#!/usr/bin/env python3
# encoding: utf-8

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

from collections import defaultdict
from contextlib import contextmanager
import os
from typing import Set
from pathlib import Path
import vim

from UltiSnips import vim_helper
from UltiSnips import err_to_scratch_buffer
from UltiSnips.diff import diff, guess_edit
from UltiSnips.position import Position, JumpDirection
from UltiSnips.snippet.definition import UltiSnipsSnippetDefinition
from UltiSnips.snippet.source import (
    AddedSnippetsSource,
    SnipMateFileSource,
    UltiSnipsFileSource,
    find_all_snippet_directories,
    find_all_snippet_files,
    find_snippet_files,
)
from UltiSnips.snippet.source.file.common import (
    normalize_file_path,
)
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_helper.eval("inputlist(%s)" % vim_helper.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_helper.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 _show_user_warning(msg):
    """Shows a Vim warning message to the user."""
    vim_helper.command("echohl WarningMsg")
    vim_helper.command('echom "%s"' % msg.replace('"', '\\"'))
    vim_helper.command("echohl None")


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


def _select_and_create_file_to_edit(potentials: Set[str]) -> str:
    assert len(potentials) >= 1

    file_to_edit = ""
    if len(potentials) > 1:
        files = sorted(potentials)
        exists = [os.path.exists(f) for f in files]
        formatted = [
            "%s %i: %s" % ("*" if exists else " ", i, escape(fn, "\\"))
            for i, (fn, exists) in enumerate(zip(files, exists), 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


def _get_potential_snippet_filenames_to_edit(
    snippet_dir: str, filetypes: str
) -> Set[str]:
    potentials = set()
    for ft in filetypes:
        ft_snippets_files = find_snippet_files(ft, snippet_dir)
        potentials.update(ft_snippets_files)
        if not ft_snippets_files:
            # If there is no snippet file yet, we just default to `ft.snippets`.
            fpath = os.path.join(snippet_dir, ft + ".snippets")
            fpath = normalize_file_path(fpath)
            potentials.add(fpath)
    return potentials


# 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:

    """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._active_snippets = []
        self._added_buffer_filetypes = defaultdict(lambda: [])

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

        self._snippet_sources = []

        self._snip_expanded_in_action = False
        self._inside_action = False

        self._last_change = ("", Position(-1, -1))

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

        self._should_update_textobjects = False
        self._should_reset_visual = False

        self._reinit()

    @err_to_scratch_buffer.wrap
    def jump_forwards(self):
        """Jumps to the next tabstop."""
        vim_helper.command("let g:ulti_jump_forwards_res = 1")
        vim_helper.command("let &undolevels = &undolevels")
        if not self._jump(JumpDirection.FORWARD):
            vim_helper.command("let g:ulti_jump_forwards_res = 0")
            return self._handle_failure(self.forward_trigger)
        return None

    @err_to_scratch_buffer.wrap
    def jump_backwards(self):
        """Jumps to the previous tabstop."""
        vim_helper.command("let g:ulti_jump_backwards_res = 1")
        vim_helper.command("let &undolevels = &undolevels")
        if not self._jump(JumpDirection.BACKWARD):
            vim_helper.command("let g:ulti_jump_backwards_res = 0")
            return self._handle_failure(self.backward_trigger)
        return None

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

    @err_to_scratch_buffer.wrap
    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_helper.command("let g:ulti_expand_or_jump_res = 1")
        rv = self._try_expand()
        if not rv:
            vim_helper.command("let g:ulti_expand_or_jump_res = 2")
            rv = self._jump(JumpDirection.FORWARD)
        if not rv:
            vim_helper.command("let g:ulti_expand_or_jump_res = 0")
            self._handle_failure(self.expand_trigger, True)

    @err_to_scratch_buffer.wrap
    def snippets_in_current_scope(self, search_all):
        """Returns the snippets that could be expanded to Vim as a global
        variable."""
        before = "" if search_all else vim_helper.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 :
            ]

            location = snip.location if snip.location else ""

            key = snip.trigger

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

            if search_all:
                vim_helper.command(
                    (
                        "let g:current_ulti_dict_info['{key}'] = {{"
                        "'description': '{description}',"
                        "'location': '{location}',"
                        "}}"
                    ).format(
                        key=key.replace("'", "''"),
                        location=location.replace("'", "''"),
                        description=description.replace("'", "''"),
                    )
                )

