mixins.py

# -*- coding: utf-8 -*-
#
# Copyright © Spyder Project Contributors
# Licensed under the terms of the MIT License
# (see spyder/__init__.py for details)

"""Mix-in classes

These classes were created to be able to provide Spyder's regular text and
console widget features to an independant widget based on QTextEdit for the
IPython console plugin.
"""

# Standard library imports
from xml.sax.saxutils import escape
import os
import os.path as osp
import re
import sre_constants
import textwrap

# Third party imports
from qtpy.QtCore import QPoint, Qt
from qtpy.QtGui import QCursor, QTextCursor, QTextDocument
from qtpy.QtWidgets import QApplication, QToolTip
from qtpy import QT_VERSION
from spyder_kernels.utils.dochelpers import (getargspecfromtext, getobj,
                                             getsignaturefromtext)

# Local imports
from spyder.config.base import _
from spyder.py3compat import is_text_string, to_text_string
from spyder.utils import encoding, sourcecode, programs
from spyder.utils.misc import get_error_match
from spyder.widgets.arraybuilder import NumpyArrayDialog

QT55_VERSION = programs.check_version(QT_VERSION, "5.5", ">=")

if QT55_VERSION:
    from qtpy.QtCore import QRegularExpression
else:
    from qtpy.QtCore import QRegExp


class BaseEditMixin(object):
    
    def __init__(self):
        self.eol_chars = None
        self.calltip_size = 600
    
    #------Line number area
    def get_linenumberarea_width(self):
        """Return line number area width"""
        # Implemented in CodeEditor, but needed for calltip/completion widgets
        return 0
    
    
    #------Calltips
    def _format_signature(self, text):
        formatted_lines = []
        name = text.split('(')[0]
        rows = textwrap.wrap(text, width=50,
                             subsequent_indent=' '*(len(name)+1))
        for r in rows:
            r = escape(r) # Escape most common html chars
            r = r.replace(' ', ' ')
            for char in ['=', ',', '(', ')', '*', '**']:
                r = r.replace(char,
                       '<span style=\'color: red; font-weight: bold\'>' + \
                       char + '</span>')
            formatted_lines.append(r)
        signature = '<br>'.join(formatted_lines)
        return signature, rows
    
    def show_calltip(self, title, text, signature=False, color='#2D62FF',
                     at_line=None, at_position=None):
        """Show calltip"""
        if text is None or len(text) == 0:
            return

        # Saving cursor position:
        if at_position is None:
            at_position = self.get_position('cursor')
        self.calltip_position = at_position

        # Preparing text:
        if signature:
            text, wrapped_textlines = self._format_signature(text)
        else:
            if isinstance(text, list):
                text = "\n    ".join(text)
            text = text.replace('\n', '<br>')
            if len(text) > self.calltip_size:
                text = text[:self.calltip_size] + " ..."

        # Formatting text
        font = self.font()
        size = font.pointSize()
        family = font.family()
        format1 = '<div style=\'font-family: "%s"; font-size: %spt; color: %s\'>'\
                  % (family, size, color)
        format2 = '<div style=\'font-family: "%s"; font-size: %spt\'>'\
                  % (family, size-1 if size > 9 else size)
        tiptext = format1 + ('<b>%s</b></div>' % title) + '<hr>' + \
                  format2 + text + "</div>"

        # Showing tooltip at cursor position:
        cx, cy = self.get_coordinates('cursor')
        if at_line is not None:
            cx = 5
            cursor = QTextCursor(self.document().findBlockByNumber(at_line-1))
            cy = self.cursorRect(cursor).top()
        point = self.mapToGlobal(QPoint(cx, cy))
        point.setX(point.x()+self.get_linenumberarea_width())
        point.setY(point.y()+font.pointSize()+5)
        if signature:
            self.calltip_widget.show_tip(point, tiptext, wrapped_textlines)
        else:
            QToolTip.showText(point, tiptext)
    
