Search providers: SearXNG and Brave with ranking (#67)

Co-authored-by: dev_agent <dev_agent@cubecraftlabs.com>

docs/ARCHITECTURE.md

@@ -239,6 +239,30 @@ automatic** (D-021).
   with two is `ErrManyRecipes`; a shape schema.org does not allow — such as
   a non-ISO-8601 duration like "20 minutes" or an empty one, or an image
   `@id` no node has — is `ErrMalformedRecipe`, never guessed at.
+- Recipe search (`recipes.SearchProvider`: `Search(ctx, query, n)` →
+  `[]Candidate{URL, Title, Snippet}`, n 1–20) appends " recipe" to a query
+  without that word. SearXNG is called at
+  `{MEALQUEST_SEARXNG_URL}/search?q=…&format=json&categories=general` —
+  directly, not through the Fetcher, since this configured endpoint may be
+  on the internal network; Brave calls the Brave Web Search API with the
+  key decrypted from `recipe_search_settings.api_key_ct`
+  (`recipes.NewSearchProvider`). Redirects are not followed; 401/403 is
+  `ErrSearchRefused`, 429 `ErrSearchRateLimited`, other non-2xx a
+  `SearchStatusError`, and a body that is not the provider's JSON (SearXNG
+  without a `results` array; Brave without `"type": "search"` or with a
+  `web` object lacking `results` — Brave omits `web` when nothing matched),
+  over 1 MB or with a result lacking an absolute http(s) URL
+  `ErrSearchResponse`.
+- Ranking (`recipes.Rank`) fetches and extracts the top 5 candidates
+  concurrently, rejects any whose recipe lacks ingredients or an image, and
+  orders the rest by the token similarity of the recipe's title to the dish
+  name (`harness.Similarity`, 0–1) plus a quarter for each of ingredients,
+  image, steps and total minutes; ties keep search order. No unranked
+  candidate is dropped silently: when some are ranked, they are returned
+  with `ErrCandidatesUnranked`; when none are, the error is
+  `ErrNoUsableRecipe`. Either is joined with each unranked candidate's URL
+  and reason (fetch failure, no valid recipe, missing ingredients or
+  image), so the caller decides per item what a failure means.
 - Photos are cached locally (`photos`) and processed with
   `golang.org/x/image`.
 

internal/ai/harness/dedupe.go

@@ -53,7 +53,14 @@ func Normalize(name string) string {
 // similarity of their normalized forms is at least SimilarThreshold. A name
 // with no words left after normalizing is similar to nothing.
 func Similar(a, b string) bool {
-	return similarity(tokenSet(a), tokenSet(b)) >= SimilarThreshold
+	return Similarity(a, b) >= SimilarThreshold
+}
+
+// Similarity is the token-set (Jaccard) similarity of a's and b's normalized
+// forms, from 0 (no shared word) to 1 (the same words). A name with no words
+// left after normalizing scores 0 against everything.
+func Similarity(a, b string) float64 {
+	return similarity(tokenSet(a), tokenSet(b))
 }
 
 // tokenSet returns the distinct words of name's normalized form.

internal/ai/harness/dedupe_test.go

@@ -114,6 +114,22 @@ func TestSimilar(t *testing.T) {
 	}
 }
 
+func TestSimilarity(t *testing.T) {
+	for _, tc := range []struct {
+		a, b string
+		want float64
+	}{
+		{"Easy Chicken Curry", "chicken curry", 1},
+		{"Thai Green Curry", "Chicken curry", 0.25},
+		{"Beef Stew", "Chicken curry", 0},
+		{"The Recipe", "chicken curry", 0},
+	} {
+		if got := Similarity(tc.a, tc.b); got != tc.want {
+			t.Errorf("Similarity(%q, %q) = %v, want %v", tc.a, tc.b, got, tc.want)
+		}
+	}
+}
+
 func TestDeduper(t *testing.T) {
 	d := NewDeduper(DedupeSources{
 		Regulars: []string{"Beef Tacos", "Spaghetti Bolognese"},

