feature(worker): context object to store runtime configurations

worker/context.go

@@ -0,0 +1,61 @@
+package worker
+
+// Context object aims to store runtime configurations
+
+import "errors"
+
+// A Context object is a layered key-value storage
+// when enters a context, the changes to the storage would be stored
+// in a new layer and when exits, the top layer poped and the storage
+// returned to the state before entering this context
+type Context struct {
+	parent *Context
+	store  map[string]interface{}
+}
+
+// NewContext returns a new context object
+func NewContext() *Context {
+	return &Context{
+		parent: nil,
+		store:  make(map[string]interface{}),
+	}
+}
+
+// Enter generates a new layer of context
+func (ctx *Context) Enter() *Context {
+
+	return &Context{
+		parent: ctx,
+		store:  make(map[string]interface{}),
+	}
+
+}
+
+// Exit return the upper  layer of context
+func (ctx *Context) Exit() (*Context, error) {
+	if ctx.parent == nil {
+		return nil, errors.New("Cannot exit the bottom layer context")
+	}
+	return ctx.parent, nil
+}
+
+// Get returns the value corresponding to key, if it's
+// not found in the current layer, return the lower layer
+// context's value
+func (ctx *Context) Get(key string) (interface{}, bool) {
+	if ctx.parent == nil {
+		if value, ok := ctx.store[key]; ok {
+			return value, true
+		}
+		return nil, false
+	}
+	if value, ok := ctx.store[key]; ok {
+		return value, true
+	}
+	return ctx.parent.Get(key)
+}
+
+// Set sets the value to the key at current layer
+func (ctx *Context) Set(key string, value interface{}) {
+	ctx.store[key] = value
+}