more plugin doc updates (#7767)

plugin/example_hello_user_test.go

@@ -0,0 +1,38 @@
+package plugin_test
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/mattermost/mattermost-server/plugin"
+	"github.com/mattermost/mattermost-server/plugin/rpcplugin"
+)
+
+type HelloUserPlugin struct {
+	api plugin.API
+}
+
+func (p *HelloUserPlugin) OnActivate(api plugin.API) {
+	// Just save api for later when we need to look up users.
+	p.api = api
+}
+
+func (p *HelloUserPlugin) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if userId := r.Header.Get("Mattermost-User-Id"); userId == "" {
+		// Our visitor is unauthenticated.
+		fmt.Fprintf(w, "Hello, stranger!")
+	} else if user, err := p.api.GetUser(userId); err == nil {
+		// Greet the user by name!
+		fmt.Fprintf(w, "Welcome back, %v!", user.Username)
+	} else {
+		// This won't happen in normal circumstances, but let's just be safe.
+		w.WriteHeader(http.StatusInternalServerError)
+		fmt.Fprintf(w, err.Error())
+	}
+}
+
+// This example demonstrates a plugin that handles HTTP requests which respond by greeting the user
+// by name.
+func Example_helloUser() {
+	rpcplugin.Main(&HelloUserPlugin{})
+}