internal/recipes/rank.go

@@ -0,0 +1,130 @@
+package recipes
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sort"
+	"sync"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/ai/harness"
+)
+
+// RankDepth is how many of the top search candidates Rank fetches and
+// extracts.
+const RankDepth = 5
+
+var (
+	// ErrNoIngredients rejects a candidate whose recipe lists no
+	// ingredients.
+	ErrNoIngredients = errors.New("recipes: recipe has no ingredients")
+	// ErrNoImage rejects a candidate whose recipe has no image.
+	ErrNoImage = errors.New("recipes: recipe has no image")
+	// ErrNoUsableRecipe is returned when Rank ranks no candidate; it is
+	// joined with each candidate's reason.
+	ErrNoUsableRecipe = errors.New("recipes: no candidate holds a usable recipe")
+	// ErrCandidatesUnranked is returned, alongside the ranked candidates,
+	// when Rank ranks some candidates but not all; it is joined with each
+	// unranked candidate's reason.
+	ErrCandidatesUnranked = errors.New("recipes: some candidates were not ranked")
+)
+
+// PageFetcher fetches a candidate's page; *Fetcher satisfies it.
+type PageFetcher interface {
+	Fetch(ctx context.Context, rawURL string) (Page, error)
+}
+
+// Ranked is a candidate whose page held a usable recipe, with its score.
+type Ranked struct {
+	Candidate Candidate
+	Recipe    Recipe
+	// Score is the token similarity of the recipe's title to the dish name
+	// (0 to 1, harness.Similarity) plus a quarter for each of ingredients,
+	// image, steps and total minutes present (0 to 1).
+	Score float64
+}
+
+// Rank fetches and extracts the first RankDepth candidates concurrently and
+// returns those whose recipe has ingredients and an image, highest Score
+// first; equal scores keep search order.
+//
+// Every candidate that is not ranked — its fetch failed, its page holds no
+// valid recipe, or the recipe lacks ingredients or an image — is reported,
+// never dropped silently: when some are ranked the error is
+// ErrCandidatesUnranked, returned together with the ranked ones; when none
+// are it is ErrNoUsableRecipe with no results. Either is joined with each
+// unranked candidate's URL and reason. A cancelled ctx returns only its
+// error.
+func Rank(ctx context.Context, f PageFetcher, dish string, cands []Candidate) ([]Ranked, error) {
+	if len(cands) > RankDepth {
+		cands = cands[:RankDepth]
+	}
+	type outcome struct {
+		ranked Ranked
+		err    error
+	}
+	outcomes := make([]outcome, len(cands))
+	var wg sync.WaitGroup
+	for i, c := range cands {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			r, err := rankOne(ctx, f, dish, c)
+			outcomes[i] = outcome{r, err}
+		}()
+	}
+	wg.Wait()
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+
+	var ranked []Ranked
+	var reasons []error
+	for i, o := range outcomes {
+		if o.err != nil {
+			reasons = append(reasons, fmt.Errorf("%s: %w", cands[i].URL, o.err))
+			continue
+		}
+		ranked = append(ranked, o.ranked)
+	}
+	if len(ranked) == 0 {
+		return nil, errors.Join(append([]error{ErrNoUsableRecipe}, reasons...)...)
+	}
+	sort.SliceStable(ranked, func(a, b int) bool { return ranked[a].Score > ranked[b].Score })
+	if len(reasons) > 0 {
+		return ranked, errors.Join(append([]error{ErrCandidatesUnranked}, reasons...)...)
+	}
+	return ranked, nil
+}
+
+// rankOne fetches, extracts and scores one candidate, or says why it is
+// rejected.
+func rankOne(ctx context.Context, f PageFetcher, dish string, c Candidate) (Ranked, error) {
+	page, err := f.Fetch(ctx, c.URL)
+	if err != nil {
+		return Ranked{}, err
+	}
+	r, err := Extract(page.Body, page.URL)
+	if err != nil {
+		return Ranked{}, err
+	}
+	if len(r.Ingredients) == 0 {
+		return Ranked{}, ErrNoIngredients
+	}
+	if r.ImageURL == "" {
+		return Ranked{}, ErrNoImage
+	}
+	return Ranked{Candidate: c, Recipe: r, Score: harness.Similarity(r.Title, dish) + completeness(r)}, nil
+}
+
+// completeness is a quarter for each of ingredients, image, steps and total
+// minutes the recipe has.
+func completeness(r Recipe) float64 {
+	score := 0.0
+	for _, present := range []bool{len(r.Ingredients) > 0, r.ImageURL != "", len(r.Steps) > 0, r.TotalMinutes != nil} {
+		if present {
+			score += 0.25
+		}
+	}
+	return score
+}

