The @FindMyPlane bot

A few days ago I wrote about the Genexus Challenge developer edition and my first Smart Devices app, Find my Plane. Once I get, what I think is, a good idea in my head I get around it a lot to improve it in every possible way. But this is not the case, sort of.

Right after I deployed the app to the Apple’s app store, I thought “how can I advertise it, without paying for advertising of course”, I needed people to find out about the app and download it, and a good word about it would be awesome too. So I thought about social networks… Facebook is for friends and I already told them to download it (did I mentioned it’s free?!) so twitter came to mind… but what can I do to promote my app from twitter, other than twitting about it of course.

So I thought of the @FindmyPlane bot and this post will tell you how I did it, not that it’s rocket science, but I found an interesting use of Windows Azure’s Worker Roles*. Wait, what?! you’re gonna tell people how to build a twitter spammer bot? No, let me get into that.

The @FindMyPlane twitter account works like this. You send a twit to @FindMyPlane with your flight number and find my plane will answer that tweet with useful info about it, the same kind of info you’d get in the Find My Plane app, but of course, only the info that fits in 140 characters.

So this is how it works. There’s a worker role (called Receiver) that every ten seconds access the twitter api looking for mentions for the @FindMyPlane account. Once it gets the list of tweets (if any of course) it saves them to a Table from Azure Storage and saves the latest tweet id in a Queue (also from Azure Storage) so the next time it just asks from that tweet on.

This is pretty much the code:

string lastTweet = "";
string previousMessageId = "";
foreach (CloudQueueMessage message in Queue.GetAllMessages(Constants.AZURE_STORAGE_ACCOUNT, Constants.AZURE_STORAGE_KEY, Constants.AZURE_QUEUE))
{
    previousMessageId = message.Id;
    lastTweet = message.AsString;
}

bool first = true;
foreach (Status status in Mentions.GetMentions(fmp, lastTweet))
{
    try
    {
        Table.Insert(Constants.AZURE_STORAGE_ACCOUNT, Constants.AZURE_STORAGE_KEY, Constants.AZURE_TABLE, TweetEntity.FromStatus(status).ToString());
    }
    catch { }

    if (first)
    {
        lastTweet = status.Id;
        first = false;
    }
}

if (!first)
{
    Queue.DeleteMessage(Constants.AZURE_STORAGE_ACCOUNT, Constants.AZURE_STORAGE_KEY, Constants.AZURE_QUEUE, previousMessageId);
    Queue.CreateMessage(Constants.AZURE_STORAGE_ACCOUNT, Constants.AZURE_STORAGE_KEY, Constants.AZURE_QUEUE, lastTweet);
}

And there’s a second Worker Role (called Replier) that every ten seconds queries the table where the tweets were saved for those that have not been replied yet and don’t have errors. For every tweet I try to get info of the flight number sent, if I do find info, I reply the tweet with that info and update the record on the table as replied. If I can’t find info, let’s say you tweeted “@FindMyPlane is awesome!” I update the record as ‘with errors’. This is just a way for me to know when I couldn’t reply because of an error on the system or because what I got was not a valid flight number.

Code here:

string query = "Replied eq 'False' and Error eq 'False'";
foreach (TableEntity entity in Table.Query(Constants.AZURE_STORAGE_ACCOUNT, Constants.AZURE_STORAGE_KEY, Constants.AZURE_TABLE, query))
{
    string flightNumber = entity["Text"].ToUpper().Replace("@FINDMYPLANE ", "");
    try
    {
        FlightInfo info = FlightStatus.GetFlightStatus(flightNumber);
        string tweet = string.Format("@{0} {1}", entity["UserScreenname"], info);
        Update.UpdateStatus(tweet, fmp, entity["Id"]);
        entity["Replied"] = "True";

        Table.UpdateEntity(Constants.AZURE_STORAGE_ACCOUNT, Constants.AZURE_STORAGE_KEY, Constants.AZURE_TABLE, entity);
    }
    catch 
    {
        try
        {
            entity["Error"] = "True";
            Table.UpdateEntity(Constants.AZURE_STORAGE_ACCOUNT, Constants.AZURE_STORAGE_KEY, Constants.AZURE_TABLE, entity);
        }
        catch
        {
            Table.DeleteEntity(Constants.AZURE_STORAGE_ACCOUNT, Constants.AZURE_STORAGE_KEY, Constants.AZURE_TABLE, entity.PartitionKey, entity.RowKey);
        }
    }
}

Cool uh?!

Here’s how all this works together

(*) for a good read on the Azure platform, Worker Roles and Storage (Table, Queues & Blobs) go to: http://bit.ly/SGAzure

You can download the ‘Find my Plane’ for Android and for iPhone.

