refactor prompt completion

This just splits the file completion.py into several files, one for each
Completer subclass.

18 files changed, 735 insertions, 622 deletions

diff --git a/alot/completion.py b/alot/completion.py
deleted file mode 100644
index dcf1383d..00000000
--- a/alot/completion.py
+++ /dev/null
@@ -1,622 +0,0 @@
-# Copyright (C) 2011-2012  Patrick Totzke <patricktotzke@gmail.com>
-# This file is released under the GNU GPL, version 3 or a later revision.
-# For further details see the COPYING file
-import abc
-import argparse
-import email.utils
-import glob
-import logging
-import os
-import re
-
-from . import crypto
-from . import commands
-from .buffers import EnvelopeBuffer
-from .settings.const import settings
-from .utils import argparse as cargparse
-from .db.utils import formataddr
-from .helper import split_commandline
-from .addressbook import AddressbookError
-from .errors import CompletionError
-from .utils.cached_property import cached_property
-
-
-class Completer:
-    """base class for completers"""
-
-    __metaclass__ = abc.ABCMeta
-
-    @abc.abstractmethod
-    def complete(self, original, pos):
-        """returns a list of completions and cursor positions for the
-        string original from position pos on.
-
-        :param original: the string to complete
-        :type original: str
-        :param pos: starting position to complete from
-        :type pos: int
-        :returns: pairs of completed string and cursor position in the
-                  new string
-        :rtype: list of (str, int)
-        :raises: :exc:`CompletionError`
-        """
-        pass
-
-    def relevant_part(self, original, pos, sep=' '):
-        """
-        calculates the subword in a `sep`-splitted list of substrings of
-        `original` that `pos` is ia.n
-        """
-        start = original.rfind(sep, 0, pos) + 1
-        end = original.find(sep, pos - 1)
-        if end == -1:
-            end = len(original)
-        return original[start:end], start, end, pos - start
-
-
-class StringlistCompleter(Completer):
-    """completer for a fixed list of strings"""
-
-    def __init__(self, resultlist, ignorecase=True, match_anywhere=False):
-        """
-        :param resultlist: strings used for completion
-        :type resultlist: list of str
-        :param liberal: match case insensitive and not prefix-only
-        :type liberal: bool
-        """
-        self.resultlist = resultlist
-        self.flags = re.IGNORECASE if ignorecase else 0
-        self.match_anywhere = match_anywhere
-
-    def complete(self, original, pos):
-        pref = original[:pos]
-
-        re_prefix = '.*' if self.match_anywhere else ''
-
-        def match(s, m):
-            r = '{}{}.*'.format(re_prefix, re.escape(m))
-            return re.match(r, s, flags=self.flags) is not None
-
-        return [(a, len(a)) for a in self.resultlist if match(a, pref)]
-
-
-class MultipleSelectionCompleter(Completer):
-    """
-    Meta-Completer that turns any Completer into one that deals with a list of
-    completion strings using the wrapped Completer.
-    This allows for example to easily construct a completer for comma separated
-    recipient-lists using a :class:`ContactsCompleter`.
-    """
-
-    def __init__(self, completer, separator=', '):
-        """
-        :param completer: completer to use for individual substrings
-        :type completer: Completer
-        :param separator: separator used to split the completion string into
-                          substrings to be fed to `completer`.
-        :type separator: str
-        """
-        self._completer = completer
-        self._separator = separator
-
-    def relevant_part(self, original, pos):
-        """
-        calculates the subword of `original` that `pos` is in
-        """
-        start = original.rfind(self._separator, 0, pos)
-        if start == -1:
-            start = 0
-        else:
-            start = start + len(self._separator)
-        end = original.find(self._separator, pos - 1)
-        if end == -1:
-            end = len(original)
-        return original[start:end], start, end, pos - start
-
-    def complete(self, original, pos):
-        mypart, start, end, mypos = self.relevant_part(original, pos)
-        res = []
-        for c, _ in self._completer.complete(mypart, mypos):
-            newprefix = original[:start] + c
-            if not original[end:].startswith(self._separator):
-                newprefix += self._separator
-            res.append((newprefix + original[end:], len(newprefix)))
-        return res
-
-
-class NamedQueryCompleter(StringlistCompleter):
-    """complete the name of a named query string"""
-
-    def __init__(self, dbman):
-        """
-        :param dbman: used to look up named query strings in the DB
-        :type dbman: :class:`~alot.db.DBManager`
-        """
-        # mapping of alias to query string (dict str -> str)
-        nqueries = dbman.get_named_queries()
-        StringlistCompleter.__init__(self, list(nqueries))
-
-
-class QueryCompleter(Completer):
-    """completion for a notmuch query string"""
-    def __init__(self, dbman):
-        """
-        :param dbman: used to look up available tagstrings
-        :type dbman: :class:`~alot.db.DBManager`
-        """
-        self.dbman = dbman
-        abooks = settings.get_addressbooks()
-        self._abookscompleter = AbooksCompleter(abooks, addressesonly=True)
-        self._tagcompleter = TagCompleter(dbman)
-        self._nquerycompleter = NamedQueryCompleter(dbman)
-        self.keywords = ['tag', 'from', 'to', 'subject', 'attachment',
-                         'is', 'id', 'thread', 'folder', 'query']
-
-    def complete(self, original, pos):
-        mypart, start, end, mypos = self.relevant_part(original, pos)
-        myprefix = mypart[:mypos]
-        m = re.search(r'(tag|is|to|from|query):(\w*)', myprefix)
-        if m:
-            cmd, _ = m.groups()
-            cmdlen = len(cmd) + 1  # length of the keyword part including colon
-            if cmd in ['to', 'from']:
-                localres = self._abookscompleter.complete(mypart[cmdlen:],
-                                                          mypos - cmdlen)
-            elif cmd in ['query']:
-                localres = self._nquerycompleter.complete(mypart[cmdlen:],
-                                                          mypos - cmdlen)
-            else:
-                localres = self._tagcompleter.complete(mypart[cmdlen:],
-                                                       mypos - cmdlen)
-            resultlist = []
-            for ltxt, lpos in localres:
-                newtext = original[:start] + cmd + ':' + ltxt + original[end:]
-                newpos = start + len(cmd) + 1 + lpos
-                resultlist.append((newtext, newpos))
-            return resultlist
-        else:
-            matched = (t for t in self.keywords if t.startswith(myprefix))
-            resultlist = []
-            for keyword in matched:
-                newprefix = original[:start] + keyword + ':'
