feat: Wikidata engine and Wikipedia knowledge infobox

- Add wikidata engine (wbsearchentities), tests, factory/planner/config
- Wikipedia REST summary: infobox from extract, thumbnail, article URL
- InfoboxView URL; render infobox list in results_inner + base styles
- Preferences Wikidata toggle; engine badge color for wikidata

Made-with: Cursor

internal/engines/factory.go

@@ -50,6 +50,7 @@ func NewDefaultPortedEngines(client *http.Client, cfg *config.Config) map[string
 
 	return map[string]Engine{
 		"wikipedia": &WikipediaEngine{client: client},
+		"wikidata":  &WikidataEngine{client: client},
 		"arxiv":     &ArxivEngine{client: client},
 		"crossref":  &CrossrefEngine{client: client},
 		"braveapi": &BraveAPIEngine{

internal/engines/planner.go

@@ -24,7 +24,7 @@ import (
 )
 
 var defaultPortedEngines = []string{
-	"wikipedia", "arxiv", "crossref", "braveapi",
+	"wikipedia", "wikidata", "arxiv", "crossref", "braveapi",
 	"brave", "qwant", "duckduckgo", "github", "reddit",
 	"bing", "google", "youtube", "stackoverflow",
 	// Image engines
@@ -106,6 +106,7 @@ func inferFromCategories(categories []string) []string {
 		switch strings.TrimSpace(strings.ToLower(c)) {
 		case "general":
 			set["wikipedia"] = true
+			set["wikidata"] = true
 			set["braveapi"] = true
 			set["qwant"] = true
 			set["duckduckgo"] = true
@@ -134,9 +135,9 @@ func inferFromCategories(categories []string) []string {
 	}
 	// stable order
 	order := map[string]int{
-		"wikipedia": 0, "braveapi": 1, "brave": 2, "qwant": 3, "duckduckgo": 4, "bing": 5, "google": 6,
-		"arxiv": 7, "crossref": 8, "github": 9, "stackoverflow": 10, "reddit": 11, "youtube": 12,
-		"bing_images": 13, "ddg_images": 14, "qwant_images": 15,
+		"wikipedia": 0, "wikidata": 1, "braveapi": 2, "brave": 3, "qwant": 4, "duckduckgo": 5, "bing": 6, "google": 7,
+		"arxiv": 8, "crossref": 9, "github": 10, "stackoverflow": 11, "reddit": 12, "youtube": 13,
+		"bing_images": 14, "ddg_images": 15, "qwant_images": 16,
 	}
 	sortByOrder(out, order)
 	return out

internal/engines/wikidata.go

@@ -0,0 +1,133 @@
+// 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
+}

internal/engines/wikidata_test.go

@@ -0,0 +1,51 @@
+package engines
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/metamorphosis-dev/samsa/internal/contracts"
+)
+
+func TestWikidataEngine_Search(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Query().Get("action") != "wbsearchentities" {
+			t.Errorf("action=%q", r.URL.Query().Get("action"))
+		}
+		if got := r.URL.Query().Get("search"); got != "test" {
+			t.Errorf("search=%q want test", got)
+		}
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"search":[{"id":"Q937","label":"Go","description":"Programming language"}]}`))
+	}))
+	defer ts.Close()
+
+	orig := wikidataAPIBase
+	t.Cleanup(func() { wikidataAPIBase = orig })
+	wikidataAPIBase = ts.URL + "/w/api.php"
+
+	e := &WikidataEngine{client: ts.Client()}
+	resp, err := e.Search(context.Background(), contracts.SearchRequest{
+		Query:    "test",
+		Language: "en",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(resp.Results) != 1 {
+		t.Fatalf("expected 1 result, got %d", len(resp.Results))
+	}
+	r0 := resp.Results[0]
+	if r0.Engine != "wikidata" {
+		t.Errorf("engine=%q", r0.Engine)
+	}
+	if r0.Title != "Go" {
+		t.Errorf("title=%q", r0.Title)
+	}
+	if r0.URL == nil || !strings.Contains(*r0.URL, "Q937") {
+		t.Errorf("url=%v", r0.URL)
+	}
+}

