from paver.tasks import BuildFailure, environment

class ShortcutTaskFinder(object):
    """Find tasks by command name initials.

    This allows the execution of a task specifying a unique `shortcut`
    made up with the first character of each word that compose the
    task name, assuming the usual ``_`` as separator.

    For example, assuming there are the following tasks:

    1. current_user_name
    2. current_project_name
    3. last_message
    4. last_login

    The first task could be executed with ``current_user_name`` as
    usual, but also with ``cun``, but not with ``cu`` since that's
    ambiguous; the second with its full name, or with ``cpn``, or even
    ``cp`` since there's no ambiguity. The latter two respectively
    with ``lm`` and ``ll``.
    """

    def get_task(self, taskname):
        all_tasks = environment.get_tasks()
        matches = [t for t in all_tasks
                   if ''.join(w[0]
                              for w in t.shortname.split('_')
                              ).startswith(taskname)]
        if len(matches) > 1:
            matched_names = [t.name for t in matches]
            raise BuildFailure("Ambiguous task name %s (%s)" %
                               (taskname, matched_names))
        elif matches:
            return matches[0]

    def get_tasks(self):
        return []

# Install the additional finder
environment.task_finders.append(ShortcutTaskFinder())