feat: add OpenSearch XML endpoint

- Serve /opensearch.xml with configurable base URL
- Browsers can now add gosearch as a search engine from the address bar
- Configurable via [server] base_url or BASE_URL env var
- XML template embedded in the binary via go:embed
- Added base_url to config.example.toml

cmd/searxng-go/main.go

@@ -63,6 +63,7 @@ func main() {
 	mux.HandleFunc("/", h.Index)
 	mux.HandleFunc("/healthz", h.Healthz)
 	mux.HandleFunc("/search", h.Search)
+	mux.HandleFunc("/opensearch.xml", h.OpenSearch(cfg.Server.BaseURL))
 
 	// Serve embedded static files (CSS, JS, images).
 	staticFS, err := views.StaticFS()

config.example.toml

@@ -9,6 +9,11 @@ port = 8080
 # HTTP timeout for engine and upstream calls (env: HTTP_TIMEOUT)
 http_timeout = "10s"
 
+# Public base URL for OpenSearch XML (env: BASE_URL)
+# Set this so browsers can add gosearch as a search engine.
+# Example: "https://search.example.com"
+base_url = ""
+
 [upstream]
 # URL of an upstream SearXNG instance for unported engines (env: UPSTREAM_SEARXNG_URL)
 # Leave empty to run without an upstream proxy.

internal/config/config.go

@@ -22,6 +22,7 @@ type Config struct {
 type ServerConfig struct {
 	Port        int    `toml:"port"`
 	HTTPTimeout string `toml:"http_timeout"`
+	BaseURL     string `toml:"base_url"` // Public URL for OpenSearch XML (e.g. "https://search.example.com")
 }
 
 type UpstreamConfig struct {
@@ -158,6 +159,9 @@ func applyEnvOverrides(cfg *Config) {
 	if v := os.Getenv("RATE_LIMIT_CLEANUP_INTERVAL"); v != "" {
 		cfg.RateLimit.CleanupInterval = v
 	}
+	if v := os.Getenv("BASE_URL"); v != "" {
+		cfg.Server.BaseURL = v
+	}
 }
 
 // HTTPTimeout parses the configured timeout string into a time.Duration.

internal/httpapi/handlers.go

@@ -33,6 +33,19 @@ func (h *Handler) Index(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+// OpenSearch serves the OpenSearch description XML.
+func (h *Handler) OpenSearch(baseURL string) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		xml, err := views.OpenSearchXML(baseURL)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		w.Header().Set("Content-Type", "application/opensearchdescription+xml; charset=utf-8")
+		w.Write(xml)
+	}
+}
+
 func (h *Handler) Search(w http.ResponseWriter, r *http.Request) {
 	// For HTML format with no query, redirect to homepage.
 	if r.FormValue("q") == "" && (r.FormValue("format") == "" || r.FormValue("format") == "html") {

internal/views/templates/opensearch.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<OpenSearchDescription xmlns="http://a9.com/-/spec/opensearch/1.1/">
+  <ShortName>gosearch</ShortName>
+  <Description>A privacy-respecting, open metasearch engine</Description>
+  <InputEncoding>UTF-8</InputEncoding>
+  <OutputEncoding>UTF-8</OutputEncoding>
+  <LongName>gosearch — Privacy-respecting metasearch</LongName>
+  <Image width="16" height="16" type="image/svg+xml">/static/img/favicon.svg</Image>
+  <Contact>https://git.ashisgreat.xyz/penal-colony/gosearch</Contact>
+  <Url type="text/html" method="GET" template="{baseUrl}/search?q={searchTerms}&amp;format=html">
+    <Param name="pageno" value="{startPage?}" />
+    <Param name="language" value="{language?}" />
+  </Url>
+  <Url type="application/json" method="GET" template="{baseUrl}/search?q={searchTerms}&amp;format=json" />
+  <Query role="example" searchTerms="golang" />
+</OpenSearchDescription>

internal/views/views.go

@@ -80,6 +80,18 @@ func StaticFS() (fs.FS, error) {
 	return fs.Sub(staticFS, "static")
 }
 
+// OpenSearchXML returns the OpenSearch description XML with {baseUrl}
+// replaced by the provided base URL.
+func OpenSearchXML(baseURL string) ([]byte, error) {
+	tmplFS, _ := fs.Sub(templatesFS, "templates")
+	data, err := fs.ReadFile(tmplFS, "opensearch.xml")
+	if err != nil {
+		return nil, err
+	}
+	result := strings.ReplaceAll(string(data), "{baseUrl}", baseURL)
+	return []byte(result), nil
+}
+
 // FromResponse builds PageData from a search response and request params.
 func FromResponse(resp contracts.SearchResponse, query string, pageno int) PageData {
 	pd := PageData{