Merge branch 'ical'

setup.py

@@ -8,6 +8,9 @@ setup(
     author = "Bram Schoenmakers",
     author_email = "me@bramschoenmakers.nl",
     url = "https://github.com/bram85/topydo",
+    extras_require = {
+        'ical': ['icalendar'],
+    },
     entry_points= {
         'console_scripts': ['topydo = topydo.cli.Main:main'],
     },

test/IcalCommandTest.py

+# Topydo - A todo.txt client written in Python.
+# Copyright (C) 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import re
+import unittest
+
+from topydo.lib.Config import config
+import CommandTest
+from topydo.lib.IcalCommand import IcalCommand
+import TestFacilities
+
+class IcalCommandTest(CommandTest.CommandTest):
+    def setUp(self):
+        super(IcalCommandTest, self).setUp()
+        self.todolist = TestFacilities.load_file_to_todolist("test/data/ListCommandTest.txt")
+
+    def test_ical(self):
+        def replace_ical_tags(p_text):
+            # replace identifiers with dots, since they're random.
+            result = re.sub(r'\bical:....\b', 'ical:....', p_text)
+            result = re.sub(r'\bUID:....\b', 'UID:....', result)
+
+            return result
+
+        command = IcalCommand([""], self.todolist, self.out, self.error)
+        command.execute()
+
+        self.assertTrue(self.todolist.is_dirty())
+
+        icaltext = ""
+        with open('test/data/ListCommandTest.ics', 'r') as ical:
+            icaltext = "".join(ical.readlines())
+
+        self.assertEquals(replace_ical_tags(self.output), replace_ical_tags(icaltext))
+        self.assertEquals(self.errors, "")
+
+    def test_help(self):
+        command = IcalCommand(["help"], self.todolist, self.out, self.error)
+        command.execute()
+
+        self.assertEquals(self.output, "")
+        self.assertEquals(self.errors, command.usage() + "\n\n" + command.help() + "\n")
+
+if __name__ == '__main__':
+    unittest.main()

test/ListCommandTest.py

@@ -26,10 +26,6 @@ class ListCommandTest(CommandTest.CommandTest):
         super(ListCommandTest, self).setUp()
         self.todolist = TestFacilities.load_file_to_todolist("test/data/ListCommandTest.txt")
 
-    def tearDown(self):
-        # restore to the default configuration in case a custom one was set
-        config("")
-
     def test_list1(self):
         command = ListCommand([""], self.todolist, self.out, self.error)
         command.execute()

test/SortCommandTest.py

@@ -26,10 +26,6 @@ class SortCommandTest(CommandTest.CommandTest):
         super(SortCommandTest, self).setUp()
         self.todolist = TestFacilities.load_file_to_todolist("test/data/SorterTest1.txt")
 
-    def tearDown(self):
-        # restore to the default configuration in case a custom one was set
-        config("")
-
     def test_sort1(self):
         """ Alphabetically sorted """
         command = SortCommand(["text"], self.todolist, self.out, self.error)

test/TodoListTest.py

@@ -36,10 +36,6 @@ class TodoListTester(TopydoTest):
         self.text = ''.join(lines)
         self.todolist = TodoList(lines)
 
-    def tearDown(self):
-        # restore to the default configuration in case a custom one was set
-        config("")
-
     def test_contexts(self):
         self.assertEquals(set(['Context1', 'Context2']), \
             self.todolist.contexts())

test/TopydoTest.py

@@ -19,9 +19,9 @@ import unittest
 from topydo.lib.Config import config
 
 class TopydoTest(unittest.TestCase):
-    def setUp(self):
+    def tearDown(self):
         """
-        Make sure that every test case starts with a clean configuration.
+        Make sure that every test case leaves a clean configuration.
         """
         config("")
 

