Trac Wiki Macro API Fun

Here is a small snippet of Python code:

import datetime
import time

def execute(hdf, txt, env):
    event, when = txt.split(',', 1)
    today = datetime.date.today()
    future = datetime.date(*time.strptime(when, '%m/%d/%Y')[0:3])
    difference = future - today
    days = difference.days
    if days <= 0:
            return event + " has already happened! (" + str(abs(days)) + " days ago.)"
    proper = "days"
    if days == "1":
            proper = "day"
    return event + " in " + str(days) + " " + proper + "!"

Small and simple. Dan asked me to write a macro for our Trac wiki that would take in a date (in a string format) and an event name and create a small warning on the page. I've never written any sort of macro for any sort of wiki before, but the macros are written in Python, so I suspected it would be fun and easy. It was both.

The first thing I did was edit the front page of our wiki, adding a call to my soon-to-be macro:

[[CountDown()]]

I saved the changes to the page, and got an error when the page reloaded, which was exactly what I wanted... the api says that you need to restart the webserver, which seemed sort of suspect since you don't need to restart after installing plugins.

I read just enough of the docs to figure out where the macros directory was. Turns out that the macros reside in the rather obvious directory: "/usr/local/share/trac/wiki-macros". I created CountDown.py there and loaded it into vi.

Back to the docs to check out the api. Only function needed in a macro is execute, which takes in an hdf, some text, and an environment. A bare-bones macro looks like this:

def execute(hdf, txt, env):
        return "Testing..."

I saved the above and reloaded the page. It worked. Now, for input. Input is passed into execute via the argument txt. Changed the macro call to:

[[CountDown(Tomorrow,11/17/2006)]]

and then changed the macro to:

def execute(hdf, txt, env):
        return txt

It returned "Tomorrow,11/17/2006" on the page. I poked around the module docs for datetime and finished the macro as it appears at the top of this post. It was just so painless. Trac has impressed me again.