internal/recipes/rank_test.go

@@ -0,0 +1,255 @@
+package recipes
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"strings"
+	"sync"
+	"testing"
+)
+
+var _ PageFetcher = (*Fetcher)(nil)
+
+// fakeFetcher serves fixture pages by URL and records what was fetched.
+type fakeFetcher struct {
+	pages map[string][]byte
+
+	mu      sync.Mutex
+	fetched []string
+}
+
+func (f *fakeFetcher) Fetch(_ context.Context, rawURL string) (Page, error) {
+	f.mu.Lock()
+	f.fetched = append(f.fetched, rawURL)
+	f.mu.Unlock()
+	body, ok := f.pages[rawURL]
+	if !ok {
+		return Page{}, &StatusError{URL: rawURL, Status: 404}
+	}
+	return Page{URL: rawURL, ContentType: "text/html", Body: body}, nil
+}
+
+// recipePage returns a page whose Recipe has the given name and, as asked,
+// ingredients, an image, steps and a total time.
+func recipePage(name string, ingredients, image, steps, minutes bool) []byte {
+	ld := fmt.Sprintf(`{"@context":"https://schema.org","@type":"Recipe","name":%q`, name)
+	if ingredients {
+		ld += `,"recipeIngredient":["1 onion","2 cloves garlic"]`
+	}
+	if image {
+		ld += `,"image":"https://img.example.com/dish.jpg"`
+	}
+	if steps {
+		ld += `,"recipeInstructions":["Chop.","Cook."]`
+	}
+	if minutes {
+		ld += `,"totalTime":"PT40M"`
+	}
+	return page("", ld+"}")
+}
+
+func TestRankOrder(t *testing.T) {
+	f := &fakeFetcher{pages: map[string][]byte{
+		"https://a.example/thai":    recipePage("Thai Green Curry", true, true, true, true),
+		"https://b.example/noimg":   recipePage("Chicken Curry", true, false, true, true),
+		"https://c.example/easy":    recipePage("Easy Chicken Curry", true, true, true, false),
+		"https://d.example/noingr":  recipePage("Chicken Curry", false, true, true, true),
+		"https://e.example/best":    recipePage("Chicken Curry", true, true, true, true),
+		"https://f.example/toodeep": recipePage("Chicken Curry", true, true, true, true),
+	}}
+	cands := []Candidate{
+		{URL: "https://a.example/thai", Title: "Thai green curry"},
+		{URL: "https://b.example/noimg"},
+		{URL: "https://c.example/easy"},
+		{URL: "https://d.example/noingr"},
+		{URL: "https://e.example/best"},
+		{URL: "https://f.example/toodeep"},
+	}
+	got, err := Rank(context.Background(), f, "Chicken curry", cands)
+	if !errors.Is(err, ErrCandidatesUnranked) || !errors.Is(err, ErrNoImage) || !errors.Is(err, ErrNoIngredients) {
+		t.Errorf("err = %v, want ErrCandidatesUnranked with ErrNoImage and ErrNoIngredients", err)
+	}
+	if errors.Is(err, ErrNoUsableRecipe) {
+		t.Errorf("err = %v, want not ErrNoUsableRecipe when some are ranked", err)
+	}
+	want := []struct {
+		url   string
+		score float64
+	}{
+		// Same words, every field: 1 + 1.
+		{"https://e.example/best", 2},
+		// "Easy" is a filler word, so the title matches; no total time.
+		{"https://c.example/easy", 1.75},
+		// Shares one of four words: 0.25 + 1.
+		{"https://a.example/thai", 1.25},
+	}
+	if len(got) != len(want) {
+		t.Fatalf("got %d ranked, want %d: %+v", len(got), len(want), got)
+	}
+	for i, w := range want {
+		if got[i].Candidate.URL != w.url || got[i].Score != w.score {
+			t.Errorf("rank %d = %s (%.2f), want %s (%.2f)", i, got[i].Candidate.URL, got[i].Score, w.url, w.score)
+		}
+	}
+	if got[2].Recipe.Title != "Thai Green Curry" || got[2].Candidate.Title != "Thai green curry" {
+		t.Errorf("ranked entry lost its recipe or candidate: %+v", got[2])
+	}
+	for _, u := range f.fetched {
+		if u == "https://f.example/toodeep" {
+			t.Errorf("fetched a candidate past RankDepth")
+		}
+	}
+	if len(f.fetched) != RankDepth {
+		t.Errorf("fetched %d pages, want %d", len(f.fetched), RankDepth)
+	}
+}
+
+func TestRankTiesKeepSearchOrder(t *testing.T) {
+	f := &fakeFetcher{pages: map[string][]byte{
+		"https://a.example/1": recipePage("Beef Stew", true, true, true, true),
+		"https://b.example/2": recipePage("Beef Stew", true, true, true, true),
+		"https://c.example/3": recipePage("Beef Stew", true, true, true, true),
+	}}
+	cands := []Candidate{{URL: "https://a.example/1"}, {URL: "https://b.example/2"}, {URL: "https://c.example/3"}}
+	got, err := Rank(context.Background(), f, "beef stew", cands)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for i, c := range cands {
+		if got[i].Candidate.URL != c.URL {
+			t.Errorf("rank %d = %s, want %s", i, got[i].Candidate.URL, c.URL)
+		}
+	}
+}
+
+// TestRankReportsFetchFailure checks a failed fetch is reported with the
+// candidates that were ranked, never swallowed.
+func TestRankReportsFetchFailure(t *testing.T) {
+	f := &fakeFetcher{pages: map[string][]byte{
+		"https://a.example/1": recipePage("Beef Stew", true, true, true, true),
+	}}
+	cands := []Candidate{{URL: "https://a.example/1"}, {URL: "https://b.example/missing"}}
+	got, err := Rank(context.Background(), f, "beef stew", cands)
