From 1c32ce19fef6e9ee61429ccddf999fe01e4b292b Mon Sep 17 00:00:00 2001
From: Soam Vasani <soamvasani@platform9.com>
Date: Sun, 30 Oct 2016 00:02:43 -0700
Subject: [PATCH] Cache -- simple threadsafe map

---
 cache/cache.go      | 133 ++++++++++++++++++++++++++++++++++++++++++++
 cache/cache_test.go |  47 ++++++++++++++++
 2 files changed, 180 insertions(+)
 create mode 100644 cache/cache.go
 create mode 100644 cache/cache_test.go

diff --git a/cache/cache.go b/cache/cache.go
new file mode 100644
index 00000000..87c24f6d
--- /dev/null
+++ b/cache/cache.go
@@ -0,0 +1,133 @@
+/*
+Copyright 2016 The Fission Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package cache
+
+import (
+	"time"
+
+	"fmt"
+	"github.com/platform9/fission"
+)
+
+type requestType int
+
+const (
+	GET requestType = iota
+	SET
+	DELETE
+)
+
+type (
+	Value struct {
+		ctime time.Time
+		atime time.Time
+		value interface{}
+	}
+	Cache struct {
+		cache          map[interface{}]Value
+		requestChannel chan *request
+	}
+
+	request struct {
+		requestType
+		key             interface{}
+		value           interface{}
+		responseChannel chan *response
+	}
+	response struct {
+		error
+		value interface{}
+	}
+)
+
+func MakeCache() *Cache {
+	c := &Cache{
+		cache:          make(map[interface{}]Value),
+		requestChannel: make(chan *request),
+	}
+	go c.service()
+	return c
+}
+
+func (c *Cache) service() {
+	for {
+		req := <-c.requestChannel
+		resp := &response{}
+		switch req.requestType {
+		case GET:
+			val, ok := c.cache[req.key]
+			if !ok {
+				resp.error = fission.MakeError(fission.ErrorNotFound,
+					fmt.Sprintf("key '%v' not found", req.key))
+			}
+			val.atime = time.Now()
+			c.cache[req.key] = val
+
+			resp.value = val.value
+			req.responseChannel <- resp
+		case SET:
+			now := time.Now()
+			c.cache[req.key] = Value{
+				value: req.value,
+				ctime: now,
+				atime: now,
+			}
+			req.responseChannel <- resp
+		case DELETE:
+			delete(c.cache, req.key)
+			req.responseChannel <- resp
+		default:
+			resp.error = fission.MakeError(fission.ErrorInvalidArgument,
+				fmt.Sprintf("invalid request type: %v", req.requestType))
+			req.responseChannel <- resp
+		}
+	}
+}
+
+func (c *Cache) Get(key interface{}) (interface{}, error) {
+	respChannel := make(chan *response)
+	c.requestChannel <- &request{
+		requestType:     GET,
+		key:             key,
+		responseChannel: respChannel,
+	}
+	resp := <-respChannel
+	return resp.value, resp.error
+}
+
+func (c *Cache) Set(key interface{}, value interface{}) error {
+	respChannel := make(chan *response)
+	c.requestChannel <- &request{
+		requestType:     SET,
+		key:             key,
+		value:           value,
+		responseChannel: respChannel,
+	}
+	resp := <-respChannel
+	return resp.error
+}
+
+func (c *Cache) Delete(key interface{}) error {
+	respChannel := make(chan *response)
+	c.requestChannel <- &request{
+		requestType:     DELETE,
+		key:             key,
+		responseChannel: respChannel,
+	}
+	resp := <-respChannel
+	return resp.error
+}
diff --git a/cache/cache_test.go b/cache/cache_test.go
new file mode 100644
index 00000000..52ba9657
--- /dev/null
+++ b/cache/cache_test.go
@@ -0,0 +1,47 @@
+/*
+Copyright 2016 The Fission Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package cache
+
+import "testing"
+import "log"
+
+func TestCache(t *testing.T) {
+	c := MakeCache()
+
+	err := c.Set("a", "b")
+	if err != nil {
+		log.Panicf("error: %v", err)
+	}
+
+	val, err := c.Get("a")
+	if err != nil {
+		log.Panicf("error: %v", err)
+	}
+	if val != "b" {
+		log.Panicf("value %v", val)
+	}
+
+	err = c.Delete("a")
+	if err != nil {
+		log.Panicf("error: %v", err)
+	}
+
+	_, err = c.Get("a")
+	if err == nil {
+		log.Panicf("error: %v", err)
+	}
+}