topydo/cli/Main.py

@@ -41,6 +41,7 @@ Available commands:
 * dep
 * do
 * edit
+* ical
 * ls
 * listcon (lscon)
 * listprojects (lsprj)
@@ -97,6 +98,7 @@ from topydo.lib.DepCommand import DepCommand
 from topydo.lib.DepriCommand import DepriCommand
 from topydo.lib.DoCommand import DoCommand
 from topydo.lib.EditCommand import EditCommand
+from topydo.lib.IcalCommand import IcalCommand
 from topydo.lib.ListCommand import ListCommand
 from topydo.lib.ListContextCommand import ListContextCommand
 from topydo.lib.ListProjectCommand import ListProjectCommand
@@ -118,6 +120,7 @@ SUBCOMMAND_MAP = {
   'depri': DepriCommand,
   'do': DoCommand,
   'edit': EditCommand,
+  'ical': IcalCommand,
   'ls': ListCommand,
   'lscon': ListContextCommand,
   'listcon': ListContextCommand,

topydo/lib/AddCommand.py

 # Topydo - A todo.txt client written in Python.
-# Copyright (C) 2014 Bram Schoenmakers <me@bramschoenmakers.nl>
+# Copyright (C) 2014 - 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -21,7 +21,7 @@ import re
 
 from topydo.lib.Config import config
 from topydo.lib.Command import Command
-from topydo.lib.PrettyPrinter import pretty_print
+from topydo.lib.PrettyPrinterFilter import PrettyPrinterNumbers
 from topydo.lib.RelativeDate import relative_date_to_date
 from topydo.lib.TodoListBase import InvalidTodoException
 
@@ -93,7 +93,8 @@ class AddCommand(Command):
             self.todo = self.todolist.add(self.text)
             self._postprocess_input_todo()
 
-            self.out(pretty_print(self.todo, [self.todolist.pp_number()]))
+            self.printer.add_filter(PrettyPrinterNumbers(self.todolist))
+            self.out(self.printer.print_todo(self.todo))
         else:
             self.error(self.usage())
 

topydo/lib/AppendCommand.py

 # Topydo - A todo.txt client written in Python.
-# Copyright (C) 2014 Bram Schoenmakers <me@bramschoenmakers.nl>
+# Copyright (C) 2014 - 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -15,7 +15,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 from topydo.lib.Command import Command, InvalidCommandArgument
-from topydo.lib.PrettyPrinter import pretty_print
+from topydo.lib.PrettyPrinterFilter import PrettyPrinterNumbers
 from topydo.lib.TodoListBase import InvalidTodoException
 
 class AppendCommand(Command):
@@ -37,7 +37,9 @@ class AppendCommand(Command):
             if text:
                 todo = self.todolist.todo(number)
                 self.todolist.append(todo, text)
-                self.out(pretty_print(todo, [self.todolist.pp_number()]))
+
+                self.printer.add_filter(PrettyPrinterNumbers(self.todolist))
+                self.out(self.printer.print_todo(todo))
             else:
                 self.error(self.usage())
         except InvalidCommandArgument:

topydo/lib/Command.py

@@ -16,6 +16,8 @@
 
 import getopt
 
+from topydo.lib.PrettyPrinter import PrettyPrinter
+
 class InvalidCommandArgument(Exception):
     pass
 
@@ -49,6 +51,9 @@ class Command(object):
         self.error = p_err
         self.prompt = p_prompt
 
+        # make pretty printer available
+        self.printer = PrettyPrinter()
+
     def execute(self):
         """
         Execute the command. Intercepts the help subsubcommand to show the help

topydo/lib/DCommand.py

@@ -16,8 +16,9 @@
 
 import re
 
-from topydo.lib.Command import Command, InvalidCommandArgument
-from topydo.lib.PrettyPrinter import pretty_print, pretty_print_list
+from topydo.lib.Command import Command
+from topydo.lib.PrettyPrinter import PrettyPrinter
+from topydo.lib.PrettyPrinterFilter import PrettyPrinterNumbers
 from topydo.lib.TodoListBase import InvalidTodoException
 
 class DCommand(Command):
@@ -72,8 +73,9 @@ class DCommand(Command):
         )
 