internal/engines/wikipedia.go

@@ -123,13 +123,13 @@ func (e *WikipediaEngine) Search(ctx context.Context, req contracts.SearchReques
 
 	if resp.StatusCode == http.StatusNotFound {
 		return contracts.SearchResponse{
-			Query:            req.Query,
-			NumberOfResults: 0,
-			Results:          []contracts.MainResult{},
-			Answers:          []map[string]any{},
-			Corrections:      []string{},
-			Infoboxes:        []map[string]any{},
-			Suggestions:      []string{},
+			Query:               req.Query,
+			NumberOfResults:     0,
+			Results:             []contracts.MainResult{},
+			Answers:             []map[string]any{},
+			Corrections:         []string{},
+			Infoboxes:           []map[string]any{},
+			Suggestions:         []string{},
 			UnresponsiveEngines: [][2]string{},
 		}, nil
 	}
@@ -141,9 +141,13 @@ func (e *WikipediaEngine) Search(ctx context.Context, req contracts.SearchReques
 	var api struct {
 		Title       string `json:"title"`
 		Description string `json:"description"`
+		Extract     string `json:"extract"`
 		Titles      struct {
 			Display string `json:"display"`
 		} `json:"titles"`
+		Thumbnail struct {
+			Source string `json:"source"`
+		} `json:"thumbnail"`
 		ContentURLs struct {
 			Desktop struct {
 				Page string `json:"page"`
@@ -160,7 +164,7 @@ func (e *WikipediaEngine) Search(ctx context.Context, req contracts.SearchReques
 		// API returned a non-standard payload; treat as no result.
 		return contracts.SearchResponse{
 			Query:               req.Query,
-			NumberOfResults:    0,
+			NumberOfResults:     0,
 			Results:             []contracts.MainResult{},
 			Answers:             []map[string]any{},
 			Corrections:         []string{},
@@ -175,36 +179,61 @@ func (e *WikipediaEngine) Search(ctx context.Context, req contracts.SearchReques
 		title = api.Title
 	}
 
-	content := api.Description
+	content := strings.TrimSpace(api.Extract)
+	if content == "" {
+		content = strings.TrimSpace(api.Description)
+	}
 
 	urlPtr := pageURL
 	pub := (*string)(nil)
 
+	// Knowledge infobox for HTML (Wikipedia REST summary: title, extract, thumbnail, link).
+	var infoboxes []map[string]any
+	ibTitle := api.Titles.Display
+	if ibTitle == "" {
+		ibTitle = api.Title
+	}
+	body := strings.TrimSpace(api.Extract)
+	if body == "" {
+		body = strings.TrimSpace(api.Description)
+	}
+	imgSrc := strings.TrimSpace(api.Thumbnail.Source)
+	if ibTitle != "" || body != "" || imgSrc != "" {
+		row := map[string]any{
+			"title":   ibTitle,
+			"infobox": body,
+			"url":     pageURL,
+		}
+		if imgSrc != "" {
+			row["img_src"] = imgSrc
+		}
+		infoboxes = append(infoboxes, row)
+	}
+
 	results := []contracts.MainResult{
 		{
-			Template: "default.html",
-			Title:    title,
-			Content:  content,
-			URL:      &urlPtr,
-			Pubdate:  pub,
-			Engine:   "wikipedia",
-			Score:    0,
-			Category: "general",
-			Priority: "",
+			Template:  "default.html",
+			Title:     title,
+			Content:   content,
+			URL:       &urlPtr,
+			Pubdate:   pub,
+			Engine:    "wikipedia",
+			Score:     0,
+			Category:  "general",
+			Priority:  "",
 			Positions: nil,
-			Engines:  []string{"wikipedia"},
+			Engines:   []string{"wikipedia"},
 		},
 	}
 
 	return contracts.SearchResponse{
 		Query:               req.Query,
-		NumberOfResults:    len(results),
+		NumberOfResults:     len(results),
 		Results:             results,
 		Answers:             []map[string]any{},
 		Corrections:         []string{},
-		Infoboxes:           []map[string]any{},
+		Infoboxes:           infoboxes,
 		Suggestions:         []string{},
 		UnresponsiveEngines: [][2]string{},
 	}, nil
 }
-