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/merge.go

@@ -0,0 +1,121 @@
+package search
+
+import (
+	"encoding/json"
+	"net/url"
+	"strings"
+
+	"github.com/ashie/gosearch/internal/contracts"
+)
+
+// MergeResponses merges multiple SearXNG-compatible JSON responses.
+//
+// MVP merge semantics:
+// - results are concatenated with a simple de-dup key (engine|title|url)
+// - suggestions/corrections are de-duplicated as sets
+// - answers/infoboxes/unresponsive_engines are concatenated (best-effort)
+func MergeResponses(responses []contracts.SearchResponse) contracts.SearchResponse {
+	var merged contracts.SearchResponse
+
+	mergedResultSeen := map[string]struct{}{}
+	mergedAnswerSeen := map[string]struct{}{}
+	mergedCorrectionsSeen := map[string]struct{}{}
+	mergedSuggestionsSeen := map[string]struct{}{}
+
+	for _, r := range responses {
+		if merged.Query == "" {
+			merged.Query = r.Query
+		}
+
+		merged.NumberOfResults = maxInt(merged.NumberOfResults, r.NumberOfResults)
+
+		for _, mr := range r.Results {
+			key := resultDedupKey(mr)
+			if _, ok := mergedResultSeen[key]; ok {
+				continue
+			}
+			mergedResultSeen[key] = struct{}{}
+			merged.Results = append(merged.Results, mr)
+		}
+
+		for _, ans := range r.Answers {
+			// De-dup by normalized JSON when possible.
+			b, err := json.Marshal(ans)
+			if err != nil {
+				merged.Answers = append(merged.Answers, ans)
+				continue
+			}
+			key := string(b)
+			if _, ok := mergedAnswerSeen[key]; ok {
+				continue
+			}
+			mergedAnswerSeen[key] = struct{}{}
+			merged.Answers = append(merged.Answers, ans)
+		}
+
+		merged.Corrections = unionStrings(merged.Corrections, r.Corrections, &mergedCorrectionsSeen)
+		merged.Suggestions = unionStrings(merged.Suggestions, r.Suggestions, &mergedSuggestionsSeen)
+
+		merged.Infoboxes = append(merged.Infoboxes, r.Infoboxes...)
+		merged.UnresponsiveEngines = append(merged.UnresponsiveEngines, r.UnresponsiveEngines...)
+	}
+
+	// Ensure non-nil slices to keep JSON shape stable.
+	if merged.Results == nil {
+		merged.Results = []contracts.MainResult{}
+	}
+	if merged.Answers == nil {
+		merged.Answers = []map[string]any{}
+	}
+	if merged.Corrections == nil {
+		merged.Corrections = []string{}
+	}
+	if merged.Infoboxes == nil {
+		merged.Infoboxes = []map[string]any{}
+	}
+	if merged.Suggestions == nil {
+		merged.Suggestions = []string{}
+	}
+	if merged.UnresponsiveEngines == nil {
+		merged.UnresponsiveEngines = [][2]string{}
+	}
+
+	return merged
+}
+
+func resultDedupKey(r contracts.MainResult) string {
+	urlStr := ""
+	if r.URL != nil {
+		urlStr = *r.URL
+	}
+	// Normalize host to reduce duplicates.
+	if u, err := url.Parse(urlStr); err == nil {
+		if u.Host != "" {
+			urlStr = u.Host + u.Path
+		}
+	}
+	return strings.ToLower(r.Engine) + "|" + strings.ToLower(r.Title) + "|" + urlStr
+}
+
+func unionStrings(dst []string, src []string, seen *map[string]struct{}) []string {
+	if *seen == nil {
+		*seen = map[string]struct{}{}
+	}
+	out := dst
+	for _, s := range src {
+		if _, ok := (*seen)[s]; ok {
+			continue
+		}
+		(*seen)[s] = struct{}{}
+		out = append(out, s)
+	}
+	return out
+}
+
+func maxInt(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+