     def _print_list(self, p_todos):
-        filters = [self.todolist.pp_number()]
-        self.out("\n".join(pretty_print_list(p_todos, filters)))
+        printer = PrettyPrinter()
+        printer.add_filter(PrettyPrinterNumbers(self.todolist))
+        self.out(printer.print_list(p_todos))
 
     def prompt_text(self):
         return "Yes or no? [y/N] "
@@ -93,7 +95,7 @@ class DCommand(Command):
             if not self.force and re.match('^y(es)?$', confirmation, re.I):
                 for child in children:
                     self.execute_specific_core(child)
-                    self.out(self.prefix() + pretty_print(child))
+                    self.out(self.prefix() + self.printer.print_todo(child))
 
     def _print_unlocked_todos(self, p_old, p_new):
         delta = [todo for todo in p_new if todo not in p_old]

topydo/lib/DeleteCommand.py

@@ -15,7 +15,6 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 from topydo.lib.DCommand import DCommand
-from topydo.lib.PrettyPrinter import pretty_print
 
 class DeleteCommand(DCommand):
     def __init__(self, p_args, p_todolist,
@@ -35,7 +34,7 @@ class DeleteCommand(DCommand):
         self.todolist.delete(p_todo)
 
     def execute_specific(self, p_todo):
-        self.out(self.prefix() + pretty_print(p_todo))
+        self.out(self.prefix() + self.printer.print_todo(p_todo))
         self.execute_specific_core(p_todo)
 
     def usage(self):

topydo/lib/DepCommand.py

@@ -97,7 +97,8 @@ class DepCommand(Command):
             if todos:
                 sorter = Sorter(config().sort_string())
                 instance_filter = Filter.InstanceFilter(todos)
-                view = View(sorter, [instance_filter], self.todolist)
+                view = View(sorter, [instance_filter], self.todolist,
+                    self.printer)
                 self.out(view.pretty_print())
         except InvalidTodoException:
             self.error("Invalid todo number given.")

topydo/lib/DepriCommand.py

 # Topydo - A todo.txt client written in Python.
-# Copyright (C) 2014 Bram Schoenmakers <me@bramschoenmakers.nl>
+# Copyright (C) 2014 - 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -15,7 +15,6 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 from topydo.lib.Command import Command, InvalidCommandArgument
-from topydo.lib.PrettyPrinter import pretty_print
 from topydo.lib.TodoListBase import InvalidTodoException
 
 class DepriCommand(Command):
@@ -37,7 +36,7 @@ class DepriCommand(Command):
             if todo.priority() != None:
                 self.todolist.set_priority(todo, None)
                 self.out("Priority removed.")
-                self.out(pretty_print(todo))
+                self.out(self.printer.print_todo(todo))
         except InvalidCommandArgument:
             self.error(self.usage())
         except (InvalidTodoException):

topydo/lib/DoCommand.py

 # Topydo - A todo.txt client written in Python.
-# Copyright (C) 2014 Bram Schoenmakers <me@bramschoenmakers.nl>
+# Copyright (C) 2014 - 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -17,7 +17,8 @@
 from datetime import date
 
 from topydo.lib.DCommand import DCommand
-from topydo.lib.PrettyPrinter import pretty_print
+from topydo.lib.PrettyPrinter import PrettyPrinter
+from topydo.lib.PrettyPrinterFilter import PrettyPrinterNumbers
 from topydo.lib.Recurrence import advance_recurring_todo, strict_advance_recurring_todo
 from topydo.lib.Utils import date_string_to_date
 
@@ -56,7 +57,10 @@ class DoCommand(DCommand):
                     self.completion_date)
 
             self.todolist.add_todo(new_todo)
-            self.out(pretty_print(new_todo, [self.todolist.pp_number()]))
+
+            printer = PrettyPrinter()
+            printer.add_filter(PrettyPrinterNumbers(self.todolist))
+            self.out(printer.print_todo(new_todo))
 
