From 178411f14814b5ea8c855e3641636164f0565e89 Mon Sep 17 00:00:00 2001
From: crusader <crusader@atgame.net>
Date: Wed, 22 Aug 2018 16:44:50 +0900
Subject: [PATCH] Ctx added

---
 ctx/ctx.go | 105 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 105 insertions(+)
 create mode 100644 ctx/ctx.go

diff --git a/ctx/ctx.go b/ctx/ctx.go
new file mode 100644
index 0000000..b9bd058
--- /dev/null
+++ b/ctx/ctx.go
@@ -0,0 +1,105 @@
+package ctx
+
+import (
+	"reflect"
+	"sync"
+)
+
+func NewCtx(parent Ctx) Ctx {
+	c := &defaultCtx{
+		parent: parent,
+	}
+	c.attributes = make(map[interface{}]interface{})
+	return c
+}
+
+type Ctx interface {
+	Parent() Ctx
+	SetAttribute(key interface{}, value interface{})
+	GetAttribute(key interface{}) (value interface{})
+	RemoveAttribute(key interface{})
+	ContainsAttribute(key interface{}) (exist bool)
+}
+
+type defaultCtx struct {
+	parent     Ctx
+	attributes map[interface{}]interface{}
+
+	mtx sync.RWMutex
+}
+
+func (dc *defaultCtx) Parent() Ctx {
+	return dc.parent
+}
+
+func (dc *defaultCtx) SetAttribute(key interface{}, value interface{}) {
+	dc.checkInitialized()
+
+	if key == nil {
+		panic("nil key")
+	}
+	if !reflect.TypeOf(key).Comparable() {
+		panic("key is not comparable")
+	}
+
+	dc.mtx.Lock()
+	defer dc.mtx.Unlock()
+
+	dc.attributes[key] = value
+}
+
+func (dc *defaultCtx) GetAttribute(key interface{}) (value interface{}) {
+	dc.checkInitialized()
+
+	dc.mtx.RLock()
+	defer dc.mtx.RUnlock()
+
+	if _, ok := dc.attributes[key]; ok {
+		return dc.attributes[key]
+	}
+
+	if nil == dc.parent {
+		return nil
+	}
+	return dc.parent.GetAttribute(key)
+}
+
+func (dc *defaultCtx) RemoveAttribute(key interface{}) {
+	dc.checkInitialized()
+
+	dc.mtx.Lock()
+	defer dc.mtx.Unlock()
+
+	if _, ok := dc.attributes[key]; ok {
+		delete(dc.attributes, key)
+		return
+	}
+
+	if nil == dc.parent {
+		return
+	}
+
+	dc.parent.RemoveAttribute(key)
+}
+
+func (dc *defaultCtx) ContainsAttribute(key interface{}) (exist bool) {
+	dc.checkInitialized()
+
+	dc.mtx.RLock()
+	defer dc.mtx.RUnlock()
+
+	if _, ok := dc.attributes[key]; ok {
+		return true
+	}
+
+	if nil == dc.parent {
+		return false
+	}
+	return dc.parent.ContainsAttribute(key)
+}
+
+func (dc *defaultCtx) checkInitialized() {
+	if nil == dc.attributes {
+		panic("Attribute Manager: must be initialized")
+	}
+}