#!/usr/bin/env python
# encoding: utf-8

"""Contains the SnippetManager facade used by all Vim Functions."""

from collections import defaultdict
from functools import wraps
import os
import platform
import traceback
import sys
import vim
import re
from contextlib import contextmanager

from UltiSnips import _vim
from UltiSnips._diff import diff, guess_edit
from UltiSnips.compatibility import as_unicode
from UltiSnips.position import Position
from UltiSnips.snippet.definition import UltiSnipsSnippetDefinition
from UltiSnips.snippet.source import UltiSnipsFileSource, SnipMateFileSource, \
    find_all_snippet_files, find_snippet_files, AddedSnippetsSource
from UltiSnips.text import escape
from UltiSnips.vim_state import VimState, VisualContentPreserver
from UltiSnips.buffer_proxy import use_proxy_buffer, suspend_proxy_edits


def _ask_user(a, formatted):
    """Asks the user using inputlist() and returns the selected element or
    None."""
    try:
        rv = _vim.eval('inputlist(%s)' % _vim.escape(formatted))
        if rv is None or rv == '0':
            return None
        rv = int(rv)
        if rv > len(a):
            rv = len(a)
        return a[rv - 1]
    except _vim.error:
        # Likely "invalid expression", but might be translated. We have no way
        # of knowing the exact error, therefore, we ignore all errors silently.
        return None
    except KeyboardInterrupt:
        return None


def _ask_snippets(snippets):
    """Given a list of snippets, ask the user which one they want to use, and
    return it."""
    display = [as_unicode('%i: %s (%s)') % (i + 1, escape(s.description, '\\'),
                                            escape(s.location, '\\')) for i, s in enumerate(snippets)]
    return _ask_user(snippets, display)


def err_to_scratch_buffer(func):
    """Decorator that will catch any Exception that 'func' throws and displays
    it in a new Vim scratch buffer."""
    @wraps(func)
    def wrapper(self, *args, **kwds):
        try:
            return func(self, *args, **kwds)
        except Exception as e:  # pylint: disable=bare-except
            msg = \
                """An error occured. This is either a bug in UltiSnips or a bug in a
snippet definition. If you think this is a bug, please report it to
https://github.com/SirVer/ultisnips/issues/new.

Following is the full stack trace:
"""

            msg += traceback.format_exc()
            if hasattr(e, 'snippet_info'):
                msg += "\nSnippet, caused error:\n"
                msg += re.sub(
                    '^(?=\S)', '  ', e.snippet_info, flags=re.MULTILINE
                )
            # snippet_code comes from _python_code.py, it's set manually for
            # providing error message with stacktrace of failed python code
            # inside of the snippet.
            if hasattr(e, 'snippet_code'):
                _, _, tb = sys.exc_info()
                tb_top = traceback.extract_tb(tb)[-1]
                msg += "\nExecuted snippet code:\n"
                lines = e.snippet_code.split("\n")
                for number, line in enumerate(lines, 1):
                    msg += str(number).rjust(3)
                    prefix = "   " if line else ""
                    if tb_top[1] == number:
                        prefix = " > "
                    msg += prefix + line + "\n"

            # Vim sends no WinLeave msg here.
            self._leaving_buffer()  # pylint:disable=protected-access
            _vim.new_scratch_buffer(msg)
    return wrapper


# TODO(sirver): This class is still too long. It should only contain public
# facing methods, most of the private methods should be moved outside of it.
class SnippetManager(object):

    """The main entry point for all UltiSnips functionality.

    All Vim functions call methods in this class.