+	if len(got) != 1 || got[0].Candidate.URL != "https://a.example/1" {
+		t.Errorf("ranked = %+v, want only https://a.example/1", got)
+	}
+	if !errors.Is(err, ErrCandidatesUnranked) {
+		t.Errorf("err = %v, want ErrCandidatesUnranked", err)
+	}
+	var se *StatusError
+	if !errors.As(err, &se) || se.Status != 404 || se.URL != "https://b.example/missing" {
+		t.Errorf("err = %v, want the 404 StatusError for https://b.example/missing", err)
+	}
+	if err != nil && !strings.Contains(err.Error(), "https://b.example/missing") {
+		t.Errorf("err = %v, want it to name the failed candidate", err)
+	}
+}
+
+func TestRankAllRejected(t *testing.T) {
+	f := &fakeFetcher{pages: map[string][]byte{
+		"https://a.example/noimg":  recipePage("Chicken Curry", true, false, true, true),
+		"https://b.example/noingr": recipePage("Chicken Curry", false, true, true, true),
+		"https://c.example/blog":   page(""),
+	}}
+	cands := []Candidate{
+		{URL: "https://a.example/noimg"},
+		{URL: "https://b.example/noingr"},
+		{URL: "https://c.example/blog"},
+		{URL: "https://d.example/missing"},
+	}
+	_, err := Rank(context.Background(), f, "chicken curry", cands)
+	for _, want := range []error{ErrNoUsableRecipe, ErrNoImage, ErrNoIngredients, ErrNoRecipe} {
+		if !errors.Is(err, want) {
+			t.Errorf("err = %v, want it to wrap %v", err, want)
+		}
+	}
+	var se *StatusError
+	if !errors.As(err, &se) || se.Status != 404 {
+		t.Errorf("err = %v, want the 404 StatusError", err)
+	}
+}
+
+func TestRankNoCandidates(t *testing.T) {
+	if _, err := Rank(context.Background(), &fakeFetcher{}, "chicken curry", nil); !errors.Is(err, ErrNoUsableRecipe) {
+		t.Errorf("err = %v, want ErrNoUsableRecipe", err)
+	}
+}
+
+func TestRankContextCancelled(t *testing.T) {
+	f := &fakeFetcher{pages: map[string][]byte{"https://a.example/1": recipePage("Beef Stew", true, true, true, true)}}
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	if _, err := Rank(ctx, f, "beef stew", []Candidate{{URL: "https://a.example/1"}}); !errors.Is(err, context.Canceled) {
+		t.Errorf("err = %v, want context.Canceled", err)
+	}
+}
+
+// TestRankOverHTTP ranks fixture candidates served over HTTPS through the
+// SSRF-safe Fetcher: every host, a subdomain the test server's certificate
+// covers, resolves to a public test address the test
+// dialer routes to one httptest server, which serves pages by host and path.
+func TestRankOverHTTP(t *testing.T) {
+	t.Parallel()
+	pages := map[string][]byte{
+		"best.example.com/curry":  recipePage("Chicken Curry", true, true, true, true),
+		"easy.example.com/curry":  recipePage("Easy Chicken Curry", true, true, true, false),
+		"thai.example.com/curry":  recipePage("Thai Green Curry", true, true, true, true),
+		"noimg.example.com/curry": recipePage("Chicken Curry", true, false, true, true),
+	}
+	env := newTestEnv(t, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, ok := pages[r.Host+r.URL.Path]
+		if !ok {
+			http.Error(w, "broken", http.StatusInternalServerError)
+			return
+		}
+		w.Header().Set("Content-Type", "text/html")
+		w.Write(body)
+	}), map[string][][]string{
+		"best.example.com":   {{publicIP}},
+		"easy.example.com":   {{publicIP}},
+		"thai.example.com":   {{publicIP}},
+		"noimg.example.com":  {{publicIP}},
+		"broken.example.com": {{publicIP}},
+	})
+	cands := []Candidate{
+		{URL: "https://thai.example.com/curry"},
+		{URL: "https://broken.example.com/curry"},
+		{URL: "https://easy.example.com/curry"},
+		{URL: "https://noimg.example.com/curry"},
+		{URL: "https://best.example.com/curry"},
+	}
+
+	got, err := Rank(t.Context(), env.f, "Chicken curry", cands)
+
+	want := []struct {
+		url   string
+		score float64
+	}{
+		{"https://best.example.com/curry", 2},
+		{"https://easy.example.com/curry", 1.75},
+		{"https://thai.example.com/curry", 1.25},
+	}
+	if len(got) != len(want) {
+		t.Fatalf("got %d ranked, want %d: %+v (err %v)", len(got), len(want), got, err)
+	}
+	for i, w := range want {
+		if got[i].Candidate.URL != w.url || got[i].Score != w.score {
+			t.Errorf("rank %d = %s (%.2f), want %s (%.2f)", i, got[i].Candidate.URL, got[i].Score, w.url, w.score)
+		}
+	}
+	if got[0].Recipe.Title != "Chicken Curry" || got[0].Recipe.ImageURL != "https://img.example.com/dish.jpg" {
+		t.Errorf("top recipe = %+v", got[0].Recipe)
+	}
+	if !errors.Is(err, ErrCandidatesUnranked) || !errors.Is(err, ErrNoImage) {
+		t.Errorf("err = %v, want ErrCandidatesUnranked with ErrNoImage", err)
+	}
+	var se *StatusError
+	if !errors.As(err, &se) || se.Status != http.StatusInternalServerError {
+		t.Errorf("err = %v, want the 500 StatusError for broken.example.com", err)
+	}
+	if n := len(env.dials()); n != len(cands) {
+		t.Errorf("dialed %d times, want %d", n, len(cands))
+	}
+}

