improved search-suggestions response time

suggestions.go

@@ -6,8 +6,62 @@ import (
 	"io"
 	"net/http"
 	"net/url"
+	"sort"
+	"sync"
+	"time"
 )
 
+// SuggestionSource represents a search suggestion source along with its latency.
+type SuggestionSource struct {
+	Name      string
+	FetchFunc func(string) []string
+	Latency   time.Duration
+	mu        sync.Mutex
+}
+
+// Initialize suggestion sources with default latency values.
+var suggestionSources = []SuggestionSource{
+	{
+		Name:      "DuckDuckGo",
+		FetchFunc: fetchDuckDuckGoSuggestions,
+		Latency:   50 * time.Millisecond,
+	},
+	{
+		Name:      "Edge",
+		FetchFunc: fetchEdgeSuggestions,
+		Latency:   50 * time.Millisecond,
+	},
+	{
+		Name:      "Brave",
+		FetchFunc: fetchBraveSuggestions,
+		Latency:   50 * time.Millisecond,
+	},
+	{
+		Name:      "Ecosia",
+		FetchFunc: fetchEcosiaSuggestions,
+		Latency:   50 * time.Millisecond,
+	},
+	{
+		Name:      "Qwant",
+		FetchFunc: fetchQwantSuggestions,
+		Latency:   50 * time.Millisecond,
+	},
+	{
+		Name:      "Startpage",
+		FetchFunc: fetchStartpageSuggestions,
+		Latency:   50 * time.Millisecond,
+	},
+	// I advise against it, but you can use it if you want to
+	// {
+	// 	Name:      "Google",
+	// 	FetchFunc: fetchGoogleSuggestions,
+	// 	Latency:   500 * time.Millisecond,
+	// },
+}
+
+// Mutex to protect the suggestionSources during sorting.
+var suggestionsMU sync.Mutex
+
 func handleSuggestions(w http.ResponseWriter, r *http.Request) {
 	query := r.URL.Query().Get("q")
 	if query == "" {
@@ -16,25 +70,27 @@ func handleSuggestions(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// Define the fallback sequence with Google lower in the hierarchy
-	suggestionSources := []func(string) []string{
-		fetchDuckDuckGoSuggestions,
-		fetchEdgeSuggestions,
-		fetchBraveSuggestions,
-		fetchEcosiaSuggestions,
-		fetchQwantSuggestions,
-		fetchStartpageSuggestions,
-		// fetchGoogleSuggestions, // I advise against it, but you can use it if you want to
-	}
+	// Sort the suggestion sources based on their latency.
+	suggestionsMU.Lock()
+	sort.Slice(suggestionSources, func(i, j int) bool {
+		return suggestionSources[i].Latency < suggestionSources[j].Latency
+	})
+	suggestionsMU.Unlock()
 
 	var suggestions []string
-	for _, fetchFunc := range suggestionSources {
-		suggestions = fetchFunc(query)
+	for i := range suggestionSources {
+		source := &suggestionSources[i]
+		start := time.Now()
+		suggestions = source.FetchFunc(query)
+		elapsed := time.Since(start)
+
+		updateLatency(source, elapsed)
+
 		if len(suggestions) > 0 {
-			printDebug("Suggestions found using %T", fetchFunc)
+			printDebug("Suggestions found using %s", source.Name)
 			break
 		} else {
-			printWarn("%T did not return any suggestions or failed.", fetchFunc)
+			printWarn("%s did not return any suggestions or failed.", source.Name)
 		}
 	}
 
@@ -42,11 +98,19 @@ func handleSuggestions(w http.ResponseWriter, r *http.Request) {
 		printErr("All suggestion services failed. Returning empty response.")
 	}
 
-	// Return the final suggestions as JSON
+	// Return the final suggestions as JSON.
 	w.Header().Set("Content-Type", "application/json")
 	fmt.Fprintf(w, `["",%s]`, toJSONStringArray(suggestions))
 }
 
+// updateLatency updates the latency of a suggestion source using an exponential moving average.
+func updateLatency(source *SuggestionSource, newLatency time.Duration) {
+	source.mu.Lock()
+	defer source.mu.Unlock()
+	const alpha = 0.5 // Smoothing factor.
+	source.Latency = time.Duration(float64(source.Latency)*(1-alpha) + float64(newLatency)*alpha)
+}
+
 func fetchGoogleSuggestions(query string) []string {
 	encodedQuery := url.QueryEscape(query)
 	url := fmt.Sprintf("http://suggestqueries.google.com/complete/search?client=firefox&q=%s", encodedQuery)
@@ -82,6 +146,7 @@ func fetchEcosiaSuggestions(query string) []string {
 	return fetchSuggestionsFromURL(url)
 }
 
+// Is this working?
 func fetchQwantSuggestions(query string) []string {
 	encodedQuery := url.QueryEscape(query)
 	url := fmt.Sprintf("https://api.qwant.com/v3/suggest?q=%s", encodedQuery)
@@ -96,6 +161,7 @@ func fetchStartpageSuggestions(query string) []string {
 	return fetchSuggestionsFromURL(url)
 }
 
+// fetchSuggestionsFromURL fetches suggestions from the given URL.
 func fetchSuggestionsFromURL(url string) []string {
 	resp, err := http.Get(url)
 	if err != nil {
@@ -110,17 +176,17 @@ func fetchSuggestionsFromURL(url string) []string {
 		return []string{}
 	}
 
-	// Log the Content-Type for debugging
+	// Log the Content-Type for debugging.
 	contentType := resp.Header.Get("Content-Type")
 	printDebug("Response Content-Type from %s: %s", url, contentType)
 
-	// Check if the body is non-empty
+	// Check if the body is non-empty.
 	if len(body) == 0 {
 		printWarn("Received empty response body from %s", url)
 		return []string{}
 	}
 
-	// Attempt to parse the response as JSON regardless of Content-Type
+	// Attempt to parse the response as JSON regardless of Content-Type.
 	var parsedResponse []interface{}
 	if err := json.Unmarshal(body, &parsedResponse); err != nil {
 		printErr("Error parsing JSON from %s: %v", url, err)
@@ -128,7 +194,7 @@ func fetchSuggestionsFromURL(url string) []string {
 		return []string{}
 	}
 
-	// Ensure the response structure is as expected
+	// Ensure the response structure is as expected.
 	if len(parsedResponse) < 2 {
 		printWarn("Unexpected response format from %v: %v", url, string(body))
 		return []string{}
@@ -148,6 +214,7 @@ func fetchSuggestionsFromURL(url string) []string {
 	return suggestions
 }
 
+// toJSONStringArray converts a slice of strings to a JSON array string.
 func toJSONStringArray(strings []string) string {
 	result := ""
 	for i, str := range strings {