import sys
import os
import code
import itertools
import tokenize
import unicodedata
from unittest.mock import patch

from typing import Optional, List, Dict, Any, TYPE_CHECKING

import pygments.style
from pygments.token import Comment, Keyword, Number, String, Punctuation, Operator, Error, Name
from qtconsole.pygments_highlighter import PygmentsHighlighter

from AnyQt.QtWidgets import (
    QPlainTextEdit, QListView, QSizePolicy, QMenu, QSplitter, QLineEdit,
    QAction, QToolButton, QFileDialog, QStyledItemDelegate,
    QStyleOptionViewItem, QPlainTextDocumentLayout,
    QLabel, QWidget, QHBoxLayout, QApplication)
from AnyQt.QtGui import (
    QColor, QBrush, QPalette, QFont, QTextDocument, QTextCharFormat,
    QTextCursor, QKeySequence, QFontMetrics, QPainter
)
from AnyQt.QtCore import (
    Qt, QByteArray, QItemSelectionModel, QSize, QRectF, QMimeDatabase,
)

from orangewidget.workflow.drophandler import SingleFileDropHandler

from Orange.data import Table
from Orange.base import Learner, Model
from Orange.util import interleave
from Orange.widgets import gui
from Orange.widgets.data.utils.pythoneditor.editor import PythonEditor
from Orange.widgets.utils import itemmodels
from Orange.widgets.settings import Setting
from Orange.widgets.utils.pathutils import samepath
from Orange.widgets.utils.widgetpreview import WidgetPreview
from Orange.widgets.widget import OWWidget, MultiInput, Output

if TYPE_CHECKING:
    from typing_extensions import TypedDict

__all__ = ["OWPythonScript"]


DEFAULT_SCRIPT = """import numpy as np
from Orange.data import Table, Domain, ContinuousVariable, DiscreteVariable

domain = Domain([ContinuousVariable("age"),
                 ContinuousVariable("height"),
                 DiscreteVariable("gender", values=("M", "F"))])
arr = np.array([
  [25, 186, 0],
  [30, 164, 1]])
out_data = Table.from_numpy(domain, arr)
"""

def text_format(foreground=Qt.black, weight=QFont.Normal):
    fmt = QTextCharFormat()
    fmt.setForeground(QBrush(foreground))
    fmt.setFontWeight(weight)
    return fmt


def read_file_content(filename, limit=None):
    try:
        with open(filename, encoding="utf-8", errors='strict') as f:
            text = f.read(limit)
            return text
    except (OSError, UnicodeDecodeError):
        return None


# pylint: disable=pointless-string-statement
"""
Adapted from jupyter notebook, which was adapted from GitHub.

Highlighting styles are applied with pygments.

pygments does not support partial highlighting; on every character
typed, it performs a full pass of the code. If performance is ever
an issue, revert to prior commit, which uses Qutepart's syntax
highlighting implementation.
"""
SYNTAX_HIGHLIGHTING_STYLES = {
    'Light': {
        Punctuation: "#000",
        Error: '#f00',

        Keyword: 'bold #008000',

        Name: '#212121',
        Name.Function: '#00f',
        Name.Variable: '#05a',
        Name.Decorator: '#aa22ff',
        Name.Builtin: '#008000',
        Name.Builtin.Pseudo: '#05a',

        String: '#ba2121',

        Number: '#080',

        Operator: 'bold #aa22ff',
        Operator.Word: 'bold #008000',

        Comment: 'italic #408080',
    },
    'Dark': {
        Punctuation: "#fff",
        Error: '#f00',

        Keyword: 'bold #4caf50',

        Name: '#e0e0e0',
        Name.Function: '#1e88e5',
        Name.Variable: '#42a5f5',
        Name.Decorator: '#aa22ff',
        Name.Builtin: '#43a047',
        Name.Builtin.Pseudo: '#42a5f5',

