feat(format-servers): add json format option

internal/models/markdown.go

@@ -1,6 +1,7 @@
 package models
 
 import (
+	"errors"
 	"fmt"
 	"strings"
 
@@ -90,8 +91,11 @@ func (s *Server) ToMarkdown(headers ...string) (markdown string) {
 	return "| " + strings.Join(fields, " | ") + " |"
 }
 
-func (s *Servers) ToMarkdown(vpnProvider string) (markdown string) {
-	headers := getMarkdownHeaders(vpnProvider)
+func (s *Servers) toMarkdown(vpnProvider string) (formatted string, err error) {
+	headers, err := getMarkdownHeaders(vpnProvider)
+	if err != nil {
+		return "", fmt.Errorf("getting markdown headers: %w", err)
+	}
 
 	legend := markdownTableHeading(headers...)
 
@@ -100,63 +104,67 @@ func (s *Servers) ToMarkdown(vpnProvider string) (markdown string) {
 		entries[i] = server.ToMarkdown(headers...)
 	}
 
-	markdown = legend + "\n" +
+	formatted = legend + "\n" +
 		strings.Join(entries, "\n") + "\n"
-	return markdown
+	return formatted, nil
 }
 
-func getMarkdownHeaders(vpnProvider string) (headers []string) {
+var (
+	ErrMarkdownHeadersNotDefined = errors.New("markdown headers not defined")
+)
+
+func getMarkdownHeaders(vpnProvider string) (headers []string, err error) {
 	switch vpnProvider {
 	case providers.Airvpn:
 		return []string{regionHeader, countryHeader, cityHeader, vpnHeader,
-			udpHeader, tcpHeader, hostnameHeader, nameHeader}
+			udpHeader, tcpHeader, hostnameHeader, nameHeader}, nil
 	case providers.Cyberghost:
-		return []string{countryHeader, hostnameHeader, tcpHeader, udpHeader}
+		return []string{countryHeader, hostnameHeader, tcpHeader, udpHeader}, nil
 	case providers.Expressvpn:
-		return []string{countryHeader, cityHeader, hostnameHeader, tcpHeader, udpHeader}
+		return []string{countryHeader, cityHeader, hostnameHeader, tcpHeader, udpHeader}, nil
 	case providers.Fastestvpn:
-		return []string{countryHeader, hostnameHeader, vpnHeader, tcpHeader, udpHeader}
+		return []string{countryHeader, hostnameHeader, vpnHeader, tcpHeader, udpHeader}, nil
 	case providers.HideMyAss:
-		return []string{countryHeader, regionHeader, cityHeader, hostnameHeader, tcpHeader, udpHeader}
+		return []string{countryHeader, regionHeader, cityHeader, hostnameHeader, tcpHeader, udpHeader}, nil
 	case providers.Ipvanish:
-		return []string{countryHeader, cityHeader, hostnameHeader, tcpHeader, udpHeader}
+		return []string{countryHeader, cityHeader, hostnameHeader, tcpHeader, udpHeader}, nil
 	case providers.Ivpn:
-		return []string{countryHeader, cityHeader, ispHeader, hostnameHeader, vpnHeader, tcpHeader, udpHeader}
+		return []string{countryHeader, cityHeader, ispHeader, hostnameHeader, vpnHeader, tcpHeader, udpHeader}, nil
 	case providers.Mullvad:
-		return []string{countryHeader, cityHeader, ispHeader, ownedHeader, hostnameHeader, vpnHeader}
+		return []string{countryHeader, cityHeader, ispHeader, ownedHeader, hostnameHeader, vpnHeader}, nil
 	case providers.Nordvpn:
-		return []string{countryHeader, regionHeader, cityHeader, hostnameHeader, vpnHeader, categoriesHeader}
+		return []string{countryHeader, regionHeader, cityHeader, hostnameHeader, vpnHeader, categoriesHeader}, nil
 	case providers.Perfectprivacy:
-		return []string{cityHeader, tcpHeader, udpHeader}
+		return []string{cityHeader, tcpHeader, udpHeader}, nil
 	case providers.Privado:
-		return []string{countryHeader, regionHeader, cityHeader, hostnameHeader}
+		return []string{countryHeader, regionHeader, cityHeader, hostnameHeader}, nil
 	case providers.PrivateInternetAccess:
-		return []string{regionHeader, hostnameHeader, nameHeader, tcpHeader, udpHeader, portForwardHeader}
+		return []string{regionHeader, hostnameHeader, nameHeader, tcpHeader, udpHeader, portForwardHeader}, nil
 	case providers.Privatevpn:
-		return []string{countryHeader, cityHeader, hostnameHeader}
+		return []string{countryHeader, cityHeader, hostnameHeader}, nil
 	case providers.Protonvpn:
 		return []string{countryHeader, regionHeader, cityHeader, hostnameHeader, vpnHeader,
-			freeHeader, portForwardHeader, secureHeader, torHeader}
+			freeHeader, portForwardHeader, secureHeader, torHeader}, nil
 	case providers.Purevpn:
-		return []string{countryHeader, regionHeader, cityHeader, hostnameHeader, tcpHeader, udpHeader}
+		return []string{countryHeader, regionHeader, cityHeader, hostnameHeader, tcpHeader, udpHeader}, nil
 	case providers.SlickVPN:
-		return []string{regionHeader, countryHeader, cityHeader, hostnameHeader}
+		return []string{regionHeader, countryHeader, cityHeader, hostnameHeader}, nil
 	case providers.Surfshark:
 		return []string{regionHeader, countryHeader, cityHeader, hostnameHeader,
-			vpnHeader, multiHopHeader, tcpHeader, udpHeader}
+			vpnHeader, multiHopHeader, tcpHeader, udpHeader}, nil
 	case providers.Torguard:
-		return []string{countryHeader, cityHeader, hostnameHeader, tcpHeader, udpHeader}
+		return []string{countryHeader, cityHeader, hostnameHeader, tcpHeader, udpHeader}, nil
 	case providers.VPNSecure:
-		return []string{regionHeader, cityHeader, hostnameHeader, premiumHeader}
+		return []string{regionHeader, cityHeader, hostnameHeader, premiumHeader}, nil
 	case providers.VPNUnlimited:
-		return []string{countryHeader, cityHeader, hostnameHeader, freeHeader, streamHeader, tcpHeader, udpHeader}
+		return []string{countryHeader, cityHeader, hostnameHeader, freeHeader, streamHeader, tcpHeader, udpHeader}, nil
 	case providers.Vyprvpn:
-		return []string{regionHeader, hostnameHeader, tcpHeader, udpHeader}
+		return []string{regionHeader, hostnameHeader, tcpHeader, udpHeader}, nil
 	case providers.Wevpn:
-		return []string{cityHeader, hostnameHeader, tcpHeader, udpHeader}
+		return []string{cityHeader, hostnameHeader, tcpHeader, udpHeader}, nil
 	case providers.Windscribe:
-		return []string{regionHeader, cityHeader, hostnameHeader, vpnHeader}
+		return []string{regionHeader, cityHeader, hostnameHeader, vpnHeader}, nil
 	default:
-		return nil
+		return nil, fmt.Errorf("%w: for %s", ErrMarkdownHeadersNotDefined, vpnProvider)
 	}
 }