internal/recipes/search.go

@@ -0,0 +1,314 @@
+package recipes
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/db"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/secretbox"
+)
+
+const (
+	// MaxSearchResults is the most candidates one search may ask for; it is
+	// Brave's largest page.
+	MaxSearchResults = 20
+	// SearchTimeout bounds one search request, reading the body included.
+	SearchTimeout = 10 * time.Second
+	// MaxSearchBodyBytes caps a search response body. A larger one is an
+	// error, never truncated.
+	MaxSearchBodyBytes = 1 << 20
+	// BraveEndpoint is the Brave Web Search API.
+	BraveEndpoint = "https://api.search.brave.com/res/v1/web/search"
+)
+
+var (
+	// ErrSearchRefused is returned for HTTP 401 or 403: Brave rejected the
+	// API key, or SearXNG does not allow format=json.
+	ErrSearchRefused = errors.New("recipes: search provider refused the request")
+	// ErrSearchRateLimited is returned for HTTP 429.
+	ErrSearchRateLimited = errors.New("recipes: search provider rate limit reached")
+	// ErrSearchResponse is returned for a response body that is not the
+	// provider's JSON shape — SearXNG without a results array, Brave without
+	// "type": "search" or with a web object lacking a results array — is
+	// over MaxSearchBodyBytes, or holds a result without an absolute http(s)
+	// URL.
+	ErrSearchResponse = errors.New("recipes: malformed search response")
+)
+
+// SearchStatusError is returned for any other non-2xx search response,
+// redirects included: a search endpoint is called directly and never
+// followed elsewhere.
+type SearchStatusError struct {
+	Provider string
+	Status   int
+}
+
+func (e *SearchStatusError) Error() string {
+	return fmt.Sprintf("recipes: %s search: HTTP %d", e.Provider, e.Status)
+}
+
+// Candidate is one search result: a page that may hold a recipe.
+type Candidate struct {
+	URL     string
+	Title   string
+	Snippet string
+}
+
+// SearchProvider finds recipe pages on the web.
+type SearchProvider interface {
+	// Search returns up to n candidates for query, best first. The query
+	// gets " recipe" appended unless it already has the word. n must be
+	// 1 to MaxSearchResults.
+	Search(ctx context.Context, query string, n int) ([]Candidate, error)
+}
+
+// NewSearchProvider returns the provider s names. SearXNG is called at
+// searxngURL, the configured MEALQUEST_SEARXNG_URL; Brave is called with the
+// API key in s.ApiKeyCt, decrypted by box.
+func NewSearchProvider(s db.RecipeSearchSetting, box *secretbox.Box, searxngURL string) (SearchProvider, error) {
+	switch s.Provider {
+	case "searxng":
+		return NewSearXNG(searxngURL)
+	case "brave":
+		if len(s.ApiKeyCt) == 0 {
+			return nil, errors.New("recipes: Brave search has no API key")
+		}
+		key, err := box.Decrypt(s.ApiKeyCt)
+		if err != nil {
+			return nil, fmt.Errorf("recipes: Brave API key: %w", err)
+		}
+		return NewBrave(string(key))
+	default:
+		return nil, fmt.Errorf("recipes: unknown search provider %q", s.Provider)
+	}
+}
+
+// SearXNG searches through a SearXNG instance. Its base URL is a configured
+// endpoint and may be on a private network, so it is called directly rather
+// than through the public-only Fetcher.
+type SearXNG struct {
+	endpoint *url.URL
+	client   *http.Client
+}
+
+// NewSearXNG returns a SearXNG provider for the instance at baseURL, an
+// absolute http:// or https:// URL without credentials, query or fragment.
+func NewSearXNG(baseURL string) (*SearXNG, error) {
+	if baseURL == "" {
+		return nil, errors.New("recipes: SearXNG URL is not set")
+	}
+	u, err := url.Parse(baseURL)
+	if err != nil || (u.Scheme != "http" && u.Scheme != "https") || u.Host == "" {
+		return nil, errors.New("recipes: SearXNG URL must be an absolute http:// or https:// URL")
+	}
+	if u.User != nil || u.RawQuery != "" || u.Fragment != "" {
+		return nil, errors.New("recipes: SearXNG URL must not have credentials, a query or a fragment")
+	}
+	return &SearXNG{endpoint: u.JoinPath("search"), client: newSearchClient()}, nil
+}
+
+// Search implements SearchProvider with
+// {base}/search?q=…&format=json&categories=general.
+func (s *SearXNG) Search(ctx context.Context, query string, n int) ([]Candidate, error) {
+	q, err := searchQuery(query, n)
+	if err != nil {
+		return nil, err
+	}
+	u := *s.endpoint
+	u.RawQuery = url.Values{"q": {q}, "format": {"json"}, "categories": {"general"}}.Encode()
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)
+	if err != nil {
+		return nil, fmt.Errorf("recipes: build SearXNG request: %w", err)
+	}
+	// Results is a pointer so a body without the array is told apart from
+	// an empty search.
+	var body struct {
+		Results *[]struct {
+			URL     string `json:"url"`
+			Title   string `json:"title"`
+			Content string `json:"content"`
+		} `json:"results"`
+	}
+	if err := doSearch(s.client, req, "SearXNG", &body); err != nil {
+		return nil, err
+	}
+	if body.Results == nil {
+		return nil, fmt.Errorf("%w: SearXNG body has no results array", ErrSearchResponse)
+	}
+	var out []Candidate
+	for _, r := range *body.Results {
+		out = append(out, Candidate{URL: r.URL, Title: r.Title, Snippet: r.Content})
+	}
+	return candidates("SearXNG", out, n)
+}
+
+// Brave searches through the Brave Web Search API.
+type Brave struct {
+	key      string
+	endpoint string
+	client   *http.Client