    
    #------EOL characters
    def set_eol_chars(self, text):
        """Set widget end-of-line (EOL) characters from text (analyzes text)"""
        if not is_text_string(text): # testing for QString (PyQt API#1)
            text = to_text_string(text)
        eol_chars = sourcecode.get_eol_chars(text)
        is_document_modified = eol_chars is not None and self.eol_chars is not None
        self.eol_chars = eol_chars
        if is_document_modified:
            self.document().setModified(True)
            if self.sig_eol_chars_changed is not None:
                self.sig_eol_chars_changed.emit(eol_chars)
        
    def get_line_separator(self):
        """Return line separator based on current EOL mode"""
        if self.eol_chars is not None:
            return self.eol_chars
        else:
            return os.linesep

    def get_text_with_eol(self):
        """Same as 'toPlainText', replace '\n' 
        by correct end-of-line characters"""
        utext = to_text_string(self.toPlainText())
        lines = utext.splitlines()
        linesep = self.get_line_separator()
        txt = linesep.join(lines)
        if utext.endswith('\n'):
            txt += linesep
        return txt


    #------Positions, coordinates (cursor, EOF, ...)
    def get_position(self, subject):
        """Get offset in character for the given subject from the start of
           text edit area"""
        cursor = self.textCursor()
        if subject == 'cursor':
            pass
        elif subject == 'sol':
            cursor.movePosition(QTextCursor.StartOfBlock)
        elif subject == 'eol':
            cursor.movePosition(QTextCursor.EndOfBlock)
        elif subject == 'eof':
            cursor.movePosition(QTextCursor.End)
        elif subject == 'sof':
            cursor.movePosition(QTextCursor.Start)
        else:
            # Assuming that input argument was already a position
            return subject
        return cursor.position()
        
    def get_coordinates(self, position):
        position = self.get_position(position)
        cursor = self.textCursor()
        cursor.setPosition(position)
        point = self.cursorRect(cursor).center()
        return point.x(), point.y()
    
    def get_cursor_line_column(self):
        """Return cursor (line, column) numbers"""
        cursor = self.textCursor()
        return cursor.blockNumber(), cursor.columnNumber()
        
    def get_cursor_line_number(self):
        """Return cursor line number"""
        return self.textCursor().blockNumber()+1

    def set_cursor_position(self, position):
        """Set cursor position"""
        position = self.get_position(position)
        cursor = self.textCursor()
        cursor.setPosition(position)
        self.setTextCursor(cursor)
        self.ensureCursorVisible()
        
    def move_cursor(self, chars=0):
        """Move cursor to left or right (unit: characters)"""
        direction = QTextCursor.Right if chars > 0 else QTextCursor.Left
        for _i in range(abs(chars)):
            self.moveCursor(direction, QTextCursor.MoveAnchor)

    def is_cursor_on_first_line(self):
        """Return True if cursor is on the first line"""
        cursor = self.textCursor()
        cursor.movePosition(QTextCursor.StartOfBlock)
        return cursor.atStart()

    def is_cursor_on_last_line(self):
        """Return True if cursor is on the last line"""
        cursor = self.textCursor()
        cursor.movePosition(QTextCursor.EndOfBlock)
        return cursor.atEnd()

    def is_cursor_at_end(self):
        """Return True if cursor is at the end of the text"""
        return self.textCursor().atEnd()

    def is_cursor_before(self, position, char_offset=0):
        """Return True if cursor is before *position*"""
        position = self.get_position(position) + char_offset
        cursor = self.textCursor()
        cursor.movePosition(QTextCursor.End)
        if position < cursor.position():
            cursor.setPosition(position)
            return self.textCursor() < cursor
                