    """

    def __init__(self, expand_trigger, forward_trigger, backward_trigger):
        self.expand_trigger = expand_trigger
        self.forward_trigger = forward_trigger
        self.backward_trigger = backward_trigger
        self._inner_state_up = False
        self._supertab_keys = None

        self._csnippets = []
        self._buffer_filetypes = defaultdict(lambda: ['all'])

        self._vstate = VimState()
        self._visual_content = VisualContentPreserver()

        self._snippet_sources = []

        self._snip_expanded_in_action = False
        self._inside_action = False

        self._last_inserted_char = ''

        self._added_snippets_source = AddedSnippetsSource()
        self.register_snippet_source('ultisnips_files', UltiSnipsFileSource())
        self.register_snippet_source('added', self._added_snippets_source)

        enable_snipmate = '1'
        if _vim.eval("exists('g:UltiSnipsEnableSnipMate')") == '1':
            enable_snipmate = _vim.eval('g:UltiSnipsEnableSnipMate')
        if enable_snipmate == '1':
            self.register_snippet_source('snipmate_files',
                                         SnipMateFileSource())

        self._reinit()

    @err_to_scratch_buffer
    def jump_forwards(self):
        """Jumps to the next tabstop."""
        _vim.command('let g:ulti_jump_forwards_res = 1')
        _vim.command('let &undolevels = &undolevels')
        if not self._jump():
            _vim.command('let g:ulti_jump_forwards_res = 0')
            return self._handle_failure(self.forward_trigger)

    @err_to_scratch_buffer
    def jump_backwards(self):
        """Jumps to the previous tabstop."""
        _vim.command('let g:ulti_jump_backwards_res = 1')
        _vim.command('let &undolevels = &undolevels')
        if not self._jump(True):
            _vim.command('let g:ulti_jump_backwards_res = 0')
            return self._handle_failure(self.backward_trigger)

    @err_to_scratch_buffer
    def expand(self):
        """Try to expand a snippet at the current position."""
        _vim.command('let g:ulti_expand_res = 1')
        if not self._try_expand():
            _vim.command('let g:ulti_expand_res = 0')
            self._handle_failure(self.expand_trigger)

    @err_to_scratch_buffer
    def expand_or_jump(self):
        """This function is used for people who wants to have the same trigger
        for expansion and forward jumping.

        It first tries to expand a snippet, if this fails, it tries to
        jump forward.

        """
        _vim.command('let g:ulti_expand_or_jump_res = 1')
        rv = self._try_expand()
        if not rv:
            _vim.command('let g:ulti_expand_or_jump_res = 2')
            rv = self._jump()
        if not rv:
            _vim.command('let g:ulti_expand_or_jump_res = 0')
            self._handle_failure(self.expand_trigger)

    @err_to_scratch_buffer
    def snippets_in_current_scope(self):
        """Returns the snippets that could be expanded to Vim as a global
        variable."""
        before = _vim.buf.line_till_cursor
        snippets = self._snips(before, True)

        # Sort snippets alphabetically
        snippets.sort(key=lambda x: x.trigger)
        for snip in snippets:
            description = snip.description[snip.description.find(snip.trigger) +
                                           len(snip.trigger) + 2:]

            key = as_unicode(snip.trigger)
            description = as_unicode(description)

            # remove surrounding "" or '' in snippet description if it exists
            if len(description) > 2:
                if (description[0] == description[-1] and
                        description[0] in "'\""):
                    description = description[1:-1]

            _vim.command(as_unicode(
                "let g:current_ulti_dict['{key}'] = '{val}'").format(
                    key=key.replace("'", "''"),
                    val=description.replace("'", "''")))

    @err_to_scratch_buffer
    def list_snippets(self):
        """Shows the snippets that could be expanded to the User and let her
        select one."""
        before = _vim.buf.line_till_cursor
        snippets = self._snips(before, True)

        if len(snippets) == 0:
            self._handle_failure(self.backward_trigger)
            return True

        # Sort snippets alphabetically
        snippets.sort(key=lambda x: x.trigger)

        if not snippets:
            return True

        snippet = _ask_snippets(snippets)
        if not snippet:
            return True

        self._do_snippet(snippet, before)

        return True

    @err_to_scratch_buffer
    def add_snippet(self, trigger, value, description,
                    options, ft='all', priority=0, context=None, actions={}):
        """Add a snippet to the list of known snippets of the given 'ft'."""
        self._added_snippets_source.add_snippet(ft,
            UltiSnipsSnippetDefinition(priority, trigger, value,
                                       description, options, {}, 'added',
                                       context, actions))

