categoriesMap).length > 0) {
    const childrenByParent = new Map();
    for (const [id, node] of Object.entries(categoriesMap)) {
      if (node && node.parentId != null) {
        const pId = String(node.parentId);
        if (!childrenByParent.has(pId)) {
          childrenByParent.set(pId, []);
        }
        childrenByParent.get(pId).push(String(node.id ?? id));
      }
    }

    while (queue.length > 0) {
      const current = queue.shift();
      const children = childrenByParent.get(current);
      if (children) {
        for (const childId of children) {
          if (!allIds.has(childId)) {
            allIds.add(childId);
            queue.push(childId);
          }
        }
      }
    }
    return allIds;
  }

  if (facets) {
    const childrenByParent = new Map();
    for (const [id, meta] of Object.entries(facets)) {
      if (meta && meta.parent != null) {
        const pId = String(meta.parent);
        if (!childrenByParent.has(pId)) {
          childrenByParent.set(pId, []);
        }
        childrenByParent.get(pId).push(String(id));
      }
    }

    while (queue.length > 0) {
      const current = queue.shift();
      const children = childrenByParent.get(current);
      if (children) {
        for (const childId of children) {
          if (!allIds.has(childId)) {
            allIds.add(childId);
            queue.push(childId);
          }
        }
      }
    }
  }

  return allIds;
}

/**
 * Checks whether an article belongs to at least one of the target categories.
 *
 * @param {object} row Article index record.
 * @param {Set<string>} expandedCategoryIds Set of category ID strings.
 * @returns {boolean} Whether the article matches.
 */
function matchesCategory(row, expandedCategoryIds) {
  if (!expandedCategoryIds || expandedCategoryIds.size === 0) return true;
  if (!row.categories) return false;
  const rowCats = String(row.categories).split(',').map((s) => s.trim());
  return rowCats.some((catId) => expandedCategoryIds.has(String(catId)));
}

/**
 * Computes facet counts for each category represented in matched articles.
 *
 * @param {Array<object>} matchedArticles Articles matching text query.
 * @returns {Record<string, {count: number, name: string, parent: any}>} Category facets.
 */
function buildCategoryFacets(matchedArticles) {
  const facets = {};
  const categoriesMap = categoryAutomat.state?.categories ?? {};
  const rootCategoryId = categoryAutomat.state?.rootCategoryId;

  for (const article of matchedArticles) {
    if (!article.categories) continue;
    const ids = String(article.categories).split(',').map((s) => s.trim()).filter(Boolean);

    // Each article rolls up to its assigned categories and all their ancestors (except root).
    const articleCats = new Set();
    for (const id of ids) {
      let currentId = id;
      while (currentId && !isRootCategory(currentId, rootCategoryId)) {
        articleCats.add(String(currentId));
        const node = categoriesMap[String(currentId)];
        currentId = node?.parentId != null && node.parentId !== 0 ? String(node.parentId) : null;
      }
    }

    for (const id of articleCats) {
      const catNode = categoriesMap[id];
      const name = catNode?.name ?? `Kategorie ${id}`;
      if (isRootCategory(id, rootCategoryId, name)) continue;

      if (!facets[id]) {
        facets[id] = {
          count: 0,
          name,
          parent: catNode?.parentId ?? null,
        };
      }
      facets[id].count += 1;
    }
  }

  return facets;
}

const actions = {
  /**
   * Executes in-memory search and derivation synchronously.
   *
   * @param {object} [params] Search parameters to merge.
   * @returns {ArticleSearchResult} Search outcome.
   */
  runSearch(params = {}) {
    const currentState = articleSearchAutomat.state;
    const target = params.target !== undefined ? String(params.target ?? '') : currentState.target;
    const filter = params.filter !== undefined ? String(params.filter ?? '') : currentState.filter;
    const pageSize = params.pageSize !== undefined ? params.pageSize : currentState.pageSize;
    const offset = params.offset !== undefined ? Math.max(0, Number(params.offset) || 0) : currentState.offset;

    const articles = articleIndexAutomat.state.items ?? [];
    const query = target.trim().toLowerCase();

    // Filter by text query across all tokens
    const textMatches = query
      ? articles.filter((row) => matches(row, query))
      : articles;

