From 8142b23bcb507456fab812889987b859e04ab22e Mon Sep 17 00:00:00 2001
From: rjbasitali <rjbasitali@gmail.com>
Date: Tue, 5 Apr 2022 04:10:40 +0500
Subject: [PATCH] cache eviction using sweeper

---
 delete_expired.go | 15 +++++++++++++++
 flush.go          |  8 ++++++++
 my_cache.go       | 22 ++++++++++++++++++++--
 set.go            |  2 +-
 sweeper.go        | 32 ++++++++++++++++++++++++++++++++
 value.go          | 14 +++++++++-----
 6 files changed, 85 insertions(+), 8 deletions(-)
 create mode 100644 delete_expired.go
 create mode 100644 flush.go
 create mode 100644 sweeper.go

diff --git a/delete_expired.go b/delete_expired.go
new file mode 100644
index 0000000..954360c
--- /dev/null
+++ b/delete_expired.go
@@ -0,0 +1,15 @@
+package gocache
+
+import "time"
+
+func (cache *myCache) deleteExpired() {
+	cache.mutex.Lock()
+	defer cache.mutex.Unlock()
+
+	now := time.Now().UnixNano()
+	for k, v := range cache.items {
+		if v.expiration > 0 && now > v.expiration {
+			delete(cache.items, k)
+		}
+	}
+}
diff --git a/flush.go b/flush.go
new file mode 100644
index 0000000..3c0c882
--- /dev/null
+++ b/flush.go
@@ -0,0 +1,8 @@
+package gocache
+
+func (cache *myCache) Flush() {
+	cache.mutex.Lock()
+	defer cache.mutex.Unlock()
+
+	cache.items = make(map[string]*value)
+}
diff --git a/my_cache.go b/my_cache.go
index 89348d1..3e115fc 100644
--- a/my_cache.go
+++ b/my_cache.go
@@ -1,12 +1,15 @@
 package gocache
 
 import (
+	"runtime"
 	"sync"
+	"time"
 )
 
 type myCache struct {
-	mutex sync.Mutex
-	items map[string]*value
+	mutex       sync.Mutex
+	items       map[string]*value
+	expireAfter int64
 }
 
 func NewCache() Cache {
@@ -14,3 +17,18 @@ func NewCache() Cache {
 		items: make(map[string]*value),
 	}
 }
+
+func NewCacheWithSweeper(interval, expireAfter time.Duration) Cache {
+	c := &myCache{
+		items:       make(map[string]*value),
+		expireAfter: expireAfter.Nanoseconds(),
+	}
+
+	if interval > 0 && expireAfter > 0 {
+		s := newSweeper(c, interval)
+		runtime.SetFinalizer(c, s.stopSweeper)
+		go s.run(c)
+	}
+
+	return c
+}
diff --git a/set.go b/set.go
index eceff2a..bf58b52 100644
--- a/set.go
+++ b/set.go
@@ -4,7 +4,7 @@ func (cache *myCache) Set(key string, data interface{}) error {
 	cache.mutex.Lock()
 	defer cache.mutex.Unlock()
 
-	value := newValue(key, data)
+	value := newValue(key, data, cache.expireAfter)
 	cache.items[key] = value
 
 	return nil
diff --git a/sweeper.go b/sweeper.go
new file mode 100644
index 0000000..c840af9
--- /dev/null
+++ b/sweeper.go
@@ -0,0 +1,32 @@
+package gocache
+
+import "time"
+
+type sweeper struct {
+	Interval time.Duration
+	stop     chan bool
+}
+
+func (s *sweeper) run(c *myCache) {
+	ticker := time.NewTicker(s.Interval)
+	for {
+		select {
+		case <-ticker.C:
+			c.deleteExpired()
+		case <-s.stop:
+			ticker.Stop()
+			return
+		}
+	}
+}
+
+func newSweeper(c *myCache, i time.Duration) *sweeper {
+	return &sweeper{
+		Interval: i,
+		stop:     make(chan bool),
+	}
+}
+
+func (s *sweeper) stopSweeper() {
+	s.stop <- true
+}
diff --git a/value.go b/value.go
index 4aaad8f..bc15281 100644
--- a/value.go
+++ b/value.go
@@ -1,13 +1,17 @@
 package gocache
 
+import "time"
+
 type value struct {
-	key  string
-	data interface{}
+	key        string
+	data       interface{}
+	expiration int64
 }
 
-func newValue(key string, data interface{}) *value {
+func newValue(key string, data interface{}, expiration int64) *value {
 	return &value{
-		key:  key,
-		data: data,
+		key:        key,
+		data:       data,
+		expiration: time.Now().UnixNano() + expiration,
 	}
 }