    @err_to_scratch_buffer
    def expand_anon(
        self, value, trigger='', description='', options='',
        context=None, actions={}
    ):
        """Expand an anonymous snippet right here."""
        before = _vim.buf.line_till_cursor
        snip = UltiSnipsSnippetDefinition(0, trigger, value, description,
                                          options, {}, '', context, actions)

        if not trigger or snip.matches(before):
            self._do_snippet(snip, before)
            return True
        else:
            return False

    def register_snippet_source(self, name, snippet_source):
        """Registers a new 'snippet_source' with the given 'name'.

        The given class must be an instance of SnippetSource. This
        source will be queried for snippets.

        """
        self._snippet_sources.append((name, snippet_source))

    def unregister_snippet_source(self, name):
        """Unregister the source with the given 'name'.

        Does nothing if it is not registered.

        """
        for index, (source_name, _) in enumerate(self._snippet_sources):
            if name == source_name:
                self._snippet_sources = self._snippet_sources[:index] + \
                    self._snippet_sources[index + 1:]
                break

    def reset_buffer_filetypes(self):
        """Reset the filetypes for the current buffer."""
        if _vim.buf.number in self._buffer_filetypes:
            del self._buffer_filetypes[_vim.buf.number]

    def add_buffer_filetypes(self, ft):
        """Checks for changes in the list of snippet files or the contents of
        the snippet files and reloads them if necessary."""
        buf_fts = self._buffer_filetypes[_vim.buf.number]
        idx = -1
        for ft in ft.split('.'):
            ft = ft.strip()
            if not ft:
                continue
            try:
                idx = buf_fts.index(ft)
            except ValueError:
                self._buffer_filetypes[_vim.buf.number].insert(idx + 1, ft)
                idx += 1

    @err_to_scratch_buffer
    def _cursor_moved(self):
        """Called whenever the cursor moved."""
        if not self._csnippets and self._inner_state_up:
            self._teardown_inner_state()
        self._vstate.remember_position()
        if _vim.eval('mode()') not in 'in':
            return


        if self._ignore_movements:
            self._ignore_movements = False
            return

        if self._csnippets:
            cstart = self._csnippets[0].start.line
            cend = self._csnippets[0].end.line + \
                self._vstate.diff_in_buffer_length
            ct = _vim.buf[cstart:cend + 1]
            lt = self._vstate.remembered_buffer
            pos = _vim.buf.cursor

            lt_span = [0, len(lt)]
            ct_span = [0, len(ct)]
            initial_line = cstart

            # Cut down on lines searched for changes. Start from behind and
            # remove all equal lines. Then do the same from the front.
            if lt and ct:
                while (lt[lt_span[1] - 1] == ct[ct_span[1] - 1] and
                        self._vstate.ppos.line < initial_line + lt_span[1] - 1 and
                        pos.line < initial_line + ct_span[1] - 1 and
                        (lt_span[0] < lt_span[1]) and
                        (ct_span[0] < ct_span[1])):
                    ct_span[1] -= 1
                    lt_span[1] -= 1
                while (lt_span[0] < lt_span[1] and
                       ct_span[0] < ct_span[1] and
                       lt[lt_span[0]] == ct[ct_span[0]] and
                       self._vstate.ppos.line >= initial_line and
                       pos.line >= initial_line):
                    ct_span[0] += 1
                    lt_span[0] += 1
                    initial_line += 1
            ct_span[0] = max(0, ct_span[0] - 1)
            lt_span[0] = max(0, lt_span[0] - 1)
            initial_line = max(cstart, initial_line - 1)

            lt = lt[lt_span[0]:lt_span[1]]
            ct = ct[ct_span[0]:ct_span[1]]

            try:
                rv, es = guess_edit(initial_line, lt, ct, self._vstate)
                if not rv:
                    lt = '\n'.join(lt)
                    ct = '\n'.join(ct)
                    es = diff(lt, ct, initial_line)
                self._csnippets[0].replay_user_edits(es, self._ctab)
            except IndexError:
                # Rather do nothing than throwing an error. It will be correct
                # most of the time
                pass

