/**
 * Client-side bulk import engine for the shop `artikeltabelle.csv` format.
 *
 * Columns: ArtNr; Name; Preis; USt; Pfand; Hersteller; Kategorie; Barcode; V/K
 *
 * Everything is created through the existing dashback API:
 *   - categories:  POST /api/category  ({ parentId, name })
 *   - brands:      PUT /api/brand       ({ name })  → { brand: { id } }
 *   - articles:    POST /api/article    ({ categoryId, name })  → { article: { sku } }
 *   - price:       PUT /api/article/:sku/prices    ({ prices: [{ price, tax }] })
 *   - brand:       PUT /api/article/:sku/brand     ({ brandId })
 *   - eans:        PUT /api/article/:sku/eans      ({ eans })
 *   - categories:  PUT /api/article/:sku/categories({ categoryIds })
 *
 * SKU is auto-allocated by the server (POST /article) — the CSV `ArtNr` is used
 * only as a de-duplication / reference key, not as the SKU.
 */

import { parseImportCsv } from './importArtikelCsv';
import { article, category, brand } from '../api';
import {
  requireObject,
  requireDefined,
} from './apiShape';

function logImport(message) {
  console.log(`[import] ${message}`);
}

/** Build a category path lookup from the normalized category map (id → node). */
function buildCategoryPathIndex(categories, rootCategoryId) {
  const byParent = new Map();
  for (const node of Object.values(categories ?? {})) {
    const key = node.parentId == null ? 'null' : String(node.parentId);
    if (!byParent.has(key)) byParent.set(key, []);
    byParent.get(key).push(node);
  }

  const pathToId = new Map();
  const rootKey = String(rootCategoryId);
  const rootName = categories?.[rootKey]?.name ?? '';

  const walk = (node, trail) => {
    const name = (node.name ?? '').trim();
    const nextTrail = [...trail, name];
    const pathKey = nextTrail.join('|').toLowerCase();
    if (!pathToId.has(pathKey)) {
      pathToId.set(pathKey, node.id);
    }
    for (const child of byParent.get(String(node.id)) ?? []) {
      walk(child, nextTrail);
    }
  };

  if (rootName) walk({ id: rootCategoryId, name: rootName, parentId: null }, []);

  // Also index each node directly by its own name so a single-segment path
  // that equals an existing category name resolves.
  for (const node of Object.values(categories ?? {})) {
    const name = (node.name ?? '').trim();
    if (name) {
      const key = name.toLowerCase();
      if (!pathToId.has(key)) pathToId.set(key, node.id);
    }
  }

  return { pathToId, rootCategoryId, rootName };
}

/**
 * Ensure a category path `A | B | C` exists under root. Returns the leaf id.
 * Reuses an in-memory cache so repeated paths are cheap.
 */
function createEnsureCategory(cache) {
  return async function ensureCategory(segments) {
    if (!Array.isArray(segments) || segments.length === 0) {
      return cache.rootCategoryId;
    }

    const clean = segments.map((s) => s.trim()).filter(Boolean);
    if (clean.length === 0) return cache.rootCategoryId;

    const cacheKey = clean.join('|').toLowerCase();
    if (cache.byPath.has(cacheKey)) return cache.byPath.get(cacheKey);

    // Walk from root to leaf, creating missing levels.
    let parentId = cache.rootCategoryId;
    let trail = [];
    for (const segment of clean) {
      trail.push(segment);
      const trailKey = trail.join('|').toLowerCase();
      const existing = cache.pathToId.get(trailKey);
      if (existing != null) {
        parentId = existing;
        continue;
      }
      // Create the missing category under the current parent.
      const res = await category.create({ parentId, name: segment });
      requireObject(res, 'POST /api/category');
      const created = res.category;
      requireDefined(created.id, 'category.id');
      cache.pathToId.set(trailKey, created.id);
      // Note: parent of next level is this new category.
      cache.byName.set(segment.toLowerCase(), created.id);
      parentId = created.id;
    }