        String: '#ff7070',

        Number: '#66bb6a',

        Operator: 'bold #aa22ff',
        Operator.Word: 'bold #4caf50',

        Comment: 'italic #408080',
    }
}


def make_pygments_style(scheme_name):
    """
    Dynamically create a PygmentsStyle class,
    given the name of one of the above highlighting schemes.
    """
    return type(
        'PygmentsStyle',
        (pygments.style.Style,),
        {'styles': SYNTAX_HIGHLIGHTING_STYLES[scheme_name]}
    )


class FakeSignatureMixin:
    def __init__(self, parent, highlighting_scheme, font):
        super().__init__(parent)
        self.highlighting_scheme = highlighting_scheme
        self.setFont(font)
        self.bold_font = QFont(font)
        self.bold_font.setBold(True)

        self.indentation_level = 0

        self._char_4_width = QFontMetrics(font).horizontalAdvance('4444')

    def setIndent(self, margins_width):
        self.setContentsMargins(max(0,
                                    round(margins_width) +
                                    ((self.indentation_level - 1) * self._char_4_width)),
                                0, 0, 0)


class FunctionSignature(FakeSignatureMixin, QLabel):
    def __init__(self, parent, highlighting_scheme, font, function_name="python_script"):
        super().__init__(parent, highlighting_scheme, font)
        self.signal_prefix = 'in_'

        # `def python_script(`
        self.prefix = ('<b style="color: ' +
                       self.highlighting_scheme[Keyword].split(' ')[-1] +
                       ';">def </b>'
                       '<span style="color: ' +
                       self.highlighting_scheme[Name.Function].split(' ')[-1] +
                       ';">' + function_name + '</span>'
                       '<span style="color: ' +
                       self.highlighting_scheme[Punctuation].split(' ')[-1] +
                       ';">(</span>')

        # `):`
        self.affix = ('<span style="color: ' +
                      self.highlighting_scheme[Punctuation].split(' ')[-1] +
                      ';">):</span>')

        self.update_signal_text({})

    def update_signal_text(self, signal_values_lengths):
        if not self.signal_prefix:
            return
        lbl_text = self.prefix
        if len(signal_values_lengths) > 0:
            for name, value in signal_values_lengths.items():
                if value == 1:
                    lbl_text += self.signal_prefix + name + ', '
                elif value > 1:
                    lbl_text += self.signal_prefix + name + 's, '
            lbl_text = lbl_text[:-2]  # shave off the trailing ', '
        lbl_text += self.affix
        if self.text() != lbl_text:
            self.setText(lbl_text)
            self.update()


class ReturnStatement(FakeSignatureMixin, QWidget):
    def __init__(self, parent, highlighting_scheme, font):
        super().__init__(parent, highlighting_scheme, font)

        self.indentation_level = 1
        self.signal_labels = {}
        self._prefix = None

        layout = QHBoxLayout(self)
        layout.setContentsMargins(0, 0, 0, 0)
        layout.setSpacing(0)

        # `return `
        ret_lbl = QLabel('<b style="color: ' + \
                         highlighting_scheme[Keyword].split(' ')[-1] + \
                         ';">return </b>', self)
        ret_lbl.setFont(self.font())
        ret_lbl.setContentsMargins(0, 0, 0, 0)
        layout.addWidget(ret_lbl)

        # `out_data[, ]` * 4
        self.make_signal_labels('out_')

        layout.addStretch()
        self.setLayout(layout)

    def make_signal_labels(self, prefix):
        self._prefix = prefix
        # `in_data[, ]`
        for i, signal in enumerate(OWPythonScript.signal_names):
            # adding an empty b tag like this adjusts the
            # line height to match the rest of the labels
            signal_display_name = signal
            signal_lbl = QLabel('<b></b>' + prefix + signal_display_name, self)
            signal_lbl.setFont(self.font())
            signal_lbl.setContentsMargins(0, 0, 0, 0)
            self.layout().addWidget(signal_lbl)

            self.signal_labels[signal] = signal_lbl

            if i >= len(OWPythonScript.signal_names) - 1:
                break

            comma_lbl = QLabel(', ')
            comma_lbl.setFont(self.font())
            comma_lbl.setContentsMargins(0, 0, 0, 0)
            comma_lbl.setStyleSheet('.QLabel { color: ' +
                                    self.highlighting_scheme[Punctuation].split(' ')[-1] +
                                    '; }')
            self.layout().addWidget(comma_lbl)

    def update_signal_text(self, signal_name, values_length):
        if not self._prefix:
            return
        lbl = self.signal_labels[signal_name]
        if values_length == 0:
            text = '<b></b>' + self._prefix + signal_name
        else:  # if values_length == 1:
            text = '<b>' + self._prefix + signal_name + '</b>'
        if lbl.text() != text:
            lbl.setText(text)
            lbl.update()