        self._check_if_still_inside_snippet()
        if self._csnippets:
            self._csnippets[0].update_textobjects()
            self._vstate.remember_buffer(self._csnippets[0])

    def _setup_inner_state(self):
        """Map keys and create autocommands that should only be defined when a
        snippet is active."""
        if self._inner_state_up:
            return
        if self.expand_trigger != self.forward_trigger:
            _vim.command('inoremap <buffer> <silent> ' + self.forward_trigger +
                         ' <C-R>=UltiSnips#JumpForwards()<cr>')
            _vim.command('snoremap <buffer> <silent> ' + self.forward_trigger +
                         ' <Esc>:call UltiSnips#JumpForwards()<cr>')
        _vim.command('inoremap <buffer> <silent> ' + self.backward_trigger +
                     ' <C-R>=UltiSnips#JumpBackwards()<cr>')
        _vim.command('snoremap <buffer> <silent> ' + self.backward_trigger +
                     ' <Esc>:call UltiSnips#JumpBackwards()<cr>')

        # Setup the autogroups.
        _vim.command('augroup UltiSnips')
        _vim.command('autocmd!')
        _vim.command('autocmd CursorMovedI * call UltiSnips#CursorMoved()')
        _vim.command('autocmd CursorMoved * call UltiSnips#CursorMoved()')

        _vim.command(
            'autocmd InsertLeave * call UltiSnips#LeavingInsertMode()')

        _vim.command('autocmd BufLeave * call UltiSnips#LeavingBuffer()')
        _vim.command(
            'autocmd CmdwinEnter * call UltiSnips#LeavingBuffer()')
        _vim.command(
            'autocmd CmdwinLeave * call UltiSnips#LeavingBuffer()')

        # Also exit the snippet when we enter a unite complete buffer.
        _vim.command('autocmd Filetype unite call UltiSnips#LeavingBuffer()')

        _vim.command('augroup END')

        _vim.command('silent doautocmd <nomodeline> User UltiSnipsEnterFirstSnippet')
        self._inner_state_up = True

    def _teardown_inner_state(self):
        """Reverse _setup_inner_state."""
        if not self._inner_state_up:
            return
        try:
            _vim.command('silent doautocmd <nomodeline> User UltiSnipsExitLastSnippet')
            if self.expand_trigger != self.forward_trigger:
                _vim.command('iunmap <buffer> %s' % self.forward_trigger)
                _vim.command('sunmap <buffer> %s' % self.forward_trigger)
            _vim.command('iunmap <buffer> %s' % self.backward_trigger)
            _vim.command('sunmap <buffer> %s' % self.backward_trigger)
            _vim.command('augroup UltiSnips')
            _vim.command('autocmd!')
            _vim.command('augroup END')
            self._inner_state_up = False
        except _vim.error:
            # This happens when a preview window was opened. This issues
            # CursorMoved, but not BufLeave. We have no way to unmap, until we
            # are back in our buffer
            pass

    @err_to_scratch_buffer
    def _save_last_visual_selection(self):
        """This is called when the expand trigger is pressed in visual mode.
        Our job is to remember everything between '< and '> and pass it on to.

        ${VISUAL} in case it will be needed.

        """
        self._visual_content.conserve()

    def _leaving_buffer(self):
        """Called when the user switches tabs/windows/buffers.

        It basically means that all snippets must be properly
        terminated.

