Init commit of the simple ttl cache

README.md

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+# Simple TTL Cache
+The Simple TTL Cache is an in memory cache with a set expiration time (TTL).
+
+# Usage
+```go
+package main
+
+import (
+	"time"
+
+	simplettlcache "github.com/GuySWatson/simple-ttl-cache"
+)
+
+func main() {
+	// Setup
+	simpleTTLCache := simplettlcache.SimpleTTLCache{}
+	simpleTTLCache.Init(time.Second * 3)
+
+	// Put object into cache
+	simpleTTLCache.Put("color", "red")
+
+	// Get object out of cache
+	simpleTTLCache.Get("color")
+
+	// Update object in the cache
+	simpleTTLCache.Update("color", 1234)
+}
+```

cache.go

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+package simplettlcache
+
+import (
+	"sync"
+	"time"
+)
+
+type SimpleTTLCache struct {
+	assets map[string]*simpleTTLItem
+	mutex  sync.Mutex
+}
+
+type simpleTTLItem struct {
+	value      interface{}
+	lastAccess time.Time
+}
+
+func (s *SimpleTTLCache) Init(maxTTL time.Duration) {
+	s.assets = make(map[string]*simpleTTLItem)
+
+	go func() {
+		for now := range time.Tick(time.Second) {
+			s.mutex.Lock()
+
+			for k, v := range s.assets {
+				if now.Sub(v.lastAccess) > maxTTL {
+					delete(s.assets, k)
+				}
+			}
+
+			s.mutex.Unlock()
+		}
+	}()
+}
+
+func (s *SimpleTTLCache) Len() int {
+	return len(s.assets)
+}
+
+func (s *SimpleTTLCache) Put(k string, value interface{}) {
+	s.mutex.Lock()
+
+	item, ok := s.assets[k]
+	if !ok {
+		item = &simpleTTLItem{
+			value: value,
+		}
+		s.assets[k] = item
+	}
+
+	item.lastAccess = time.Now()
+
+	s.mutex.Unlock()
+}
+
+func (s *SimpleTTLCache) Get(k string) (v interface{}) {
+	s.mutex.Lock()
+
+	if item, ok := s.assets[k]; ok {
+		v = item.value
+		item.lastAccess = time.Now()
+	}
+
+	s.mutex.Unlock()
+	return
+}
+
+func (s *SimpleTTLCache) Update(k string, value interface{}) {
+	s.mutex.Lock()
+
+	item, ok := s.assets[k]
+	if ok {
+		item.value = value
+		item.lastAccess = time.Now()
+	}
+
+	s.mutex.Unlock()
+}

cache_test.go

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+package simplettlcache
+
+import (
+	"testing"
+	"time"
+)
+
+func TestSimpleTTLCache(t *testing.T) {
+	key := "a1"
+
+	// Setup cache for test
+	simpleTTLCache := SimpleTTLCache{}
+	simpleTTLCache.Init(time.Second * 3)
+
+	// Put item in cache and check it exists
+	simpleTTLCache.Put(key, "red")
+	if simpleTTLCache.Get(key) != "red" {
+		t.Error("Item missing from cache")
+	}
+
+	// Sleep to test TTL works
+	time.Sleep(time.Second * 4)
+	if simpleTTLCache.Get(key) != nil {
+		t.Error("Should be empty")
+	}
+}
+
+func TestSimpleTTLCacheLen(t *testing.T) {
+	key := "b2"
+
+	// Setup cache for test
+	simpleTTLCache := SimpleTTLCache{}
+	simpleTTLCache.Init(time.Second * 3)
+
+	// Put item in cache and check length
+	simpleTTLCache.Put(key, "apple")
+	if simpleTTLCache.Len() != 1 {
+		t.Error("Len of cache is wrong")
+	}
+}
+
+func TestSimpleTTLCacheUpdate(t *testing.T) {
+	key := "b2"
+
+	// Setup cache for test
+	simpleTTLCache := SimpleTTLCache{}
+	simpleTTLCache.Init(time.Second * 3)
+
+	// Put item in cache and check it exists
+	simpleTTLCache.Put(key, "apple")
+	if simpleTTLCache.Get(key) != "apple" {
+		t.Error("Item missing from cache")
+	}
+
+	// Update item in cache and check it changed
+	simpleTTLCache.Update(key, "banana")
+	if simpleTTLCache.Get(key) != "banana" {
+		t.Error("Item update failed")
+	}
+}

go.mod

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+module github.com/GuySWatson/simple-ttl-cache
+
+go 1.15