class VimIndicator(QWidget):
    def __init__(self, parent):
        super().__init__(parent)
        self.indicator_color = QColor('#33cc33')
        self.indicator_text = 'normal'

    def paintEvent(self, event):
        super().paintEvent(event)
        p = QPainter(self)
        p.setRenderHint(QPainter.Antialiasing)
        p.setBrush(self.indicator_color)

        p.save()
        p.setPen(Qt.NoPen)
        fm = QFontMetrics(self.font())
        width = self.rect().width()
        height = fm.height() + 6
        rect = QRectF(0, 0, width, height)
        p.drawRoundedRect(rect, 5, 5)
        p.restore()

        textstart = (width - fm.horizontalAdvance(self.indicator_text)) // 2
        p.drawText(textstart, height // 2 + 5, self.indicator_text)

    def minimumSizeHint(self):
        fm = QFontMetrics(self.font())
        width = int(round(fm.horizontalAdvance(self.indicator_text)) + 10)
        height = fm.height() + 6
        return QSize(width, height)


class PythonConsole(QPlainTextEdit, code.InteractiveConsole):
    # `locals` is reasonably used as argument name
    # pylint: disable=redefined-builtin
    def __init__(self, locals=None, parent=None):
        QPlainTextEdit.__init__(self, parent)
        code.InteractiveConsole.__init__(self, locals)
        self.newPromptPos = 0
        self.history, self.historyInd = [""], 0
        self.loop = self.interact()
        next(self.loop)

    def setLocals(self, locals):
        self.locals = locals

    def updateLocals(self, locals):
        self.locals.update(locals)

    def interact(self, banner=None, _=None):
        try:
            sys.ps1
        except AttributeError:
            sys.ps1 = ">>> "
        try:
            sys.ps2
        except AttributeError:
            sys.ps2 = "... "
        cprt = ('Type "help", "copyright", "credits" or "license" '
                'for more information.')
        if banner is None:
            self.write("Python %s on %s\n%s\n(%s)\n" %
                       (sys.version, sys.platform, cprt,
                        self.__class__.__name__))
        else:
            self.write("%s\n" % str(banner))
        more = 0
        while 1:
            try:
                if more:
                    prompt = sys.ps2
                else:
                    prompt = sys.ps1
                self.new_prompt(prompt)
                yield
                try:
                    line = self.raw_input(prompt)
                except EOFError:
                    self.write("\n")
                    break
                else:
                    more = self.push(line)
            except KeyboardInterrupt:
                self.write("\nKeyboardInterrupt\n")
                self.resetbuffer()
                more = 0

    def raw_input(self, prompt=""):
        input_str = str(self.document().lastBlock().previous().text())
        return input_str[len(prompt):]

    def new_prompt(self, prompt):
        self.write(prompt)
        self.newPromptPos = self.textCursor().position()
        self.repaint()

    def write(self, data):
        cursor = QTextCursor(self.document())
        cursor.movePosition(QTextCursor.End, QTextCursor.MoveAnchor)
        cursor.insertText(data)
        self.setTextCursor(cursor)
        self.ensureCursorVisible()

    def writelines(self, lines):
        for line in lines:
            self.write(line)

    def flush(self):
        pass

    def push(self, line):
        if self.history[0] != line:
            self.history.insert(0, line)
        self.historyInd = 0

        # prevent console errors to trigger error reporting & patch stdout, stderr
        with patch('sys.excepthook', sys.__excepthook__),\
             patch('sys.stdout', self),\
             patch('sys.stderr', self):
            return code.InteractiveConsole.push(self, line)

    def setLine(self, line):
        cursor = QTextCursor(self.document())
        cursor.movePosition(QTextCursor.End)
        cursor.setPosition(self.newPromptPos, QTextCursor.KeepAnchor)
        cursor.removeSelectedText()
        cursor.insertText(line)
        self.setTextCursor(cursor)

