Caffeinated Simpleton

Palm’s Mojo SDK has just been released to the public this past week. I thought I would take the opportunity to show off some of the awesome things the SDK can do. The Mojo SDK is exceptionally good at tying your life together with the web services you use every day, so my first series will be on building a simple Meetup.com client. At first, we’ll just sync down meetups using the api key that’s associated with every individual account. Another day, we’ll add OAuth authentication to make it generally useful for anybody.

This article assumes that you have some knowledge of how to create an app, new scenes, and how to debug. If you aren’t somewhat comfortable with the SDK yet, check out the Hello World tutorial.

Setup

At first, we’ll just create a big button that puts all our meetups into the calendar. Nothing fancy. To create the scene, run:

$ palm-generate -t new_scene -p "name=sync"

Then in the stage-assistant.js file, put:

this.controller.pushScene("sync");

Creating a Calendar

The first thing that we will do is create a new calender for Meetup.com. This calendar will appear in the calendar app right next to your Google Calendar or Exchange calendar using the Palm Synergy APIs. This is great because it allows you to deliver new data to your users without having to write yet another way of presenting it. All contacts and calendars can be plugged straight into the core webOS applications.

To create a calendar, you first need to make an account:

self.accountServiceId = "palm://com.palm.accounts/crud/";
 
 /* Retrieves account if it exists, otherwise creates it */
setupAccount: function(self, k) {
    self.controller.serviceRequest(self.accountServiceId, {
        method: 'listAccounts',
        parameters: {},
        onSuccess: function(list) {
            Mojo.Log.info("Got account list: %j", list);
            if (list.list && list.list.length > 0) {
                self.account = list.list[0];
                k();
            }
            else {
                self.account = {
                    username: "justin",
                    domain: "meetup.com",
                    displayName: "Meetup.com",
                    dataTypes: ["CALENDAR"],
                    isDataReadOnly: true,
                    icons: {largeIcon: '', smallIcon: ''}
                };
                self.controller.serviceRequest(self.accountServiceId, {
                    method: 'createAccount',
                    parameters: self.account,
                    onSuccess: function(response) {
                        Mojo.Log.info("Got %j for %j", response, self.account);
                        self.account.accountId = response.accountId;
                        k();
                    }
                });
            }
        },
        onFailure: function() {
            Mojo.Controller.errorDialog("Failed to create account");
        },
        onError: function(error) {
            Mojo.Controller.errorDialog("Error creating account");
        }
    })
},

You’ll notice a few different things about this code, the odd things which are just my style. Using self instead of this is an idiom from Cobra, a JavaScript class library I wrote. k is a continuation, or the function that should be called after the account is created. k I believe is an idiom for Continuation Passing Style in Scheme.

Beyond that, this is very standard Mojo code. Services are identified as “palm://com.palm.” and all methods support onSuccess, onFailure, and onError callbacks. This code checks to see if there is already an account associated with this appId, and if there is, calls its continuation. If there is not, it creates the account and calls its continuation.

After the account is created, we can create the calendar.

self.calendarServiceId = "palm://com.palm.calendar/crud/";
 
/* Retrieves calendar if it exists, otherwise creates it */
setupCalendar: function(self, k) {
    self.controller.serviceRequest(self.calendarServiceId, {
        method: 'listCalendars',
        parameters: {
            accountId: self.account.accountId
        },
        onSuccess: function(calList) {
            Mojo.Log.info("Got calendar list");
            if (calList.calendars.length > 0) {
                self.calendar = calList.calendars[0];
                k();
            }
            else {
                self.calendar = {
                    name: "Meetup.com"
                }
                self.controller.serviceRequest(self.calendarServiceId, {
                    method: 'createCalendar',
                    parameters: {
                        accountId: self.account.accountId,
                        calendar: self.calendar
                    },
                    onSuccess: function(response) {
                        self.calendar.calendarId = response.calendarId
                        k();
                    },
                    onFailure: function(error) {
                        Mojo.Log.error("Creating calendar failed: %j", error);
                        Mojo.Controller.errorDialog("Failed to create calendar");
                    },
                    onError: function(error) {
                        Mojo.Log.error("Creating calendar failed: %j", error);
                        Mojo.Controller.errorDialog("Error creating calendar");
                    }
                });
            }
        },
        onFailure: function() {
            Mojo.Controller.errorDialog("Failed to create calendar");
        },
        onError: function(error) {
            Mojo.Controller.errorDialog("Error creating calendar");
        }
    });
},

This is almost identical to the account creation code, except it’s creating a calendar.

