added cmd/listen2/main.go

uses 2 simultaneous Listeners
Unmarshal json-encoded event data

Author: johndelavega

cmd/listen2/main.go

@@ -0,0 +1,162 @@
+// Copyright 2019 Google Inc. All Rights Reserved.
+//
+// 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 main
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	"golang.org/x/net/context"
+	"google.golang.org/api/option"
+
+	firebase "firebase.google.com/go"
+	"firebase.google.com/go/db"
+)
+
+// Key is a json-serializable type.
+type Key struct {
+	Key1 string `json:"key1"`
+}
+
+func main() {
+
+	// opt := option.WithCredentialsFile("c:/users/username/.firebase/firebase.json") // Windows
+	//
+	opt := option.WithCredentialsFile("/home/username/.firebase/firebase.json") // Linux, edit 1.
+
+	config := &firebase.Config{
+		DatabaseURL: "https://databaseName.firebaseio.com", // edit 2.
+	}
+
+	app, err := firebase.NewApp(context.Background(), config, opt)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	ctx := context.Background()
+
+	// DatabaseWithURL
+	client, err := app.Database(ctx)
+
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// https://firebase.google.com/docs/reference/js/firebase.database.Reference.html#key
+	//
+	// key = The last part of the Reference's path.
+
+	testpath := "user1/path1"
+	ref := client.NewRef(testpath)
+
+	args := os.Args
+	if len(args) > 1 {
+		triggerEvent(ctx, client, testpath, args[1])
+		return // exit app
+	}
+
+	// SnapshotIterator
+	iter, err := ref.Listen(ctx)
+	if err != nil {
+		fmt.Printf(" Error: failed to create Listener %v\n", err)
+		return // exit app
+	}
+
+	fmt.Printf("Initial snapshots:\n")
+
+	fmt.Printf("1st Listener | Ref Path: %s | iter.Snapshot = %v\n", ref.Path, iter.Snapshot)
+	fmt.Printf("             | Ref Key: %s \n", ref.Key)
+
+	defer iter.Stop()
+
+	var key Key
+
+	go func() {
+		for {
+			event, err := iter.Next()
+
+			if err != nil {
+				break
+			}
+
+			err = event.Unmarshal(&key)
+
+			if err != nil {
+				fmt.Printf("1st Listener | Error: Unmarshal %v\n", err)
+			} else {
+				fmt.Printf("1st Listener | Ref Path: %s | event.Path %s | event.Unmarshal(&key) key.Key1 = %s\n", ref.Path, event.Path, key.Key1)
+				fmt.Printf("1st Listener | Ref Path: %s | event.Path %s | event.Unmarshal(&key) key = %v\n", ref.Path, event.Path, key)
+			}
+
+			fmt.Printf("1st Listener | Ref Path: %s | event.Path %s | event.Snapshot() = %v\n", ref.Path, event.Path, event.Snapshot())
+			fmt.Printf("\n")
+		}
+	}()
+
+	// 2nd listener
+	testpath2 := "user1/path1/path2"
+	ref2 := client.NewRef(testpath2)
+
+	iter2, err := ref2.Listen(ctx)
+	if err != nil {
+		fmt.Printf(" Error: failed to create Listener %v\n", err)
+		return
+	}
+
+	fmt.Printf("2nd Listener | Ref Path: %s | iter.Snapshot = %v\n", ref2.Path, iter2.Snapshot)
+	fmt.Printf("             | Ref Key: %s \n", ref2.Key)
+
+	defer iter2.Stop()
+
+	go func() {
+		for {
+			event, err := iter2.Next()
+
+			if err != nil {
+				break
+			}
+
+			fmt.Printf("2nd Listener | Ref Path: %s | event.Path %s | event.Snapshot() = %v\n", ref2.Path, event.Path, event.Snapshot())
+			fmt.Printf("\n")
+		}
+	}()
+
+	fmt.Printf("\n >>> open a new separate command line terminal, to trigger events, run: go run . anyvalue\n")
+	fmt.Printf("\n >>> OR edit value of any key from %s in firebase console to trigger events\n\n", testpath)
+	fmt.Printf("\n >>> press <enter> to close http connection\n\n")
+	fmt.Printf("Waiting for events...\n\n")
+
+	fmt.Scanln()
+	iter.Stop()
+
+	fmt.Printf("\n >>> press <enter> to exit app\n\n\n")
+	fmt.Scanln()
+}
+
+func triggerEvent(ctx context.Context, client *db.Client, testpath string, val string) {
+
+	var key Key
+
+	key.Key1 = val
+
+	ref := client.NewRef(testpath + "/path2/path3")
+
+	if err := ref.Set(ctx, key); err != nil {
+		log.Fatal(err)
+	} else {
+		fmt.Printf("OK - Set %s to key.Key1=%v\n", testpath+"/path2/path3", val)
+	}
+}