+}
+
+// NewBrave returns a Brave provider that authenticates with key, the
+// decrypted API key.
+func NewBrave(key string) (*Brave, error) {
+	if key == "" {
+		return nil, errors.New("recipes: Brave API key is empty")
+	}
+	for i := 0; i < len(key); i++ {
+		if key[i] < 0x21 || key[i] > 0x7e {
+			// The key is never echoed.
+			return nil, errors.New("recipes: Brave API key has a character not allowed in a header")
+		}
+	}
+	return &Brave{key: key, endpoint: BraveEndpoint, client: newSearchClient()}, nil
+}
+
+// Search implements SearchProvider with GET BraveEndpoint?q=…&count=n.
+func (b *Brave) Search(ctx context.Context, query string, n int) ([]Candidate, error) {
+	q, err := searchQuery(query, n)
+	if err != nil {
+		return nil, err
+	}
+	u := b.endpoint + "?" + url.Values{"q": {q}, "count": {strconv.Itoa(n)}}.Encode()
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
+	if err != nil {
+		return nil, fmt.Errorf("recipes: build Brave request: %w", err)
+	}
+	req.Header.Set("X-Subscription-Token", b.key)
+	// Brave leaves out "web" when nothing matched, so a search response is
+	// recognised by its "type"; a web object present must hold the results
+	// array.
+	var body struct {
+		Type string `json:"type"`
+		Web  *struct {
+			Results *[]struct {
+				URL         string `json:"url"`
+				Title       string `json:"title"`
+				Description string `json:"description"`
+			} `json:"results"`
+		} `json:"web"`
+	}
+	if err := doSearch(b.client, req, "Brave", &body); err != nil {
+		return nil, err
+	}
+	if body.Type != "search" {
+		return nil, fmt.Errorf("%w: Brave body type is %q, not \"search\"", ErrSearchResponse, body.Type)
+	}
+	if body.Web == nil {
+		return nil, nil
+	}
+	if body.Web.Results == nil {
+		return nil, fmt.Errorf("%w: Brave web object has no results array", ErrSearchResponse)
+	}
+	var out []Candidate
+	for _, r := range *body.Web.Results {
+		out = append(out, Candidate{URL: r.URL, Title: r.Title, Snippet: r.Description})
+	}
+	return candidates("Brave", out, n)
+}
+
+func newSearchClient() *http.Client {
+	return &http.Client{
+		Timeout: SearchTimeout,
+		CheckRedirect: func(*http.Request, []*http.Request) error {
+			return http.ErrUseLastResponse
+		},
+	}
+}
+
+// searchQuery validates n and returns query with " recipe" appended unless
+// one of its words already is "recipe", in any case.
+func searchQuery(query string, n int) (string, error) {
+	if n < 1 || n > MaxSearchResults {
+		return "", fmt.Errorf("recipes: search result count %d is outside 1-%d", n, MaxSearchResults)
+	}
+	q := strings.TrimSpace(query)
+	if q == "" {
+		return "", errors.New("recipes: search query is empty")
+	}
+	for _, w := range strings.Fields(q) {
+		if strings.EqualFold(w, "recipe") {
+			return q, nil
+		}
+	}
+	return q + " recipe", nil
+}
+
+// doSearch sends req and decodes a 2xx JSON body into v, mapping failures to
+// the search errors.
+func doSearch(client *http.Client, req *http.Request, provider string, v any) error {
+	req.Header.Set("Accept", "application/json")
+	req.Header.Set("User-Agent", UserAgent)
+	resp, err := client.Do(req)
+	if err != nil {
+		if ctxErr := req.Context().Err(); ctxErr != nil {
+			return ctxErr
+		}
+		return fmt.Errorf("recipes: %s search: %w", provider, err)
+	}
+	defer resp.Body.Close()
+	switch {
+	case resp.StatusCode == http.StatusUnauthorized || resp.StatusCode == http.StatusForbidden:
+		return fmt.Errorf("%w: %s HTTP %d", ErrSearchRefused, provider, resp.StatusCode)
+	case resp.StatusCode == http.StatusTooManyRequests:
+		return fmt.Errorf("%w: %s", ErrSearchRateLimited, provider)
+	case resp.StatusCode < 200 || resp.StatusCode > 299:
+		return &SearchStatusError{Provider: provider, Status: resp.StatusCode}
+	}
+	data, err := io.ReadAll(io.LimitReader(resp.Body, MaxSearchBodyBytes+1))
+	if err != nil {
+		return fmt.Errorf("recipes: %s search: read body: %w", provider, err)
+	}
+	if len(data) > MaxSearchBodyBytes {
+		return fmt.Errorf("%w: %s body is over %d bytes", ErrSearchResponse, provider, MaxSearchBodyBytes)
+	}
+	if err := json.Unmarshal(data, v); err != nil {
+		return fmt.Errorf("%w: %s: %v", ErrSearchResponse, provider, err)
+	}
+	return nil
+}
+
+// candidates cleans results — HTML tags and entities, which both providers
+// leave in titles and snippets, are removed — checks every URL is absolute
+// http(s) and keeps the first n.
+func candidates(provider string, results []Candidate, n int) ([]Candidate, error) {
+	if len(results) > n {
+		results = results[:n]
+	}
+	out := make([]Candidate, 0, len(results))
+	for i, r := range results {
+		u, err := url.Parse(r.URL)
+		if err != nil || (u.Scheme != "http" && u.Scheme != "https") || u.Host == "" {
+			return nil, fmt.Errorf("%w: %s result %d has no absolute http(s) URL", ErrSearchResponse, provider, i)
+		}
+		out = append(out, Candidate{URL: r.URL, Title: stripTags(r.Title), Snippet: stripTags(r.Snippet)})
+	}
+	return out, nil
+}
+
+// stripTags drops HTML tags such as Brave's <strong> highlights, then
+// decodes entities and trims space.
+func stripTags(s string) string {
+	var b strings.Builder
+	inTag := false
+	for _, r := range s {
+		switch {
+		case r == '<':
+			inTag = true
+		case r == '>' && inTag:
+			inTag = false
+		case !inTag:
+			b.WriteRune(r)
+		}
+	}
+	return cleanText(b.String())
+}