Now calling these functions is easy:

self.setupAccount(function() {
    self.setupCalendar(function() {
        self.buttonModel.disabled = false;
        self.controller.modelChanged(self.buttonModel)
    });
});

Pulling down events

To get the events that are associated with the account, I am using the Meetup.com JavaScript client. The client requires jQuery, but since it only requires jQuery to do JSONP, we replace that line with a Mojo call. There is no reason that we couldn’t use jQuery, but jQuery is overkill for just doing JSONP.

jQuery.getJSON(urlprefix + call_type + url, params, function(json){callback(json)})

Becomes:

var query = $H(params).toQueryString();
url = urlprefix + call_type + url + query;
Mojo.loadScriptWithCallback(url, Mojo.doNothing);

After we have the Meetup client library, getting the events is easy, but a little indirect. It takes three API calls, one to get the member id, one to get every group associated with the member id, and one to get every event in all those groups. You can see the details on Meetup’s API page.

self.client = new MeetupApiClient(Meet.Auth.apiKey);
syncCalendar: function(self) {
    // Gets my member id
    Mojo.Log.info("Syncing calendar");
    self.client.get_members({
        relation: "self"
    }, self._getGroups);
},
 
_getGroups: function(self, members) {
    Mojo.Log.info("Got members");
    var memberId = members.results[0].id;
    self.client.get_groups({
        member_id: memberId
    }, self._getEvents);
},
 
_getEvents: function(self, groups) {
    Mojo.Log.info("Got events");
    groups = groups.results;
    var groupString = groups[0].id;
    var today = new Date();
    for (var i = 1; i < groups.length; i++) {
        groupString += "," + groups[i].id;
    }
    self.client.get_events({
        group_id: groupString,
        after: today.getMonth() + today.getDay() + today.getFullYear()
    }, self._saveEvents);
},

Now self._saveEvents will receive a list of events that are coming up after today. All we need to do is loop over the list, format them as Palm calendar events, and pass them to the calendar service.

_saveEvents: function(self, events) {
    Mojo.Log.info("Saving events");
 
    self.numEventsProcessed = 0;
    self.events = events;
 
    events.results.each(function(meetupEvent) {
        var time = new Date(meetupEvent.time).getTime();
        if (meetupEvent.myrsvp != "no") {
            self.controller.serviceRequest(self.calendarServiceId, {
                method: 'createEvent',
                parameters: {
                    calendarId: self.calendar.calendarId,
                    event: {
                        eventId: meetupEvent.id,
                        subject: meetupEvent.name,
                        startTimestamp: time,
                        endTimestamp: time + 3600000, // 1 hour in ms
                        allDay: false,
                        note: self._formatNote(meetupEvent),
                        location: meetupEvent.lat + ", " + meetupEvent.lon,
                        alarm: 'none',
                    }
                },
                onSuccess: self._createdEvent,
                onError: self._errorCreatingEvent,
                onFailure: self._failureCreatingEvent
            });
        }
    });
},
 
_createdEvent: function(self, response) {
    self._checkIfSyncFinished();
},
 
_errorCreatingEvent: function(self, response) {
    Mojo.Log.error("Could not create event: %j", response);
    self._checkIfSyncFinished();
},
 
_failureCreatingEvent: function(self, response) {
    Mojo.Log.error("Failed to create event: %d, %j", self._eventsReturned, response);
    self._checkIfSyncFinished();
},
 
_checkIfSyncFinished: function(self) {
    self.numEventsProcessed++;
    if (self.numEventsProcessed == self.events.meta.count) {
 
        if (self.events.meta.next) {
            Mojo.Log.info("Fetching the next page of results...");
            self.client.nextPage(self._saveEvents);
        }
        else {
            Mojo.Log.info("Fetched all the events");
            self.buttonModel.disabled = false;
            self.controller.modelChanged(self.buttonModel);
            self.controller.get("sync-button").mojo.deactivate();
        }
    }
},

And that’s basically it! With the code above, all your Meetup.com events can be inserted into your webOS calendar. All you need is an event handler for your button.