     def prompt_text(self):
         return "Also mark subtasks as done? [y/N] "
@@ -77,7 +81,9 @@ class DoCommand(DCommand):
         """ Actions specific to this command. """
         self._handle_recurrence(p_todo)
         self.execute_specific_core(p_todo)
-        self.out(self.prefix() + pretty_print(p_todo))
+
+        printer = PrettyPrinter()
+        self.out(self.prefix() + printer.print_todo(p_todo))
 
     def execute_specific_core(self, p_todo):
         """

topydo/lib/IcalCommand.py

+# Topydo - A todo.txt client written in Python.
+# Copyright (C) 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+Implements a subcommand that outputs an iCalendar file.
+"""
+
+from topydo.lib.IcalPrinter import IcalPrinter
+from topydo.lib.ListCommand import ListCommand
+
+class IcalCommand(ListCommand):
+    def __init__(self, p_args, p_todolist,
+                 p_out=lambda a: None,
+                 p_err=lambda a: None,
+                 p_prompt=lambda a: None):
+        super(IcalCommand, self).__init__(
+            p_args, p_todolist, p_out, p_err, p_prompt)
+
+        self.printer = IcalPrinter(p_todolist)
+
+    def _print(self):
+        self.out(str(self._view()))
+
+    def execute(self):
+        try:
+            import icalendar as _
+        except ImportError:
+            self.error("icalendar package is not installed.")
+            return False
+
+        return super(IcalCommand, self).execute()
+
+    def usage(self):
+        return """Synopsis: ical [-x] [expression]"""
+
+    def help(self):
+        return """\
+Similar to the 'ls' subcommand, except that the todos are printed in iCalendar
+format (RFC 2445) that can be imported by other calendar applications.
+
+By default prints the active todo items, possibly filtered by the given
+expression.
+
+For the supported options, please refer to the help text of 'ls'
+(topydo help ls).
+
+While specifying the sort order is supported (-s flag), like in 'ls', this is
+not meaningful in the context of an iCalendar file.
+
+Note: be aware that this is not necessarily a read-only operation. This
+subcommand may add ical tags to the printed todo items containing a unique ID.
+Completed todo items may be archived.
+
+Note: topydo does not support reading iCal files, this is merely a dump.
+Changes made with other iCalendar enabled applications will not be processed.
+Suggested usage is to use the output as a read-only calendar.
+"""