internal/recipes/search_test.go

@@ -0,0 +1,294 @@
+package recipes
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/base64"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"reflect"
+	"strings"
+	"testing"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/db"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/secretbox"
+)
+
+const searxngBody = `{
+	"query": "chicken curry recipe",
+	"results": [
+		{"url": "https://www.bbcgoodfood.com/recipes/easy-chicken-curry", "title": "Easy chicken curry recipe | BBC Good Food", "content": "Make our easy chicken curry & rice.", "engine": "duckduckgo"},
+		{"url": "https://www.recipetineats.com/chicken-curry/", "title": "Chicken Curry", "content": "A proper curry."},
+		{"url": "https://example.com/third", "title": "Third", "content": ""}
+	],
+	"number_of_results": 0
+}`
+
+const braveBody = `{
+	"type": "search",
+	"web": {
+		"type": "search",
+		"results": [
+			{"url": "https://www.bbcgoodfood.com/recipes/easy-chicken-curry", "title": "Easy <strong>chicken curry</strong> recipe", "description": "Make our <strong>easy</strong> chicken curry &amp; rice.", "language": "en"},
+			{"url": "https://www.recipetineats.com/chicken-curry/", "title": "Chicken Curry", "description": "A proper curry."}
+		]
+	}
+}`
+
+func newSearXNGServer(t *testing.T, status int, body string, got *http.Request) *SearXNG {
+	t.Helper()
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if got != nil {
+			*got = *r.Clone(context.Background())
+		}
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(status)
+		w.Write([]byte(body))
+	}))
+	t.Cleanup(srv.Close)
+	s, err := NewSearXNG(srv.URL + "/searx")
+	if err != nil {
+		t.Fatal(err)
+	}
+	return s
+}
+
+func newBraveServer(t *testing.T, key string, status int, body string, got *http.Request) *Brave {
+	t.Helper()
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if got != nil {
+			*got = *r.Clone(context.Background())
+		}
+		w.WriteHeader(status)
+		w.Write([]byte(body))
+	}))
+	t.Cleanup(srv.Close)
+	b, err := NewBrave(key)
+	if err != nil {
+		t.Fatal(err)
+	}
+	b.endpoint = srv.URL + "/res/v1/web/search"
+	return b
+}
+
+func TestSearXNGSearch(t *testing.T) {
+	var req http.Request
+	s := newSearXNGServer(t, http.StatusOK, searxngBody, &req)
+	got, err := s.Search(context.Background(), "chicken curry", 2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if req.URL.Path != "/searx/search" {
+		t.Errorf("path = %q, want /searx/search", req.URL.Path)
+	}
+	q := req.URL.Query()
+	if q.Get("q") != "chicken curry recipe" || q.Get("format") != "json" || q.Get("categories") != "general" {
+		t.Errorf("query = %v", q)
+	}
+	if req.Header.Get("User-Agent") != UserAgent {
+		t.Errorf("User-Agent = %q", req.Header.Get("User-Agent"))
+	}
+	want := []Candidate{
+		{URL: "https://www.bbcgoodfood.com/recipes/easy-chicken-curry", Title: "Easy chicken curry recipe | BBC Good Food", Snippet: "Make our easy chicken curry & rice."},
+		{URL: "https://www.recipetineats.com/chicken-curry/", Title: "Chicken Curry", Snippet: "A proper curry."},
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("candidates =\n%#v\nwant\n%#v", got, want)
+	}
+}
+
+func TestBraveSearch(t *testing.T) {
+	var req http.Request
+	b := newBraveServer(t, "brave-key-123", http.StatusOK, braveBody, &req)
+	got, err := b.Search(context.Background(), "Chicken curry RECIPE", 5)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if req.Header.Get("X-Subscription-Token") != "brave-key-123" {
+		t.Errorf("X-Subscription-Token = %q", req.Header.Get("X-Subscription-Token"))
+	}
+	if req.Header.Get("Accept") != "application/json" {
+		t.Errorf("Accept = %q", req.Header.Get("Accept"))
+	}
+	q := req.URL.Query()
+	if q.Get("q") != "Chicken curry RECIPE" || q.Get("count") != "5" {
+		t.Errorf("query = %v", q)
+	}
+	want := []Candidate{
+		{URL: "https://www.bbcgoodfood.com/recipes/easy-chicken-curry", Title: "Easy chicken curry recipe", Snippet: "Make our easy chicken curry & rice."},
+		{URL: "https://www.recipetineats.com/chicken-curry/", Title: "Chicken Curry", Snippet: "A proper curry."},
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("candidates =\n%#v\nwant\n%#v", got, want)
+	}
+}
+
+func TestSearchQuery(t *testing.T) {
+	for _, tc := range []struct{ in, want string }{
+		{"chicken curry", "chicken curry recipe"},
+		{"  chicken curry  ", "chicken curry recipe"},
+		{"chicken curry recipe", "chicken curry recipe"},
+		{"Recipe for chicken curry", "Recipe for chicken curry"},
+		{"recipes for curry", "recipes for curry recipe"},
+	} {
+		got, err := searchQuery(tc.in, 3)
+		if err != nil || got != tc.want {
+			t.Errorf("searchQuery(%q) = %q, %v; want %q", tc.in, got, err, tc.want)
+		}
+	}
+	for _, tc := range []struct {
+		q string
+		n int
+	}{{"", 3}, {"   ", 3}, {"curry", 0}, {"curry", MaxSearchResults + 1}} {
+		if _, err := searchQuery(tc.q, tc.n); err == nil {
+			t.Errorf("searchQuery(%q, %d) succeeded, want error", tc.q, tc.n)
+		}
+	}
+}
+
+func TestSearchErrors(t *testing.T) {
+	tests := []struct {
+		name   string
+		status int
+		body   string
+		check  func(error) bool
+	}{
+		{"unauthorized", http.StatusUnauthorized, `{}`, func(err error) bool { return errors.Is(err, ErrSearchRefused) }},
+		{"forbidden", http.StatusForbidden, `{}`, func(err error) bool { return errors.Is(err, ErrSearchRefused) }},
+		{"rate limited", http.StatusTooManyRequests, `{}`, func(err error) bool { return errors.Is(err, ErrSearchRateLimited) }},
+		{"server error", http.StatusBadGateway, `{}`, func(err error) bool {