    def keyPressEvent(self, event):
        if event.key() == Qt.Key_Return:
            self.write("\n")
            next(self.loop)
        elif event.key() == Qt.Key_Up:
            self.historyUp()
        elif event.key() == Qt.Key_Down:
            self.historyDown()
        elif event.key() == Qt.Key_Tab:
            self.complete()
        elif event.key() in [Qt.Key_Left, Qt.Key_Backspace]:
            if self.textCursor().position() > self.newPromptPos:
                QPlainTextEdit.keyPressEvent(self, event)
        else:
            QPlainTextEdit.keyPressEvent(self, event)

    def historyUp(self):
        self.setLine(self.history[self.historyInd])
        self.historyInd = min(self.historyInd + 1, len(self.history) - 1)

    def historyDown(self):
        self.setLine(self.history[self.historyInd])
        self.historyInd = max(self.historyInd - 1, 0)

    def complete(self):
        pass

    def _moveCursorToInputLine(self):
        """
        Move the cursor to the input line if not already there. If the cursor
        if already in the input line (at position greater or equal to
        `newPromptPos`) it is left unchanged, otherwise it is moved at the
        end.

        """
        cursor = self.textCursor()
        pos = cursor.position()
        if pos < self.newPromptPos:
            cursor.movePosition(QTextCursor.End)
            self.setTextCursor(cursor)

    def pasteCode(self, source):
        """
        Paste source code into the console.
        """
        self._moveCursorToInputLine()

        for line in interleave(source.splitlines(), itertools.repeat("\n")):
            if line != "\n":
                self.insertPlainText(line)
            else:
                self.write("\n")
                next(self.loop)

    def insertFromMimeData(self, source):
        """
        Reimplemented from QPlainTextEdit.insertFromMimeData.
        """
        if source.hasText():
            self.pasteCode(str(source.text()))
            return


class Script:
    Modified = 1
    MissingFromFilesystem = 2

    def __init__(self, name, script, flags=0, filename=None):
        self.name = name
        self.script = script
        self.flags = flags
        self.filename = filename

    def asdict(self) -> '_ScriptData':
        return dict(name=self.name, script=self.script, filename=self.filename)

    @classmethod
    def fromdict(cls, state: '_ScriptData') -> 'Script':
        return Script(state["name"], state["script"], filename=state["filename"])


class ScriptItemDelegate(QStyledItemDelegate):
    # pylint: disable=no-self-use
    def displayText(self, script, _locale):
        if script.flags & Script.Modified:
            return "*" + script.name
        else:
            return script.name

    def paint(self, painter, option, index):
        script = index.data(Qt.DisplayRole)

        if script.flags & Script.Modified:
            option = QStyleOptionViewItem(option)
            option.palette.setColor(QPalette.Text, QColor(Qt.red))
            option.palette.setColor(QPalette.Highlight, QColor(Qt.darkRed))
        super().paint(painter, option, index)

    def createEditor(self, parent, _option, _index):
        return QLineEdit(parent)

    def setEditorData(self, editor, index):
        script = index.data(Qt.DisplayRole)
        editor.setText(script.name)

    def setModelData(self, editor, model, index):
        model[index.row()].name = str(editor.text())


def select_row(view, row):
    """
    Select a `row` in an item view
    """
    selmodel = view.selectionModel()
    selmodel.select(view.model().index(row, 0),
                    QItemSelectionModel.ClearAndSelect)


if TYPE_CHECKING:
    # pylint: disable=used-before-assignment
    _ScriptData = TypedDict("_ScriptData", {
        "name": str, "script": str, "filename": Optional[str]
    })


class OWPythonScript(OWWidget):
    name = "Python Script"
    description = "Write a Python script and run it on input data or models."
    category = "Transform"
    icon = "icons/PythonScript.svg"
    priority = 3150
    keywords = "program, function"

    class Inputs:
        data = MultiInput(
            "Data", Table, replaces=["in_data"], default=True
        )
        learner = MultiInput(
            "Learner", Learner, replaces=["in_learner"], default=True
        )
        classifier = MultiInput(
            "Classifier", Model, replaces=["in_classifier"], default=True
        )
        object = MultiInput(
            "Object", object, replaces=["in_object"], default=False, auto_summary=False
        )

    class Outputs:
        data = Output("Data", Table, replaces=["out_data"])
        learner = Output("Learner", Learner, replaces=["out_learner"])
        classifier = Output("Classifier", Model, replaces=["out_classifier"])
        object = Output("Object", object, replaces=["out_object"], auto_summary=False)

