platform: modularize api/gui, add docs-tests-web foundation, and refresh root config

selective-vpn-api/app/egress_identity.go

@@ -0,0 +1,78 @@
+package app
+
+import (
+	"net/http"
+	"sync"
+	"time"
+)
+
+const (
+	egressIdentityFreshTTL       = 3 * time.Minute
+	egressIdentityBackoffMin     = 3 * time.Second
+	egressIdentityBackoffMax     = 2 * time.Minute
+	egressIdentityProbeTimeout   = 4 * time.Second
+	egressIdentityGeoTimeout     = 4 * time.Second
+	egressIdentityGeoCacheTTL    = 24 * time.Hour
+	egressIdentityGeoFailTTL     = 30 * time.Second
+	egressIdentityMaxConcurrency = 2
+)
+
+var (
+	egressIdentitySWR = newEgressIdentityService(
+		envInt("SVPN_EGRESS_MAX_PARALLEL", egressIdentityMaxConcurrency),
+	)
+	egressHTTPClient = &http.Client{}
+)
+
+type egressScopeTarget struct {
+	Scope    string
+	Source   string
+	SourceID string
+}
+
+type egressSourceProvider interface {
+	Probe(target egressScopeTarget) (string, error)
+}
+
+type egressIdentityEntry struct {
+	item EgressIdentity
+	swr  refreshCoordinator
+}
+
+type egressGeoCacheEntry struct {
+	CountryCode string
+	CountryName string
+	LastError   string
+	ExpiresAt   time.Time
+}
+
+type egressIdentityService struct {
+	mu        sync.Mutex
+	entries   map[string]*egressIdentityEntry
+	sem       chan struct{}
+	providers map[string]egressSourceProvider
+
+	geoMu    sync.Mutex
+	geoCache map[string]egressGeoCacheEntry
+}
+
+type egressSystemProvider struct{}
+type egressAdGuardProvider struct{}
+type egressTransportProvider struct{}
+
+func newEgressIdentityService(maxConcurrent int) *egressIdentityService {
+	n := maxConcurrent
+	if n <= 0 {
+		n = egressIdentityMaxConcurrency
+	}
+	return &egressIdentityService{
+		entries: map[string]*egressIdentityEntry{},
+		sem:     make(chan struct{}, n),
+		providers: map[string]egressSourceProvider{
+			"system":     egressSystemProvider{},
+			"adguardvpn": egressAdGuardProvider{},
+			"transport":  egressTransportProvider{},
+		},
+		geoCache: map[string]egressGeoCacheEntry{},
+	}
+}