+			var se *SearchStatusError
+			return errors.As(err, &se) && se.Status == http.StatusBadGateway
+		}},
+		{"redirect not followed", http.StatusFound, ``, func(err error) bool {
+			var se *SearchStatusError
+			return errors.As(err, &se) && se.Status == http.StatusFound
+		}},
+		{"not JSON", http.StatusOK, `<html>`, func(err error) bool { return errors.Is(err, ErrSearchResponse) }},
+		{"result without URL", http.StatusOK, `{"type":"search","results":[{"title":"x"}],"web":{"results":[{"title":"x"}]}}`, func(err error) bool { return errors.Is(err, ErrSearchResponse) }},
+		{"relative URL", http.StatusOK, `{"type":"search","results":[{"url":"/x"}],"web":{"results":[{"url":"/x"}]}}`, func(err error) bool { return errors.Is(err, ErrSearchResponse) }},
+		{"empty object", http.StatusOK, `{}`, func(err error) bool { return errors.Is(err, ErrSearchResponse) }},
+		{"null results", http.StatusOK, `{"type":"search","results":null,"web":{"results":null}}`, func(err error) bool { return errors.Is(err, ErrSearchResponse) }},
+		{"results not an array", http.StatusOK, `{"type":"search","results":{},"web":{"results":{}}}`, func(err error) bool { return errors.Is(err, ErrSearchResponse) }},
+		{"body too large", http.StatusOK, `{"results":[],"pad":"` + strings.Repeat("x", MaxSearchBodyBytes) + `"}`, func(err error) bool { return errors.Is(err, ErrSearchResponse) }},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			providers := map[string]SearchProvider{
+				"SearXNG": newSearXNGServer(t, tc.status, tc.body, nil),
+				"Brave":   newBraveServer(t, "secret-key", tc.status, tc.body, nil),
+			}
+			for name, p := range providers {
+				_, err := p.Search(context.Background(), "curry", 3)
+				if err == nil || !tc.check(err) {
+					t.Errorf("%s: err = %v", name, err)
+				}
+				if err != nil && strings.Contains(err.Error(), "secret-key") {
+					t.Errorf("%s: error leaks the API key: %v", name, err)
+				}
+			}
+		})
+	}
+}
+
+// TestSearchNoMatches checks a well-formed response with nothing found is an
+// empty search, not an error.
+func TestSearchNoMatches(t *testing.T) {
+	providers := map[string]SearchProvider{
+		"SearXNG":           newSearXNGServer(t, http.StatusOK, `{"query":"x recipe","results":[]}`, nil),
+		"Brave without web": newBraveServer(t, "secret-key", http.StatusOK, `{"type":"search","query":{"original":"x recipe"}}`, nil),
+		"Brave empty web":   newBraveServer(t, "secret-key", http.StatusOK, `{"type":"search","web":{"type":"search","results":[]}}`, nil),
+	}
+	for name, p := range providers {
+		got, err := p.Search(context.Background(), "x", 3)
+		if err != nil || len(got) != 0 {
+			t.Errorf("%s: got %v, %v; want no candidates and no error", name, got, err)
+		}
+	}
+}
+
+func TestSearchContextCancelled(t *testing.T) {
+	s := newSearXNGServer(t, http.StatusOK, searxngBody, nil)
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	if _, err := s.Search(ctx, "curry", 3); !errors.Is(err, context.Canceled) {
+		t.Errorf("err = %v, want context.Canceled", err)
+	}
+}
+
+func TestSearchUnreachable(t *testing.T) {
+	srv := httptest.NewServer(http.NotFoundHandler())
+	url := srv.URL
+	srv.Close()
+	s, err := NewSearXNG(url)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = s.Search(context.Background(), "curry", 3)
+	if err == nil || !strings.Contains(err.Error(), "SearXNG search") {
+		t.Errorf("err = %v", err)
+	}
+}
+
+func TestNewSearXNGRejects(t *testing.T) {
+	for _, u := range []string{"", "searxng:8080", "ftp://searxng", "http://", "http://u:p@searxng", "http://searxng?x=1", "http://searxng#f"} {
+		if _, err := NewSearXNG(u); err == nil {
+			t.Errorf("NewSearXNG(%q) succeeded, want error", u)
+		}
+	}
+	if _, err := NewSearXNG("http://searxng:8080"); err != nil {
+		t.Errorf("internal URL rejected: %v", err)
+	}
+}
+
+func TestNewBraveRejects(t *testing.T) {
+	for _, k := range []string{"", "with space", "line\nbreak"} {
+		if _, err := NewBrave(k); err == nil {
+			t.Errorf("NewBrave(%q) succeeded, want error", k)
+		}
+	}
+}
+
+func TestNewSearchProvider(t *testing.T) {
+	raw := make([]byte, secretbox.KeySize)
+	rand.Read(raw)
+	box, err := secretbox.New(base64.StdEncoding.EncodeToString(raw))
+	if err != nil {
+		t.Fatal(err)
+	}
+	ct, err := box.Encrypt([]byte("brave-key"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	p, err := NewSearchProvider(db.RecipeSearchSetting{Provider: "brave", ApiKeyCt: ct}, box, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if b, ok := p.(*Brave); !ok || b.key != "brave-key" || b.endpoint != BraveEndpoint {
+		t.Errorf("provider = %#v, want Brave with decrypted key", p)
+	}
+
+	p, err = NewSearchProvider(db.RecipeSearchSetting{Provider: "searxng"}, box, "http://searxng:8080")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if s, ok := p.(*SearXNG); !ok || s.endpoint.String() != "http://searxng:8080/search" {
+		t.Errorf("provider = %#v, want SearXNG at http://searxng:8080/search", p)
+	}
+
+	for name, tc := range map[string]struct {
+		s   db.RecipeSearchSetting
+		url string
+	}{
+		"brave without key":   {db.RecipeSearchSetting{Provider: "brave"}, ""},
+		"brave bad key":       {db.RecipeSearchSetting{Provider: "brave", ApiKeyCt: []byte("not a token at all, far too plain")}, ""},
+		"searxng without URL": {db.RecipeSearchSetting{Provider: "searxng"}, ""},
+		"unknown provider":    {db.RecipeSearchSetting{Provider: "google"}, ""},
+	} {
+		if _, err := NewSearchProvider(tc.s, box, tc.url); err == nil {
+			t.Errorf("%s: succeeded, want error", name)
+		}
+	}
+}