Build post chat and attachment workflows

backend/internal/auth/rate_limit.go

@@ -0,0 +1,68 @@
+package auth
+
+import (
+	"strings"
+	"sync"
+	"time"
+)
+
+type LoginRateLimiter struct {
+	mu       sync.Mutex
+	attempts map[string]loginAttempt
+	limit    int
+	window   time.Duration
+}
+
+type loginAttempt struct {
+	Count     int
+	ExpiresAt time.Time
+}
+
+func NewLoginRateLimiter(limit int, window time.Duration) *LoginRateLimiter {
+	return &LoginRateLimiter{
+		attempts: map[string]loginAttempt{},
+		limit:    limit,
+		window:   window,
+	}
+}
+
+func (l *LoginRateLimiter) IsBlocked(key string) bool {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	attempt, ok := l.attempts[key]
+	if !ok || time.Now().After(attempt.ExpiresAt) {
+		delete(l.attempts, key)
+		return false
+	}
+
+	return attempt.Count >= l.limit
+}
+
+func (l *LoginRateLimiter) RecordFailure(key string) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	now := time.Now()
+	attempt, ok := l.attempts[key]
+	if !ok || now.After(attempt.ExpiresAt) {
+		l.attempts[key] = loginAttempt{
+			Count:     1,
+			ExpiresAt: now.Add(l.window),
+		}
+		return
+	}
+
+	attempt.Count++
+	l.attempts[key] = attempt
+}
+
+func (l *LoginRateLimiter) Clear(key string) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	delete(l.attempts, key)
+}
+
+func LoginRateLimitKey(ip string, email string) string {
+	return strings.TrimSpace(ip) + ":" + strings.ToLower(strings.TrimSpace(email))
+}