topydo/lib/IcalPrinter.py

+# Topydo - A todo.txt client written in Python.
+# Copyright (C) 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+Provides a printer that transforms a list of Todo items to an iCalendar
+file according to RFC 2445.
+"""
+
+try:
+    import icalendar as ical
+    ICAL_PRESENT = True
+except ImportError:
+    ICAL_PRESENT = False
+
+from datetime import datetime, time
+import random
+import string
+
+from topydo.lib.PrettyPrinter import Printer
+
+def _convert_priority(p_priority):
+    """
+    Converts todo.txt priority to an iCalendar priority (RFC 2445).
+
+    Priority A gets priority 1, priority B gets priority 5 and priority C-F get
+    priorities 6-9. This scheme makes sure that clients that use "high",
+    "medium" and "low" show the correct priority.
+    """
+    result = 0
+
+    prio_map = {
+        'A': 1,
+        'B': 5,
+        'C': 6,
+        'D': 7,
+        'E': 8,
+        'F': 9,
+    }
+
+    try:
+        result = prio_map[p_priority]
+    except KeyError:
+        if p_priority:
+            # todos with no priority have priority None, and result of this
+            # function will be 0. For all other letters, return 9 (lowest
+            # priority in RFC 2445).
+            result = 9
+
+    return result
+
+class IcalPrinter(Printer):
+    """
+    A printer that converts a list of Todo items to a string in iCalendar
+    format (RFC 2445).
+
+    https://www.rfc-editor.org/rfc/rfc2445.txt
+    """
+    def __init__(self, p_todolist):
+        super(IcalPrinter, self).__init__()
+        self.todolist = p_todolist
+
+    def print_todo(self, p_todo):
+        return self._convert_todo(p_todo).to_ical() if ICAL_PRESENT else ""
+
+    def print_list(self, p_todos):
+        result = ""
+
+        if ICAL_PRESENT:
+            cal = ical.Calendar()
+            cal.add('prodid', '-//bramschoenmakers.nl//topydo//')
+            cal.add('version', '2.0')
+
+            for todo in p_todos:
+                cal.add_component(self._convert_todo(todo))
+
+            result = cal.to_ical()
+
+        return result
+
+    def _convert_todo(self, p_todo):
+        """ Converts a Todo instance (Topydo) to an icalendar Todo instance. """
+
+        def _get_uid(p_todo):
+            """
+            Gets a unique ID from a todo item, stored by the ical tag. If the
+            tag is not present, a random value is assigned to it and returned.
+            """
+            def generate_uid(p_length=4):
+                """
+                Generates a random string of the given length, used as
+                identifier.
+                """
+                return ''.join(
+                    random.choice(string.ascii_letters + string.digits)
+                        for i in xrange(p_length))
+
+            uid = p_todo.tag_value('ical')
+            if not uid:
+                uid = generate_uid()
+                p_todo.set_tag('ical', uid)
+                self.todolist.set_dirty()
+
+            return uid
+
+        result = ical.Todo()
+
+        # this should be called first, it may set the ical: tag and therefore
+        # change the source() output.
+        result['uid'] = _get_uid(p_todo)
+
+        result['summary'] = ical.vText(p_todo.text())
+        result['description'] = ical.vText(p_todo.source())
+        result.add('priority', _convert_priority(p_todo.priority()))
+
+        start = p_todo.start_date()
+        if start:
+            result.add('dtstart', start)
+
+        due = p_todo.due_date()
+        if due:
+            result.add('due', due)
+
+        created = p_todo.creation_date()
+        if created:
+            result.add('created', created)
+
+        completed = p_todo.completion_date()
+        if completed:
+            completed = datetime.combine(completed, time(0, 0))
+            result.add('completed', completed)
+
+        return result

topydo/lib/ListCommand.py

 # Topydo - A todo.txt client written in Python.
-# Copyright (C) 2014 Bram Schoenmakers <me@bramschoenmakers.nl>
+# Copyright (C) 2014 - 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -19,8 +19,9 @@ import re
 from topydo.lib.Command import Command
 from topydo.lib.Config import config
 from topydo.lib import Filter
-from topydo.lib.PrettyPrinter import pp_indent
+from topydo.lib.PrettyPrinterFilter import PrettyPrinterIndentFilter
 from topydo.lib.Sorter import Sorter
+from topydo.lib.View import View
 
 class ListCommand(Command):
     def __init__(self, p_args, p_todolist,
@@ -74,17 +75,23 @@ class ListCommand(Command):
 
         return filters
 
+    def _view(self):
+        sorter = Sorter(self.sort_expression)
+        filters = self._filters()
+
+        return View(sorter, filters, self.todolist, self.printer)
+
+    def _print(self):
+        """ Prints the todos. """
+        indent = config().list_indent()
+        self.out(self._view().pretty_print([PrettyPrinterIndentFilter(indent)]))
+
     def execute(self):
         if not super(ListCommand, self).execute():
             return False
 
         self._process_flags()
-
-        sorter = Sorter(self.sort_expression)
-        filters = self._filters()
-
-        pp_filters = [pp_indent(config().list_indent())]
-        self.out(self.todolist.view(sorter, filters).pretty_print(pp_filters))
+        self._print()
 
     def usage(self):
         return """Synopsis: ls [-x] [-s <sort_expression>] [expression]"""

topydo/lib/PostponeCommand.py

 # Topydo - A todo.txt client written in Python.
-# Copyright (C) 2014 Bram Schoenmakers <me@bramschoenmakers.nl>
+# Copyright (C) 2014 - 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -18,7 +18,7 @@ from datetime import date, timedelta
 
