Maintenance: refactor servers updater code

- Require at least 80% of number of servers now to pass
- Each provider is in its own package with a common structure
- Unzip package with unzipper interface
- Openvpn package with extraction and download functions

internal/updater/providers/pia/api.go

@@ -0,0 +1,74 @@
+package pia
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"net/http"
+)
+
+var (
+	ErrHTTPStatusCodeNotOK = errors.New("HTTP status code not OK")
+)
+
+type apiData struct {
+	Regions []regionData `json:"regions"`
+}
+
+type regionData struct {
+	Name        string `json:"name"`
+	PortForward bool   `json:"port_forward"`
+	Offline     bool   `json:"offline"`
+	Servers     struct {
+		UDP []serverData `json:"ovpnudp"`
+		TCP []serverData `json:"ovpntcp"`
+	} `json:"servers"`
+}
+
+type serverData struct {
+	IP net.IP `json:"ip"`
+	CN string `json:"cn"`
+}
+
+func fetchAPI(ctx context.Context, client *http.Client) (
+	data apiData, err error) {
+	const url = "https://serverlist.piaservers.net/vpninfo/servers/v5"
+
+	request, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return data, err
+	}
+
+	response, err := client.Do(request)
+	if err != nil {
+		return data, err
+	}
+	defer response.Body.Close()
+
+	if response.StatusCode != http.StatusOK {
+		return data, fmt.Errorf("%w: %s", ErrHTTPStatusCodeNotOK, response.Status)
+	}
+
+	b, err := ioutil.ReadAll(response.Body)
+	if err != nil {
+		return data, err
+	}
+
+	if err := response.Body.Close(); err != nil {
+		return data, err
+	}
+
+	// remove key/signature at the bottom
+	i := bytes.IndexRune(b, '\n')
+	b = b[:i]
+
+	if err := json.Unmarshal(b, &data); err != nil {
+		return data, err
+	}
+
+	return data, nil
+}

internal/updater/providers/pia/servers.go

@@ -0,0 +1,90 @@
+// Package pia contains code to obtain the server information
+// for the Private Internet Access provider.
+package pia
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+
+	"github.com/qdm12/gluetun/internal/models"
+)
+
+var ErrNotEnoughServers = errors.New("not enough servers found")
+
+func GetServers(ctx context.Context, client *http.Client, minServers int) (
+	servers []models.PIAServer, err error) {
+	data, err := fetchAPI(ctx, client)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, region := range data.Regions {
+		// Deduplicate servers with the same common name
+		commonNameToProtocols := dedupByProtocol(region)
+
+		// newServers can support only UDP or both TCP and UDP
+		newServers := dataToServers(region.Servers.UDP, region.Name,
+			region.PortForward, commonNameToProtocols)
+		servers = append(servers, newServers...)
+
+		// tcpServers only support TCP as mixed servers were found above.
+		tcpServers := dataToServers(region.Servers.TCP, region.Name,
+			region.PortForward, commonNameToProtocols)
+		servers = append(servers, tcpServers...)
+	}
+
+	if len(servers) < minServers {
+		return nil, fmt.Errorf("%w: %d and expected at least %d",
+			ErrNotEnoughServers, len(servers), minServers)
+	}
+
+	sortServers(servers)
+
+	return servers, nil
+}
+
+type protocols struct {
+	tcp bool
+	udp bool
+}
+
+// Deduplicate servers with the same common name for different protocols.
+func dedupByProtocol(region regionData) (commonNameToProtocols map[string]protocols) {
+	commonNameToProtocols = make(map[string]protocols)
+	for _, udpServer := range region.Servers.UDP {
+		protocols := commonNameToProtocols[udpServer.CN]
+		protocols.udp = true
+		commonNameToProtocols[udpServer.CN] = protocols
+	}
+	for _, tcpServer := range region.Servers.TCP {
+		protocols := commonNameToProtocols[tcpServer.CN]
+		protocols.tcp = true
+		commonNameToProtocols[tcpServer.CN] = protocols
+	}
+	return commonNameToProtocols
+}
+
+func dataToServers(data []serverData, region string, portForward bool,
+	commonNameToProtocols map[string]protocols) (
+	servers []models.PIAServer) {
+	servers = make([]models.PIAServer, 0, len(data))
+	for _, serverData := range data {
+		proto, ok := commonNameToProtocols[serverData.CN]
+		if !ok {
+			continue // server already added
+		}
+		delete(commonNameToProtocols, serverData.CN)
+		server := models.PIAServer{
+			Region:      region,
+			ServerName:  serverData.CN,
+			TCP:         proto.tcp,
+			UDP:         proto.udp,
+			PortForward: portForward,
+			IP:          serverData.IP,
+		}
+		servers = append(servers, server)
+	}
+	return servers
+}

internal/updater/providers/pia/sort.go

@@ -0,0 +1,16 @@
+package pia
+
+import (
+	"sort"
+
+	"github.com/qdm12/gluetun/internal/models"
+)
+
+func sortServers(servers []models.PIAServer) {
+	sort.Slice(servers, func(i, j int) bool {
+		if servers[i].Region == servers[j].Region {
+			return servers[i].ServerName < servers[j].ServerName
+		}
+		return servers[i].Region < servers[j].Region
+	})
+}

internal/updater/providers/pia/string.go

@@ -0,0 +1,14 @@
+package pia
+
+import "github.com/qdm12/gluetun/internal/models"
+
+func Stringify(servers []models.PIAServer) (s string) {
+	s = "func PIAServers() []models.PIAServer {\n"
+	s += "	return []models.PIAServer{\n"
+	for _, server := range servers {
+		s += "		" + server.String() + ",\n"
+	}
+	s += "	}\n"
+	s += "}"
+	return s
+}