-                resultlist.append((newprefix + original[end:], len(newprefix)))
-            return resultlist
-
-
-class TagCompleter(StringlistCompleter):
-    """complete a tagstring"""
-
-    def __init__(self, dbman):
-        """
-        :param dbman: used to look up available tagstrings
-        :type dbman: :class:`~alot.db.DBManager`
-        """
-        resultlist = dbman.get_all_tags()
-        StringlistCompleter.__init__(self, resultlist)
-
-
-class TagsCompleter(MultipleSelectionCompleter):
-    """completion for a comma separated list of tagstrings"""
-
-    def __init__(self, dbman):
-        """
-        :param dbman: used to look up available tagstrings
-        :type dbman: :class:`~alot.db.DBManager`
-        """
-        self._completer = TagCompleter(dbman)
-        self._separator = ','
-
-
-class ContactsCompleter(MultipleSelectionCompleter):
-    """completes contacts from given address books"""
-    def __init__(self, abooks, addressesonly=False):
-        """
-        :param abooks: used to look up email addresses
-        :type abooks: list of :class:`~alot.account.AddresBook`
-        :param addressesonly: only insert address, not the realname of the
-                              contact
-        :type addressesonly: bool
-        """
-        self._completer = AbooksCompleter(abooks, addressesonly=addressesonly)
-        self._separator = ', '
-
-
-class AbooksCompleter(Completer):
-    """completes a contact from given address books"""
-    def __init__(self, abooks, addressesonly=False):
-        """
-        :param abooks: used to look up email addresses
-        :type abooks: list of :class:`~alot.account.AddresBook`
-        :param addressesonly: only insert address, not the realname of the
-                              contact
-        :type addressesonly: bool
-        """
-        self.abooks = abooks
-        self.addressesonly = addressesonly
-
-    def complete(self, original, pos):
-        if not self.abooks:
-            return []
-        prefix = original[:pos]
-        res = []
-        for abook in self.abooks:
-            try:
-                res = res + abook.lookup(prefix)
-            except AddressbookError as e:
-                raise CompletionError(e)
-        if self.addressesonly:
-            returnlist = [(addr, len(addr)) for (name, addr) in res]
-        else:
-            returnlist = []
-            for name, addr in res:
-                newtext = formataddr((name, addr))
-                returnlist.append((newtext, len(newtext)))
-        return returnlist
-
-
-class ArgparseOptionCompleter(Completer):
-    """completes option parameters for a given argparse.Parser"""
-    def __init__(self, parser):
-        """
-        :param parser: the option parser we look up parameter and  choices from
-        :type parser: `argparse.ArgumentParser`
-        """
-        self.parser = parser
-        self.actions = parser._optionals._actions
-
-    def complete(self, original, pos):
-        pref = original[:pos]
-
-        res = []
-        for act in self.actions:
-            if '=' in pref:
-                optionstring = pref[:pref.rfind('=') + 1]
-                # get choices
-                if 'choices' in act.__dict__:
-                    # TODO: respect prefix
-                    choices = act.choices or []
-                    res = res + [optionstring + a for a in choices]
-            else:
-                for optionstring in act.option_strings:
-                    if optionstring.startswith(pref):
-                        # append '=' for options that await a string value
-                        if isinstance(act, (argparse._StoreAction,
-                                            cargparse.BooleanAction)):
-                            optionstring += '='
-                        res.append(optionstring)
-
-        return [(a, len(a)) for a in res]
-
-
-class AccountCompleter(StringlistCompleter):
-    """completes users' own mailaddresses"""
-
-    def __init__(self, **kwargs):
-        accounts = settings.get_accounts()
-        resultlist = [email.utils.formataddr((a.realname, str(a.address)))
-                      for a in accounts]
-        StringlistCompleter.__init__(self, resultlist, match_anywhere=True,
-                                     **kwargs)
-
-
-class CommandNameCompleter(Completer):
-    """completes command names"""
-
-    def __init__(self, mode):
-        """
-        :param mode: mode identifier
-        :type mode: str
-        """
-        self.mode = mode
-
-    def complete(self, original, pos):
-        # TODO refine <tab> should get current querystring
-        commandprefix = original[:pos]
-        logging.debug('original="%s" prefix="%s"', original, commandprefix)
-        cmdlist = commands.COMMANDS['global'].copy()
-        cmdlist.update(commands.COMMANDS[self.mode])
-        matching = [t for t in cmdlist if t.startswith(commandprefix)]
-        return [(t, len(t)) for t in matching]
-
-
-class CommandCompleter(Completer):
-    """completes one command consisting of command name and parameters"""
-
-    def __init__(self, dbman, mode, currentbuffer=None):
-        """
-        :param dbman: used to look up available tagstrings
-        :type dbman: :class:`~alot.db.DBManager`
-        :param mode: mode identifier
-        :type mode: str
-        :param currentbuffer: currently active buffer. If defined, this will be
-                              used to dynamically extract possible completion
-                              strings
-        :type currentbuffer: :class:`~alot.buffers.Buffer`
-        """
-        self.dbman = dbman
-        self.mode = mode
-        self.currentbuffer = currentbuffer
-        self._commandnamecompleter = CommandNameCompleter(mode)
-
-    @cached_property
-    def _querycompleter(self):
-        return QueryCompleter(self.dbman)
-
-    @cached_property
-    def _tagcompleter(self):
-        return TagCompleter(self.dbman)
-
-    @cached_property
-    def _contactscompleter(self):
-        abooks = settings.get_addressbooks()
-        return ContactsCompleter(abooks)
-
-    @cached_property
-    def _pathcompleter(self):
-        return PathCompleter()
-
-    @cached_property
-    def _accountscompleter(self):
-        return AccountCompleter()
-
-    @cached_property
-    def _secretkeyscompleter(self):
-        return CryptoKeyCompleter(private=True)
-
-    @cached_property
-    def _publickeyscompleter(self):
-        return CryptoKeyCompleter(private=False)
-
-    def complete(self, line, pos):
-        # remember how many preceding space characters we see until the command
-        # string starts. We'll continue to complete from there on and will add
-        # these whitespaces again at the very end
-        whitespaceoffset = len(line) - len(line.lstrip())
-        line = line[whitespaceoffset:]
-        pos = pos - whitespaceoffset
-
-        words = line.split(' ', 1)
-
-        res = []
-        if pos <= len(words[0]):  # we complete commands
-            for cmd, cpos in self._commandnamecompleter.complete(line, pos):