    def __move_cursor_anchor(self, what, direction, move_mode):
        assert what in ('character', 'word', 'line')
        if what == 'character':
            if direction == 'left':
                self.moveCursor(QTextCursor.PreviousCharacter, move_mode)
            elif direction == 'right':
                self.moveCursor(QTextCursor.NextCharacter, move_mode)
        elif what == 'word':
            if direction == 'left':
                self.moveCursor(QTextCursor.PreviousWord, move_mode)
            elif direction == 'right':
                self.moveCursor(QTextCursor.NextWord, move_mode)
        elif what == 'line':
            if direction == 'down':
                self.moveCursor(QTextCursor.NextBlock, move_mode)
            elif direction == 'up':
                self.moveCursor(QTextCursor.PreviousBlock, move_mode)
                
    def move_cursor_to_next(self, what='word', direction='left'):
        """
        Move cursor to next *what* ('word' or 'character')
        toward *direction* ('left' or 'right')
        """
        self.__move_cursor_anchor(what, direction, QTextCursor.MoveAnchor)


    #------Selection
    def clear_selection(self):
        """Clear current selection"""
        cursor = self.textCursor()
        cursor.clearSelection()
        self.setTextCursor(cursor)

    def extend_selection_to_next(self, what='word', direction='left'):
        """
        Extend selection to next *what* ('word' or 'character')
        toward *direction* ('left' or 'right')
        """
        self.__move_cursor_anchor(what, direction, QTextCursor.KeepAnchor)


    #------Text: get, set, ...
    def __select_text(self, position_from, position_to):
        position_from = self.get_position(position_from)
        position_to = self.get_position(position_to)
        cursor = self.textCursor()
        cursor.setPosition(position_from)
        cursor.setPosition(position_to, QTextCursor.KeepAnchor)
        return cursor

    def get_text_line(self, line_nb):
        """Return text line at line number *line_nb*"""
        # Taking into account the case when a file ends in an empty line,
        # since splitlines doesn't return that line as the last element
        # TODO: Make this function more efficient
        try:
            return to_text_string(self.toPlainText()).splitlines()[line_nb]
        except IndexError:
            return self.get_line_separator()
    
    def get_text(self, position_from, position_to):
        """
        Return text between *position_from* and *position_to*
        Positions may be positions or 'sol', 'eol', 'sof', 'eof' or 'cursor'
        """
        cursor = self.__select_text(position_from, position_to)
        text = to_text_string(cursor.selectedText())
        all_text = position_from == 'sof' and position_to == 'eof'
        if text and not all_text:
            while text.endswith("\n"):
                text = text[:-1]
            while text.endswith(u"\u2029"):
                text = text[:-1]
        return text
    
    def get_character(self, position, offset=0):
        """Return character at *position* with the given offset."""
        position = self.get_position(position) + offset
        cursor = self.textCursor()
        cursor.movePosition(QTextCursor.End)
        if position < cursor.position():
            cursor.setPosition(position)
            cursor.movePosition(QTextCursor.Right,
                                QTextCursor.KeepAnchor)
            return to_text_string(cursor.selectedText())
        else:
            return ''
    
    def insert_text(self, text):
        """Insert text at cursor position"""
        if not self.isReadOnly():
            self.textCursor().insertText(text)
    
    def replace_text(self, position_from, position_to, text):
        cursor = self.__select_text(position_from, position_to)
        cursor.removeSelectedText()
        cursor.insertText(text)
        
    def remove_text(self, position_from, position_to):
        cursor = self.__select_text(position_from, position_to)
        cursor.removeSelectedText()
        
    def get_current_word(self):
        """Return current word, i.e. word at cursor position"""
        cursor = self.textCursor()

        if cursor.hasSelection():
            # Removes the selection and moves the cursor to the left side 
            # of the selection: this is required to be able to properly 
            # select the whole word under cursor (otherwise, the same word is 
            # not selected when the cursor is at the right side of it):
            cursor.setPosition(min([cursor.selectionStart(),
                                    cursor.selectionEnd()]))
        else:
            # Checks if the first character to the right is a white space
            # and if not, moves the cursor one word to the left (otherwise,
            # if the character to the left do not match the "word regexp" 
            # (see below), the word to the left of the cursor won't be 
            # selected), but only if the first character to the left is not a
            # white space too.
            def is_space(move):
                curs = self.textCursor()
                curs.movePosition(move, QTextCursor.KeepAnchor)
                return not to_text_string(curs.selectedText()).strip()
            if is_space(QTextCursor.NextCharacter):
                if is_space(QTextCursor.PreviousCharacter):
                    return
                cursor.movePosition(QTextCursor.WordLeft)