 from topydo.lib.Command import Command, InvalidCommandArgument
 from topydo.lib.Config import config
-from topydo.lib.PrettyPrinter import pretty_print
+from topydo.lib.PrettyPrinterFilter import PrettyPrinterNumbers
 from topydo.lib.RelativeDate import relative_date_to_date
 from topydo.lib.TodoListBase import InvalidTodoException
 from topydo.lib.Utils import date_string_to_date
@@ -74,7 +74,8 @@ class PostponeCommand(Command):
                 todo.set_tag(config().tag_due(), new_due.isoformat())
 
                 self.todolist.set_dirty()
-                self.out(pretty_print(todo, [self.todolist.pp_number()]))
+                self.printer.add_filter(PrettyPrinterNumbers(self.todolist))
+                self.out(self.printer.print_todo(todo))
             else:
                 self.error("Invalid date pattern given.")
 

topydo/lib/PrettyPrinter.py

 # Topydo - A todo.txt client written in Python.
-# Copyright (C) 2014 Bram Schoenmakers <me@bramschoenmakers.nl>
+# Copyright (C) 2014 - 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -14,75 +14,52 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-""" Provides a function to pretty print a list of todo items. """
-
-import re
-
-from topydo.lib.Config import config
-
-PRIORITY_COLORS = {
-    'A': '\033[36m', # cyan
-    'B': '\033[33m', # yellow
-    'C': '\033[34m'  # blue
-}
-
-PROJECT_COLOR = '\033[31m' # red
-NEUTRAL_COLOR = '\033[0m'
-
-def pp_color(p_todo_str, p_todo):
+class Printer(object):
     """
-    Adds colors to the todo string by inserting ANSI codes.
+    An abstract class that turns todo items into strings.
 
-    Should be passed as a filter in the filter list of pretty_print()
+    Subclasses must at least implement the print_todo method.
     """
+    def print_todo(self, p_todo):
+        """ Base implementation. Simply returns the string conversion. """
+        return str(p_todo)
 
-    if config().colors():
-        color = NEUTRAL_COLOR
-        try:
-            color = PRIORITY_COLORS[p_todo.priority()]
-        except KeyError:
-            pass
-
-        p_todo_str = color + p_todo_str + NEUTRAL_COLOR
-
-        if config().highlight_projects_contexts():
-            p_todo_str = re.sub(
-                r'\B(\+|@)(\S*\w)',
-                PROJECT_COLOR + r'\g<0>' + color,
-                p_todo_str)
-
-        p_todo_str += NEUTRAL_COLOR
-
-    return p_todo_str
-
-def pp_indent(p_indent=0):
-    return lambda s, t: ' ' * p_indent + s
+    def print_list(self, p_todos):
+        """
+        Given a list of todo items, pretty print it and return a list of
+        formatted strings.
+        """
+        return "\n".join([self.print_todo(todo) for todo in p_todos])
 
-def pretty_print(p_todo, p_filters=None):
+class PrettyPrinter(Printer):
     """
-    Given a todo item, pretty print it and return a list of formatted strings.
+    Prints todo items on a single line, decorated by the filters passed by
+    the caller.
 
-    p_filters is a list of functions that transform the output string, each
-    function accepting two arguments:
+    The caller can adjust the output by passing on a set of filters, that may
+    add colors, indentation, etc. These filters are found in the
+    PrettyPrinterFilter module.
+    """
+    def __init__(self):
+        """
+        Constructor.
+        """
+        super(PrettyPrinter, self).__init__()
+        self.filters = []
 
-    * the todo's text that has to be modified;
-    * the todo object itself which allows for obtaining relevant information.
+    def add_filter(self, p_filter):
+        """
+        Adds a filter to be applied when calling print_todo.
 
