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

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

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

# 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.
fac = Chilkat::CkFileAccess.new()
accessToken = fac.readEntireTextFile("qa_data/tokens/firebaseToken.txt","utf-8")
if (fac.get_LastMethodSuccess() != true)
    print fac.lastErrorText() + "\n";
    exit
end

rest = Chilkat::CkRest.new()

# 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 != true)
    print rest.lastErrorText() + "\n";
    exit
end

authGoogle = Chilkat::CkAuthGoogle.new()
authGoogle.put_AccessToken(accessToken)
rest.SetAuthGoogle(authGoogle)

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

responseBody = rest.fullRequestNoBody("GET","/.json")

# A 307 redirect response is expected.
if (rest.get_ResponseStatusCode() != 307)
    print "Unexpected response code: " + rest.get_ResponseStatusCode().to_s() + "\n";
    print responseBody + "\n";
    print "Failed." + "\n";
    exit
end

# Get the redirect URL
# url is a CkUrl
url = rest.RedirectUrl()
if (rest.get_LastMethodSuccess() != true)
    print rest.lastErrorText() + "\n";
    exit
end

print "redirect URL domain: " + url.host() + "\n";
print "redirect URL path: " + url.path() + "\n";
print "redirect URL query params: " + url.query() + "\n";
print "redirect URL path with query params: " + url.pathWithQueryParams() + "\n";

# Our text/event-stream will be obtained from the redirect URL...
rest2 = Chilkat::CkRest.new()

success = rest2.Connect(url.host(),443,true,true)
if (success != true)
    print rest2.lastErrorText() + "\n";

    exit
end

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)
    print rest2.lastErrorText() + "\n";

    exit
end

# 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.
responseStatusCode = rest2.ReadResponseHeader()
if (responseStatusCode < 0)
    print rest2.lastErrorText() + "\n";
    exit
end

# 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)
    print "Response Code: " + responseStatusCode.to_s() + "\n";
    print "Response Status Text: " + rest2.responseStatusText() + "\n";
    print "Response Header: " + rest2.responseHeader() + "\n";
    responseBody = rest2.readRespBodyString()
    if (rest2.get_LastMethodSuccess() == true)
        print "Error Response Body: " + responseBody + "\n";
    end

    print "Failed." + "\n";
    exit
end

# For this example, our JSON database will be empty at the beginning.
# The incoming events (put and patch) will be applied to this database.
jsonDb = Chilkat::CkJsonObject.new()

# Make sure to set the JSON path delimiter to "/".  The default is "." and this
# is not compatible with Firebase paths.
jsonDb.put_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..
eventStream = Chilkat::CkStream.new()

# This sse object will be used as a helper to parse the server-sent event stream.
sse = Chilkat::CkServerSentEvent.new()

# task is a CkTask
task = rest2.ReadRespBodyStreamAsync(eventStream,true)
task.Run()

# For this example, we'll just read a few events, and then cancel the
# async task.
count = 0
while (count < 3) and (task.get_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.
    eventStr = eventStream.readUntilMatch("\r\n\r\n")
    if (eventStream.get_LastMethodSuccess() != true)
        print eventStream.lastErrorText() + "\n";
        # Force the loop to exit by setting the count to a high number.
        count = 99999
    else
        print "Event: [" + eventStr + "]" + "\n";

        # We have an event. Let's update our local copy of the JSON database.
        success = sse.LoadEvent(eventStr)
        if (success != true)
            print "Failed to load sse event: " + eventStr + "\n";
        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)
                print "Failed to apply event: " + sse.eventName() + ": " + sse.data() + "\n";
            else
                print "Successfully applied event: " + sse.eventName() + ": " + sse.data() + "\n";
            end

        end

    end

    count = count + 1
end

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

# Examine the JSON database after applying events..
jsonDb.put_EmitCompact(false)
print "----" + "\n";
print jsonDb.emit() + "\n";