feat(session): add session management utility

unstable/session/sessionmanager.go

@@ -0,0 +1,116 @@
+package Session
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/hex"
+	"net/http"
+	"time"
+)
+
+// returns the session identified by session_id or creates a new one and returns that
+func (sm *sessionManager) Session(session_id string) *session {
+	sm.mtx.Lock()
+	s, ok := sm.sessions[session_id]
+	if !ok {
+		s = &session{
+			data:   make(map[string]any),
+			expiry: time.Now().Add(Session_Lifetime),
+		}
+		sm.sessions[session_id] = s
+
+		sm.mtx.Unlock()
+	} else {
+		sm.mtx.Unlock()
+		s.mtx.Lock()
+		if time.Now().After(s.expiry) {
+			// expired, clear it
+			s.data = make(map[string]any)
+			s.expiry = time.Now().Add(Session_Lifetime)
+		} else {
+			// valid, extend expiry
+			s.expiry = time.Now().Add(Session_Lifetime)
+		}
+		s.mtx.Unlock()
+	}
+
+	return s
+}
+
+func GetSession(ctx context.Context) *session {
+	s, _ := ctx.Value("session").(*session)
+	return s
+}
+
+func (sm *sessionManager) SessionMW(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var sid string
+
+		cookie, err := r.Cookie(cookie_key)
+		if err == http.ErrNoCookie {
+			sid = newSessionID()
+		} else if err == nil {
+			sid = cookie.Value
+		} else {
+			http.Error(w, "Invalid session", http.StatusBadRequest)
+			return
+		}
+
+		http.SetCookie(w, &http.Cookie{
+			Name:     cookie_key,
+			Value:    sid,
+			Path:     "/",
+			MaxAge:   int(Session_Lifetime.Seconds()),
+			HttpOnly: true,
+			Secure:   true,
+		})
+
+		ctx := context.WithValue(r.Context(), "session", sm.Session(sid))
+		r = r.WithContext(ctx)
+
+		next.ServeHTTP(w, r)
+	})
+}
+
+func (sm *sessionManager) StartGC(interval time.Duration) {
+	go func() {
+		ticker := time.NewTicker(interval)
+		defer ticker.Stop()
+
+		for range ticker.C {
+			sm.cleanup()
+		}
+	}()
+}
+
+func newSessionID() string {
+	b := make([]byte, 32)
+	rand.Read(b)
+	return hex.EncodeToString(b)
+}
+
+func (sm *sessionManager) cleanup() {
+	now := time.Now()
+
+	sm.mtx.Lock()
+	defer sm.mtx.Unlock()
+
+	for id, s := range sm.sessions {
+		s.mtx.Lock()
+		expired := now.After(s.expiry)
+		s.mtx.Unlock()
+
+		if expired {
+			delete(sm.sessions, id)
+		}
+	}
+}
+
+func NewSessionManager(gc_interval time.Duration) *sessionManager {
+	sm := &sessionManager{
+		sessions: make(map[string]*session),
+	}
+
+	sm.StartGC(gc_interval)
+	return sm
+}

unstable/session/types.go

@@ -0,0 +1,20 @@
+package Session
+
+import (
+	"sync"
+	"time"
+)
+
+const Session_Lifetime time.Duration = time.Duration(120) * time.Second
+const cookie_key string = "GSESSID"
+
+type session struct {
+	mtx    sync.Mutex
+	data   map[string]any
+	expiry time.Time
+}
+
+type sessionManager struct {
+	sessions map[string]*session
+	mtx      sync.Mutex
+}