-    Example is pp_color in this fle.
+        p_filter is an instance of a PrettyPrinterFilter.
         """
-    p_filters = p_filters or []
+        self.filters.append(p_filter)
 
+    def print_todo(self, p_todo):
+        """ Given a todo item, pretty print it. """
         todo_str = str(p_todo)
 
-    for f in p_filters:
-        todo_str = f(todo_str, p_todo)
+        for ppf in self.filters:
+            todo_str = ppf.filter(todo_str, p_todo)
 
         return todo_str
-
-def pretty_print_list(p_todos, p_filters=None):
-    """
-    Given a list of todo items, pretty print it and return a list of
-    formatted strings.
-    """
-    p_filters = p_filters or []
-    return [pretty_print(todo, p_filters) for todo in p_todos]

topydo/lib/PrettyPrinterFilter.py

+# Topydo - A todo.txt client written in Python.
+# Copyright (C) 2014 - 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+""" Provides filters used for pretty printing. """
+
+import re
+
+from topydo.lib.Config import config
+
+class PrettyPrinterFilter(object):
+    """
+    Base class for a pretty printer filter.
+
+    Subclasses must reimplement the filter method.
+    """
+
+    def filter(self, p_todo_str, _):
+        """ Default implementation returns an unmodified todo string. """
+        return p_todo_str
+
+PRIORITY_COLORS = {
+    'A': '\033[36m', # cyan
+    'B': '\033[33m', # yellow
+    'C': '\033[34m'  # blue
+}
+
+PROJECT_COLOR = '\033[31m' # red
+NEUTRAL_COLOR = '\033[0m'
+
+class PrettyPrinterColorFilter(PrettyPrinterFilter):
+    """
+    Adds colors to the todo string by inserting ANSI codes.
+
+    Should be passed as a filter in the filter list of pretty_print()
+    """
+
+    def filter(self, p_todo_str, p_todo):
+        """ Applies the colors. """
+
+        if config().colors():
+            color = NEUTRAL_COLOR
+            try:
+                color = PRIORITY_COLORS[p_todo.priority()]
+            except KeyError:
+                pass
+
+            p_todo_str = color + p_todo_str + NEUTRAL_COLOR
+
+            if config().highlight_projects_contexts():
+                p_todo_str = re.sub(
+                    r'\B(\+|@)(\S*\w)',
+                    PROJECT_COLOR + r'\g<0>' + color,
+                    p_todo_str)
+
+            p_todo_str += NEUTRAL_COLOR
+
+        return p_todo_str
+
+class PrettyPrinterIndentFilter(PrettyPrinterFilter):
+    """ Adds indentation to the todo item. """
+    def __init__(self, p_indent=0):
+        super(PrettyPrinterIndentFilter, self).__init__()
+        self.indent = p_indent
+
+    def filter(self, p_todo_str, _):
+        """ Applies the indentation. """
+        return ' ' * self.indent + p_todo_str
+
+class PrettyPrinterNumbers(PrettyPrinterFilter):
+    """ Prepends the todo's number, retrieved from the todolist. """
+    def __init__(self, p_todolist):
+        super(PrettyPrinterNumbers, self).__init__()
+        self.todolist = p_todolist
+
+    def filter(self, p_todo_str, p_todo):
+        """ Prepends the number to the todo string. """
+        return "|{:>3}| {}".format(self.todolist.number(p_todo), p_todo_str)

topydo/lib/PriorityCommand.py

 # Topydo - A todo.txt client written in Python.
-# Copyright (C) 2014 Bram Schoenmakers <me@bramschoenmakers.nl>
+# Copyright (C) 2014 - 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -15,7 +15,6 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 from topydo.lib.Command import Command, InvalidCommandArgument
-from topydo.lib.PrettyPrinter import pretty_print
 from topydo.lib.TodoListBase import InvalidTodoException
 from topydo.lib.Utils import is_valid_priority
 
@@ -48,7 +47,7 @@ class PriorityCommand(Command):
                 elif not old_priority:
                     self.out("Priority set to {}.".format(priority))
 
