Initial commit - FR: realtime event listener for RTDB (#229)

cmd/listen/main.go

@@ -0,0 +1,115 @@
+// 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"
+)
+
+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://mydb.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)
+	}
+
+	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
+	}
+
+	fmt.Printf("client app | Ref Path: %s | iter.Snapshot = %v\n", ref.Path, iter.Snapshot)
+	fmt.Printf("           | Ref Key: %s \n", ref.Key)
+
+	defer iter.Stop()
+
+	go func() {
+		for {
+
+			if iter.Done() {
+				break
+			}
+
+			event, err := iter.Next()
+
+			if err != nil {
+				// Handle error here based on specific usecase
+				// We can continue Listening
+				log.Printf("%v\n", err)
+				continue // go back to beginning of for loop
+			}
+
+			fmt.Printf("client app | Ref Path: %s | event.Path %s | event.Snapshot() = %v\n", ref.Path, event.Path, event.Snapshot())
+			fmt.Printf("\n")
+		}
+	}()
+
+	fmt.Printf("\n >>> edit value of any key from %s in firebase console to trigger event\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) {
+
+	ref := client.NewRef(testpath + "/key1")
+
+	if err := ref.Set(ctx, val); err != nil {
+		log.Fatal(err)
+	} else {
+		fmt.Printf("OK - Set %s to %v\n", testpath+"/key1", val)
+	}
+}

cmd/listen2/main.go

@@ -0,0 +1,182 @@
+// 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 {
+
+			if iter.Done() {
+				break
+			}
+
+			event, err := iter.Next()
+
+			if err != nil {
+				// Handle error here based on specific usecase
+				// We can continue Listening
+				log.Printf("%v\n", err)
+				continue // go back to beginning of for loop
+			}
+
+			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 {
+
+			if iter2.Done() {
+				break
+			}
+
+			event, err := iter2.Next()
+
+			if err != nil {
+				// Handle error here based on specific usecase
+				// We can continue Listening
+				log.Printf("%v\n", err)
+				continue // go back to beginning of for loop
+			}
+
+			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 stop 1st Listener and close http connection\n\n")
+	fmt.Printf("Waiting for events...\n\n")
+
+	fmt.Scanln()
+	iter.Stop()
+
+	fmt.Printf("\n >>> press <enter> to stop 2nd Listener and close http connection\n\n")
+	fmt.Scanln()
+	iter2.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)
+	}
+}

db/event.go

@@ -0,0 +1,98 @@
+// 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 db
+
+import (
+	"encoding/json"
+	"errors"
+	"net/http"
+)
+
+// SSE = Sever-Sent Events = ssevent
+
+// EventType specific event type changes
+type EventType uint
+
+// EventType ...
+const (
+	ChildChanged EventType = iota
+	ChildAdded             // to be implemented
+	ChildRemoved           // to be implemented
+	ValueChanged           // to be implemented
+)
+
+// Event Sever-Sent Event object
+type Event struct {
+	EventType EventType // ChildChanged, ValueChanged, ChildAdded, ChildRemoved
+
+	Data string // JSON-encoded snapshot
+	Path string // snapshot path
+}
+
+// SnapshotIterator iterator for continuous events
+type SnapshotIterator struct {
+	Snapshot    string         // initial snapshot, JSON-encoded, returned from http Respoonse, server sent event, data part
+	SSEDataChan <-chan string  // continuous event snapshot, channel receive only, directional channel
+	done        *bool          // Done listening to events, also used to prevent channel block
+	resp        *http.Response // http connection keep alive
+}
+
+// Snapshot ssevent data, data part
+func (e *Event) Snapshot() string {
+
+	return e.Data // ssevent data (snapshot), snapshot only, data part of ssevent data
+}
+
+// Unmarshal current snapshot Event.Data
+func (e *Event) Unmarshal(v interface{}) error {
+
+	return json.Unmarshal([]byte(e.Data), v)
+}
+
+// Next realtime event
+func (it *SnapshotIterator) Next() (*Event, error) {
+
+	// prevent channel block
+	if *it.done == true {
+		return nil, errors.New("SnapshotIterator is done or no longer active")
+	}
+
+	sseDataString := <-it.SSEDataChan
+
+	// todo: determine EventType
+
+	path, snapshot, err := splitSSEData(sseDataString)
+
+	return &Event{
+		EventType: ChildChanged,
+		Data:      snapshot,
+		Path:      path,
+	}, err
+
+} // Next()
+
+// Stop listening for realtime events
+// close http connection
+func (it *SnapshotIterator) Stop() {
+	*it.done = true
+	if it.resp != nil {
+		it.resp.Body.Close()
+	}
+}
+
+// Done can be used to check if Stop() have been called
+func (it *SnapshotIterator) Done() bool {
+	return *it.done
+}