samsa/internal/engines/wikidata.go

// samsa — a privacy-respecting metasearch engine
// Copyright (C) 2026-present metamorphosis-dev
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

package engines

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strings"

	"github.com/metamorphosis-dev/samsa/internal/contracts"
)

// wikidataAPIBase is the Wikidata MediaWiki API endpoint (overridable in tests).
var wikidataAPIBase = "https://www.wikidata.org/w/api.php"

// WikidataEngine searches entity labels and descriptions via the Wikidata API.
// See: https://www.wikidata.org/w/api.php?action=help&modules=wbsearchentities
type WikidataEngine struct {
	client *http.Client
}

func (e *WikidataEngine) Name() string { return "wikidata" }

func (e *WikidataEngine) Search(ctx context.Context, req contracts.SearchRequest) (contracts.SearchResponse, error) {
	if e == nil || e.client == nil {
		return contracts.SearchResponse{}, errors.New("wikidata engine not initialized")
	}
	q := strings.TrimSpace(req.Query)
	if q == "" {
		return contracts.SearchResponse{Query: req.Query}, nil
	}

	lang := strings.TrimSpace(req.Language)
	if lang == "" || lang == "auto" {
		lang = "en"
	}
	lang = strings.SplitN(lang, "-", 2)[0]
	lang = strings.ReplaceAll(lang, "_", "-")
	if _, ok := validWikipediaLangs[lang]; !ok {
		lang = "en"
	}

	u, err := url.Parse(wikidataAPIBase)
	if err != nil {
		return contracts.SearchResponse{}, err
	}
	qv := u.Query()
	qv.Set("action", "wbsearchentities")
	qv.Set("search", q)
	qv.Set("language", lang)
	qv.Set("limit", "10")
	qv.Set("format", "json")
	u.RawQuery = qv.Encode()

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)
	if err != nil {
		return contracts.SearchResponse{}, err
	}
	httpReq.Header.Set("User-Agent", "samsa/1.0 (Wikidata search; +https://github.com/metamorphosis-dev/samsa)")

	resp, err := e.client.Do(httpReq)
	if err != nil {
		return contracts.SearchResponse{}, err
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		io.Copy(io.Discard, io.LimitReader(resp.Body, 16*1024))
		return contracts.SearchResponse{}, fmt.Errorf("wikidata upstream error: status %d", resp.StatusCode)
	}

	body, err := io.ReadAll(io.LimitReader(resp.Body, 2*1024*1024))
	if err != nil {
		return contracts.SearchResponse{}, err
	}

	var api struct {
		Search []struct {
			ID          string `json:"id"`
			Label       string `json:"label"`
			Description string `json:"description"`
		} `json:"search"`
	}
	if err := json.Unmarshal(body, &api); err != nil {
		return contracts.SearchResponse{}, fmt.Errorf("wikidata JSON parse error: %w", err)
	}

	results := make([]contracts.MainResult, 0, len(api.Search))
	for _, hit := range api.Search {
		id := strings.TrimSpace(hit.ID)
		if id == "" || !strings.HasPrefix(id, "Q") {
			continue
		}
		pageURL := "https://www.wikidata.org/wiki/" + url.PathEscape(id)
		title := strings.TrimSpace(hit.Label)
		if title == "" {
			title = id
		}
		content := strings.TrimSpace(hit.Description)
		urlPtr := pageURL
		results = append(results, contracts.MainResult{
			Template: "default.html",
			Title:    title,
			Content:  content,
			URL:      &urlPtr,
			Engine:   "wikidata",
			Category: "general",
			Engines:  []string{"wikidata"},
		})
	}

	return contracts.SearchResponse{
		Query:               req.Query,
		NumberOfResults:     len(results),
		Results:             results,
		Answers:             []map[string]any{},
		Corrections:         []string{},
		Infoboxes:           []map[string]any{},
		Suggestions:         []string{},
		UnresponsiveEngines: [][2]string{},
	}, nil
}