-                self.out(pretty_print(todo))
+                self.out(self.printer.print_todo(todo))
             else:
                 self.error("Invalid priority given.")
         except InvalidCommandArgument:

topydo/lib/TagCommand.py

 # Topydo - A todo.txt client written in Python.
-# Copyright (C) 2014 Bram Schoenmakers <me@bramschoenmakers.nl>
+# Copyright (C) 2014 - 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -15,8 +15,8 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 from topydo.lib.Command import Command, InvalidCommandArgument
+from topydo.lib.PrettyPrinterFilter import PrettyPrinterNumbers
 from topydo.lib.TodoListBase import InvalidTodoException
-from topydo.lib.PrettyPrinter import pretty_print
 
 class TagCommand(Command):
     def __init__(self, p_args, p_todolist,
@@ -60,7 +60,8 @@ class TagCommand(Command):
             self.value = ""
 
     def _print(self):
-        self.out(pretty_print(self.todo, [self.todolist.pp_number()]))
+        self.printer.add_filter(PrettyPrinterNumbers(self.todolist))
+        self.out(self.printer.print_todo(self.todo))
 
     def _choose(self):
         """

topydo/lib/TodoListBase.py

@@ -24,7 +24,7 @@ import re
 from topydo.lib.Config import config
 from topydo.lib import Filter
 from topydo.lib.HashListValues import hash_list_values
-from topydo.lib.PrettyPrinter import pretty_print_list
+from topydo.lib.PrettyPrinter import PrettyPrinter
 from topydo.lib.Todo import Todo
 from topydo.lib.View import View
 
@@ -242,14 +242,6 @@ class TodoListBase(object):
         except (ValueError, KeyError):
             raise InvalidTodoException
 
-    def pp_number(self):
-        """
-        A filter for the pretty printer to append the todo number to the
-        printed todo.
-        """
-        return lambda p_todo_str, p_todo: \
-                "|{:>3}| {}".format(self.number(p_todo), p_todo_str)
-
     def _update_todo_ids(self):
         # the idea is to have a hash that is independent of the position of the
         # todo. Use the text (without tags) of the todo to keep the id as stable
@@ -264,5 +256,6 @@ class TodoListBase(object):
             self._id_todo_map[uid] = todo
 
     def __str__(self):
-        return '\n'.join(pretty_print_list(self._todos))
+        printer = PrettyPrinter()
+        return printer.print_list(self._todos)
 

topydo/lib/View.py

 # Topydo - A todo.txt client written in Python.
-# Copyright (C) 2014 Bram Schoenmakers <me@bramschoenmakers.nl>
+# Copyright (C) 2014 - 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -16,19 +16,29 @@
 
 """ A view is a list of todos, sorted and filtered. """
 
-from topydo.lib.PrettyPrinter import pretty_print_list, pp_color
+from topydo.lib.PrettyPrinterFilter import (
+    PrettyPrinterColorFilter,
+    PrettyPrinterNumbers
+)
+from topydo.lib.PrettyPrinter import PrettyPrinter
 
 class View(object):
     """
     A view is instantiated by a todo list, usually obtained from a todo.txt
     file. Also a sorter and a list of filters should be given that is applied
     to the list.
+
+    A printer can be passed, but it won't be used when pretty_print() is
+    called, since it will instantiate its own pretty printer instance.
     """
-    def __init__(self, p_sorter, p_filters, p_todolist):
+    def __init__(self, p_sorter, p_filters, p_todolist,
+            p_printer=PrettyPrinter()):
+
         self._todolist = p_todolist
         self._viewdata = []
         self._sorter = p_sorter
         self._filters = p_filters
+        self._printer = p_printer
 
         self.update()
 
@@ -45,8 +55,16 @@ class View(object):
     def pretty_print(self, p_pp_filters=None):
         """ Pretty prints the view. """
         p_pp_filters = p_pp_filters or []
-        pp_filters = [self._todolist.pp_number(), pp_color] + p_pp_filters
-        return '\n'.join(pretty_print_list(self._viewdata, pp_filters))
+
+        # since we're using filters, always use PrettyPrinter
+        printer = PrettyPrinter()
+        printer.add_filter(PrettyPrinterNumbers(self._todolist))
+        printer.add_filter(PrettyPrinterColorFilter())
+
+        for ppf in p_pp_filters:
+            printer.add_filter(ppf)
+
+        return printer.print_list(self._viewdata)
 
     def __str__(self):
-        return '\n'.join(pretty_print_list(self._viewdata))
+        return self._printer.print_list(self._viewdata)