        """
        while len(self._csnippets):
            self._current_snippet_is_done()
        self._reinit()

    def _reinit(self):
        """Resets transient state."""
        self._ctab = None
        self._ignore_movements = False

    def _check_if_still_inside_snippet(self):
        """Checks if the cursor is outside of the current snippet."""
        if self._cs and (
            not self._cs.start <= _vim.buf.cursor <= self._cs.end
        ):
            self._current_snippet_is_done()
            self._reinit()
            self._check_if_still_inside_snippet()

    def _current_snippet_is_done(self):
        """The current snippet should be terminated."""
        self._csnippets.pop()
        if not self._csnippets:
            self._teardown_inner_state()

    def _jump(self, backwards=False):
        # we need to set 'onemore' there, because of limitations of the vim
        # API regarding cursor movements; without that test
        # 'CanExpandAnonSnippetInJumpActionWhileSelected' will fail
        with _vim.toggle_opt('ve', 'onemore'):
            """Helper method that does the actual jump."""
            jumped = False

            # We need to remember current snippets stack here because of
            # post-jump action on the last tabstop should be able to access
            # snippet instance which is ended just now.
            stack_for_post_jump = self._csnippets[:]

            # If next tab has length 1 and the distance between itself and
            # self._ctab is 1 then there is 1 less CursorMove events.  We
            # cannot ignore next movement in such case.
            ntab_short_and_near = False

            if self._cs:
                snippet_for_action = self._cs
            elif stack_for_post_jump:
                snippet_for_action = stack_for_post_jump[-1]
            else:
                snippet_for_action = None

            if self._cs:
                ntab = self._cs.select_next_tab(backwards)
                if ntab:
                    if self._cs.snippet.has_option('s'):
                        lineno = _vim.buf.cursor.line
                        _vim.buf[lineno] = _vim.buf[lineno].rstrip()
                    _vim.select(ntab.start, ntab.end)
                    jumped = True
                    if (self._ctab is not None
                            and ntab.start - self._ctab.end == Position(0, 1)
                            and ntab.end - ntab.start == Position(0, 1)):
                        ntab_short_and_near = True
                    if ntab.number == 0:
                        self._current_snippet_is_done()
                    self._ctab = ntab
                else:
                    # This really shouldn't happen, because a snippet should
                    # have been popped when its final tabstop was used.
                    # Cleanup by removing current snippet and recursing.
                    self._current_snippet_is_done()
                    jumped = self._jump(backwards)
            if jumped:
                self._vstate.remember_position()
                self._vstate.remember_unnamed_register(self._ctab.current_text)
                if not ntab_short_and_near:
                    self._ignore_movements = True

            if len(stack_for_post_jump) > 0 and ntab is not None:
                with use_proxy_buffer(stack_for_post_jump, self._vstate):
                    snippet_for_action.snippet.do_post_jump(
                        ntab.number,
                        -1 if backwards else 1,
                        stack_for_post_jump,
                        snippet_for_action
                    )

        return jumped

    def _leaving_insert_mode(self):
        """Called whenever we leave the insert mode."""
        self._vstate.restore_unnamed_register()

    def _handle_failure(self, trigger):
        """Mainly make sure that we play well with SuperTab."""
        if trigger.lower() == '<tab>':
            feedkey = '\\' + trigger
        elif trigger.lower() == '<s-tab>':
            feedkey = '\\' + trigger
        else:
            feedkey = None
        mode = 'n'
        if not self._supertab_keys:
            if _vim.eval("exists('g:SuperTabMappingForward')") != '0':
                self._supertab_keys = (
                    _vim.eval('g:SuperTabMappingForward'),
                    _vim.eval('g:SuperTabMappingBackward'),
                )
            else:
                self._supertab_keys = ['', '']

        for idx, sttrig in enumerate(self._supertab_keys):
            if trigger.lower() == sttrig.lower():
                if idx == 0:
                    feedkey = r"\<Plug>SuperTabForward"
                    mode = 'n'
                elif idx == 1:
                    feedkey = r"\<Plug>SuperTabBackward"
                    mode = 'p'
                # Use remap mode so SuperTab mappings will be invoked.
                break

        if (feedkey == r"\<Plug>SuperTabForward" or
                feedkey == r"\<Plug>SuperTabBackward"):
            _vim.command('return SuperTab(%s)' % _vim.escape(mode))
        elif feedkey:
            _vim.command('return %s' % _vim.escape(feedkey))

    def _snips(self, before, partial, autotrigger_only=False):
        """Returns all the snippets for the given text before the cursor.