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

        if len(snippets) == 0:
            self._handle_failure(vim.eval("g:UltiSnipsListSnippets"))
            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.wrap
    def add_snippet(
        self,
        trigger,
        value,
        description,
        options,
        ft="all",
        priority=0,
        context=None,
        actions=None,
    ):
        """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.wrap
    def expand_anon(
        self, value, trigger="", description="", options="", context=None, actions=None
    ):
        """Expand an anonymous snippet right here."""
        before = vim_helper.buf.line_till_cursor
        snip = UltiSnipsSnippetDefinition(
            0, trigger, value, description, options, {}, "", context, actions
        )

        if not trigger or snip.matches(before, self._visual_content):
            self._do_snippet(snip, before)
            return True
        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 get_buffer_filetypes(self):
        return (
            self._added_buffer_filetypes[vim_helper.buf.number]
            + vim_helper.buf.filetypes
            + ["all"]
        )

    def add_buffer_filetypes(self, filetypes: str):
        """'filetypes' is a dotted filetype list, for example 'cuda.cpp'"""
        buf_fts = self._added_buffer_filetypes[vim_helper.buf.number]
        idx = -1
        for ft in filetypes.split("."):
            ft = ft.strip()
            if not ft:
                continue
            try:
                idx = buf_fts.index(ft)
            except ValueError:
                self._added_buffer_filetypes[vim_helper.buf.number].insert(idx + 1, ft)
                idx += 1

    @err_to_scratch_buffer.wrap
    def _cursor_moved(self):
        """Called whenever the cursor moved."""
        self._should_update_textobjects = False

        self._vstate.remember_position()
        if vim_helper.eval("mode()") not in "in":
            return

        if self._ignore_movements:
            self._ignore_movements = False
            return

        if self._active_snippets:
            cstart = self._active_snippets[0].start.line
            cend = (
                self._active_snippets[0].end.line + self._vstate.diff_in_buffer_length
            )
            ct = vim_helper.buf[cstart : cend + 1]
            lt = self._vstate.remembered_buffer
            pos = vim_helper.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._active_snippets[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._active_snippets:
            self._active_snippets[0].update_textobjects(vim_helper.buf)
            self._vstate.remember_buffer(self._active_snippets[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_helper.command(
                "inoremap <buffer><nowait><silent> "
                + self.forward_trigger
                + " <C-R>=UltiSnips#JumpForwards()<cr>"
            )
            vim_helper.command(
                "snoremap <buffer><nowait><silent> "
                + self.forward_trigger
                + " <Esc>:call UltiSnips#JumpForwards()<cr>"
            )
        vim_helper.command(
            "inoremap <buffer><nowait><silent> "
            + self.backward_trigger
            + " <C-R>=UltiSnips#JumpBackwards()<cr>"
        )
        vim_helper.command(
            "snoremap <buffer><nowait><silent> "
            + self.backward_trigger
            + " <Esc>:call UltiSnips#JumpBackwards()<cr>"
        )

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

        vim_helper.command("autocmd InsertLeave * call UltiSnips#LeavingInsertMode()")

        vim_helper.command("autocmd BufEnter * call UltiSnips#LeavingBuffer()")
        vim_helper.command("autocmd CmdwinEnter * call UltiSnips#LeavingBuffer()")
        vim_helper.command("autocmd CmdwinLeave * call UltiSnips#LeavingBuffer()")

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

        vim_helper.command("augroup END")

        vim_helper.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_helper.command(
                "silent doautocmd <nomodeline> User UltiSnipsExitLastSnippet"
            )
            if self.expand_trigger != self.forward_trigger:
                vim_helper.command("iunmap <buffer> %s" % self.forward_trigger)
                vim_helper.command("sunmap <buffer> %s" % self.forward_trigger)
            vim_helper.command("iunmap <buffer> %s" % self.backward_trigger)
            vim_helper.command("sunmap <buffer> %s" % self.backward_trigger)
            vim_helper.command("augroup UltiSnips")
            vim_helper.command("autocmd!")
            vim_helper.command("augroup END")
        except vim_helper.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
        finally:
            self._inner_state_up = False

