Emulate django's QuerySet API for filtering tasks

diff --git a/tasklib/task.py b/tasklib/task.py
index a220264f79b0203d773902628afdb3fe9ce893d2..cd4b92f1d3af491bc001229406ac26f3e509c5a7 100644 (file)
--- a/tasklib/task.py
+++ b/tasklib/task.py
@@ -1,3 +1,4 @@
+import copy
 import json
 import os
 import subprocess
@@ -5,6 +6,7 @@ import tempfile
 import uuid
 
 
+REPR_OUTPUT_SIZE = 10
 PENDING = 'pending'
 
 
@@ -14,6 +16,9 @@ class TaskWarriorException(Exception):
 
 class Task(object):
 
+    class DoesNotExist(Exception):
+        pass
+
     def __init__(self, warrior, data={}):
         self.warrior = warrior
         self._data = data
@@ -46,6 +51,131 @@ class Task(object):
     __repr__ = __unicode__
 
 
+class TaskFilter(object):
+    """
+    A set of parameters to filter the task list with.
+    """
+
+    def __init__(self, filter_params=()):
+        self.filter_params = filter_params
+
+    def add_filter(self, param, value):
+        self.filter_params += ((param, value),)
+
+    def get_filter_params(self):
+        return self.filter_params
+
+    def clone(self):
+        c = self.__class__()
+        c.filter_params = tuple(self.filter_params)
+        return c
+
+
+class TaskQuerySet(object):
+    """
+    Represents a lazy lookup for a task objects.
+    """
+
+    def __init__(self, warrior=None, filter_obj=None):
+        self.warrior = warrior
+        self._result_cache = None
+        self.filter_obj = filter_obj or TaskFilter()
+
+    def __deepcopy__(self, memo):
+        """
+        Deep copy of a QuerySet doesn't populate the cache
+        """
+        obj = self.__class__()
+        for k,v in self.__dict__.items():
+            if k in ('_iter','_result_cache'):
+                obj.__dict__[k] = None
+            else:
+                obj.__dict__[k] = copy.deepcopy(v, memo)
+        return obj
+
+    def __repr__(self):
+        data = list(self[:REPR_OUTPUT_SIZE + 1])
+        if len(data) > REPR_OUTPUT_SIZE:
+            data[-1] = "...(remaining elements truncated)..."
+        return repr(data)
+
+    def __len__(self):
+        if self._result_cache is None:
+            self._result_cache = list(self)
+        return len(self._result_cache)
+
+    def __iter__(self):
+        if self._result_cache is None:
+            self._result_cache = self._execute()
+        return iter(self._result_cache)
+
+    def __getitem__(self, k):
+        if self._result_cache is None:
+            self._result_cache = list(self)
+        return self._result_cache.__getitem__(k)
+
+    def __bool__(self):
+        if self._result_cache is not None:
+            return bool(self._result_cache)
+        try:
+            next(iter(self))
+        except StopIteration:
+            return False
+        return True
+
+    def __nonzero__(self):
+        return type(self).__bool__(self)
+
+    def _clone(self, klass=None, **kwargs):
+        if klass is None:
+            klass = self.__class__
+        filter_obj = self.filter_obj.clone()
+        c = klass(warrior=self.warrior, filter_obj=filter_obj)
+        c.__dict__.update(kwargs)
+        return c
+
+    def _execute(self):
+        """
+        Fetch the tasks which match the current filters.
+        """
+        return self.warrior._execute_filter(self.filter_obj)
+
+    def all(self):
+        """
+        Returns a new TaskQuerySet that is a copy of the current one.
+        """
+        return self._clone()
+
+    def pending(self):
+        return self.filter(status=PENDING)
+
+    def filter(self, **kwargs):
+        """
+        Returns a new TaskQuerySet with the given filters added.
+        """
+        clone = self._clone()
+        for param, value in kwargs.items():
+            clone.filter_obj.add_filter(param, value)
+        return clone
+
+    def get(self, **kwargs):
+        """
+        Performs the query and returns a single object matching the given
+        keyword arguments.
+        """
+        clone = self.filter(**kwargs)
+        num = len(clone)
+        if num == 1:
+            return clone._result_cache[0]
+        if not num:
+            raise Task.DoesNotExist(
+                'Task matching query does not exist. '
+                'Lookup parameters were {0}'.format(kwargs))
+        raise ValueError(
+            'get() returned more than one Task -- it returned {0}! '
+            'Lookup parameters were {1}'.format(num, kwargs))
+
+
 class TaskWarrior(object):
     DEFAULT_FILTERS = {
         'status': 'pending',
@@ -57,6 +187,7 @@ class TaskWarrior(object):
         self.config = {
             'data.location': os.path.expanduser(data_location),
         }
+        self.tasks = TaskQuerySet(self)
 
     def _generate_command(self, command):
         args = ['task', 'rc:/']
@@ -65,7 +196,7 @@ class TaskWarrior(object):
         args.append(command)
         return ' '.join(args)
 
-    def _execute(self, command):
+    def _execute_command(self, command):
         p = subprocess.Popen(self._generate_command(command), shell=True,
                              stdout=subprocess.PIPE, stderr=subprocess.PIPE)
         stdout, stderr = p.communicate()
@@ -75,41 +206,33 @@ class TaskWarrior(object):
 
     def _format_filter_kwarg(self, kwarg):
         key, val = kwarg[0], kwarg[1]
-        if key in ['tag', 'tags']:
-            key = 'tags.equal'
         key = key.replace('__', '.')
         return '{0}:{1}'.format(key, val)
 
-    def get_tasks(self, **filter_kwargs):
-        filters = dict(self.DEFAULT_FILTERS)
-        filters.update(filter_kwargs)
+    def _execute_filter(self, filter_obj):
         filter_commands = ' '.join(map(self._format_filter_kwarg,
-                                       filters.items()))
+                                       filter_obj.get_filter_params()))
         command = '{0} export'.format(filter_commands)
         tasks = []
-        for line in self._execute(command):
+        for line in self._execute_command(command):
             if line:
                 tasks.append(Task(self, json.loads(line.strip(','))))
         return tasks
 
-    def get_task(self, task_id):
-        command = '{0} export'.format(task_id)
-        return Task(self, json.loads(self._execute(command)[0]))
-
     def add_task(self, description, project=None):
         args = ['add', description]
         if project is not None:
             args.append('project:{0}'.format(project))
-        self._execute(' '.join(args))
+        self._execute_command(' '.join(args))
 
     def delete_task(self, task_id):
-        self._execute('{0} rc.confirmation:no delete'.format(task_id))
+        self._execute_command('{0} rc.confirmation:no delete'.format(task_id))
 
     def complete_task(self, task_id):
-        self._execute('{0} done'.format(task_id))
+        self._execute_command('{0} done'.format(task_id))
 
     def import_tasks(self, tasks):
         fd, path = tempfile.mkstemp()
         with open(path, 'w') as f:
             f.write(json.dumps(tasks))
-        self._execute('import {0}'.format(path))
+        self._execute_command('import {0}'.format(path))