feat(backend): separate rate limits into buckets

backend/server/rate/rate.go

@@ -0,0 +1,83 @@
+package rate
+
+import (
+	"net/http"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/go-chi/httprate"
+	"github.com/gobwas/glob"
+)
+
+type Limiter struct {
+	scopes         []*scopedLimiter
+	defaultLimiter func(http.Handler) http.Handler
+
+	windowLength time.Duration
+	options      []httprate.Option
+
+	wildcardScopes []*scopedLimiter
+}
+
+type scopedLimiter struct {
+	Method, Pattern string
+
+	glob    glob.Glob
+	handler func(http.Handler) http.Handler
+}
+
+func NewLimiter(defaultLimit int, windowLength time.Duration, options ...httprate.Option) *Limiter {
+	return &Limiter{
+		windowLength: windowLength,
+		options:      options,
+	}
+}
+
+func (l *Limiter) Scope(method, pattern string, requestLimit int) error {
+	handler := httprate.Limit(requestLimit, l.windowLength, l.options...)
+
+	g, err := glob.Compile("/v*"+pattern, '/')
+	if err != nil {
+		return err
+	}
+
+	if method == "*" {
+		l.wildcardScopes = append(l.wildcardScopes, &scopedLimiter{method, pattern, g, handler})
+	} else {
+		l.scopes = append(l.scopes, &scopedLimiter{method, pattern, g, handler})
+	}
+	return nil
+}
+
+func (l *Limiter) Handler() func(http.Handler) http.Handler {
+	sort.Slice(l.scopes, func(i, j int) bool {
+		len1 := len(strings.Split(l.scopes[i].Pattern, "/"))
+		len2 := len(strings.Split(l.scopes[j].Pattern, "/"))
+
+		return len1 > len2
+	})
+	l.scopes = append(l.scopes, l.wildcardScopes...)
+
+	return l.handle
+}
+
+func (l *Limiter) handle(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		for _, s := range l.scopes {
+			if (r.Method == s.Method || s.Method == "*") && s.glob.Match(r.URL.Path) {
+				bucket := s.Pattern
+				if s.Method != "*" {
+					bucket = s.Method + " " + s.Pattern
+				}
+				w.Header().Set("X-RateLimit-Bucket", bucket)
+
+				s.handler(next).ServeHTTP(w, r)
+				return
+			}
+		}
+
+		w.Header().Set("X-RateLimit-Bucket", "/")
+		l.defaultLimiter(next).ServeHTTP(w, r)
+	})
+}