tercul-frontend/server/routes/filter.ts

import { Router } from "express";
import type { Request } from "express";
import { graphqlClient } from "../lib/graphqlClient";
import { respondWithError } from "../lib/error";
import { gql } from "graphql-request";
import type { Work } from "../../shared/generated/graphql";

const router = Router();

interface GqlRequest extends Request {
  gql?: typeof graphqlClient;
}

// Define a type that includes fields we need for filtering
interface WorkWithFilters extends Pick<Work, "id" | "name" | "language" | "createdAt"> {
    tags?: { id: string; name: string }[];
    authors?: { id: string; name: string }[];
}

const WORKS_WITH_FILTERS_QUERY = gql`
  query WorksWithFilters($search: String, $limit: Int) {
    works(search: $search, limit: $limit) {
      id
      name
      language
      createdAt
      tags {
        id
        name
      }
      authors {
        id
        name
      }
    }
  }
`;

// GET /api/filter
router.get("/", async (req: GqlRequest, res) => {
  try {
    const q = req.query.q as string | undefined;
    const language = req.query.language as string | undefined;
    const type = req.query.type as string | undefined;
    const yearStart = req.query.yearStart ? parseInt(req.query.yearStart as string) : undefined;
    const yearEnd = req.query.yearEnd ? parseInt(req.query.yearEnd as string) : undefined;
    const tags = req.query.tags ? (req.query.tags as string).split(",") : undefined;
    const authorIds = req.query.authorIds ? (req.query.authorIds as string).split(",") : undefined;

    // We ignore page param because we are doing client-side pagination for now,
    // returning all matching results (up to limit).
    // const page = req.query.page ? parseInt(req.query.page as string) : 1;

    const client = req.gql || graphqlClient;

    // Fetch a larger set to filter in memory.
    const variables = {
      search: q,
      limit: 1000,
    };

    const response = await client.request<{ works: WorkWithFilters[] }>(
      WORKS_WITH_FILTERS_QUERY,
      variables
    );

    let filteredWorks = response.works;

    // Filter by language
    if (language) {
      filteredWorks = filteredWorks.filter(w => w.language === language);
    }

    // Filter by type
    if (type) {
        filteredWorks = filteredWorks.filter(w => {
            const typeLower = type.toLowerCase();
            const hasTag = w.tags?.some(t => t.name.toLowerCase().includes(typeLower));
            return hasTag;
        });
    }

    // Filter by year
    if (yearStart !== undefined || yearEnd !== undefined) {
      filteredWorks = filteredWorks.filter(w => {
        const year = new Date(w.createdAt).getFullYear();
        if (yearStart !== undefined && year < yearStart) return false;
        if (yearEnd !== undefined && year > yearEnd) return false;
        return true;
      });
    }

    // Filter by tags
    if (tags && tags.length > 0) {
      filteredWorks = filteredWorks.filter(w => {
        if (!w.tags) return false;
        const workTagIds = w.tags.map(t => t.id);
        return tags.every(tagId => workTagIds.includes(tagId));
      });
    }

    // Filter by authors
    if (authorIds && authorIds.length > 0) {
      filteredWorks = filteredWorks.filter(w => {
         if (!w.authors) return false;
         const workAuthorIds = w.authors.map(a => a.id);
         return authorIds.some(authorId => workAuthorIds.includes(authorId));
      });
    }

    // Return all results for client-side pagination
    res.json(filteredWorks);
  } catch (error) {
    respondWithError(res, error, "Failed to filter works");
  }
});

export default router;