chore: initial commit of ai site platform

Co-authored-by: Cursor <cursoragent@cursor.com>

platform/internal/ratelimit/limiter.go

@@ -0,0 +1,84 @@
+package ratelimit
+
+import (
+	"net/http"
+	"sync"
+	"time"
+
+	"aijianzhan/platform/internal/authx"
+)
+
+type Limiter struct {
+	mu       sync.Mutex
+	visitors map[string]*visitor
+	rate     int
+	window   time.Duration
+}
+
+type visitor struct {
+	count int
+	reset time.Time
+}
+
+func New(ratePerMinute int) *Limiter {
+	if ratePerMinute <= 0 {
+		ratePerMinute = 120
+	}
+	return &Limiter{
+		visitors: map[string]*visitor{},
+		rate:     ratePerMinute,
+		window:   time.Minute,
+	}
+}
+
+func (l *Limiter) Middleware(next http.HandlerFunc) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		key := r.RemoteAddr
+		if tid := authx.TenantID(r.Context()); tid > 0 {
+			key = "t:" + itoa(tid)
+		}
+		if !l.allow(key) {
+			authx.WriteError(w, http.StatusTooManyRequests, "rate limit exceeded")
+			return
+		}
+		next(w, r)
+	}
+}
+
+func (l *Limiter) allow(key string) bool {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	now := time.Now()
+	v, ok := l.visitors[key]
+	if !ok || now.After(v.reset) {
+		l.visitors[key] = &visitor{count: 1, reset: now.Add(l.window)}
+		return true
+	}
+	if v.count >= l.rate {
+		return false
+	}
+	v.count++
+	return true
+}
+
+func itoa(n int64) string {
+	if n == 0 {
+		return "0"
+	}
+	neg := n < 0
+	if neg {
+		n = -n
+	}
+	var b [20]byte
+	i := len(b)
+	for n > 0 {
+		i--
+		b[i] = byte('0' + n%10)
+		n /= 10
+	}
+	if neg {
+		i--
+		b[i] = '-'
+	}
+	return string(b[i:])
+}