        cursor.select(QTextCursor.WordUnderCursor)
        text = to_text_string(cursor.selectedText())
        # find a valid python variable name
        match = re.findall(r'([^\d\W]\w*)', text, re.UNICODE)
        if match:
            return match[0]
    
    def get_current_line(self):
        """Return current line's text"""
        cursor = self.textCursor()
        cursor.select(QTextCursor.BlockUnderCursor)
        return to_text_string(cursor.selectedText())
    
    def get_current_line_to_cursor(self):
        """Return text from prompt to cursor"""
        return self.get_text(self.current_prompt_pos, 'cursor')
    
    def get_line_number_at(self, coordinates):
        """Return line number at *coordinates* (QPoint)"""
        cursor = self.cursorForPosition(coordinates)
        return cursor.blockNumber()-1
    
    def get_line_at(self, coordinates):
        """Return line at *coordinates* (QPoint)"""
        cursor = self.cursorForPosition(coordinates)
        cursor.select(QTextCursor.BlockUnderCursor)
        return to_text_string(cursor.selectedText()).replace(u'\u2029', '')
    
    def get_word_at(self, coordinates):
        """Return word at *coordinates* (QPoint)"""
        cursor = self.cursorForPosition(coordinates)
        cursor.select(QTextCursor.WordUnderCursor)
        return to_text_string(cursor.selectedText())
    
    def get_block_indentation(self, block_nb):
        """Return line indentation (character number)"""
        text = to_text_string(self.document().findBlockByNumber(block_nb).text())
        text = text.replace("\t", " "*self.tab_stop_width_spaces)
        return len(text)-len(text.lstrip())
    
    def get_selection_bounds(self):
        """Return selection bounds (block numbers)"""
        cursor = self.textCursor()
        start, end = cursor.selectionStart(), cursor.selectionEnd()
        block_start = self.document().findBlock(start)
        block_end = self.document().findBlock(end)
        return sorted([block_start.blockNumber(), block_end.blockNumber()])
        

    #------Text selection
    def has_selected_text(self):
        """Returns True if some text is selected"""
        return bool(to_text_string(self.textCursor().selectedText()))

    def get_selected_text(self):
        """
        Return text selected by current text cursor, converted in unicode
        
        Replace the unicode line separator character \u2029 by 
        the line separator characters returned by get_line_separator
        """
        return to_text_string(self.textCursor().selectedText()).replace(u"\u2029",
                                                     self.get_line_separator())
    
    def remove_selected_text(self):
        """Delete selected text"""
        self.textCursor().removeSelectedText()
        
    def replace(self, text, pattern=None):
        """Replace selected text by *text*
        If *pattern* is not None, replacing selected text using regular
        expression text substitution"""
        cursor = self.textCursor()
        cursor.beginEditBlock()
        if pattern is not None:
            seltxt = to_text_string(cursor.selectedText())
        cursor.removeSelectedText()
        if pattern is not None:
            text = re.sub(to_text_string(pattern),
                          to_text_string(text), to_text_string(seltxt))
        cursor.insertText(text)
        cursor.endEditBlock()


    #------Find/replace
    def find_multiline_pattern(self, regexp, cursor, findflag):
        """Reimplement QTextDocument's find method
        