-                newtext = ('%s %s' % (cmd, ' '.join(words[1:])))
-                res.append((newtext, cpos + 1))
-        else:
-            cmd, params = words
-            localpos = pos - (len(cmd) + 1)
-            parser = commands.lookup_parser(cmd, self.mode)
-            if parser is not None:
-                # set 'res' - the result set of matching completionstrings
-                # depending on the current mode and command
-
-                # detect if we are completing optional parameter
-                arguments_until_now = params[:localpos].split(' ')
-                all_optionals = True
-                logging.debug(str(arguments_until_now))
-                for a in arguments_until_now:
-                    logging.debug(a)
-                    if a and not a.startswith('-'):
-                        all_optionals = False
-                # complete optional parameter if
-                # 1. all arguments prior to current position are optional
-                # 2. the parameter starts with '-' or we are at its beginning
-                if all_optionals:
-                    myarg = arguments_until_now[-1]
-                    start_myarg = params.rindex(myarg)
-                    beforeme = params[:start_myarg]
-                    # set up local stringlist completer
-                    # and let it complete for given list of options
-                    localcompleter = ArgparseOptionCompleter(parser)
-                    localres = localcompleter.complete(myarg, len(myarg))
-                    res = [(
-                        beforeme + c, p + start_myarg) for (c, p) in localres]
-
-                # global
-                elif cmd == 'search':
-                    res = self._querycompleter.complete(params, localpos)
-                elif cmd == 'help':
-                    res = self._commandnamecompleter.complete(params, localpos)
-                elif cmd in ['compose']:
-                    res = self._contactscompleter.complete(params, localpos)
-                # search
-                elif self.mode == 'search' and cmd == 'refine':
-                    res = self._querycompleter.complete(params, localpos)
-                elif self.mode == 'search' and cmd in ['tag', 'retag', 'untag',
-                                                       'toggletags']:
-                    localcomp = MultipleSelectionCompleter(self._tagcompleter,
-                                                           separator=',')
-                    res = localcomp.complete(params, localpos)
-                elif self.mode == 'search' and cmd == 'toggletag':
-                    localcomp = MultipleSelectionCompleter(self._tagcompleter,
-                                                           separator=' ')
-                    res = localcomp.complete(params, localpos)
-                # envelope
-                elif self.mode == 'envelope' and cmd == 'set':
-                    plist = params.split(' ', 1)
-                    if len(plist) == 1:  # complete from header keys
-                        localprefix = params
-                        headers = ['Subject', 'To', 'Cc', 'Bcc', 'In-Reply-To',
-                                   'From']
-                        localcompleter = StringlistCompleter(headers)
-                        localres = localcompleter.complete(
-                            localprefix, localpos)
-                        res = [(c, p + 6) for (c, p) in localres]
-                    else:  # must have 2 elements
-                        header, params = plist
-                        localpos = localpos - (len(header) + 1)
-                        if header.lower() in ['to', 'cc', 'bcc']:
-                            res = self._contactscompleter.complete(params,
-                                                                   localpos)
-                        elif header.lower() == 'from':
-                            res = self._accountscompleter.complete(params,
-                                                                   localpos)
-
-                        # prepend 'set ' + header and correct position
-                        def f(completed, pos):
-                            return ('%s %s' % (header, completed),
-                                    pos + len(header) + 1)
-                        res = [f(c, p) for c, p in res]
-                        logging.debug(res)
-
-                elif self.mode == 'envelope' and cmd == 'unset':
-                    plist = params.split(' ', 1)
-                    if len(plist) == 1:  # complete from header keys
-                        localprefix = params
-                        buf = self.currentbuffer
-                        if buf:
-                            if isinstance(buf, EnvelopeBuffer):
-                                available = buf.envelope.headers.keys()
-                                localcompleter = StringlistCompleter(available)
-                                localres = localcompleter.complete(localprefix,
-                                                                   localpos)
-                                res = [(c, p + 6) for (c, p) in localres]
-
-                elif self.mode == 'envelope' and cmd == 'attach':
-                    res = self._pathcompleter.complete(params, localpos)
-                elif self.mode == 'envelope' and cmd in ['sign', 'togglesign']:
-                    res = self._secretkeyscompleter.complete(params, localpos)
-                elif self.mode == 'envelope' and cmd in ['encrypt',
-                                                         'rmencrypt',
-                                                         'toggleencrypt']:
-                    res = self._publickeyscompleter.complete(params, localpos)
-                elif self.mode == 'envelope' and cmd in ['tag', 'toggletags',
-                                                         'untag', 'retag']:
-                    localcomp = MultipleSelectionCompleter(self._tagcompleter,
-                                                           separator=',')
-                    res = localcomp.complete(params, localpos)
-                # thread
-                elif self.mode == 'thread' and cmd == 'save':
-                    res = self._pathcompleter.complete(params, localpos)
-                elif self.mode == 'thread' and cmd in ['fold', 'unfold',
-                                                       'togglesource',
-                                                       'toggleheaders']:
-                    res = self._querycompleter.complete(params, localpos)
-                elif self.mode == 'thread' and cmd in ['tag', 'retag', 'untag',
-                                                       'toggletags']:
-                    localcomp = MultipleSelectionCompleter(self._tagcompleter,
-                                                           separator=',')
-                    res = localcomp.complete(params, localpos)
-                elif cmd == 'move':
-                    directions = ['up', 'down', 'page up', 'page down',