    signal_names = ("data", "learner", "classifier", "object")

    settings_version = 2
    scriptLibrary: 'List[_ScriptData]' = Setting([{
        "name": "Table from numpy",
        "script": DEFAULT_SCRIPT,
        "filename": None
    }])
    currentScriptIndex = Setting(0)
    scriptText: Optional[str] = Setting(None, schema_only=True)
    splitterState: Optional[bytes] = Setting(None)

    vimModeEnabled = Setting(False)

    class Error(OWWidget.Error):
        pass

    def __init__(self):
        super().__init__()

        for name in self.signal_names:
            setattr(self, name, [])

        self.splitCanvas = QSplitter(Qt.Vertical, self.mainArea)
        self.mainArea.layout().addWidget(self.splitCanvas)

        # Styling

        self.defaultFont = defaultFont = (
            'Menlo' if sys.platform == 'darwin' else
            'Courier' if sys.platform in ['win32', 'cygwin'] else
            'DejaVu Sans Mono'
        )
        self.defaultFontSize = defaultFontSize = 13

        self.editorBox = gui.vBox(self, box="Editor", spacing=4)
        self.splitCanvas.addWidget(self.editorBox)

        darkMode = QApplication.instance().property('darkMode')
        scheme_name = 'Dark' if darkMode else 'Light'
        syntax_highlighting_scheme = SYNTAX_HIGHLIGHTING_STYLES[scheme_name]
        self.pygments_style_class = make_pygments_style(scheme_name)

        eFont = QFont(defaultFont)
        eFont.setPointSize(defaultFontSize)

        # Fake Signature

        self.func_sig = func_sig = FunctionSignature(
            self.editorBox,
            syntax_highlighting_scheme,
            eFont
        )

        # Editor

        editor = PythonEditor(self)
        editor.setFont(eFont)
        editor.setup_completer_appearance((300, 180), eFont)

        # Fake return

        return_stmt = ReturnStatement(
            self.editorBox,
            syntax_highlighting_scheme,
            eFont
        )
        self.return_stmt = return_stmt

        # Match indentation

        textEditBox = QWidget(self.editorBox)
        textEditBox.setLayout(QHBoxLayout())
        char_4_width = QFontMetrics(eFont).horizontalAdvance('0000')

        @editor.viewport_margins_updated.connect
        def _(width):
            func_sig.setIndent(width)
            textEditMargin = max(0, round(char_4_width - width))
            return_stmt.setIndent(textEditMargin + width)
            textEditBox.layout().setContentsMargins(
                textEditMargin, 0, 0, 0
            )

        self.text = editor
        textEditBox.layout().addWidget(editor)
        self.editorBox.layout().addWidget(func_sig)
        self.editorBox.layout().addWidget(textEditBox)
        self.editorBox.layout().addWidget(return_stmt)

        self.editorBox.setAlignment(Qt.AlignVCenter)

        self.text.modificationChanged[bool].connect(self.onModificationChanged)

        # Controls

        self.editor_controls = gui.vBox(self.controlArea, box='Preferences')

        self.vim_box = gui.hBox(self.editor_controls, spacing=20)
        self.vim_indicator = VimIndicator(self.vim_box)

        vim_sp = QSizePolicy(
            QSizePolicy.Expanding, QSizePolicy.Fixed
        )
        vim_sp.setRetainSizeWhenHidden(True)
        self.vim_indicator.setSizePolicy(vim_sp)

        def enable_vim_mode():
            editor.vimModeEnabled = self.vimModeEnabled
            self.vim_indicator.setVisible(self.vimModeEnabled)
        enable_vim_mode()

        gui.checkBox(
            self.vim_box, self, 'vimModeEnabled', 'Vim mode',
            tooltip="Only for the coolest.",
            callback=enable_vim_mode
        )
        self.vim_box.layout().addWidget(self.vim_indicator)
        @editor.vimModeIndicationChanged.connect
        def _(color, text):
            self.vim_indicator.indicator_color = color
            self.vim_indicator.indicator_text = text
            self.vim_indicator.update()