        Add support for *multiline* regular expressions"""
        pattern = to_text_string(regexp.pattern())
        text = to_text_string(self.toPlainText())
        try:
            regobj = re.compile(pattern)
        except sre_constants.error:
            return
        if findflag & QTextDocument.FindBackward:
            # Find backward
            offset = min([cursor.selectionEnd(), cursor.selectionStart()])
            text = text[:offset]
            matches = [_m for _m in regobj.finditer(text, 0, offset)]
            if matches:
                match = matches[-1]
            else:
                return
        else:
            # Find forward
            offset = max([cursor.selectionEnd(), cursor.selectionStart()])
            match = regobj.search(text, offset)
        if match:
            pos1, pos2 = match.span()
            fcursor = self.textCursor()
            fcursor.setPosition(pos1)
            fcursor.setPosition(pos2, QTextCursor.KeepAnchor)
            return fcursor

    def find_text(self, text, changed=True, forward=True, case=False,
                  words=False, regexp=False):
        """Find text"""
        cursor = self.textCursor()
        findflag = QTextDocument.FindFlag()

        if not forward:
            findflag = findflag | QTextDocument.FindBackward

        if case:
            findflag = findflag | QTextDocument.FindCaseSensitively

        moves = [QTextCursor.NoMove]
        if forward:
            moves += [QTextCursor.NextWord, QTextCursor.Start]
            if changed:
                if to_text_string(cursor.selectedText()):
                    new_position = min([cursor.selectionStart(),
                                        cursor.selectionEnd()])
                    cursor.setPosition(new_position)
                else:
                    cursor.movePosition(QTextCursor.PreviousWord)
        else:
            moves += [QTextCursor.End]

        if regexp:
            text = to_text_string(text)
        else:
            text = re.escape(to_text_string(text))

        if QT55_VERSION:
            pattern = QRegularExpression(u"\\b{}\\b".format(text) if words else
                                         text)
            if case:
                pattern.setPatternOptions(
                    QRegularExpression.CaseInsensitiveOption)
        else:
            pattern = QRegExp(u"\\b{}\\b".format(text)
                              if words else text, Qt.CaseSensitive if case else
                              Qt.CaseInsensitive, QRegExp.RegExp2)

        for move in moves:
            cursor.movePosition(move)
            if regexp and '\\n' in text:
                # Multiline regular expression
                found_cursor = self.find_multiline_pattern(pattern, cursor,
                                                           findflag)
            else:
                # Single line find: using the QTextDocument's find function,
                # probably much more efficient than ours
                found_cursor = self.document().find(pattern, cursor, findflag)
            if found_cursor is not None and not found_cursor.isNull():
                self.setTextCursor(found_cursor)
                return True

        return False

    def is_editor(self):
        """Needs to be overloaded in the codeeditor where it will be True"""
        return False

    def get_number_matches(self, pattern, source_text='', case=False,
                           regexp=False):
        """Get the number of matches for the searched text."""
        pattern = to_text_string(pattern)
        if not pattern:
            return 0

        if not regexp:
            pattern = re.escape(pattern)

        if not source_text:
            source_text = to_text_string(self.toPlainText())

        try:
            if case:
                regobj = re.compile(pattern)
            else:
                regobj = re.compile(pattern, re.IGNORECASE)
        except sre_constants.error:
            return None

        number_matches = 0
        for match in regobj.finditer(source_text):
            number_matches += 1

        return number_matches

    def get_match_number(self, pattern, case=False, regexp=False):
        """Get number of the match for the searched text."""
        position = self.textCursor().position()
        source_text = self.get_text(position_from='sof', position_to=position)
        match_number = self.get_number_matches(pattern,
                                               source_text=source_text,
                                               case=case, regexp=regexp)
        return match_number

    # --- Numpy matrix/array helper / See 'spyder/widgets/arraybuilder.py'
    def enter_array_inline(self):
        """ """
        self._enter_array(True)

    def enter_array_table(self):
        """ """
        self._enter_array(False)

    def _enter_array(self, inline):
        """ """
        offset = self.get_position('cursor') - self.get_position('sol')
        rect = self.cursorRect()
        dlg = NumpyArrayDialog(self, inline, offset)

        # TODO: adapt to font size
        x = rect.left()
        x = x + self.get_linenumberarea_width() - 14
        y = rect.top() + (rect.bottom() - rect.top())/2
        y = y - dlg.height()/2 - 3

        pos = QPoint(x, y)
        dlg.move(self.mapToGlobal(pos))

