#First Discovery Chrome Extension

####About This Chrome extension is responsible for passing messages from a First Discovery Tool web site to a Chrome native messaging host. This extension is simply a middle man between a web site and a native host to facilitate communication.

This repository is not useful by itself. It should be used with its companion native messaging host and a first discovery server:

1. https://github.com/pga03/first-discovery-native-host
2. https://github.com/pga03/first-discovery-server

####Messaging background

See these links for additional information on Chrome's messaging capabilities:

1. https://developer.chrome.com/extensions/messaging
2. https://developer.chrome.com/extenions/nativeMessaging

###Installation

1. Simply navigate to https://chrome.google.com/webstore/detail/comibmfirstdiscovery/nkojgcmaioingjndknblmghefcfijobm and install from the webstore

NOTE: The extension is configured to only connect to these URL's:

  http://extension-demo-jtworkme.mybluemix.net/*,
  http://first-discovery-demo.mybluemix.net/demos/prefsServerIntegration/*,
  http://first-discovery.mybluemix.net/*,
  http://first-discovery2.mybluemix.net/*,
  http://first-discovery3.mybluemix.net/*

As a result, the extension will not cooperate with a web app hosted at any other URL pattern.

###Uninstall

1. Access chrome://extensions in Chrome
2. Delete the extension

###Troubleshooting

####Debugging Chrome lets you inspect background views using the Chrome developer tools. You can access a link to inspect the plugin from chrome://extensions

####Extension ID When installed in development mode, the extension's ID can sometimes change. You can view your extension ID at chrome://extensions and use it in your first discovery server and native messaging hosts.

###Message Format Per the Chrome messaging documentation, the extension can be sent messages in this manner:

chrome.runtime.sendMessage(extension_id, msg_object, callback_function);

The general msg_object argument must be a JSON object with this structure

{
    message: {
      message_type: "string",
      message_body: {}
    }
}

Supported values for message_type are write_usb and request_version.

####write_usb message This message requires additional information and is used to write the GPII user token and preference set to a USB device (that writing is performed by the native messaging host).

Example of type write_usb:

{
    message: {
      message_type: "write_usb",
      message_body: {
        userToken: "the user's GPII user token",
        preferences: {} # an object with the user's Needs & Preference set
      }
    }
}

The callback function is supplied with an object in this format:

{
    is_successful: true/false  
}

####request_version message This message requires no additional information. Its purpose is to allow the web page to inspect the environment for the existence of the extension, and always returns quickly without performing any real operation.

Example msg_object:

{
    message: {
      message_type: "request_version"     
    }
}

The callback function is supplied with an object in this format:

{
    extension: "extension version number",
    native: "unknown" 
}

####Example usage

This example shows how to detect the extension and use it, or run some other code when it is not present.

// If the plugin hasn't responded in 2 seconds with the version, it is a user without a
// plugin installed
var successTimeoutId = setTimeout(function(){
    function_to_execute_when_no_extension_is_present();
}, 2000);

window.chrome.runtime.sendMessage(
    that.options.chromeExtensionId,
    {"message": {"message_type":"request_version"}},
    function onVersionCallback(version){
        // If we got a version, the plugin is installed, so clear the timeout and let the plugin write to usb
        if (version){                   
            clearTimeout(successTimeoutId);
            var message = {
                message: {
                    message_type: "write_usb",
                    message_body: {
                        userToken: data.userToken,
                        preferences: data.preferences
                    }
                }
            };
            window.chrome.runtime.sendMessage(
                that.options.chromeExtensionId,
                message,
                function onChromeExtensionResponse(response) {
                    if (response.is_successful == "true") {
                        that.events.onSuccess.fire(data);
                    } else {
                        that.events.onError.fire();
                    }
                });
        }
    });

####Testing Navigate to tests and run node tests.js