        # Library

        self.libraryListSource = []
        self._cachedDocuments = {}

        self.libraryList = itemmodels.PyListModel(
            [], self,
            flags=Qt.ItemIsSelectable | Qt.ItemIsEnabled | Qt.ItemIsEditable)

        self.libraryList.wrap(self.libraryListSource)

        self.controlBox = gui.vBox(self.controlArea, 'Library')
        self.controlBox.layout().setSpacing(1)

        self.libraryView = QListView(
            editTriggers=QListView.DoubleClicked | QListView.EditKeyPressed,
            sizePolicy=QSizePolicy(QSizePolicy.Ignored,
                                   QSizePolicy.Preferred)
        )
        self.libraryView.setItemDelegate(ScriptItemDelegate(self))
        self.libraryView.setModel(self.libraryList)

        self.libraryView.selectionModel().selectionChanged.connect(
            self.onSelectedScriptChanged
        )
        self.controlBox.layout().addWidget(self.libraryView)

        w = itemmodels.ModelActionsWidget()

        self.addNewScriptAction = action = QAction("+", self)
        action.setToolTip("Add a new script to the library")
        action.triggered.connect(self.onAddScript)
        w.addAction(action)

        action = QAction(unicodedata.lookup("MINUS SIGN"), self)
        action.setToolTip("Remove script from library")
        action.triggered.connect(self.onRemoveScript)
        w.addAction(action)

        action = QAction("Update", self)
        action.setToolTip("Save changes in the editor to library")
        action.setShortcut(QKeySequence(QKeySequence.Save))
        action.triggered.connect(self.commitChangesToLibrary)
        w.addAction(action)

        action = QAction("More", self, toolTip="More actions")

        new_from_file = QAction("Import Script from File", self)
        save_to_file = QAction("Save Selected Script to File", self)
        restore_saved = QAction("Undo Changes to Selected Script", self)
        save_to_file.setShortcut(QKeySequence(QKeySequence.SaveAs))

        new_from_file.triggered.connect(self.onAddScriptFromFile)
        save_to_file.triggered.connect(self.saveScript)
        restore_saved.triggered.connect(self.restoreSaved)

        menu = QMenu(w)
        menu.addAction(new_from_file)
        menu.addAction(save_to_file)
        menu.addAction(restore_saved)
        action.setMenu(menu)
        button = w.addAction(action)
        button.setPopupMode(QToolButton.InstantPopup)

        w.layout().setSpacing(1)

        self.controlBox.layout().addWidget(w)

        self.execute_button = gui.button(self.buttonsArea, self, 'Run', callback=self.commit)

        self.run_action = QAction("Run script", self, triggered=self.commit,
                                  shortcut=QKeySequence(Qt.ControlModifier | Qt.Key_R))
        self.addAction(self.run_action)

        self.saveAction = action = QAction("&Save", self.text)
        action.setToolTip("Save script to file")
        action.setShortcut(QKeySequence(QKeySequence.Save))
        action.setShortcutContext(Qt.WidgetWithChildrenShortcut)
        action.triggered.connect(self.saveScript)

        self.consoleBox = gui.vBox(self.splitCanvas, 'Console')
        self.console = PythonConsole({}, self)
        self.consoleBox.layout().addWidget(self.console)
        self.console.document().setDefaultFont(QFont(defaultFont))
        self.consoleBox.setAlignment(Qt.AlignBottom)
        self.splitCanvas.setSizes([2, 1])
        self.controlArea.layout().addStretch(10)

        self._restoreState()
        self.settingsAboutToBePacked.connect(self._saveState)

    def sizeHint(self) -> QSize:
        return super().sizeHint().expandedTo(QSize(800, 600))

    def _restoreState(self):
        self.libraryListSource = [Script.fromdict(s) for s in self.scriptLibrary]
        self.libraryList.wrap(self.libraryListSource)
        select_row(self.libraryView, self.currentScriptIndex)

        if self.scriptText is not None:
            current = self.text.toPlainText()
            # do not mark scripts as modified
            if self.scriptText != current:
                self.text.document().setPlainText(self.scriptText)

        if self.splitterState is not None:
            self.splitCanvas.restoreState(QByteArray(self.splitterState))

    def _saveState(self):
        self.scriptLibrary = [s.asdict() for s in self.libraryListSource]
        self.scriptText = self.text.toPlainText()
        self.splitterState = bytes(self.splitCanvas.saveState())

    def set_input(self, index, obj, signal):
        dic = getattr(self, signal)
        dic[index] = obj

    def insert_input(self, index, obj, signal):
        dic = getattr(self, signal)
        dic.insert(index, obj)

    def remove_input(self, index, signal):
        dic = getattr(self, signal)
        dic.pop(index)