-                                  'halfpage up', 'halfpage down', 'first',
-                                  'last']
-                    if self.mode == 'thread':
-                        directions += ['parent', 'first reply', 'last reply',
-                                       'next sibling', 'previous sibling',
-                                       'next', 'previous', 'next unfolded',
-                                       'previous unfolded']
-                    localcompleter = StringlistCompleter(directions)
-                    res = localcompleter.complete(params, localpos)
-
-                # prepend cmd and correct position
-                res = [('%s %s' % (cmd, t), p + len(cmd) +
-                        1) for (t, p) in res]
-
-        # re-insert whitespaces and correct position
-        wso = whitespaceoffset
-        res = [(' ' * wso + cmdstr, p + wso) for cmdstr, p in res]
-        return res
-
-
-class CommandLineCompleter(Completer):
-    """completes command lines: semicolon separated command strings"""
-
-    def __init__(self, dbman, mode, currentbuffer=None):
-        """
-        :param dbman: used to look up available tagstrings
-        :type dbman: :class:`~alot.db.DBManager`
-        :param mode: mode identifier
-        :type mode: str
-        :param currentbuffer: currently active buffer. If defined, this will be
-                              used to dynamically extract possible completion
-                              strings
-        :type currentbuffer: :class:`~alot.buffers.Buffer`
-        """
-        self._commandcompleter = CommandCompleter(dbman, mode, currentbuffer)
-
-    @staticmethod
-    def get_context(line, pos):
-        """
-        computes start and end position of substring of line that is the
-        command string under given position
-        """
-        commands = split_commandline(line) + ['']
-        i = 0
-        start = 0
-        end = len(commands[i])
-        while pos > end:
-            i += 1
-            start = end + 1
-            end += 1 + len(commands[i])
-        return start, end
-
-    def complete(self, line, pos):
-        cstart, cend = self.get_context(line, pos)
-        before = line[:cstart]
-        after = line[cend:]
-        cmdstring = line[cstart:cend]
-        cpos = pos - cstart
-
-        res = []
-        for ccmd, ccpos in self._commandcompleter.complete(cmdstring, cpos):
-            newtext = before + ccmd + after
-            newpos = pos + (ccpos - cpos)
-            res.append((newtext, newpos))
-        return res
-
-
-class PathCompleter(Completer):
-
-    """completion for paths"""
-
-    def complete(self, original, pos):
-        if not original:
-            return [('~/', 2)]
-        prefix = os.path.expanduser(original[:pos])
-
-        def escape(path):
-            """Escape all backslashes and spaces in given path with a
-            backslash.
-
-            :param path: the path to escape
-            :type path: str
-            :returns: the escaped path
-            :rtype: str
-            """
-            return path.replace('\\', '\\\\').replace(' ', r'\ ')
-
-        def deescape(escaped_path):
-            """Remove escaping backslashes in front of spaces and backslashes.
-
-            :param escaped_path: a path potentially with escaped spaces and
-                backslashs
-            :type escaped_path: str
-            :returns: the actual path
-            :rtype: str
-            """
-            return escaped_path.replace('\\ ', ' ').replace('\\\\', '\\')
-
-        def prep(path):
-            escaped_path = escape(path)
-            return escaped_path, len(escaped_path)
-
-        return [prep(g) for g in glob.glob(deescape(prefix) + '*')]
-
-
-class CryptoKeyCompleter(StringlistCompleter):
-    """completion for gpg keys"""
-
-    def __init__(self, private=False):
-        """
-        :param private: return private keys
-        :type private: bool
-        """
-        keys = crypto.list_keys(private=private)
-        resultlist = []
-        for k in keys:
-            for s in k.subkeys:
-                resultlist.append(s.keyid)
-            for u in k.uids:
-                resultlist.append(u.email)
-        StringlistCompleter.__init__(self, resultlist, match_anywhere=True)
diff --git a/alot/completion/__init__.py b/alot/completion/__init__.py
new file mode 100644
index 00000000..86e5d93c
--- /dev/null
+++ b/alot/completion/__init__.py
@@ -0,0 +1,17 @@
+from .completer import Completer
+
+from .abooks import AbooksCompleter
+from .accounts import AccountCompleter
+from .argparse import ArgparseOptionCompleter
+from .command import CommandCompleter
+from .commandline import CommandLineCompleter
+from .commandname import CommandNameCompleter
+from .contacts import ContactsCompleter
+from .cryptokey import CryptoKeyCompleter
+from .multipleselection import MultipleSelectionCompleter
+from .namedquery import NamedQueryCompleter
+from .path import PathCompleter
+from .query import QueryCompleter
+from .stringlist import StringlistCompleter
+from .tag import TagCompleter
+from .tags import TagsCompleter
diff --git a/alot/completion/abooks.py b/alot/completion/abooks.py
new file mode 100644
index 00000000..bc2fa20b
--- /dev/null
+++ b/alot/completion/abooks.py
@@ -0,0 +1,42 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+
+from .completer import Completer
+from ..addressbook import AddressbookError
+from ..db.utils import formataddr
+from ..errors import CompletionError
+
+
+class AbooksCompleter(Completer):
+    """Complete a contact from given address books."""
+
+    def __init__(self, abooks, addressesonly=False):
+        """
+        :param abooks: used to look up email addresses
+        :type abooks: list of :class:`~alot.account.AddresBook`
+        :param addressesonly: only insert address, not the realname of the
+                              contact
+        :type addressesonly: bool
+        """
+        self.abooks = abooks
+        self.addressesonly = addressesonly
+
+    def complete(self, original, pos):
+        if not self.abooks:
+            return []
+        prefix = original[:pos]
+        res = []
+        for abook in self.abooks:
+            try:
+                res = res + abook.lookup(prefix)
+            except AddressbookError as e:
+                raise CompletionError(e)
+        if self.addressesonly:
+            returnlist = [(addr, len(addr)) for (name, addr) in res]
+        else:
+            returnlist = []
+            for name, addr in res:
+                newtext = formataddr((name, addr))
+                returnlist.append((newtext, len(newtext)))
+        return returnlist
diff --git a/alot/completion/accounts.py b/alot/completion/accounts.py
new file mode 100644
index 00000000..c83ce09c
--- /dev/null
+++ b/alot/completion/accounts.py
@@ -0,0 +1,19 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+
+import email.utils
+
+from .stringlist import StringlistCompleter
+from ..settings.const import settings
+
+
+class AccountCompleter(StringlistCompleter):
+    """Completes users' own mailaddresses."""