        # called from editor
        if self.is_editor():
            python_like_check = self.is_python_like()
            suffix = '\n'
        # called from a console
        else:
            python_like_check = True
            suffix = ''

        if python_like_check and dlg.exec_():
            text = dlg.text() + suffix
            if text != '':
                cursor = self.textCursor()
                cursor.beginEditBlock()
                cursor.insertText(text)
                cursor.endEditBlock()


class TracebackLinksMixin(object):
    """ """
    QT_CLASS = None
    go_to_error = None
    
    def __init__(self):
        self.__cursor_changed = False
        self.setMouseTracking(True)
        
    #------Mouse events
    def mouseReleaseEvent(self, event):
        """Go to error"""
        self.QT_CLASS.mouseReleaseEvent(self, event)            
        text = self.get_line_at(event.pos())
        if get_error_match(text) and not self.has_selected_text():
            if self.go_to_error is not None:
                self.go_to_error.emit(text)

    def mouseMoveEvent(self, event):
        """Show Pointing Hand Cursor on error messages"""
        text = self.get_line_at(event.pos())
        if get_error_match(text):
            if not self.__cursor_changed:
                QApplication.setOverrideCursor(QCursor(Qt.PointingHandCursor))
                self.__cursor_changed = True
            event.accept()
            return
        if self.__cursor_changed:
            QApplication.restoreOverrideCursor()
            self.__cursor_changed = False
        self.QT_CLASS.mouseMoveEvent(self, event)
        
    def leaveEvent(self, event):
        """If cursor has not been restored yet, do it now"""
        if self.__cursor_changed:
            QApplication.restoreOverrideCursor()
            self.__cursor_changed = False
        self.QT_CLASS.leaveEvent(self, event)


class GetHelpMixin(object):
    def __init__(self):
        self.help = None
        self.help_enabled = False

    def set_help(self, help_plugin):
        """Set Help DockWidget reference"""
        self.help = help_plugin

    def set_help_enabled(self, state):
        self.help_enabled = state

    def inspect_current_object(self):
        text = ''
        text1 = self.get_text('sol', 'cursor')
        tl1 = re.findall(r'([a-zA-Z_]+[0-9a-zA-Z_\.]*)', text1)
        if tl1 and text1.endswith(tl1[-1]):
            text += tl1[-1]
        text2 = self.get_text('cursor', 'eol')
        tl2 = re.findall(r'([0-9a-zA-Z_\.]+[0-9a-zA-Z_\.]*)', text2)
        if tl2 and text2.startswith(tl2[0]):
            text += tl2[0]
        if text:
            self.show_object_info(text, force=True)

    def show_object_info(self, text, call=False, force=False):
        """Show signature calltip and/or docstring in the Help plugin"""
        text = to_text_string(text)

        # Show docstring
        help_enabled = self.help_enabled or force
        if force and self.help is not None:
            self.help.dockwidget.setVisible(True)
            self.help.dockwidget.raise_()
        if help_enabled and (self.help is not None) and \
           (self.help.dockwidget.isVisible()):
            # Help widget exists and is visible
            if hasattr(self, 'get_doc'):
                self.help.set_shell(self)
            else:
                self.help.set_shell(self.parent())
            self.help.set_object_text(text, ignore_unknown=False)
            self.setFocus() # if help was not at top level, raising it to
                            # top will automatically give it focus because of
                            # the visibility_changed signal, so we must give
                            # focus back to shell
        