    @Inputs.data
    def set_data(self, index, data):
        self.set_input(index, data, "data")

    @Inputs.data.insert
    def insert_data(self, index, data):
        self.insert_input(index, data, "data")

    @Inputs.data.remove
    def remove_data(self, index):
        self.remove_input(index, "data")

    @Inputs.learner
    def set_learner(self, index, learner):
        self.set_input(index, learner, "learner")

    @Inputs.learner.insert
    def insert_learner(self, index, learner):
        self.insert_input(index, learner, "learner")

    @Inputs.learner.remove
    def remove_learner(self, index):
        self.remove_input(index, "learner")

    @Inputs.classifier
    def set_classifier(self, index, classifier):
        self.set_input(index, classifier, "classifier")

    @Inputs.classifier.insert
    def insert_classifier(self, index, classifier):
        self.insert_input(index, classifier, "classifier")

    @Inputs.classifier.remove
    def remove_classifier(self, index):
        self.remove_input(index, "classifier")

    @Inputs.object
    def set_object(self, index, object):
        self.set_input(index, object, "object")

    @Inputs.object.insert
    def insert_object(self, index, object):
        self.insert_input(index, object, "object")

    @Inputs.object.remove
    def remove_object(self, index):
        self.remove_input(index, "object")

    def handleNewSignals(self):
        # update fake signature labels
        self.func_sig.update_signal_text({
            n: len(getattr(self, n)) for n in self.signal_names
        })

        self.commit()

    def selectedScriptIndex(self):
        rows = self.libraryView.selectionModel().selectedRows()
        if rows:
            return [i.row() for i in rows][0]
        else:
            return None

    def setSelectedScript(self, index):
        select_row(self.libraryView, index)

    def onAddScript(self, *_):
        self.libraryList.append(Script("New script", self.text.toPlainText(), 0))
        self.setSelectedScript(len(self.libraryList) - 1)

    def onAddScriptFromFile(self, *_):
        filename, _ = QFileDialog.getOpenFileName(
            self, 'Open Python Script',
            os.path.expanduser("~/"),
            'Python files (*.py)\nAll files(*.*)'
        )
        if filename:
            name = os.path.basename(filename)
            with tokenize.open(filename) as f:
                contents = f.read()
            self.libraryList.append(Script(name, contents, 0, filename))
            self.setSelectedScript(len(self.libraryList) - 1)

    def onRemoveScript(self, *_):
        index = self.selectedScriptIndex()
        if index is not None:
            del self.libraryList[index]
            select_row(self.libraryView, max(index - 1, 0))

    def onSaveScriptToFile(self, *_):
        index = self.selectedScriptIndex()
        if index is not None:
            self.saveScript()

    def onSelectedScriptChanged(self, selected, _deselected):
        index = [i.row() for i in selected.indexes()]
        if index:
            current = index[0]
            if current >= len(self.libraryList):
                self.addNewScriptAction.trigger()
                return

            self.text.setDocument(self.documentForScript(current))
            self.currentScriptIndex = current

    def documentForScript(self, script=0):
        if not isinstance(script, Script):
            script = self.libraryList[script]
        if script not in self._cachedDocuments:
            doc = QTextDocument(self)
            doc.setDocumentLayout(QPlainTextDocumentLayout(doc))
            doc.setPlainText(script.script)
            doc.setDefaultFont(QFont(self.defaultFont))
            doc.highlighter = PygmentsHighlighter(doc)
            doc.highlighter.set_style(self.pygments_style_class)
            doc.setDefaultFont(QFont(self.defaultFont, pointSize=self.defaultFontSize))
            doc.modificationChanged[bool].connect(self.onModificationChanged)
            doc.setModified(False)
            self._cachedDocuments[script] = doc
        return self._cachedDocuments[script]

    def commitChangesToLibrary(self, *_):
        index = self.selectedScriptIndex()
        if index is not None:
            self.libraryList[index].script = self.text.toPlainText()
            self.text.document().setModified(False)
            self.libraryList.emitDataChanged(index)