Find my Plane

At Genexus we had a little contest. We had a few contest before where we asked customers and friends to create a cool app for Smart Devices with our brand new Smart Devices generator. Of course we could not participate, it would be unfair… (or at least that’s what they thought).

So a month ago, Gastón told us we would have an internal contest, it was called “GX Challenge (Developer Edition)” in which whoever wanted to participate had to build an app. Who wins? whoever gets the most downloads per app.

The most difficult thing is of course to come up with a good/cool idea, and I’m not saying that I finally came to a real good idea, with it was something that I’d definitely enjoy doing. So that’s how Find my Plane appeared.

Find my Plane is a simple app where you enter a flight number and the app would give you info about the flight. From where to where, terminal and gate (where available) and if the flight is on time or delayed, and even as Nicolás found out, if the plane was diverted to a different location.

But it was still too simple. Who would download an app like that if you can get that info and more from other apps? So I added a few things. First, thanks to wunderground.com API I added the weather of both departure and arrival airports of the flight, plus another small feature that is being able to listen to the air traffic controllers available from the mentioned airports. You can get all that from different apps, but I haven’t seen one with all those features combined so I thought it would be a cool app, and fun to develop.

It’s been on the Android Marketplace (AKA Google Play) for over 2 weeks now with a little over 100 downloads plus 200+ downloads from the Apple Marketplace in less than a week.

Here’s a little video of what the app looks like (on the Android emulator)

Like what you see? Download it now!

http://bit.ly/FMPAndroid

http://bit.ly/FMPiOS

p.s: Did I mention it is FREE!

Colored log4net log files in Notepad++

Some time ago, I can’t tell exactly when, I discovered Notepad++ (NPP). NPP is a great light weight text editor with tons of cool features.
I’m also a big fun of log4Net since I discovered when I added the logging features to Genexus and GXserver. It is so easy to implement and helpful that I have used it in every project I worked ever since.
So in my daily basis I get to work with log4net log files a lot. I was doing so last Saturday when it hit me, “I need syntax coloring for this”.
So I looked up and found a great post from Jon Galloway that explains how you can create your own “User Defined Language” in NPP. To my surprise it was pretty simple since NPP has a dialog to do so, I thought I’d have to some xml editing. The dialog does that for you and what’s even better you can see the results of what you’re changing while you’re doing it. 

The result is (to me) pretty cool. It’s now a lot easier to find the ERROR or WARN lines.
I also added a couple of features that basically are a better way to focus on what’s important.
Numbers are in yellow, single quoted strings are in red, each keyword (INFO, DEBUG, ERROR, WARN, FATAL) has its own color, plus I also added “comments”. By using the good old // to comment a line or /* to comment a block */, you can help you and others to pay attention to what really matters, or at least what you think matters.
So, how do you get this?
Simple way: If you have never defined of modified a User defined Language, you can simply download the posted file and override your existent in %APPDATA%\Notepad++ (Make sure you backup your file first)
“Harder” way: if you have modified of added a user defined language, you probably know what to do but anyways, download the file (same from above) open it in your favorite text editor ;) and copy the UserLang tag with its content and copy it to your current userDefineLang.xml file.

**We moved to GitHub! Download the file from: https://github.com/sebagomez/log4net-for-notepadpp

As usual, this is 100% “works on my machine” certified.

Featuring GXpowerCommands

After @gmilano’s Cool Commands for Visual Studio I thought I should write my own “cool commands” for Genexus. There a few tasks the I need to do quite often and I thought I’d be great if I could have right there on a contextual menu, like completely deleting a folder and it’s content or “Rebuild and run” an object… or even run (execute) an object as is, no further specification of analysis needed.

So I created this package with the extensions I found useful to myself. Here’s a little description of every command:

Empty and delete folder: I tries to delete every object in a folder and the folder itself. The success will depend on the references the contained objects have to. I any object A outside the selected folder) is referencing an object B from the folder, B won’t be able to be deleted, thus, the folder either. This command is not transactional.
Build/Rebuild folder objects: Ever wanted to build every object in a folder? It’s kind of painful to select every single object, right? Now you can step on a folder and choose to build or rebuild every single object in it.
Rebuild and run: Only valid for main objects, this command will execute a forced build (rebuild) and then execute (run) the generated program.
Run as is: What was that message again? I know the state of the generated program, I just want to execute it, no validation needed. This is the command that will fire the browser and show you the program “as is”. 
Command prompt here: This is a command that’s now built-in in Visual Studio. Applied to Genexus you can open a command prompt at the Knowledge Base directory or at your different environments directories. Just click on the desired node from the Preferences tree and voilá.
Windows Explorer here: Same as command prompt but for Windows Explorer. Enough said.

