Purevpn support (#208)

Fixes #192

cmd/locationToSubdomain/main.go

@@ -0,0 +1,111 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"net/http"
+	"os"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/qdm12/golibs/network"
+)
+
+func main() {
+	os.Exit(_main())
+}
+
+func _main() int {
+	provider := flag.String("provider", "purevpn", "VPN provider to map location to subdomain, can be 'purevpn'")
+	flag.Parse()
+
+	client := network.NewClient(5 * time.Second)
+	switch *provider {
+	case "purevpn":
+		servers, warnings, err := purevpn(client)
+		if err != nil {
+			fmt.Println(err)
+			return 1
+		}
+		for _, server := range servers {
+			fmt.Printf(
+				"{subdomain: %q, region: %q, country: %q, city: %q},\n",
+				server.subdomain, server.region, server.country, server.city,
+			)
+		}
+		fmt.Print("\n\n")
+		for _, warning := range warnings {
+			fmt.Println(warning)
+		}
+	default:
+		fmt.Printf("Provider %q is not supported\n", *provider)
+		return 1
+	}
+	return 0
+}
+
+type purevpnServer struct {
+	region    string
+	country   string
+	city      string
+	subdomain string // without -tcp or -udp suffix
+}
+
+func purevpn(client network.Client) (servers []purevpnServer, warnings []string, err error) {
+	content, status, err := client.GetContent("https://support.purevpn.com/vpn-servers")
+	if err != nil {
+		return nil, nil, err
+	} else if status != http.StatusOK {
+		return nil, nil, fmt.Errorf("HTTP status %d from Purevpn", status)
+	}
+	const jsonPrefix = "<script>var servers = "
+	const jsonSuffix = "</script>"
+	s := string(content)
+	jsonPrefixIndex := strings.Index(s, jsonPrefix)
+	if jsonPrefixIndex == -1 {
+		return nil, nil, fmt.Errorf("cannot find prefix %s in html", jsonPrefix)
+	}
+	if len(s[jsonPrefixIndex:]) == len(jsonPrefix) {
+		return nil, nil, fmt.Errorf("no body after json prefix %s", jsonPrefix)
+	}
+	s = s[jsonPrefixIndex+len(jsonPrefix):]
+	endIndex := strings.Index(s, jsonSuffix)
+	s = s[:endIndex]
+	var data []struct {
+		Region  string `json:"region_name"`
+		Country string `json:"country_name"`
+		City    string `json:"city_name"`
+		TCP     string `json:"tcp"`
+		UDP     string `json:"udp"`
+	}
+	if err := json.Unmarshal([]byte(s), &data); err != nil {
+		return nil, nil, err
+	}
+	sort.Slice(data, func(i, j int) bool {
+		if data[i].Region == data[j].Region {
+			if data[i].Country == data[j].Country {
+				return data[i].City < data[j].City
+			}
+			return data[i].Country < data[j].Country
+		}
+		return data[i].Region < data[j].Region
+	})
+	for i := range data {
+		if data[i].UDP == "" && data[i].TCP == "" {
+			warnings = append(warnings, fmt.Sprintf("server %s %s %s does not support TCP and UDP for openvpn", data[i].Region, data[i].Country, data[i].City))
+			continue
+		}
+		if data[i].UDP == "" || data[i].TCP == "" {
+			warnings = append(warnings, fmt.Sprintf("server %s %s %s does not support TCP or udp for openvpn", data[i].Region, data[i].Country, data[i].City))
+		}
+		servers = append(servers, purevpnServer{
+			region:    data[i].Region,
+			country:   data[i].Country,
+			city:      data[i].City,
+			subdomain: strings.TrimSuffix(data[i].TCP, "-tcp.pointtoserver.com"),
+		})
+	}
+	return servers, warnings, nil
+}