self.buttonModel = {
    buttonLabel: 'Sync',
    disabled: true
};
 
self.controller.setupWidget('sync-button', {
    type: Mojo.Widget.activityButton
}, self.buttonModel);
 
Mojo.Event.listen($('sync-button'), Mojo.Event.tap, function() {
    self.buttonModel.disabled = true;
    self.controller.modelChanged(self.buttonModel)
    self.controller.get("sync-button").mojo.activate();
    self.syncCalendar();
});

This works assuming a view containing:

<div x-mojo-element="Button" id="sync-button"></div>

Debugging Tips

Creating a file called framework_config.json allows you to change the logging level. That will permit JavaScript messages to be output into /var/log/messages on the device. This is especially valuable if you’re working on a 64-bit linux machine where the inspector is currently not supported.

{
    "logLevel": 99 // 0 means no logging, 99 will max it out
}

Removing /var/luna/data/dbdata/PalmDatabase.db3 removes all data you may have inserted. This allows you to start over fresh, but I wouldn’t recommend doing this on your actual device. You’ll lose all your data!

Todo

This program isn’t really complete, but it’s a good start. A couple of things we still have to do are:

• Add Authentication with OAuth
• Keep track of already inserted appointments so we don’t insert duplicates
• Add automatic synchronization in the background
• Add push updates (this is impossible without server side support)
• Make things look nice

Stay tuned for articles on some or all of these exciting new features! Until then, the code is available on github.

I don’t like Java. I haven’t learned Java well because I don’t enjoy using it. I don’t enjoy using it because it’s verbose, for one, but mostly because it’s constantly making things hard for me to do. I know there are ways to do what I want, after all, millions of people use Java successfully every day, but I don’t know what they are. Furthermore, finding out what they are is excruciatingly painful.

I recently did a series of articles on a project I was doing to learn Clojure. It kind of petered out for a number of reasons, but one constant annoyance in learning Clojure was dealing with the Java-isms. Java has given Clojure a vast library of high quality software essentially for free, but it’s also brought on a lot of the pain, much of which I think needs to be fixed before Clojure can have the nice feel of my favorite dynamic languages.

Installing Clojure

The first thing one has to do is install Clojure. It’s not a package in Ubuntu yet, but it’s young, so that’s ok cause we’re veterans and don’t need no stinking packages. To compile, we just download the source and type “ant”.

And that’s it. There’s no install process that makes a nice pretty “clojure” command that takes us to the REPL or executes scripts that are passed to it. To run clojure, you need to run it using Java:

$ java -cp clojure.jar clojure.lang.Repl

That is a lot to type just to get a Repl, and getting a usable command line is even harder. After installing JLine ConsoleRunner, you need to get the library into your classpath (a rant on which is upcoming) and then run

$ java -cp jline-0.9.91.jar:clojure.jar jline.ConsoleRunner clojure.lang.Repl

Not exactly intuitive, but whatever. We put it in a bash script, put it in our path, and head off to the races. After a while, we have a few lines of a quality script we would like to save and run. How do we do that?

Obviously, it’s:

$ java -cp clojure.jar clojure.lang.Script my-script.clj

This assumes that clojure.jar is in the same directory as the script you want to run. If you don’t have clojure.jar there, you must provide a specific path to the jar file. There is no idea of a default directory where Java will look for jar files. You must provide every single jar file to Java at runtime.

Contrast this with the Python install process:

$ sudo apt-get install python
$ python
... Have fun in the interpreter
... Write a script
$ python my_script.py

Simple.

The Classpath

First of all, I’m no expert on the classpath, but it seems like an unholy abomination thrust upon us by invisible powers that must be extinguished at all costs. It would appear, and again, I am no expert, but it would appear that every single dependency of a program must be explicitly passed to Java at the time you run your program. I wrote a bash script to automate the process, but viewing the command line for running my simple Compojure-based webapp is apalling:

