Add support for context counter

Author: creack

httprate.go

@@ -1,6 +1,7 @@
 package httprate
 
 import (
+	"context"
 	"net"
 	"net/http"
 	"strings"
@@ -64,7 +65,27 @@ func WithLimitHandler(h http.HandlerFunc) Option {
 	}
 }
 
+// noContextLimitCounter wraps the context-less LimitCounter to implement the ContextLimitCounter interface.
+// Exists to maintain compatiblity.
+type noContextLimitCounter struct {
+	LimitCounter
+}
+
+func (l *noContextLimitCounter) Increment(_ context.Context, key string, currentWindow time.Time) error {
+	return l.LimitCounter.Increment(key, currentWindow)
+}
+
+func (l *noContextLimitCounter) Get(_ context.Context, key string, previousWindow, currentWindow time.Time) (int, int, error) {
+	return l.LimitCounter.Get(key, previousWindow, currentWindow)
+}
+
 func WithLimitCounter(c LimitCounter) Option {
+	return func(rl *rateLimiter) {
+		rl.limitCounter = &noContextLimitCounter{LimitCounter: c}
+	}
+}
+
+func WithContextLimitCounter(c ContextLimitCounter) Option {
 	return func(rl *rateLimiter) {
 		rl.limitCounter = c
 	}

limiter.go

@@ -1,6 +1,7 @@
 package httprate
 
 import (
+	"context"
 	"fmt"
 	"math"
 	"net/http"
@@ -15,6 +16,11 @@ type LimitCounter interface {
 	Get(key string, previousWindow, currentWindow time.Time) (int, int, error)
 }
 
+type ContextLimitCounter interface {
+	Increment(ctx context.Context, key string, currentWindow time.Time) error
+	Get(ctx context.Context, key string, previousWindow, currentWindow time.Time) (int, int, error)
+}
+
 func NewRateLimiter(requestLimit int, windowLength time.Duration, options ...Option) *rateLimiter {
 	return newRateLimiter(requestLimit, windowLength, options...)
 }
@@ -58,24 +64,42 @@ func LimitCounterKey(key string, window time.Time) uint64 {
 	return h.Sum64()
 }
 
+// limitCounterWrap implements the LimitCounter interface without context.
+// Calls ContextLimitCounter with context.Background(), exists to maintain compatibility.
+type limitCounterWrap struct {
+	ContextLimitCounter
+}
+
+func (l *limitCounterWrap) Increment(key string, currentWindow time.Time) error {
+	return l.ContextLimitCounter.Increment(context.Background(), key, currentWindow)
+}
+
+func (l *limitCounterWrap) Get(key string, previousWindow, currentWindow time.Time) (int, int, error) {
+	return l.ContextLimitCounter.Get(context.Background(), key, previousWindow, currentWindow)
+}
+
 type rateLimiter struct {
 	requestLimit   int
 	windowLength   time.Duration
 	keyFn          KeyFunc
-	limitCounter   LimitCounter
+	limitCounter   ContextLimitCounter
 	onRequestLimit http.HandlerFunc
 }
 
 func (r *rateLimiter) Counter() LimitCounter {
+	return &limitCounterWrap{ContextLimitCounter: r.limitCounter}
+}
+
+func (r *rateLimiter) ContextCounter() ContextLimitCounter {
 	return r.limitCounter
 }
 
-func (r *rateLimiter) Status(key string) (bool, float64, error) {
+func (r *rateLimiter) ContextStatus(ctx context.Context, key string) (bool, float64, error) {
 	t := time.Now().UTC()
 	currentWindow := t.Truncate(r.windowLength)
 	previousWindow := currentWindow.Add(-r.windowLength)
 
-	currCount, prevCount, err := r.limitCounter.Get(key, currentWindow, previousWindow)
+	currCount, prevCount, err := r.limitCounter.Get(ctx, key, currentWindow, previousWindow)
 	if err != nil {
 		return false, 0, err
 	}
@@ -89,8 +113,14 @@ func (r *rateLimiter) Status(key string) (bool, float64, error) {
 	return true, rate, nil
 }
 
+func (r *rateLimiter) Status(key string) (bool, float64, error) {
+	return r.ContextStatus(context.Background(), key)
+}
+
 func (l *rateLimiter) Handler(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		ctx := r.Context()
+
 		key, err := l.keyFn(r)
 		if err != nil {
 			http.Error(w, err.Error(), http.StatusPreconditionRequired)
@@ -120,7 +150,7 @@ func (l *rateLimiter) Handler(next http.Handler) http.Handler {
 			return
 		}
 
-		err = l.limitCounter.Increment(key, currentWindow)
+		err = l.limitCounter.Increment(ctx, key, currentWindow)
 		if err != nil {
 			http.Error(w, err.Error(), http.StatusInternalServerError)
 			return
@@ -137,14 +167,17 @@ type localCounter struct {
 	mu           sync.Mutex
 }
 
-var _ LimitCounter = &localCounter{}
+var (
+	_ LimitCounter        = &limitCounterWrap{ContextLimitCounter: &localCounter{}}
+	_ ContextLimitCounter = &localCounter{}
+)
 
 type count struct {
 	value     int
 	updatedAt time.Time
 }
 
-func (c *localCounter) Increment(key string, currentWindow time.Time) error {
+func (c *localCounter) Increment(_ context.Context, key string, currentWindow time.Time) error {
 	c.evict()
 
 	c.mu.Lock()
@@ -163,7 +196,7 @@ func (c *localCounter) Increment(key string, currentWindow time.Time) error {
 	return nil
 }
 
-func (c *localCounter) Get(key string, currentWindow, previousWindow time.Time) (int, int, error) {
+func (c *localCounter) Get(_ context.Context, key string, currentWindow, previousWindow time.Time) (int, int, error) {
 	c.mu.Lock()
 	defer c.mu.Unlock()