        # Show calltip
        if call and self.calltips:
            # Display argument list if this is a function call
            iscallable = self.iscallable(text)
            if iscallable is not None:
                if iscallable:
                    arglist = self.get_arglist(text)
                    name =  text.split('.')[-1]
                    argspec = signature = ''
                    if isinstance(arglist, bool):
                        arglist = []
                    if arglist:
                        argspec = '(' + ''.join(arglist) + ')'
                    else:
                        doc = self.get__doc__(text)
                        if doc is not None:
                            # This covers cases like np.abs, whose docstring is
                            # the same as np.absolute and because of that a
                            # proper signature can't be obtained correctly
                            argspec = getargspecfromtext(doc)
                            if not argspec:
                                signature = getsignaturefromtext(doc, name)
                    if argspec or signature:
                        if argspec:
                            tiptext = name + argspec
                        else:
                            tiptext = signature
                        self.show_calltip(_("Arguments"), tiptext,
                                          signature=True, color='#2D62FF')
    
    def get_last_obj(self, last=False):
        """
        Return the last valid object on the current line
        """
        return getobj(self.get_current_line_to_cursor(), last=last)


class SaveHistoryMixin(object):
    
    INITHISTORY = None
    SEPARATOR = None
    HISTORY_FILENAMES = []

    append_to_history = None
    
    def __init__(self, history_filename=''):
        self.history_filename = history_filename
        self.create_history_filename()

    def create_history_filename(self):
        """Create history_filename with INITHISTORY if it doesn't exist."""
        if self.history_filename and not osp.isfile(self.history_filename):
            try:
                encoding.writelines(self.INITHISTORY, self.history_filename)
            except EnvironmentError:
                pass

    def add_to_history(self, command):
        """Add command to history"""
        command = to_text_string(command)
        if command in ['', '\n'] or command.startswith('Traceback'):
            return
        if command.endswith('\n'):
            command = command[:-1]
        self.histidx = None
        if len(self.history) > 0 and self.history[-1] == command:
            return
        self.history.append(command)
        text = os.linesep + command
        
        # When the first entry will be written in history file,
        # the separator will be append first:
        if self.history_filename not in self.HISTORY_FILENAMES:
            self.HISTORY_FILENAMES.append(self.history_filename)
            text = self.SEPARATOR + text
        # Needed to prevent errors when writing history to disk
        # See issue 6431
        try:
            encoding.write(text, self.history_filename, mode='ab')
        except EnvironmentError:
            pass
        if self.append_to_history is not None:
            self.append_to_history.emit(self.history_filename, text)


class BrowseHistoryMixin(object):

    def __init__(self):
        self.history = []
        self.histidx = None
        self.hist_wholeline = False

    def clear_line(self):
        """Clear current line (without clearing console prompt)"""
        self.remove_text(self.current_prompt_pos, 'eof')

    def browse_history(self, backward):
        """Browse history"""
        if self.is_cursor_before('eol') and self.hist_wholeline:
            self.hist_wholeline = False
        tocursor = self.get_current_line_to_cursor()
        text, self.histidx = self.find_in_history(tocursor, self.histidx,
                                                  backward)
        if text is not None:
            if self.hist_wholeline:
                self.clear_line()
                self.insert_text(text)
            else:
                cursor_position = self.get_position('cursor')
                # Removing text from cursor to the end of the line
                self.remove_text('cursor', 'eol')
                # Inserting history text
                self.insert_text(text)
                self.set_cursor_position(cursor_position)

    def find_in_history(self, tocursor, start_idx, backward):
        """Find text 'tocursor' in history, from index 'start_idx'"""
        if start_idx is None:
            start_idx = len(self.history)
        # Finding text in history
        step = -1 if backward else 1
        idx = start_idx
        if len(tocursor) == 0 or self.hist_wholeline:
            idx += step
            if idx >= len(self.history) or len(self.history) == 0:
                return "", len(self.history)
            elif idx < 0:
                idx = 0
            self.hist_wholeline = True
            return self.history[idx], idx
        else:
            for index in range(len(self.history)):
                idx = (start_idx+step*(index+1)) % len(self.history)
                entry = self.history[idx]
                if entry.startswith(tocursor):
                    return entry[len(tocursor):], idx
            else:
                return None, start_idx

    def reset_search_pos(self):
        """Reset the position from which to search the history"""
        self.histidx = None