java -Djava.library.path=/usr/local/lib -cp :/mnt/data/Users/justin/bin/compojure/compojure.jar:/mnt/data/Users/justin/bin/compojure/deps/clojure-contrib.jar:/mnt/data/Users/justin/bin/compojure/deps/clojure.jar:/mnt/data/Users/justin/bin/compojure/deps/fact.jar:/mnt/data/Users/justin/bin/compojure/deps/jetty-6.1.14.jar:/mnt/data/Users/justin/bin/compojure/deps/jetty-util-6.1.14.jar:/mnt/data/Users/justin/bin/compojure/deps/re-rand.jar:/mnt/data/Users/justin/bin/compojure/deps/servlet-api-2.5-6.1.14.jar:/mnt/data/Users/justin/lib/clj-http-client.jar:/mnt/data/Users/justin/lib/clojure-contrib.jar:/mnt/data/Users/justin/lib/clojure.jar:/mnt/data/Users/justin/lib/commons-codec-1.3.jar:/mnt/data/Users/justin/lib/commons-httpclient-3.1.jar:/mnt/data/Users/justin/lib/commons-io-1.4-javadoc.jar:/mnt/data/Users/justin/lib/commons-io-1.4-sources.jar:/mnt/data/Users/justin/lib/commons-io-1.4.jar:/mnt/data/Users/justin/lib/commons-logging-1.1.1-javadoc.jar:/mnt/data/Users/justin/lib/commons-logging-1.1.1-sources.jar:/mnt/data/Users/justin/lib/commons-logging-1.1.1.jar:/mnt/data/Users/justin/lib/commons-logging-adapters-1.1.1.jar:/mnt/data/Users/justin/lib/commons-logging-api-1.1.1.jar:/mnt/data/Users/justin/lib/commons-logging-tests.jar:/mnt/data/Users/justin/lib/compojure.jar:/mnt/data/Users/justin/lib/jline-0.9.94.jar:/mnt/data/Users/justin/lib/tokyo-cabinet-clj.jar:/mnt/data/Users/justin/lib/tokyo-cabinet.jar:/mnt/data/Users/justin/lib/tokyocabinet.jar:/mnt/data/Users/justin/lib/tokyotyrant-0.6.jar clojure.lang.Script index.clj

That is bad. That is not correct, that is not how software should be designed, I object. Every other language I can think of off the top of my head (except JavaScript) has some structured way of finding its dependencies, and most have a way of adding additional rules to that search should the defaults not be adequate. While this can lead to “DLL hell”, I do not see how the Java situation is any better when everybody just ends up with scripts to automate the process and then those scripts pick up the wrong things and you can’t figure out why.

The classpath makes me very upset. If Clojure can find a way to mask it, I would appreciate it very much.

Maven

First of all, what the hell is Maven? A quick trip to their site reveals a huge chunk of text with hundreds of links and an initial sentence that describes it as:

Maven, a Yiddish word meaning accumulator of knowledge, was originally started as an attempt to simplify the build processes in the Jakarta Turbine project.

I went to the site with some hope that it would provide some relief to my dependency issues (All I want is “pip install”, or “gem install”), and I get greeted with a dense paragraph of history combined with some mumbo-jumbo about “best practices”.

After reading a bit I find that Maven downloads and builds dependencies and installs them in a local repository, along with the library you are trying to compile. Perfect! Sounds like exactly what I want. However, it doesn’t mention anything about the classpath. Am I still responsible for dealing with all that muck, even though it’s tucking my libraries in a hidden directory (implying that it’s responsible for managing them)?

To answer that question I need to wade through dozens of other pages that alternately describe how to accomplish basic tasks and lecture me on software engineering. Finally I come to the conclusion that while Maven does indeed find dependencies for you, it does not actually help you execute programs with those dependencies in place. This means you either need a script that automatically passes your entire maven local repository to Java, or you need to know the dependencies that Maven was conveniently supposed to hide from you. To top it off, it doesn’t play well with Clojure. Completely useless.

(For the record, there is a Maven extension that does exactly this.)

The Last Word

Dependency management is a hard problem that all languages must learn to deal with. Higher level languages have an even harder time in that they must not only deal with whatever dependencies they have written in their own language, but also with extensions written in other languages. Clojure, which is still very young, suffers tremendously from the godawful environment that Java has ensconsed itself in. I am largely a veteran of the *nix world, which seems quite different from the world Java developers have built around themselves. They have their own tools, their own build systems, their own set of “best practices”, and the Apache foundation. What I have seen in my brief saunter over the wall has appalled me. It has appalled me far more than similar saunters into the somewhat exciting world of Microsoft and .NET. It strikes me very much as a world in need of fixing, and I hope that Clojure (or Scala) can do it. Heck, I may even do my part to help.

But probably I’ll just run back to Python.