From 217eccac48004306446aad92e762c70d1cf1de85 Mon Sep 17 00:00:00 2001
From: Artjom Nemiro <artjom.nemiro@transactpro.lv>
Date: Thu, 15 Jun 2017 18:05:18 +0300
Subject: [PATCH] Added example of proxy realisation

---
 README.md                |  2 +-
 structural/proxy.md      | 14 ++++++++
 structural/proxy/main.go | 72 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 87 insertions(+), 1 deletion(-)
 create mode 100644 structural/proxy.md
 create mode 100644 structural/proxy/main.go

diff --git a/README.md b/README.md
index 4d7dbf4..7d9f5f7 100644
--- a/README.md
+++ b/README.md
@@ -30,7 +30,7 @@ A curated collection of idiomatic design & application patterns for Go language.
 | [Decorator](/structural/decorator.md) | Adds behavior to an object, statically or dynamically | ✔ |
 | [Facade](/structural/facade.md) | Uses one type as an API to a number of others | ✘ |
 | [Flyweight](/structural/flyweight.md) | Reuses existing instances of objects with similar/identical state to minimize resource usage | ✘ |
-| [Proxy](/structural/proxy.md) | Provides a surrogate for an object to control it's actions | ✘ |
+| [Proxy](/structural/proxy.md) | Provides a surrogate for an object to control it's actions | ✔ |
 
 ## Behavioral Patterns
 
diff --git a/structural/proxy.md b/structural/proxy.md
new file mode 100644
index 0000000..621479b
--- /dev/null
+++ b/structural/proxy.md
@@ -0,0 +1,14 @@
+# Proxy Pattern
+
+The [proxy pattern](https://en.wikipedia.org/wiki/Proxy_pattern) provides an object that controls access to another object, intercepting all calls.
+
+## Implementation
+
+The proxy could interface to anything: a network connection, a large object in memory, a file, or some other resource that is expensive or impossible to duplicate.
+
+```go
+    // Some short examples
+```
+
+## Usage
+For usage, see [observer/main.go](proxy/main.go) or [view in the Playground](https://play.golang.org/p/cr8jEmDmw0).
diff --git a/structural/proxy/main.go b/structural/proxy/main.go
new file mode 100644
index 0000000..9976e08
--- /dev/null
+++ b/structural/proxy/main.go
@@ -0,0 +1,72 @@
+package main
+
+import "fmt"
+
+// Terminal represents a public methods
+// whose allows to interact with "client"
+type ITerminal interface {
+	Execute(someCommand string) string
+}
+
+// GopherTerminal incapsulated terminal
+type GopherTerminal struct {
+	// User is a authorized user
+	user string
+}
+
+// Implements Terminal interface for GopherTerminal
+// Execute just run known command
+func (gt *GopherTerminal) Execute(cmd string) (resp string) {
+	resp = "Unknown command"
+
+	if cmd == "say_hi" {
+		resp = fmt.Sprintf("Hi %s", gt.user)
+	}
+
+	return
+}
+
+// Implements Proxy terminal to validate if user can use it
+// As example before send command user, must be authorized to do it
+type Terminal struct {
+	gopherTerminal *GopherTerminal
+}
+
+// ExecuteCommand intercepts execution of command, implements authorizing user, validates it and
+// poxing command to real terminal (gopherTerminal) method
+func (t *Terminal) ExecuteCommand(user, command string) (resp string, err error) {
+	// As we use terminal like proxy, then
+	// we will intercept user name to validate if it's allowed to execute commands
+	if user != "gopher" {
+		err = fmt.Errorf("You are not allowed to execute commands")
+		return
+	}
+
+	// if user allowed to execute send commands then,
+	// create new instance of terminal, set current user and send user command to execution
+	t.gopherTerminal = new(GopherTerminal)
+	t.gopherTerminal.user = user
+	if resp = t.gopherTerminal.Execute(command); resp == "Unknown command" {
+		err = fmt.Errorf("I know only how to say hello (type: say_hi)")
+		return
+	}
+
+	return
+}
+
+// For example:
+// we must a execute some command
+// so before that we must to create new terminal session
+// and provide our user name and command
+func main() {
+	// Create new instance of terminal
+	newTerm := new(Terminal)
+	// Try execute command
+	resp, err := newTerm.ExecuteCommand("gopher", "doJob")
+	if err != nil {
+		fmt.Println(err.Error()) // print Unknown command
+	}
+
+	// Handle result of execution
+	fmt.Println(resp)
+}