    // Build facets for all text matches (before category filtering)
    const categoryFacets = buildCategoryFacets(textMatches);

    // Apply category filter if set (expanding to include all child categories)
    const selectedCategories = parseFilter(filter);
    const categoriesMap = categoryAutomat.state?.categories ?? {};
    let filteredArticles = textMatches;

    if (selectedCategories.length > 0) {
      const expandedCategoryIds = getCategoryAndDescendantIds(
        selectedCategories,
        categoriesMap,
        categoryFacets,
      );
      filteredArticles = textMatches.filter((row) =>
        matchesCategory(row, expandedCategoryIds),
      );
    }

    const sortedArticles = sortArticlesByRelevance(filteredArticles, query);

    const totalCount = sortedArticles.length;
    const safePageSize = pageSize != null && pageSize > 0 ? pageSize : null;
    const pageCount = safePageSize ? Math.max(1, Math.ceil(totalCount / safePageSize)) : 1;
    const currentPage = safePageSize ? Math.floor(offset / safePageSize) + 1 : 1;
    const recordset = safePageSize
      ? sortedArticles.slice(offset, offset + safePageSize)
      : sortedArticles;

    const result = {
      categoryFacets,
      totalCount,
      recordset,
      offset,
      pageSize: safePageSize,
      pageCount,
      currentPage,
      error: null,
    };

    articleSearchAutomat.setState({
      result,
      target,
      filter,
      offset,
      pageSize: safePageSize,
      loading: articleIndexAutomat.state.status === 'loading',
    });

    return result;
  },

  /**
   * Runs a client-side search over the article index with pagination.
   *
   * Does not block on network calls: evaluates immediately against whatever
   * articles are currently loaded, and ensures index derivation is running in the background.
   *
   * @param {string|object} [targetOrParams] Search term or options object.
   * @param {object} [options] Secondary options when first argument is target string.
   * @returns {Promise<ArticleSearchResult>} Search outcome.
   */
  async search(targetOrParams, options = {}) {
    const params = typeof targetOrParams === 'object' && targetOrParams !== null
      ? targetOrParams
      : targetOrParams !== undefined
        ? { target: targetOrParams, ...options }
        : options;

    // Kick off index loading in the background if not ready yet
    if (articleIndexAutomat.state.status === 'idle') {
      void articleIndexAutomat.actions.ensureLoaded().catch(() => {});
    }

    return actions.runSearch(params);
  },

  /**
   * Updates the page size and re-derives the result set.
   *
   * @param {number} pageSize Number of articles per page.
   * @returns {ArticleSearchResult}
   */
  setPageSize(pageSize) {
    return actions.runSearch({ pageSize });
  },

  /**
   * Sets page number (1-based) and re-derives the result set.
   *
   * @param {number} page 1-based page number.
   * @returns {ArticleSearchResult}
   */
  setPage(page) {
    const safeSize = articleSearchAutomat.state.pageSize ?? 1;
    const offset = Math.max(0, (page - 1) * safeSize);
    return actions.runSearch({ offset });
  },

  /**
   * Sets 0-based offset and re-derives the result set.
   *
   * @param {number} offset 0-based record offset.
   * @returns {ArticleSearchResult}
   */
  setOffset(offset) {
    return actions.runSearch({ offset });
  },

  /** Reset the search state. */
  reset() {
    articleSearchAutomat.setState(initialState);
  },
};

/**
 * Article search and pagination state for the `/artikel` overview page.
 *
 * Components subscribe to `result` to receive paginated records, facets,
 * page counts, and total counts.
 *
 * @type {Automat<ArticleSearchState>}
 */
articleSearchAutomat = new Automat(initialState, actions, { name: 'articleSearch' });

// Continuously re-derive and update subscribers as category views load their article lists.
articleIndexAutomat.subscribe(() => {
  actions.runSearch();
});

// Update facet names whenever the category tree is loaded/updated.
categoryAutomat.subscribe((catState) => {
  if (catState.treeStatus === 'succeeded') {
    actions.runSearch();
  }
});

/**
 * Selects the latest search result.
 *
 * @param {ArticleSearchState} state Automat state.
 * @returns {ArticleSearchResult} Search outcome.
 */
export function selectSearchResult(state) {
  return state.result;
}

export default articleSearchAutomat;