+
+    def __init__(self, **kwargs):
+        accounts = settings.get_accounts()
+        resultlist = [email.utils.formataddr((a.realname, str(a.address)))
+                      for a in accounts]
+        StringlistCompleter.__init__(self, resultlist, match_anywhere=True,
+                                     **kwargs)
diff --git a/alot/completion/argparse.py b/alot/completion/argparse.py
new file mode 100644
index 00000000..ac15b2c6
--- /dev/null
+++ b/alot/completion/argparse.py
@@ -0,0 +1,41 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+
+import argparse
+from .completer import Completer
+from ..utils import argparse as cargparse
+
+
+class ArgparseOptionCompleter(Completer):
+    """completes option parameters for a given argparse.Parser"""
+    def __init__(self, parser):
+        """
+        :param parser: the option parser we look up parameter and  choices from
+        :type parser: `argparse.ArgumentParser`
+        """
+        self.parser = parser
+        self.actions = parser._optionals._actions
+
+    def complete(self, original, pos):
+        pref = original[:pos]
+
+        res = []
+        for act in self.actions:
+            if '=' in pref:
+                optionstring = pref[:pref.rfind('=') + 1]
+                # get choices
+                if 'choices' in act.__dict__:
+                    # TODO: respect prefix
+                    choices = act.choices or []
+                    res = res + [optionstring + a for a in choices]
+            else:
+                for optionstring in act.option_strings:
+                    if optionstring.startswith(pref):
+                        # append '=' for options that await a string value
+                        if isinstance(act, (argparse._StoreAction,
+                                            cargparse.BooleanAction)):
+                            optionstring += '='
+                        res.append(optionstring)
+
+        return [(a, len(a)) for a in res]
diff --git a/alot/completion/command.py b/alot/completion/command.py
new file mode 100644
index 00000000..305e445f
--- /dev/null
+++ b/alot/completion/command.py
@@ -0,0 +1,221 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+
+import logging
+
+from alot import commands
+from alot.buffers import EnvelopeBuffer
+from alot.settings.const import settings
+from alot.utils.cached_property import cached_property
+from .completer import Completer
+from .commandname import CommandNameCompleter
+from .tag import TagCompleter
+from .query import QueryCompleter
+from .contacts import ContactsCompleter
+from .accounts import AccountCompleter
+from .path import PathCompleter
+from .stringlist import StringlistCompleter
+from .multipleselection import MultipleSelectionCompleter
+from .cryptokey import CryptoKeyCompleter
+from .argparse import ArgparseOptionCompleter
+
+
+class CommandCompleter(Completer):
+    """completes one command consisting of command name and parameters"""
+
+    def __init__(self, dbman, mode, currentbuffer=None):
+        """
+        :param dbman: used to look up available tagstrings
+        :type dbman: :class:`~alot.db.DBManager`
+        :param mode: mode identifier
+        :type mode: str
+        :param currentbuffer: currently active buffer. If defined, this will be
+                              used to dynamically extract possible completion
+                              strings
+        :type currentbuffer: :class:`~alot.buffers.Buffer`
+        """
+        self.dbman = dbman
+        self.mode = mode
+        self.currentbuffer = currentbuffer
+        self._commandnamecompleter = CommandNameCompleter(mode)
+
+    @cached_property
+    def _querycompleter(self):
+        return QueryCompleter(self.dbman)
+
+    @cached_property
+    def _tagcompleter(self):
+        return TagCompleter(self.dbman)
+
+    @cached_property
+    def _contactscompleter(self):
+        abooks = settings.get_addressbooks()
+        return ContactsCompleter(abooks)
+
+    @cached_property
+    def _pathcompleter(self):
+        return PathCompleter()
+
+    @cached_property
+    def _accountscompleter(self):
+        return AccountCompleter()
+
+    @cached_property
+    def _secretkeyscompleter(self):
+        return CryptoKeyCompleter(private=True)
+
+    @cached_property
+    def _publickeyscompleter(self):
+        return CryptoKeyCompleter(private=False)
+
+    def complete(self, line, pos):
+        # remember how many preceding space characters we see until the command
+        # string starts. We'll continue to complete from there on and will add
+        # these whitespaces again at the very end
+        whitespaceoffset = len(line) - len(line.lstrip())
+        line = line[whitespaceoffset:]
+        pos = pos - whitespaceoffset
+
+        words = line.split(' ', 1)
+
+        res = []
+        if pos <= len(words[0]):  # we complete commands
+            for cmd, cpos in self._commandnamecompleter.complete(line, pos):
+                newtext = ('%s %s' % (cmd, ' '.join(words[1:])))
+                res.append((newtext, cpos + 1))
+        else:
+            cmd, params = words
+            localpos = pos - (len(cmd) + 1)
+            parser = commands.lookup_parser(cmd, self.mode)
+            if parser is not None:
+                # set 'res' - the result set of matching completionstrings
+                # depending on the current mode and command
+
+                # detect if we are completing optional parameter
+                arguments_until_now = params[:localpos].split(' ')
+                all_optionals = True
+                logging.debug(str(arguments_until_now))
+                for a in arguments_until_now:
+                    logging.debug(a)
+                    if a and not a.startswith('-'):
+                        all_optionals = False
+                # complete optional parameter if
+                # 1. all arguments prior to current position are optional
+                # 2. the parameter starts with '-' or we are at its beginning
+                if all_optionals:
+                    myarg = arguments_until_now[-1]
+                    start_myarg = params.rindex(myarg)
+                    beforeme = params[:start_myarg]
+                    # set up local stringlist completer
+                    # and let it complete for given list of options
+                    localcompleter = ArgparseOptionCompleter(parser)
+                    localres = localcompleter.complete(myarg, len(myarg))
+                    res = [(
+                        beforeme + c, p + start_myarg) for (c, p) in localres]
+
+                # global
+                elif cmd == 'search':
+                    res = self._querycompleter.complete(params, localpos)
+                elif cmd == 'help':
+                    res = self._commandnamecompleter.complete(params, localpos)
+                elif cmd in ['compose']:
+                    res = self._contactscompleter.complete(params, localpos)
+                # search
+                elif self.mode == 'search' and cmd == 'refine':
+                    res = self._querycompleter.complete(params, localpos)
+                elif self.mode == 'search' and cmd in ['tag', 'retag', 'untag',
+                                                       'toggletags']:
+                    localcomp = MultipleSelectionCompleter(self._tagcompleter,
+                                                           separator=',')
+                    res = localcomp.complete(params, localpos)
+                elif self.mode == 'search' and cmd == 'toggletag':
+                    localcomp = MultipleSelectionCompleter(self._tagcompleter,