    def onModificationChanged(self, modified):
        index = self.selectedScriptIndex()
        if index is not None:
            self.libraryList[index].flags = Script.Modified if modified else 0
            self.libraryList.emitDataChanged(index)

    def restoreSaved(self):
        index = self.selectedScriptIndex()
        if index is not None:
            self.text.document().setPlainText(self.libraryList[index].script)
            self.text.document().setModified(False)

    def saveScript(self):
        index = self.selectedScriptIndex()
        if index is not None:
            script = self.libraryList[index]
            filename = script.filename
        else:
            filename = os.path.expanduser("~/")

        filename, _ = QFileDialog.getSaveFileName(
            self, 'Save Python Script',
            filename,
            'Python files (*.py)\nAll files(*.*)'
        )

        if filename:
            fn = ""
            head, tail = os.path.splitext(filename)
            if not tail:
                fn = head + ".py"
            else:
                fn = filename

            f = open(fn, 'w')
            f.write(self.text.toPlainText())
            f.close()

    def initial_locals_state(self):
        d = {}
        for name in self.signal_names:
            value = getattr(self, name)
            all_values = list(value)
            one_value = all_values[0] if len(all_values) == 1 else None
            d["in_" + name + "s"] = all_values
            d["in_" + name] = one_value
        return d

    def commit(self):
        self.Error.clear()
        lcls = self.initial_locals_state()
        lcls["_script"] = str(self.text.toPlainText())
        self.console.updateLocals(lcls)
        self.console.write("\nRunning script:\n")
        self.console.push("exec(_script)")
        self.console.new_prompt(sys.ps1)
        for signal in self.signal_names:
            out_var = self.console.locals.get("out_" + signal)
            signal_type = getattr(self.Outputs, signal).type
            if not isinstance(out_var, signal_type) and out_var is not None:
                self.Error.add_message(signal,
                                       "'{}' has to be an instance of '{}'.".
                                       format(signal, signal_type.__name__))
                getattr(self.Error, signal)()
                out_var = None
            getattr(self.Outputs, signal).send(out_var)

    def keyPressEvent(self, e):
        if e.matches(QKeySequence.InsertLineSeparator):
            # run on Shift+Enter, Ctrl+Enter
            self.run_action.trigger()
            e.accept()
        else:
            super().keyPressEvent(e)

    def dragEnterEvent(self, event):  # pylint: disable=no-self-use
        urls = event.mimeData().urls()
        if urls:
            # try reading the file as text
            c = read_file_content(urls[0].toLocalFile(), limit=1000)
            if c is not None:
                event.acceptProposedAction()

    @classmethod
    def migrate_settings(cls, settings, version):
        if version is not None and version < 2:
            scripts = settings.pop("libraryListSource")  # type: List[Script]
            library = [dict(name=s.name, script=s.script, filename=s.filename)
                       for s in scripts]  # type: List[_ScriptData]
            settings["scriptLibrary"] = library

    def onDeleteWidget(self):
        self.text.terminate()
        super().onDeleteWidget()


class OWPythonScriptDropHandler(SingleFileDropHandler):
    WIDGET = OWPythonScript

    def canDropFile(self, path: str) -> bool:
        md = QMimeDatabase()
        mt = md.mimeTypeForFile(path)
        return mt.inherits("text/x-python")

    def parametersFromFile(self, path: str) -> Dict[str, Any]:
        with open(path, "rt") as f:
            content = f.read()

        item: '_ScriptData' = {
            "name": os.path.basename(path),
            "script": content,
            "filename": path,
        }
        defaults: List['_ScriptData'] = \
            OWPythonScript.settingsHandler.defaults.get("scriptLibrary", [])

        def is_same(item: '_ScriptData'):
            """Is item same file as the dropped path."""
            return item["filename"] is not None \
                   and samepath(item["filename"], path)

        defaults = [it for it in defaults if not is_same(it)]
        params = {
            "__version__": OWPythonScript.settings_version,
            "scriptLibrary": [item] + defaults,
            "scriptText": content
        }
        return params


if __name__ == "__main__":  # pragma: no cover
    WidgetPreview(OWPythonScript).run()