Split localCounter into its own file

limiter.go

@@ -6,8 +6,6 @@ import (
 	"net/http"
 	"sync"
 	"time"
-
-	"github.com/cespare/xxhash/v2"
 )
 
 type LimitCounter interface {
@@ -153,87 +151,6 @@ func (l *rateLimiter) calculateRate(key string, requestLimit int) (bool, float64
 	return true, rate, nil
 }
 
-type localCounter struct {
-	counters     map[uint64]*count
-	windowLength time.Duration
-	lastEvict    time.Time
-	mu           sync.Mutex
-}
-
-var _ LimitCounter = &localCounter{}
-
-type count struct {
-	value     int
-	updatedAt time.Time
-}
-
-func (c *localCounter) Config(requestLimit int, windowLength time.Duration) {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-	c.windowLength = windowLength
-}
-
-func (c *localCounter) Increment(key string, currentWindow time.Time) error {
-	return c.IncrementBy(key, currentWindow, 1)
-}
-
-func (c *localCounter) IncrementBy(key string, currentWindow time.Time, amount int) error {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-
-	c.evict()
-
-	hkey := LimitCounterKey(key, currentWindow)
-
-	v, ok := c.counters[hkey]
-	if !ok {
-		v = &count{}
-		c.counters[hkey] = v
-	}
-	v.value += amount
-	v.updatedAt = time.Now()
-
-	return nil
-}
-
-func (c *localCounter) Get(key string, currentWindow, previousWindow time.Time) (int, int, error) {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-
-	curr, ok := c.counters[LimitCounterKey(key, currentWindow)]
-	if !ok {
-		curr = &count{value: 0, updatedAt: time.Now()}
-	}
-	prev, ok := c.counters[LimitCounterKey(key, previousWindow)]
-	if !ok {
-		prev = &count{value: 0, updatedAt: time.Now()}
-	}
-
-	return curr.value, prev.value, nil
-}
-
-func (c *localCounter) evict() {
-	d := c.windowLength * 3
-
-	if time.Since(c.lastEvict) < d {
-		return
-	}
-	c.lastEvict = time.Now()
-
-	for k, v := range c.counters {
-		if time.Since(v.updatedAt) >= d {
-			delete(c.counters, k)
-		}
-	}
-}
-
-func LimitCounterKey(key string, window time.Time) uint64 {
-	h := xxhash.New()
-	h.WriteString(key)
-	h.WriteString(fmt.Sprintf("%d", window.Unix()))
-	return h.Sum64()
-}
-
 func setHeader(w http.ResponseWriter, key string, value string) {
 	if key != "" {
 		w.Header().Set(key, value)

local_counter.go

@@ -0,0 +1,90 @@
+package httprate
+
+import (
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/cespare/xxhash/v2"
+)
+
+var _ LimitCounter = &localCounter{}
+
+type localCounter struct {
+	counters     map[uint64]*count
+	windowLength time.Duration
+	lastEvict    time.Time
+	mu           sync.Mutex
+}
+
+type count struct {
+	value     int
+	updatedAt time.Time
+}
+
+func (c *localCounter) Config(requestLimit int, windowLength time.Duration) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.windowLength = windowLength
+}
+
+func (c *localCounter) Increment(key string, currentWindow time.Time) error {
+	return c.IncrementBy(key, currentWindow, 1)
+}
+
+func (c *localCounter) IncrementBy(key string, currentWindow time.Time, amount int) error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	c.evict()
+
+	hkey := LimitCounterKey(key, currentWindow)
+
+	v, ok := c.counters[hkey]
+	if !ok {
+		v = &count{}
+		c.counters[hkey] = v
+	}
+	v.value += amount
+	v.updatedAt = time.Now()
+
+	return nil
+}
+
+func (c *localCounter) Get(key string, currentWindow, previousWindow time.Time) (int, int, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	curr, ok := c.counters[LimitCounterKey(key, currentWindow)]
+	if !ok {
+		curr = &count{value: 0, updatedAt: time.Now()}
+	}
+	prev, ok := c.counters[LimitCounterKey(key, previousWindow)]
+	if !ok {
+		prev = &count{value: 0, updatedAt: time.Now()}
+	}
+
+	return curr.value, prev.value, nil
+}
+
+func (c *localCounter) evict() {
+	d := c.windowLength * 3
+
+	if time.Since(c.lastEvict) < d {
+		return
+	}
+	c.lastEvict = time.Now()
+
+	for k, v := range c.counters {
+		if time.Since(v.updatedAt) >= d {
+			delete(c.counters, k)
+		}
+	}
+}
+
+func LimitCounterKey(key string, window time.Time) uint64 {
+	h := xxhash.New()
+	h.WriteString(key)
+	h.WriteString(fmt.Sprintf("%d", window.Unix()))
+	return h.Sum64()
+}