+                                                           separator=' ')
+                    res = localcomp.complete(params, localpos)
+                # envelope
+                elif self.mode == 'envelope' and cmd == 'set':
+                    plist = params.split(' ', 1)
+                    if len(plist) == 1:  # complete from header keys
+                        localprefix = params
+                        headers = ['Subject', 'To', 'Cc', 'Bcc', 'In-Reply-To',
+                                   'From']
+                        localcompleter = StringlistCompleter(headers)
+                        localres = localcompleter.complete(
+                            localprefix, localpos)
+                        res = [(c, p + 6) for (c, p) in localres]
+                    else:  # must have 2 elements
+                        header, params = plist
+                        localpos = localpos - (len(header) + 1)
+                        if header.lower() in ['to', 'cc', 'bcc']:
+                            res = self._contactscompleter.complete(params,
+                                                                   localpos)
+                        elif header.lower() == 'from':
+                            res = self._accountscompleter.complete(params,
+                                                                   localpos)
+
+                        # prepend 'set ' + header and correct position
+                        def f(completed, pos):
+                            return ('%s %s' % (header, completed),
+                                    pos + len(header) + 1)
+                        res = [f(c, p) for c, p in res]
+                        logging.debug(res)
+
+                elif self.mode == 'envelope' and cmd == 'unset':
+                    plist = params.split(' ', 1)
+                    if len(plist) == 1:  # complete from header keys
+                        localprefix = params
+                        buf = self.currentbuffer
+                        if buf:
+                            if isinstance(buf, EnvelopeBuffer):
+                                available = buf.envelope.headers.keys()
+                                localcompleter = StringlistCompleter(available)
+                                localres = localcompleter.complete(localprefix,
+                                                                   localpos)
+                                res = [(c, p + 6) for (c, p) in localres]
+
+                elif self.mode == 'envelope' and cmd == 'attach':
+                    res = self._pathcompleter.complete(params, localpos)
+                elif self.mode == 'envelope' and cmd in ['sign', 'togglesign']:
+                    res = self._secretkeyscompleter.complete(params, localpos)
+                elif self.mode == 'envelope' and cmd in ['encrypt',
+                                                         'rmencrypt',
+                                                         'toggleencrypt']:
+                    res = self._publickeyscompleter.complete(params, localpos)
+                elif self.mode == 'envelope' and cmd in ['tag', 'toggletags',
+                                                         'untag', 'retag']:
+                    localcomp = MultipleSelectionCompleter(self._tagcompleter,
+                                                           separator=',')
+                    res = localcomp.complete(params, localpos)
+                # thread
+                elif self.mode == 'thread' and cmd == 'save':
+                    res = self._pathcompleter.complete(params, localpos)
+                elif self.mode == 'thread' and cmd in ['fold', 'unfold',
+                                                       'togglesource',
+                                                       'toggleheaders']:
+                    res = self._querycompleter.complete(params, localpos)
+                elif self.mode == 'thread' and cmd in ['tag', 'retag', 'untag',
+                                                       'toggletags']:
+                    localcomp = MultipleSelectionCompleter(self._tagcompleter,
+                                                           separator=',')
+                    res = localcomp.complete(params, localpos)
+                elif cmd == 'move':
+                    directions = ['up', 'down', 'page up', 'page down',
+                                  'halfpage up', 'halfpage down', 'first',
+                                  'last']
+                    if self.mode == 'thread':
+                        directions += ['parent', 'first reply', 'last reply',
+                                       'next sibling', 'previous sibling',
+                                       'next', 'previous', 'next unfolded',
+                                       'previous unfolded']
+                    localcompleter = StringlistCompleter(directions)
+                    res = localcompleter.complete(params, localpos)
+
+                # prepend cmd and correct position
+                res = [('%s %s' % (cmd, t), p + len(cmd) + 1)
+                       for (t, p) in res]
+
+        # re-insert whitespaces and correct position
+        wso = whitespaceoffset
+        res = [(' ' * wso + cmdstr, p + wso) for cmdstr, p in res]
+        return res
diff --git a/alot/completion/commandline.py b/alot/completion/commandline.py
new file mode 100644
index 00000000..f5739f38
--- /dev/null
+++ b/alot/completion/commandline.py
@@ -0,0 +1,54 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+
+from .completer import Completer
+from .command import CommandCompleter
+from ..helper import split_commandline
+
+
+class CommandLineCompleter(Completer):
+    """completes command lines: semicolon separated command strings"""
+
+    def __init__(self, dbman, mode, currentbuffer=None):
+        """
+        :param dbman: used to look up available tagstrings
+        :type dbman: :class:`~alot.db.DBManager`
+        :param mode: mode identifier
+        :type mode: str
+        :param currentbuffer: currently active buffer. If defined, this will be
+                              used to dynamically extract possible completion
+                              strings
+        :type currentbuffer: :class:`~alot.buffers.Buffer`
+        """
+        self._commandcompleter = CommandCompleter(dbman, mode, currentbuffer)
+
+    @staticmethod
+    def get_context(line, pos):
+        """
+        computes start and end position of substring of line that is the
+        command string under given position
+        """
+        commands = split_commandline(line) + ['']
+        i = 0
+        start = 0
+        end = len(commands[i])
+        while pos > end:
+            i += 1
+            start = end + 1
+            end += 1 + len(commands[i])
+        return start, end
+
+    def complete(self, line, pos):
+        cstart, cend = self.get_context(line, pos)
+        before = line[:cstart]
+        after = line[cend:]
+        cmdstring = line[cstart:cend]
+        cpos = pos - cstart
+
+        res = []
+        for ccmd, ccpos in self._commandcompleter.complete(cmdstring, cpos):
+            newtext = before + ccmd + after
+            newpos = pos + (ccpos - cpos)
+            res.append((newtext, newpos))
+        return res
diff --git a/alot/completion/commandname.py b/alot/completion/commandname.py
new file mode 100644
index 00000000..5c946eb6
--- /dev/null
+++ b/alot/completion/commandname.py
@@ -0,0 +1,26 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+
+import logging
+from alot import commands
+from .completer import Completer
+
+
+class CommandNameCompleter(Completer):
+    """Completes command names."""
