feat: build Go-based SearXNG-compatible search service

Implement an API-first Go rewrite with local engine adapters, upstream fallback, and Nix-based tooling so searches can run without matching the original UI while preserving response compatibility.

Made-with: Cursor

internal/engines/braveapi_test.go

@@ -0,0 +1,92 @@
+package engines
+
+import (
+	"context"
+	"net/http"
+	"testing"
+
+	"github.com/ashie/gosearch/internal/contracts"
+)
+
+func TestBraveEngine_GatingAndHeader(t *testing.T) {
+	wantToken := "letmein"
+	wantAPIKey := "api-key"
+
+	transport := roundTripperFunc(func(r *http.Request) (*http.Response, error) {
+		if r.Header.Get("X-Subscription-Token") != wantAPIKey {
+			t.Fatalf("missing/incorrect X-Subscription-Token header: got %q", r.Header.Get("X-Subscription-Token"))
+		}
+		if r.URL.Host != "api.search.brave.com" {
+			t.Fatalf("unexpected host: %s", r.URL.Host)
+		}
+		if r.URL.Path != "/res/v1/web/search" {
+			t.Fatalf("unexpected path: %s", r.URL.Path)
+		}
+		// basic query assertions
+		q := r.URL.Query().Get("q")
+		if q != "hugo" {
+			t.Fatalf("unexpected q: %q", q)
+		}
+
+		body := `{
+		  "web": {
+		    "results": [
+		      {"url":"https://example.com/a","title":"A","description":"B","age":"2024-06-03T00:00:00Z","thumbnail":{"src":"x"}}
+		    ]
+		  }
+		}`
+		return httpResponse(http.StatusOK, body, "application/json"), nil
+	})
+
+	client := &http.Client{Transport: transport}
+	engine := &BraveEngine{
+		client:          client,
+		apiKey:          wantAPIKey,
+		accessGateToken: wantToken,
+		resultsPerPage: 20,
+	}
+
+	// Wrong token => no upstream call / unresponsive engine.
+	{
+		resp, err := engine.Search(context.Background(), contracts.SearchRequest{
+			Query:       "hugo",
+			Pageno:      1,
+			Safesearch:  0,
+			Language:    "en",
+			AccessToken: "wrong",
+		})
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if len(resp.Results) != 0 {
+			t.Fatalf("expected no results on unauthorized, got %d", len(resp.Results))
+		}
+		if len(resp.UnresponsiveEngines) != 1 {
+			t.Fatalf("expected 1 unresponsive engine entry, got %v", resp.UnresponsiveEngines)
+		}
+	}
+
+	// Correct token => upstream call.
+	{
+		resp, err := engine.Search(context.Background(), contracts.SearchRequest{
+			Query:       "hugo",
+			Pageno:      1,
+			Safesearch:  0,
+			Language:    "en",
+			AccessToken: wantToken,
+		})
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if len(resp.Results) != 1 {
+			t.Fatalf("expected 1 result, got %d", len(resp.Results))
+		}
+		if resp.Results[0].Title != "A" {
+			t.Fatalf("unexpected title: %q", resp.Results[0].Title)
+		}
+		if resp.Results[0].URL == nil || *resp.Results[0].URL != "https://example.com/a" {
+			t.Fatalf("unexpected url: %v", resp.Results[0].URL)
+		}
+	}
+}
+