        If partial is True, then get also return partial matches.

        """
        filetypes = self._buffer_filetypes[_vim.buf.number][::-1]
        matching_snippets = defaultdict(list)
        clear_priority = None
        cleared = {}
        for _, source in self._snippet_sources:
            source.ensure(filetypes, cached=autotrigger_only)

        # Collect cleared information from sources.
        for _, source in self._snippet_sources:
            sclear_priority = source.get_clear_priority(filetypes)
            if sclear_priority is not None and (clear_priority is None
                                                or sclear_priority > clear_priority):
                clear_priority = sclear_priority
            for key, value in source.get_cleared(filetypes).items():
                if key not in cleared or value > cleared[key]:
                    cleared[key] = value

        for _, source in self._snippet_sources:
            possible_snippets = source.get_snippets(
                filetypes,
                before,
                partial,
                autotrigger_only
            )

            for snippet in possible_snippets:
                if ((clear_priority is None or snippet.priority > clear_priority)
                        and (snippet.trigger not in cleared or
                             snippet.priority > cleared[snippet.trigger])):
                    matching_snippets[snippet.trigger].append(snippet)
        if not matching_snippets:
            return []

        # Now filter duplicates and only keep the one with the highest
        # priority.
        snippets = []
        for snippets_with_trigger in matching_snippets.values():
            highest_priority = max(s.priority for s in snippets_with_trigger)
            snippets.extend(s for s in snippets_with_trigger
                            if s.priority == highest_priority)

        # For partial matches we are done, but if we want to expand a snippet,
        # we have to go over them again and only keep those with the maximum
        # priority.
        if partial:
            return snippets

        highest_priority = max(s.priority for s in snippets)
        return [s for s in snippets if s.priority == highest_priority]

    def _do_snippet(self, snippet, before):
        """Expands the given snippet, and handles everything that needs to be
        done with it."""
        self._setup_inner_state()

        self._snip_expanded_in_action = False

        # Adjust before, maybe the trigger is not the complete word
        text_before = before
        if snippet.matched:
            text_before = before[:-len(snippet.matched)]

        with use_proxy_buffer(self._csnippets, self._vstate):
            with self._action_context():
                cursor_set_in_action = snippet.do_pre_expand(
                    self._visual_content.text,
                    self._csnippets
                )

        if cursor_set_in_action:
            text_before = _vim.buf.line_till_cursor
            before = _vim.buf.line_till_cursor

        with suspend_proxy_edits():
            if self._cs:
                start = Position(_vim.buf.cursor.line, len(text_before))
                end = Position(_vim.buf.cursor.line, len(before))

                # If cursor is set in pre-action, then action was modified
                # cursor line, in that case we do not need to do any edits, it
                # can break snippet
                if not cursor_set_in_action:
                    # It could be that our trigger contains the content of
                    # TextObjects in our containing snippet. If this is indeed
                    # the case, we have to make sure that those are properly
                    # killed. We do this by pretending that the user deleted
                    # and retyped the text that our trigger matched.
                    edit_actions = [
                        ('D', start.line, start.col, snippet.matched),
                        ('I', start.line, start.col, snippet.matched),
                    ]
                    self._csnippets[0].replay_user_edits(edit_actions)

                si = snippet.launch(text_before, self._visual_content,
                    self._cs.find_parent_for_new_to(start),
                    start, end
                )
            else:
                start = Position(_vim.buf.cursor.line, len(text_before))
                end = Position(_vim.buf.cursor.line, len(before))
                si = snippet.launch(text_before, self._visual_content,
                                    None, start, end)

            self._visual_content.reset()
            self._csnippets.append(si)

            si.update_textobjects()

            with use_proxy_buffer(self._csnippets, self._vstate):
                with self._action_context():
                    snippet.do_post_expand(
                        si._start, si._end, self._csnippets
                    )

            self._vstate.remember_buffer(self._csnippets[0])

            if not self._snip_expanded_in_action:
                self._jump()
            elif self._cs.current_text != '':
                self._jump()
            else:
                self._current_snippet_is_done()