+
+    def __init__(self, mode):
+        """
+        :param mode: mode identifier
+        :type mode: str
+        """
+        self.mode = mode
+
+    def complete(self, original, pos):
+        commandprefix = original[:pos]
+        logging.debug('original="%s" prefix="%s"', original, commandprefix)
+        cmdlist = commands.COMMANDS['global'].copy()
+        cmdlist.update(commands.COMMANDS[self.mode])
+        matching = [t for t in cmdlist if t.startswith(commandprefix)]
+        return [(t, len(t)) for t in matching]
diff --git a/alot/completion/completer.py b/alot/completion/completer.py
new file mode 100644
index 00000000..de15d312
--- /dev/null
+++ b/alot/completion/completer.py
@@ -0,0 +1,37 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+import abc
+
+
+class Completer:
+    """base class for completers"""
+
+    __metaclass__ = abc.ABCMeta
+
+    @abc.abstractmethod
+    def complete(self, original, pos):
+        """returns a list of completions and cursor positions for the
+        string original from position pos on.
+
+        :param original: the string to complete
+        :type original: str
+        :param pos: starting position to complete from
+        :type pos: int
+        :returns: pairs of completed string and cursor position in the
+                  new string
+        :rtype: list of (str, int)
+        :raises: :exc:`CompletionError`
+        """
+        pass
+
+    def relevant_part(self, original, pos, sep=' '):
+        """
+        calculates the subword in a `sep`-splitted list of substrings of
+        `original` that `pos` is ia.n
+        """
+        start = original.rfind(sep, 0, pos) + 1
+        end = original.find(sep, pos - 1)
+        if end == -1:
+            end = len(original)
+        return original[start:end], start, end, pos - start
diff --git a/alot/completion/contacts.py b/alot/completion/contacts.py
new file mode 100644
index 00000000..ae4e71cd
--- /dev/null
+++ b/alot/completion/contacts.py
@@ -0,0 +1,21 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+
+from .multipleselection import MultipleSelectionCompleter
+from .abooks import AbooksCompleter
+
+
+class ContactsCompleter(MultipleSelectionCompleter):
+    """completes contacts from given address books"""
+
+    def __init__(self, abooks, addressesonly=False):
+        """
+        :param abooks: used to look up email addresses
+        :type abooks: list of :class:`~alot.account.AddresBook`
+        :param addressesonly: only insert address, not the realname of the
+                              contact
+        :type addressesonly: bool
+        """
+        self._completer = AbooksCompleter(abooks, addressesonly=addressesonly)
+        self._separator = ', '
diff --git a/alot/completion/cryptokey.py b/alot/completion/cryptokey.py
new file mode 100644
index 00000000..0631eee3
--- /dev/null
+++ b/alot/completion/cryptokey.py
@@ -0,0 +1,24 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+
+from alot import crypto
+from .stringlist import StringlistCompleter
+
+
+class CryptoKeyCompleter(StringlistCompleter):
+    """completion for gpg keys"""
+
+    def __init__(self, private=False):
+        """
+        :param private: return private keys
+        :type private: bool
+        """
+        keys = crypto.list_keys(private=private)
+        resultlist = []
+        for k in keys:
+            for s in k.subkeys:
+                resultlist.append(s.keyid)
+            for u in k.uids:
+                resultlist.append(u.email)
+        StringlistCompleter.__init__(self, resultlist, match_anywhere=True)
diff --git a/alot/completion/multipleselection.py b/alot/completion/multipleselection.py
new file mode 100644
index 00000000..45de5a28
--- /dev/null
+++ b/alot/completion/multipleselection.py
@@ -0,0 +1,48 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+
+
+from .completer import Completer
+
+
+class MultipleSelectionCompleter(Completer):
+    """
+    Meta-Completer that turns any Completer into one that deals with a list of
+    completion strings using the wrapped Completer.
+    This allows for example to easily construct a completer for comma separated
+    recipient-lists using a :class:`ContactsCompleter`.
+    """
+
+    def __init__(self, completer, separator=', '):
+        """
+        :param completer: completer to use for individual substrings
+        :type completer: Completer
+        :param separator: separator used to split the completion string into
+                          substrings to be fed to `completer`.
+        :type separator: str
+        """
+        self._completer = completer
+        self._separator = separator
+
+    def relevant_part(self, original, pos):
+        """Calculate the subword of `original` that `pos` is in."""
+        start = original.rfind(self._separator, 0, pos)
+        if start == -1:
+            start = 0
+        else:
+            start = start + len(self._separator)
+        end = original.find(self._separator, pos - 1)
+        if end == -1:
+            end = len(original)
+        return original[start:end], start, end, pos - start
+
+    def complete(self, original, pos):
+        mypart, start, end, mypos = self.relevant_part(original, pos)
+        res = []
+        for c, _ in self._completer.complete(mypart, mypos):
+            newprefix = original[:start] + c
+            if not original[end:].startswith(self._separator):
+                newprefix += self._separator
+            res.append((newprefix + original[end:], len(newprefix)))
+        return res
diff --git a/alot/completion/namedquery.py b/alot/completion/namedquery.py
new file mode 100644
index 00000000..bcad5d2c
--- /dev/null
+++ b/alot/completion/namedquery.py
@@ -0,0 +1,18 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+
+from .stringlist import StringlistCompleter
+
+
+class NamedQueryCompleter(StringlistCompleter):
+    """Complete the name of a named query string."""
+
+    def __init__(self, dbman):
+        """
+        :param dbman: used to look up named query strings in the DB
+        :type dbman: :class:`~alot.db.DBManager`
+        """
+        # mapping of alias to query string (dict str -> str)
+        nqueries = dbman.get_named_queries()
+        StringlistCompleter.__init__(self, list(nqueries))
diff --git a/alot/completion/path.py b/alot/completion/path.py
new file mode 100644
index 00000000..c05f42df
--- /dev/null
+++ b/alot/completion/path.py
@@ -0,0 +1,43 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+
+import glob
+import os
+from .completer import Completer
+
+
+class PathCompleter(Completer):
+    """Completes for file system paths."""
