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// Eko: A terminal-native social media platform
// Copyright (C) 2025 Kyren223
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
package session
import (
"context"
"crypto/ed25519"
"crypto/rand"
"log/slog"
"net"
"sync"
"time"
"github.com/kyren223/eko/internal/packet"
"github.com/kyren223/eko/internal/server/ctxkeys"
"github.com/kyren223/eko/pkg/assert"
"github.com/kyren223/eko/pkg/rate"
"github.com/kyren223/eko/pkg/snowflake"
)
const (
WriteQueueSize = 10
NonceSize = 32
DefaultRate = 0.1 // ms per second
DefaultLimit = 3 // ms burst
AuthenticatedRate = 1 // ms per second
AuthenticatedLimit = 20 // ms burst
)
type SessionManager interface {
AddSession(session *Session, userId snowflake.ID, pubKey ed25519.PublicKey)
RemoveSession(id snowflake.ID)
Session(id snowflake.ID) *Session
UseSessions(f func(map[snowflake.ID]*Session))
Node() *snowflake.Node
}
type Session struct {
manager SessionManager
addr *net.TCPAddr
cancel context.CancelFunc
writeQueue chan packet.Payload
writerWg *sync.WaitGroup
writeMu sync.RWMutex
issuedTime time.Time
challenge []byte
challengeMu sync.Mutex
isTosAccepted bool
pubKey ed25519.PublicKey
id snowflake.ID
rl rate.Limiter
start time.Time
analytics *packet.DeviceAnalytics
mu sync.RWMutex
}
func NewSession(
manager SessionManager,
addr *net.TCPAddr, cancel context.CancelFunc,
writerWg *sync.WaitGroup,
) *Session {
assert.NotNil(addr, "tcp address should be valid")
assert.NotNil(manager, "session manager should be valid")
session := &Session{
manager: manager,
addr: addr,
cancel: cancel,
writeQueue: make(chan packet.Payload, WriteQueueSize),
writerWg: writerWg,
writeMu: sync.RWMutex{},
issuedTime: time.Time{},
challenge: make([]byte, NonceSize),
pubKey: ed25519.PublicKey{},
id: snowflake.InvalidID,
challengeMu: sync.Mutex{},
isTosAccepted: false,
rl: rate.NewLimiter(DefaultRate, DefaultLimit),
start: time.Time{},
analytics: nil,
mu: sync.RWMutex{},
}
return session
}
func (s *Session) Addr() *net.TCPAddr {
assert.NotNil(s.addr, "tcp address should be valid")
return s.addr
}
func (s *Session) RateLimiter() *rate.Limiter {
return &s.rl
}
func (s *Session) IsTosAccepted() bool {
s.mu.RLock()
defer s.mu.RUnlock()
return s.isTosAccepted
}
func (s *Session) ReceivedTosAcceptance() {
s.mu.Lock()
defer s.mu.Unlock()
s.isTosAccepted = true
}
func (s *Session) IsAuthenticated() bool {
s.mu.RLock()
defer s.mu.RUnlock()
return s.id != snowflake.InvalidID
}
func (s *Session) ID() snowflake.ID {
s.mu.RLock()
defer s.mu.RUnlock()
assert.Assert(s.IsAuthenticated(), "use of ID in an unauthenticated session", "addr", s.addr)
return s.id
}
func (s *Session) PubKey() ed25519.PublicKey {
s.mu.RLock()
defer s.mu.RUnlock()
assert.Assert(s.IsAuthenticated(), "use of PubKey in an unauthenticated session", "addr", s.addr)
return s.pubKey
}
func (s *Session) Promote(userId snowflake.ID, pubKey ed25519.PublicKey) {
s.mu.Lock()
defer s.mu.Unlock()
s.id = userId
s.pubKey = pubKey
s.rl.SetLimit(AuthenticatedLimit)
s.rl.SetRate(AuthenticatedRate)
s.start = time.Now().UTC()
}
func (s *Session) Duration() time.Duration {
assert.Assert(s.IsAuthenticated(), "tried accessing session duration in an authenticated session")
s.mu.RLock()
defer s.mu.RUnlock()
return time.Since(s.start)
}
func (s *Session) Analytics() *packet.DeviceAnalytics {
s.mu.RLock()
defer s.mu.RUnlock()
return s.analytics
}
func (s *Session) SetAnalytics(analytics *packet.DeviceAnalytics) {
s.mu.Lock()
defer s.mu.Unlock()
s.analytics = analytics
}
func (s *Session) Manager() SessionManager {
return s.manager
}
func (s *Session) Challenge() []byte {
s.challengeMu.Lock()
defer s.challengeMu.Unlock()
if time.Since(s.issuedTime) > time.Minute {
s.issuedTime = time.Now()
_, err := rand.Read(s.challenge)
assert.NoError(err, "random should always produce a value")
}
return s.challenge
}
func (s *Session) Write(ctx context.Context, payload packet.Payload) bool {
s.writerWg.Add(1)
defer s.writerWg.Done()
s.writeMu.RLock()
defer s.writeMu.RUnlock()
select {
case s.writeQueue <- payload:
return true
case <-ctx.Done():
return false
}
}
func (s *Session) Read() <-chan packet.Payload {
s.writeMu.RLock()
defer s.writeMu.RUnlock()
return s.writeQueue
}
func (s *Session) CloseWriteQueue() {
s.writeMu.Lock()
defer s.writeMu.Unlock()
close(s.writeQueue)
s.writeQueue = nil
}
func (s *Session) Close() {
s.cancel()
}
func (s *Session) LogValue() slog.Value {
if s.IsAuthenticated() {
return slog.GroupValue(
slog.Any(ctxkeys.IpAddr.String(), s.Addr()),
slog.Any(ctxkeys.UserID.String(), s.ID()),
slog.Any("public_key", s.PubKey()),
)
} else {
return slog.GroupValue(
slog.Any(ctxkeys.IpAddr.String(), s.Addr()),
)
}
}
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