removed unnecessary pointer indirection, added rate limiter middleware

internal/net/http/middleware/rate_limit.go

@@ -0,0 +1,81 @@
+package middleware
+
+import (
+	"net/http"
+	"sync"
+	"time"
+
+	E "github.com/yusing/go-proxy/internal/error"
+	"golang.org/x/time/rate"
+)
+
+type (
+	requestMap  = map[string]*rate.Limiter
+	rateLimiter struct {
+		requestMap requestMap
+		newLimiter func() *rate.Limiter
+		m          *Middleware
+
+		mu sync.Mutex
+	}
+
+	rateLimiterOpts struct {
+		Average int           `json:"average"`
+		Burst   int           `json:"burst"`
+		Period  time.Duration `json:"period"`
+	}
+)
+
+var (
+	RateLimiter            = &Middleware{withOptions: NewRateLimiter}
+	rateLimiterOptsDefault = rateLimiterOpts{
+		Average: 100,
+		Burst:   1,
+		Period:  time.Second,
+	}
+)
+
+func NewRateLimiter(optsRaw OptionsRaw) (*Middleware, E.Error) {
+	rl := new(rateLimiter)
+	opts := rateLimiterOptsDefault
+	err := Deserialize(optsRaw, &opts)
+	if err != nil {
+		return nil, err
+	}
+	switch {
+	case opts.Average == 0:
+		return nil, ErrZeroValue.Subject("average")
+	case opts.Burst == 0:
+		return nil, ErrZeroValue.Subject("burst")
+	case opts.Period == 0:
+		return nil, ErrZeroValue.Subject("period")
+	}
+	rl.requestMap = make(requestMap, 0)
+	rl.newLimiter = func() *rate.Limiter {
+		return rate.NewLimiter(rate.Limit(opts.Average)*rate.Every(opts.Period), opts.Burst)
+	}
+	rl.m = &Middleware{
+		impl:   rl,
+		before: rl.limit,
+	}
+	return rl.m, nil
+}
+
+func (rl *rateLimiter) limit(next http.HandlerFunc, w ResponseWriter, r *Request) {
+	rl.mu.Lock()
+
+	limiter, ok := rl.requestMap[r.RemoteAddr]
+	if !ok {
+		limiter = rl.newLimiter()
+		rl.requestMap[r.RemoteAddr] = limiter
+	}
+
+	rl.mu.Unlock()
+
+	if limiter.Allow() {
+		next(w, r)
+		return
+	}
+
+	http.Error(w, "rate limit exceeded", http.StatusTooManyRequests)
+}