refactor config and nginx parsers

internal/hostnginx/nodessr.go

@@ -78,44 +78,60 @@ func parseNodeSsrBlock(content []byte) (nodeSsrBlock, error) {
 		return nodeSsrBlock{}, errors.New("host Nginx configuration is empty")
 	}
 	lines := strings.Split(string(content), "\n")
+	begin, end, err := findNodeSsrMarkers(lines)
+	if err != nil {
+		return nodeSsrBlock{}, err
+	}
+	servers, err := collectNodeSsrServers(lines, begin, end)
+	if err != nil {
+		return nodeSsrBlock{}, err
+	}
+	return nodeSsrBlock{lines: lines, servers: servers}, nil
+}
+
+func findNodeSsrMarkers(lines []string) (int, int, error) {
 	begin, end := -1, -1
 	for index, line := range lines {
 		switch strings.TrimSpace(line) {
 		case nodeSsrManagedBegin:
 			if begin != -1 {
-				return nodeSsrBlock{}, errors.New("host Nginx configuration contains duplicate Node SSR upstream begin markers")
+				return 0, 0, errors.New("host Nginx configuration contains duplicate Node SSR upstream begin markers")
 			}
 			begin = index
 		case nodeSsrManagedEnd:
 			if end != -1 {
-				return nodeSsrBlock{}, errors.New("host Nginx configuration contains duplicate Node SSR upstream end markers")
+				return 0, 0, errors.New("host Nginx configuration contains duplicate Node SSR upstream end markers")
 			}
 			end = index
 		}
 	}
 	if begin == -1 || end <= begin {
-		return nodeSsrBlock{}, errors.New("host Nginx configuration requires one ordered Node SSR upstream marker pair")
+		return 0, 0, errors.New("host Nginx configuration requires one ordered Node SSR upstream marker pair")
 	}
+	return begin, end, nil
+}
+
+func collectNodeSsrServers(lines []string, begin, end int) ([]nodeSsrServer, error) {
 	servers := make([]nodeSsrServer, 0, 2)
 	seen := make(map[int]struct{}, 2)
 	for index := begin + 1; index < end; index++ {
 		server, found, err := parseNodeSsrServer(lines[index], index)
 		if err != nil {
-			return nodeSsrBlock{}, err
+			return nil, err
 		}
 		if !found {
 			continue
 		}
 		if _, exists := seen[server.port]; exists {
-			return nodeSsrBlock{}, fmt.Errorf("managed Node SSR upstream contains duplicate port %d", server.port)
+			return nil, fmt.Errorf("managed Node SSR upstream contains duplicate port %d", server.port)
 		}
 		seen[server.port] = struct{}{}
 		servers = append(servers, server)
 	}
 	if len(servers) != 2 {
-		return nodeSsrBlock{}, fmt.Errorf("managed Node SSR upstream must contain exactly two servers, got %d", len(servers))
+		return nil, fmt.Errorf("managed Node SSR upstream must contain exactly two servers, got %d", len(servers))
 	}
-	return nodeSsrBlock{lines: lines, servers: servers}, nil
+	return servers, nil
 }
 
 // parseNodeSsrServer parses one server line inside the managed Node SSR block.