    @err_to_scratch_buffer.wrap
    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 self._active_snippets:
            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._current_snippet and (
            not self._current_snippet.start
            <= vim_helper.buf.cursor
            <= self._current_snippet.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._active_snippets.pop()
        if not self._active_snippets:
            self._teardown_inner_state()

    def _jump(self, jump_direction: JumpDirection):
        """Helper method that does the actual jump."""
        if self._should_update_textobjects:
            self._should_reset_visual = False
            self._cursor_moved()

        # we need to set 'onemore' there, because of limitations of the vim
        # API regarding cursor movements; without that test
        # 'CanExpandAnonSnippetInJumpActionWhileSelected' will fail
        with vim_helper.option_set_to("ve", "onemore"):
            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._active_snippets[:]

            # 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._current_snippet:
                snippet_for_action = self._current_snippet
            elif stack_for_post_jump:
                snippet_for_action = stack_for_post_jump[-1]
            else:
                snippet_for_action = None

            if self._current_snippet:
                ntab = self._current_snippet.select_next_tab(jump_direction)
                if ntab:
                    if self._current_snippet.snippet.has_option("s"):
                        lineno = vim_helper.buf.cursor.line
                        vim_helper.buf[lineno] = vim_helper.buf[lineno].rstrip()
                    vim_helper.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

                    self._ctab = ntab

                    # Run interpolations again to update new placeholder
                    # values, binded to currently newly jumped placeholder.
                    self._visual_content.conserve_placeholder(self._ctab)
                    self._current_snippet.current_placeholder = (
                        self._visual_content.placeholder
                    )
                    self._should_reset_visual = False
                    self._active_snippets[0].update_textobjects(vim_helper.buf)
                    # Open any folds this might have created
                    vim_helper.command("normal! zv")
                    self._vstate.remember_buffer(self._active_snippets[0])

                    if ntab.number == 0 and self._active_snippets:
                        self._current_snippet_is_done()
                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(jump_direction)

            if jumped:
                if self._ctab:
                    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 jump_direction == JumpDirection.BACKWARD 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, pass_through=False):
        """Mainly make sure that we play well with SuperTab."""
        if trigger.lower() == "<tab>":
            feedkey = "\\" + trigger
        elif trigger.lower() == "<s-tab>":
            feedkey = "\\" + trigger
        elif pass_through:
            # pass through the trigger key if it did nothing
            feedkey = "\\" + trigger
        else:
            feedkey = None
        mode = "n"
        if not self._supertab_keys:
            if vim_helper.eval("exists('g:SuperTabMappingForward')") != "0":
                self._supertab_keys = (
                    vim_helper.eval("g:SuperTabMappingForward"),
                    vim_helper.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 in (r"\<Plug>SuperTabForward", r"\<Plug>SuperTabBackward"):
            vim_helper.command("return SuperTab(%s)" % vim_helper.escape(mode))
        elif feedkey:
            vim_helper.command("return %s" % vim_helper.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.get_buffer_filetypes()[::-1]
        matching_snippets = defaultdict(list)
        clear_priority = None
        cleared = {}
        for _, source in self._snippet_sources:
            source.ensure(filetypes)

        # 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, self._visual_content
            )

            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
        self._should_update_textobjects = 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._active_snippets, self._vstate):
            with self._action_context():
                cursor_set_in_action = snippet.do_pre_expand(
                    self._visual_content.text, self._active_snippets
                )

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

        with suspend_proxy_edits():
            start = Position(vim_helper.buf.cursor.line, len(text_before))
            end = Position(vim_helper.buf.cursor.line, len(before))
            parent = None
            if self._current_snippet:
                # 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._active_snippets[0].replay_user_edits(edit_actions)
                parent = self._current_snippet.find_parent_for_new_to(start)
            snippet_instance = snippet.launch(
                text_before, self._visual_content, parent, start, end
            )
            # Open any folds this might have created
            vim_helper.command("normal! zv")

            self._visual_content.reset()
            self._active_snippets.append(snippet_instance)

            with use_proxy_buffer(self._active_snippets, self._vstate):
                with self._action_context():
                    snippet.do_post_expand(
                        snippet_instance.start,
                        snippet_instance.end,
                        self._active_snippets,
                    )