            if self._inside_action:
                self._snip_expanded_in_action = True


    def _try_expand(self, autotrigger_only=False):
        """Try to expand a snippet in the current place."""
        before = _vim.buf.line_till_cursor
        snippets = self._snips(before, False, autotrigger_only)
        if snippets:
            # prefer snippets with context if any
            snippets_with_context = [s for s in snippets if s.context]
            if snippets_with_context:
                snippets = snippets_with_context
        if not snippets:
            # No snippet found
            return False
        _vim.command('let &undolevels = &undolevels')
        if len(snippets) == 1:
            snippet = snippets[0]
        else:
            snippet = _ask_snippets(snippets)
            if not snippet:
                return True
        self._do_snippet(snippet, before)
        _vim.command('let &undolevels = &undolevels')
        return True

    @property
    def _cs(self):
        """The current snippet or None."""
        if not len(self._csnippets):
            return None
        return self._csnippets[-1]

    def _file_to_edit(self, requested_ft, bang):  # pylint: disable=no-self-use
        """Returns a file to be edited for the given requested_ft.

        If 'bang' is
        empty only private files in g:UltiSnipsSnippetsDir are considered,
        otherwise all files are considered and the user gets to choose.

        """
        # This method is not using self, but is called by UltiSnips.vim and is
        # therefore in this class because it is the facade to Vim.
        potentials = set()

        if _vim.eval("exists('g:UltiSnipsSnippetsDir')") == '1':
            snippet_dir = _vim.eval('g:UltiSnipsSnippetsDir')
        else:
            home = _vim.eval('$HOME')
            if platform.system() == 'Windows':
                snippet_dir = os.path.join(home, 'vimfiles', 'UltiSnips')
            elif _vim.eval("has('nvim')") == '1':
                xdg_home_config = _vim.eval('$XDG_CONFIG_HOME') or os.path.join(home, ".config")
                snippet_dir = os.path.join(xdg_home_config, 'nvim', 'UltiSnips')
            else:
                snippet_dir = os.path.join(home, '.vim', 'UltiSnips')

        filetypes = []
        if requested_ft:
            filetypes.append(requested_ft)
        else:
            if bang:
                filetypes.extend(self._buffer_filetypes[_vim.buf.number])
            else:
                filetypes.append(self._buffer_filetypes[_vim.buf.number][0])

        for ft in filetypes:
            potentials.update(find_snippet_files(ft, snippet_dir))
            potentials.add(os.path.join(snippet_dir,
                                        ft + '.snippets'))
            if bang:
                potentials.update(find_all_snippet_files(ft))

        potentials = set(os.path.realpath(os.path.expanduser(p))
                         for p in potentials)

        if len(potentials) > 1:
            files = sorted(potentials)
            formatted = [as_unicode('%i: %s') % (i, escape(fn, '\\')) for
                         i, fn in enumerate(files, 1)]
            file_to_edit = _ask_user(files, formatted)
            if file_to_edit is None:
                return ''
        else:
            file_to_edit = potentials.pop()

        dirname = os.path.dirname(file_to_edit)
        if not os.path.exists(dirname):
            os.makedirs(dirname)
        return file_to_edit

    @contextmanager
    def _action_context(self):
        try:
            old_flag = self._inside_action
            self._inside_action = True
            yield
        finally:
            self._inside_action = old_flag

    @err_to_scratch_buffer
    def _track_change(self):
        inserted_char = _vim.eval('v:char')
        try:
            if inserted_char == '':
                before = _vim.buf.line_till_cursor
                if before and before[-1] == self._last_inserted_char:
                    self._try_expand(autotrigger_only=True)
        finally:
            self._last_inserted_char = inserted_char


UltiSnips_Manager = SnippetManager(  # pylint:disable=invalid-name
    vim.eval('g:UltiSnipsExpandTrigger'),
    vim.eval('g:UltiSnipsJumpForwardTrigger'),
    vim.eval('g:UltiSnipsJumpBackwardTrigger'))