+
+    def complete(self, original, pos):
+        if not original:
+            return [('~/', 2)]
+        prefix = os.path.expanduser(original[:pos])
+
+        def escape(path):
+            """Escape all backslashes and spaces in path with a backslash.
+
+            :param path: the path to escape
+            :type path: str
+            :returns: the escaped path
+            :rtype: str
+            """
+            return path.replace('\\', '\\\\').replace(' ', r'\ ')
+
+        def deescape(escaped_path):
+            """Remove escaping backslashes in front of spaces and backslashes.
+
+            :param escaped_path: a path potentially with escaped spaces and
+                backslashs
+            :type escaped_path: str
+            :returns: the actual path
+            :rtype: str
+            """
+            return escaped_path.replace('\\ ', ' ').replace('\\\\', '\\')
+
+        def prep(path):
+            escaped_path = escape(path)
+            return escaped_path, len(escaped_path)
+
+        return [prep(g) for g in glob.glob(deescape(prefix) + '*')]
diff --git a/alot/completion/query.py b/alot/completion/query.py
new file mode 100644
index 00000000..42ea64a0
--- /dev/null
+++ b/alot/completion/query.py
@@ -0,0 +1,57 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+
+import re
+
+from alot.settings.const import settings
+from .completer import Completer
+from .abooks import AbooksCompleter
+from .tag import TagCompleter
+from .namedquery import NamedQueryCompleter
+
+
+class QueryCompleter(Completer):
+    """completion for a notmuch query string"""
+    def __init__(self, dbman):
+        """
+        :param dbman: used to look up available tagstrings
+        :type dbman: :class:`~alot.db.DBManager`
+        """
+        self.dbman = dbman
+        abooks = settings.get_addressbooks()
+        self._abookscompleter = AbooksCompleter(abooks, addressesonly=True)
+        self._tagcompleter = TagCompleter(dbman)
+        self._nquerycompleter = NamedQueryCompleter(dbman)
+        self.keywords = ['tag', 'from', 'to', 'subject', 'attachment',
+                         'is', 'id', 'thread', 'folder', 'query']
+
+    def complete(self, original, pos):
+        mypart, start, end, mypos = self.relevant_part(original, pos)
+        myprefix = mypart[:mypos]
+        m = re.search(r'(tag|is|to|from|query):(\w*)', myprefix)
+        if m:
+            cmd, _ = m.groups()
+            cmdlen = len(cmd) + 1  # length of the keyword part including colon
+            if cmd in ['to', 'from']:
+                localres = self._abookscompleter.complete(mypart[cmdlen:],
+                                                          mypos - cmdlen)
+            elif cmd in ['query']:
+                localres = self._nquerycompleter.complete(mypart[cmdlen:],
+                                                          mypos - cmdlen)
+            else:
+                localres = self._tagcompleter.complete(mypart[cmdlen:],
+                                                       mypos - cmdlen)
+            resultlist = []
+            for ltxt, lpos in localres:
+                newtext = original[:start] + cmd + ':' + ltxt + original[end:]
+                newpos = start + len(cmd) + 1 + lpos
+                resultlist.append((newtext, newpos))
+            return resultlist
+        else:
+            matched = (t for t in self.keywords if t.startswith(myprefix))
+            resultlist = []
+            for keyword in matched:
+                newprefix = original[:start] + keyword + ':'
+                resultlist.append((newprefix + original[end:], len(newprefix)))
+            return resultlist
diff --git a/alot/completion/stringlist.py b/alot/completion/stringlist.py
new file mode 100644
index 00000000..9d7fa3d3
--- /dev/null
+++ b/alot/completion/stringlist.py
@@ -0,0 +1,32 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+import re
+
+from .completer import Completer
+
+
+class StringlistCompleter(Completer):
+    """Completer for a fixed list of strings."""
+
+    def __init__(self, resultlist, ignorecase=True, match_anywhere=False):
+        """
+        :param resultlist: strings used for completion
+        :type resultlist: list of str
+        :param liberal: match case insensitive and not prefix-only
+        :type liberal: bool
+        """
+        self.resultlist = resultlist
+        self.flags = re.IGNORECASE if ignorecase else 0
+        self.match_anywhere = match_anywhere
+
+    def complete(self, original, pos):
+        pref = original[:pos]
+
+        re_prefix = '.*' if self.match_anywhere else ''
+
+        def match(s, m):
+            r = '{}{}.*'.format(re_prefix, re.escape(m))
+            return re.match(r, s, flags=self.flags) is not None
+
+        return [(a, len(a)) for a in self.resultlist if match(a, pref)]
diff --git a/alot/completion/tag.py b/alot/completion/tag.py
new file mode 100644
index 00000000..fd6ed119
--- /dev/null
+++ b/alot/completion/tag.py
@@ -0,0 +1,17 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+
+from .stringlist import StringlistCompleter
+
+
+class TagCompleter(StringlistCompleter):
+    """Complete a tagstring."""
+
+    def __init__(self, dbman):
+        """
+        :param dbman: used to look up available tagstrings
+        :type dbman: :class:`~alot.db.DBManager`
+        """
+        resultlist = dbman.get_all_tags()
+        StringlistCompleter.__init__(self, resultlist)
diff --git a/alot/completion/tags.py b/alot/completion/tags.py
new file mode 100644
index 00000000..b151e6f5
--- /dev/null
+++ b/alot/completion/tags.py
@@ -0,0 +1,18 @@
+# Copyright (C) 2011-2019  Patrick Totzke <patricktotzke@gmail.com>
+# This file is released under the GNU GPL, version 3 or a later revision.
+# For further details see the COPYING file
+
+from .multipleselection import MultipleSelectionCompleter
+from .tag import TagCompleter
+
+
+class TagsCompleter(MultipleSelectionCompleter):
+    """Complete a comma separated list of tagstrings."""
+
+    def __init__(self, dbman):
+        """
+        :param dbman: used to look up available tagstrings
+        :type dbman: :class:`~alot.db.DBManager`
+        """
+        self._completer = TagCompleter(dbman)
+        self._separator = ','