/**
 * KB-article public search — hot-path migration to Meilisearch.
 *
 * The function exposes the same return shape as the legacy
 * `findKnowledgeBaseArticles` SQL implementation so the consuming
 * KnowledgeBaseService.search code path can adopt it without further
 * refactors. When MEILI_URL is unset (local dev that did not enable
 * Meilisearch), or SEARCH_BACKEND=sql is forced, we transparently fall
 * back to the legacy LIKE-based query. The same SQL path also engages
 * automatically when Meilisearch raises a connectivity error — that is
 * what `searchWithFallback` is for.
 */

import {
  createSearchClient,
  kbArticlesIndex,
  searchWithFallback,
  type SearchClient,
  type SearchFallback,
} from "@toolctrl/search";
import {
  findKnowledgeBaseArticlesByIds,
  findKnowledgeBaseArticles,
  type KnowledgeBaseArticleWithDetails,
} from "../db/kbArticles.db.server";

let cachedClient: SearchClient | undefined;
let cachedUrl: string | undefined;

// Escape values interpolated into a Meilisearch filter expression so a crafted
// `language` (sourced from the optional `($lang)` URL segment) cannot break out
// of the quoted string and inject filter operators. Mirrors rowSearch.server.ts.
function escapeFilterValue(value: string): string {
  return value.replace(/\\/gu, "\\\\").replace(/"/gu, '\\"');
}

function getSearchClient(): SearchClient | undefined {
  const url = process.env.MEILI_URL;
  if (!url || process.env.SEARCH_BACKEND === "sql") return undefined;
  if (cachedClient && cachedUrl === url) return cachedClient;
  cachedClient = createSearchClient({ url, apiKey: process.env.MEILI_API_KEY ?? undefined });
  cachedUrl = url;
  return cachedClient;
}

export interface SearchKnowledgeBaseArticlesInput {
  readonly knowledgeBaseSlug: string;
  readonly language: string | undefined;
  readonly query: string;
  /**
   * Tenant scope. Required when the Meilisearch path is engaged; the SQL
   * fallback ignores it because the (knowledgeBaseSlug, language) filter
   * already isolates results within a KB.
   */
  readonly tenantId: string | undefined;
}

export async function searchKnowledgeBaseArticles(
  input: SearchKnowledgeBaseArticlesInput
): Promise<KnowledgeBaseArticleWithDetails[]> {
  const sqlFallback: SearchFallback = async () => {
    const rows = await findKnowledgeBaseArticles({
      knowledgeBaseSlug: input.knowledgeBaseSlug,
      language: input.language,
      query: input.query,
    });
    return {
      hits: rows.map((row) => ({ document: { ...row, id: row.id, tenantId: input.tenantId ?? "" } as Record<string, unknown> & { id: string | number } })),
      estimatedTotalHits: rows.length,
      processingTimeMs: 0,
    };
  };

  const client = getSearchClient();
  if (!client || !input.tenantId) {
    // No Meilisearch backend configured or no tenantId in scope —
    // the SQL path is the authoritative source.
    const rows = await findKnowledgeBaseArticles({
      knowledgeBaseSlug: input.knowledgeBaseSlug,
      language: input.language,
      query: input.query,
    });
    return rows;
  }

  const hits = await searchWithFallback({
    client,
    schema: kbArticlesIndex,
    tenantId: input.tenantId,
    query: input.query,
    fallback: sqlFallback,
    options: input.language
      ? { extraFilters: `language = "${escapeFilterValue(input.language)}" AND isPublished = true` }
      : { extraFilters: "isPublished = true" },
  });

  // The Meilisearch hit-stream doesn't carry the full ORM relation graph
  // the route expects (category/section/related-articles); look the
  // resolved IDs back up against the SQL store so the consumer keeps
  // its existing typed return shape.
  const ids = hits.hits.map((hit) => String(hit.document.id));
  if (ids.length === 0) return [];
  const rows = await findKnowledgeBaseArticlesByIds({
    knowledgeBaseSlug: input.knowledgeBaseSlug,
    language: input.language,
    ids,
  });
  const byId = new Map(rows.map((row) => [row.id, row]));
  return ids.map((id) => byId.get(id)).filter((row): row is KnowledgeBaseArticleWithDetails => row !== undefined);
}