Node.js

Firebase Receive Server-Sent Events (text/event-stream)

See more Firebase Examples

Demonstrates how to start receiving server-sent events and update your JSON database with each event. Node.js

NODEJS_PRELUDE

function chilkatExample() {

    var success = false;

    // Demonstrates how to begin receiving server-sent events, and to update
    // your JSON database for each event.

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // This example assumes a JWT authentication token, if required, has been previously obtained.
    // See Get Firebase Access Token from JSON Service Account Private Key for sample code.

    // Load the previously obtained Firebase access token into a string.
    var fac = new chilkat.FileAccess();
    var accessToken = fac.ReadEntireTextFile("qa_data/tokens/firebaseToken.txt","utf-8");
    if (fac.LastMethodSuccess == false) {
        console.log(fac.LastErrorText);
        return;
    }

    var rest = new chilkat.Rest();

    // Make the initial connection (without sending a request yet).
    // Once connected, any number of requests may be sent.  It is not necessary to explicitly
    // call Connect before each request.  
    success = rest.Connect("chilkat.firebaseio.com",443,true,true);
    if (success == false) {
        console.log(rest.LastErrorText);
        return;
    }

    var authGoogle = new chilkat.AuthGoogle();
    authGoogle.AccessToken = accessToken;
    rest.SetAuthGoogle(authGoogle);

    rest.AddHeader("Accept","text/event-stream");
    rest.AddHeader("Cache-Control","no-cache");

    var responseBody = rest.FullRequestNoBody("GET","/.json");

    // A 307 redirect response is expected.
    if (rest.ResponseStatusCode !== 307) {
        console.log("Unexpected response code: " + rest.ResponseStatusCode);
        console.log(responseBody);
        console.log("Failed.");
        return;
    }

    // Get the redirect URL
    var urlStr = rest.LastRedirectUrl;
    var url = new chilkat.Url();
    url.ParseUrl(urlStr);

    console.log("redirect URL domain: " + url.Host);
    console.log("redirect URL path: " + url.Path);
    console.log("redirect URL query params: " + url.Query);
    console.log("redirect URL path with query params: " + url.PathWithQueryParams);

    // Our text/event-stream will be obtained from the redirect URL...
    var rest2 = new chilkat.Rest();

    success = rest2.Connect(url.Host,443,true,true);
    if (success !== true) {
        console.log(rest2.LastErrorText);
        return;
    }

    rest2.AddHeader("Accept","text/event-stream");
    rest2.AddHeader("Cache-Control","no-cache");

    // Add the redirect query params to the request
    rest2.AddQueryParams(url.Query);

    // In our case, we don't actually need the auth query param,
    // so remove it.
    rest2.RemoveQueryParam("auth");

    // Send the request.  (We are only sending the request here.
    // We are not yet getting the response because the response
    // will be a text/event-stream.)
    success = rest2.SendReqNoBody("GET",url.Path);
    if (success !== true) {
        console.log(rest2.LastErrorText);
        return;
    }

    // Read the response header.  
    // We want to first get the response header to see if it's a successful
    // response status code.  If not, then the response will not be a text/event-stream
    // and we should read the response body normally.
    var responseStatusCode = rest2.ReadResponseHeader();
    if (responseStatusCode < 0) {
        console.log(rest2.LastErrorText);
        return;
    }

    // If successful, a 200 response code is expected.
    // If the reponse code is not 200, then read the response body and fail..
    if (responseStatusCode !== 200) {
        console.log("Response Code: " + responseStatusCode);
        console.log("Response Status Text: " + rest2.ResponseStatusText);
        console.log("Response Header: " + rest2.ResponseHeader);
        responseBody = rest2.ReadRespBodyString();
        if (rest2.LastMethodSuccess == true) {
            console.log("Error Response Body: " + responseBody);
        }

        console.log("Failed.");
        return;
    }

    // For this example, our JSON database will be empty at the beginning.
    // The incoming events (put and patch) will be applied to this database.
    var jsonDb = new chilkat.JsonObject();

    // Make sure to set the JSON path delimiter to "/".  The default is "." and this
    // is not compatible with Firebase paths.
    jsonDb.DelimiterChar = "/";

    // At this point, we've received the response header.  Now it's time to begin
    // receiving the event stream.  We'll start a background thread to read the 
    // stream.  (Our main application (foreground) thread can cancel it at any time.)  
    // While receiving in the background thread, our foreground thread can read the stream
    // as it desires..
    var eventStream = new chilkat.Stream();

    // This sse object will be used as a helper to parse the server-sent event stream.
    var sse = new chilkat.ServerSentEvent();

    // task: Task
    var task = rest2.ReadRespBodyStreamAsync(eventStream,true);
    task.Run();

    // For this example, we'll just read a few events, and then cancel the
    // async task.
    var count = 0;
    while ((count < 3) && (task.Finished == false)) {

        // Get the next event, which is a series of text lines ending with
        // a blank line. 
        // Note: This method blocks the calling thread until a message arrives.
        // a program might instead periodically check the availability of
        // data via the stream's DataAvailable property, and then do the read.

        // An alternative to writing a while loop to read the event stream
        // would be to setup some sort of timer event in your program (using whatever timer functionality
        // is provided in a programming language/environment), to periodically check the eventStream's
        // DataAvailable property and consume the incoming event.
        var eventStr = eventStream.ReadUntilMatch("\r\n\r\n");
        if (eventStream.LastMethodSuccess !== true) {
            console.log(eventStream.LastErrorText);
            // Force the loop to exit by setting the count to a high number.
            count = 99999;
        }
        else {
            console.log("Event: [" + eventStr + "]");

            // We have an event. Let's update our local copy of the JSON database.
            success = sse.LoadEvent(eventStr);
            if (success !== true) {
                console.log("Failed to load sse event: " + eventStr);
            }
            else {
                // Now we can easily access the event name and data, and apply it to our JSON database:
                success = jsonDb.FirebaseApplyEvent(sse.EventName,sse.Data);
                if (success !== true) {
                    console.log("Failed to apply event: " + sse.EventName + ": " + sse.Data);
                }
                else {
                    console.log("Successfully applied event: " + sse.EventName + ": " + sse.Data);
                }

            }

        }

        count = count+1;
    }

    // Make sure the background task is cancelled if still running.
    task.Cancel();

    // Examine the JSON database after applying events..
    jsonDb.EmitCompact = false;
    console.log("----");
    console.log(jsonDb.Emit());

}

chilkatExample();