    cache.byPath.set(cacheKey, parentId);
    return parentId;
  };
}

/**
 * Upsert a brand by name → brandId.
 * PUT /api/brand upserts by name (same name ⇒ update, otherwise create).
 */
function createEnsureBrand(cache) {
  return async function ensureBrand(name) {
    const clean = String(name ?? '').trim();
    if (!clean) return null;
    const key = clean.toLowerCase();
    if (cache.brandByKey.has(key)) return cache.brandByKey.get(key);

    const res = await brand.upsert({ name: clean });
    requireObject(res, 'PUT /api/brand');
    requireObject(res.brand, 'brand');
    requireDefined(res.brand.id, 'brand.id');
    cache.brandByKey.set(key, res.brand.id);
    return res.brand.id;
  };
}

/**
 * Import one normalized CSV row through the API.
 * Returns a summary object for the caller to aggregate.
 */
async function importRow(row, { ensureCategory, ensureBrand }) {
  const name = String(row.name ?? '').trim();
  if (!name) return { status: 'skipped', reason: 'name-empty' };

  const leafCategoryId = await ensureCategory(row.categoryPath);
  const brandId = row.brand ? await ensureBrand(row.brand) : null;

  // Create the article under the leaf category.
  const createRes = await article.create({ categoryId: leafCategoryId, name });
  requireObject(createRes, 'POST /api/article');
  const created = createRes.article;
  requireDefined(created, 'article');
  requireDefined(created.sku, 'article.sku');
  const sku = created.sku;

  const applied = { sku, artNr: row.artNr || null, name };

  // Price (net) + tax. CSV `Preis` is treated as net in the shop export.
  if (row.price != null) {
    const tax = row.tax == null ? 19 : row.tax;
    await article.setPrices(sku, { prices: [{ price: row.price, tax }] });
    applied.price = { net: row.price, tax };
  }

  if (brandId != null) {
    await article.setBrandIdBySku(sku, brandId);
    applied.brandId = brandId;
  }

  if (row.ean) {
    await article.setEansBySku(sku, { eans: [row.ean] });
    applied.ean = row.ean;
  }

  // Article is created under the leaf category; keep the category membership.
  await article.setCategories(sku, { categoryIds: [leafCategoryId] });
  applied.categoryId = leafCategoryId;

  return { status: 'created', ...applied };
}

/**
 * Import a full CSV text into the selected company.
 *
 * @param {string} csvText            Raw CSV text.
 * @param {object} options
 * @param {object} options.categories Normalized category map (id → node) from the store.
 * @param {number|string} options.rootCategoryId Company root category id.
 * @param {(msg: string) => void} [options.onProgress] Progress callback.
 * @returns {Promise<{ok:number, skipped:number, rows:Array}>}
 */
export async function importArtikelCsv(csvText, { categories, rootCategoryId, onProgress } = {}) {
  const rows = parseImportCsv(csvText);
  if (rows.length === 0) {
    throw new Error('Keine Artikel in der CSV gefunden.');
  }
  if (rootCategoryId == null) {
    throw new Error('Keine Root-Kategorie ausgewählt.');
  }

  const cache = {
    rootCategoryId,
    pathToId: new Map(),
    byPath: new Map(),
    byName: new Map(),
    brandByKey: new Map(),
  };
  const { pathToId, rootName } = buildCategoryPathIndex(categories, rootCategoryId);
  cache.pathToId = pathToId;
  cache.rootName = rootName;

  const ensureCategory = createEnsureCategory(cache);
  const ensureBrand = createEnsureBrand(cache);

  const results = [];
  let ok = 0;
  let skipped = 0;

  for (let i = 0; i < rows.length; i++) {
    onProgress?.(`${i + 1}/${rows.length}`);
    const row = rows[i];
    try {
      const result = await importRow(row, { ensureCategory, ensureBrand });
      results.push(result);
      if (result.status === 'created') ok += 1;
      else skipped += 1;
      logImport(`ok ${row.name ?? ''} → ${result.sku ?? ''}`);
    } catch (err) {
      skipped += 1;
      logImport(`skip ${row.name ?? ''}: ${err.message ?? err}`);
      results.push({ status: 'error', name: row.name, error: err.message ?? String(err) });
    }
  }

  return { ok, skipped, rows: results };
}