This package can be freely downloaded from the Genexus Marketplace, so go ahead and give it a try.

In this post I’ll like to answer the question I know some people must be wondering: “dude! you work at the Genexus Development Team, why aren’t these commands available in Genexus out of the box?”. Well, I’m no traditional Genexus developer so I’m not sure if these commands will actually be useful to the entire community so I don’t want to add “noise” to the already pretty big menus we have in Genexus. So depending on the adoption of these commands you might see some of them in Genexus in the near future.

Spanish instructions here, download here.

Like every other set of bits from this blog, this extension is “Works on my machine” certified, but this one has actually been tested by the guys at the Genexus marketplace

EDIT 25-Oct-2011: Genexus X Evolution 2 support is now available.

WCF RIA Services Compositions with Entity Framework

I haven't been working on anything outside Genexus, Deklarit and Genexus Server for a while, so when my friend Mateo asked to help him on a new project for a client of his, based on brand new Microsoft technologies, I was saying yes before the end of the sentence.

This blog post and probably some more to come will be related to our experience with Entity Framework 4, RIA Services 1 and Silverlight 4.

But in this particular case I wanted to blog about a problem we had with Compositions. Compositions are very useful when you have an Association where a Parent entity needs to have its children all the time.

The Update method of parent entities is a bit different than regular entities. I took the patter from this article (Compositional Hierarchies) but things didn’t work as expected. I have to add that “m generating POCO entities and using the Unit Of Work pattern so it wasn’t easy just copy and paste the code for the article. I posted a few questions to the RIA services forum and found out that that pattern exposed a bug :(

Fortunately I was redirected this post from Brett Samblament which described the new pattern to follow to write a fully functional UpdateParent method. But again, I can’t just copy and paste, so here’s the code I wrote for it. Also, by using generic, I’m able to call the exact pattern for every composition in my model, cool uh?!

public void UpdateParent(Parent parent)
{
    EntityHelper.UpdateParentEntity(parent, ObjectContext.Parents, ChangeSet, ObjectContext);

    foreach (Child child in ChangeSet.GetAssociatedChanges(parent, o => o.Children))
        EntityHelper.UpdateChildEntity(child, ObjectContext.Children, ChangeSet, ObjectContext);

}

And my EntityHelper class has the following methods:

public static void UpdateParentEntity<T>(T entity, IRepository<T> repository, ChangeSet chgSet, IUnitOfWork oc)
    where T : class
{
    try
    {
        ObjectContext ctx = oc as ObjectContext;
        repository.ObjectSet.AddObject(entity);

        T originalEntity = chgSet.GetOriginal<T>(entity);

        if (originalEntity == null)
            ctx.ObjectStateManager.ChangeObjectState(entity, EntityState.Unchanged);
        else
            repository.ObjectSet.AttachAsModified(entity, originalEntity);
    }
    catch (Exception ex)
    {
        TraceManager.Error(string.Format("An error occurred updating a {0}", typeof(T)), ex);
        throw;
    }
}

public static void UpdateChildEntity<T>(T entity, IRepository<T> repository, ChangeSet chgSet, IUnitOfWork oc)
    where T : class
{
    try
    {
        ObjectContext ctx = oc as ObjectContext;
        ChangeOperation change = chgSet.GetChangeOperation(entity);
        
        switch (change)
        {
            case ChangeOperation.Delete:
                if (GetEntityState(entity, ctx) == EntityState.Detached)
                    repository.ObjectSet.Attach(entity);
                ctx.DeleteObject(entity);
                break;
            case ChangeOperation.Insert:
                // do nothing
                break;
            case ChangeOperation.None:
                ctx.ObjectStateManager.ChangeObjectState(entity, EntityState.Unchanged);
                break;
            case ChangeOperation.Update:
                T original = chgSet.GetOriginal<T>(entity);
                if (original == null) { throw new Exception("Update with no original value found"); }
                if (GetEntityState(entity, ctx) == EntityState.Detached)
                    repository.ObjectSet.Attach(entity);
                repository.ObjectSet.AttachAsModified(entity, original);
                break;
            default:
                break;
        }
    }
    catch (Exception ex)
    {
        TraceManager.Error(string.Format("An error occurred updating a {0}", typeof(T)), ex);
        throw;
    }
}

public static EntityState GetEntityState(object entity, ObjectContext ctx)
{
    System.Data.Objects.ObjectStateEntry ose;
    if (ctx.ObjectStateManager.TryGetObjectStateEntry(entity, out ose))
        return ose.State;
    else
        return EntityState.Detached;
}

I hope this helps someone clear the way… and I promise I’ll post more (and more often) about this.

As usual, this code is ‘works on my machine’ certified.

I never get tired of this