JavaScript Requires Chilkat v11.0.0+

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

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

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 CkFileAccess();
var accessToken = fac.ReadEntireTextFile("qa_data/tokens/firebaseToken.txt","utf-8");
if (fac.LastMethodSuccess == false) {
    console.log(fac.LastErrorText);
    return;
}

var rest = new CkRest();

//  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 CkAuthGoogle();
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 CkUrl();
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 CkRest();

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 CkJsonObject();

//  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 CkStream();

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

// task: CkTask
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());