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/search/request_params_test.go

@@ -0,0 +1,74 @@
+package search
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+)
+
+func TestParseSearchRequest_MissingQ(t *testing.T) {
+	r := httptest.NewRequest(http.MethodGet, "/search?format=json", nil)
+	_, err := ParseSearchRequest(r)
+	if err == nil {
+		t.Fatalf("expected error, got nil")
+	}
+}
+
+func TestParseSearchRequest_InvalidPageno(t *testing.T) {
+	r := httptest.NewRequest(http.MethodGet, "/search?q=hi&pageno=0", nil)
+	_, err := ParseSearchRequest(r)
+	if err == nil {
+		t.Fatalf("expected error for pageno, got nil")
+	}
+}
+
+func TestParseSearchRequest_InvalidLanguage(t *testing.T) {
+	r := httptest.NewRequest(http.MethodGet, "/search?q=hi&language=bad!", nil)
+	_, err := ParseSearchRequest(r)
+	if err == nil {
+		t.Fatalf("expected error for language, got nil")
+	}
+}
+
+func TestParseSearchRequest_CategoriesAndEngineData(t *testing.T) {
+	values := url.Values{}
+	values.Set("q", "hello")
+	values.Set("format", "json")
+	values.Set("categories", "general,science")
+	values.Set("category_science", "off")
+	values.Set("engines", "wikipedia,arxiv")
+	values.Set("engine_data-wikipedia-timeout", "123")
+
+	r := httptest.NewRequest(http.MethodPost, "/search", strings.NewReader(values.Encode()))
+	r.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+
+	req, err := ParseSearchRequest(r)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	// categories should drop `science` due to category_science=off
+	wantCats := map[string]bool{"general": true}
+	gotCats := map[string]bool{}
+	for _, c := range req.Categories {
+		gotCats[c] = true
+	}
+	for c := range wantCats {
+		if !gotCats[c] {
+			t.Fatalf("expected category %q in result, got %v", c, req.Categories)
+		}
+	}
+	if gotCats["science"] {
+		t.Fatalf("expected category science to be removed, got %v", req.Categories)
+	}
+
+	if len(req.Engines) != 2 {
+		t.Fatalf("expected 2 engines, got %v", req.Engines)
+	}
+	if req.EngineData["wikipedia"]["timeout"] != "123" {
+		t.Fatalf("expected engine_data parsed, got %#v", req.EngineData)
+	}
+}
+