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

            if not self._snip_expanded_in_action:
                self._jump(JumpDirection.FORWARD)
            elif self._current_snippet.current_text != "":
                self._jump(JumpDirection.FORWARD)
            else:
                self._current_snippet_is_done()

            if self._inside_action:
                self._snip_expanded_in_action = True

    def _can_expand(self, autotrigger_only=False):
        before = vim_helper.buf.line_till_cursor
        return before, self._snips(before, False, autotrigger_only)

    def _try_expand(self, autotrigger_only=False):
        """Try to expand a snippet in the current place."""
        before, snippets = self._can_expand(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_helper.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_helper.command("let &undolevels = &undolevels")
        return True

    def can_expand(self, autotrigger_only=False):
        """Check if we would be able to successfully find a snippet in the current position."""
        return bool(self._can_expand(autotrigger_only)[1])

    def can_jump(self, direction):
        if self._current_snippet == None:
            return False
        return self._current_snippet.has_next_tab(direction)

    def can_jump_forwards(self):
        return self.can_jump(JumpDirection.FORWARD)

    def can_jump_backwards(self):
        return self.can_jump(JumpDirection.BACKWARD)

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

    def _file_to_edit(self, requested_ft, bang):
        """Returns a file to be edited for the given requested_ft.

        If 'bang' is empty a reasonable first choice is opened (see docs), otherwise
        all files are considered and the user gets to choose.
        """
        filetypes = []
        if requested_ft:
            filetypes.append(requested_ft)
        else:
            if bang:
                filetypes.extend(self.get_buffer_filetypes())
            else:
                filetypes.append(self.get_buffer_filetypes()[0])

        potentials = set()

        all_snippet_directories = find_all_snippet_directories()
        has_storage_dir = (
            vim_helper.eval(
                "exists('g:UltiSnipsSnippetStorageDirectoryForUltiSnipsEdit')"
            )
            == "1"
        )
        if has_storage_dir:
            snippet_storage_dir = vim_helper.eval(
                "g:UltiSnipsSnippetStorageDirectoryForUltiSnipsEdit"
            )
            full_path = os.path.expanduser(snippet_storage_dir)
            potentials.update(
                _get_potential_snippet_filenames_to_edit(full_path, filetypes)
            )
        if len(all_snippet_directories) == 1:
            # Most likely the user has set g:UltiSnipsSnippetDirectories to a
            # single absolute path.
            potentials.update(
                _get_potential_snippet_filenames_to_edit(
                    all_snippet_directories[0], filetypes
                )
            )

        if (len(all_snippet_directories) != 1 and not has_storage_dir) or (
            has_storage_dir and bang
        ):
            # Likely the array contains things like ["UltiSnips",
            # "mycoolsnippets"] There is no more obvious way to edit than in
            # the users vim config directory.
            dot_vim_dir = vim_helper.get_dot_vim()
            for snippet_dir in all_snippet_directories:
                if Path(dot_vim_dir) != Path(snippet_dir).parent:
                    continue
                potentials.update(
                    _get_potential_snippet_filenames_to_edit(snippet_dir, filetypes)
                )

        if bang:
            for ft in filetypes:
                potentials.update(find_all_snippet_files(ft))
        else:
            if not potentials:
                _show_user_warning(
                    "UltiSnips was not able to find a default directory for snippets. "
                    "Do you have a .vim directory? Try :UltiSnipsEdit! instead of :UltiSnipsEdit."
                )
                return ""
        return _select_and_create_file_to_edit(potentials)

    @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.wrap
    def _track_change(self):
        self._should_update_textobjects = True

        try:
            inserted_char = vim_helper.eval("v:char")
        except UnicodeDecodeError:
            return

        if isinstance(inserted_char, bytes):
            return

        try:
            if inserted_char == "":
                before = vim_helper.buf.line_till_cursor

                if (
                    before
                    and self._last_change[0] != ""
                    and before[-1] == self._last_change[0]
                ):
                    self._try_expand(autotrigger_only=True)
        finally:
            self._last_change = (inserted_char, vim_helper.buf.cursor)

        if self._should_reset_visual and self._visual_content.mode == "":
            self._visual_content.reset()

        self._should_reset_visual = True

    @err_to_scratch_buffer.wrap
    def _refresh_snippets(self):
        for _, source in self._snippet_sources:
            source.refresh()


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