import re
import html
from enum import IntEnum
from typing import Optional, Tuple, Union, Callable, NamedTuple, Dict, List

from AnyQt.QtCore import (
    Qt, QTimer, QPoint, QItemSelectionModel, QSize, QAbstractListModel,
)
from AnyQt.QtGui import (
    QValidator, QPalette, QDoubleValidator, QIntValidator,  QColor)
from AnyQt.QtWidgets import (
    QListView, QHBoxLayout, QStyledItemDelegate, QButtonGroup, QWidget,
    QLineEdit, QToolTip, QLabel, QApplication,
    QSpinBox, QSizePolicy, QRadioButton, QComboBox)

from orangewidget.settings import Setting
from orangewidget.utils import listview

from Orange.data import (
    Variable, ContinuousVariable, DiscreteVariable, TimeVariable, Domain, Table)
import Orange.preprocess.discretize as disc
from Orange.widgets.utils.localization import pl
from Orange.widgets import widget, gui
from Orange.widgets.utils import unique_everseen
from Orange.widgets.utils.itemmodels import DomainModel
from Orange.widgets.utils.widgetpreview import WidgetPreview
from Orange.widgets.widget import Input, Output
from Orange.widgets.data.oweditdomain import FixedSizeButton

re_custom_sep = re.compile(r"\s*,\s*")
time_units = ["year", "month", "day", "week", "hour", "minute", "second"]
INVALID_WIDTH = "invalid width"
TOO_MANY_INTERVALS = "too many intervals"


def _fixed_width_discretization(
        data: Table,
        var: Union[ContinuousVariable, str, int],
        width: str) -> Union[DiscreteVariable, str]:
    """
    Discretize numeric variable with fixed bin width. Used in method definition.

    Width is given as string (coming from line edit). The labels for the new
    variable will have the same number of digits; this is more appropriate
    than the number of digits in the original variable, which may be too large.

    Args:
        data: data used to deduce the interval of values
        var: variable to discretize
        width: interval width

    Returns:
        Discrete variable, if successful; a string with error otherwise
    """
    digits = len(width) - width.index(".") - 1 if "." in width else 0
    try:
        width = float(width)
    except ValueError:
        return INVALID_WIDTH
    if width <= 0:
        return INVALID_WIDTH
    try:
        return disc.FixedWidth(width, digits)(data, var)
    except disc.TooManyIntervals:
        return TOO_MANY_INTERVALS


# pylint: disable=invalid-name
def _fixed_time_width_discretization(
        data: Table,
        var: Union[TimeVariable, str, int],
        width: str, unit: int) -> Union[DiscreteVariable]:
    """
    Discretize time variable with fixed bin width. Used in method definition.

    Width is given as string (coming from line edit).

    Args:
        data: data used to deduce the interval of values
        var: variable to discretize
        width: interval width
        unit: 0 = year, 1 = month, 2 = week, 3 = day, 4 = hour, 5 = min, 6 = sec

    Returns:
        Discrete variable, if successful; a string with error otherwise
    """
    try:
        width = int(width)
    except ValueError:
        return INVALID_WIDTH
    if width <= 0:
        return INVALID_WIDTH
    if unit == 3:  # week
        width *= 7
    unit -= unit >= 3
    try:
        return disc.FixedTimeWidth(width, unit)(data, var)
    except disc.TooManyIntervals:
        return TOO_MANY_INTERVALS


def _mdl_discretization(
        data: Table,
        var: Union[ContinuousVariable, str, int]) -> Union[DiscreteVariable, str]:
    if not data.domain.has_discrete_class:
        return "no discrete class"
    return disc.EntropyMDL()(data, var)


def _custom_discretization(
        _,
        var: Union[ContinuousVariable, str, int],
        points: str) -> Union[DiscreteVariable, str]:
    """
    Discretize variable using custom thresholds. Used in method definition.

    Thresholds are given as string (coming from line edit).

    Args:
        data: data used to deduce the interval of values
        var: variable to discretize
        points: thresholds

    Returns:
        Discrete variable, if successful; a string with error otherwise
    """
    try:
        cuts = [float(x) for x in re_custom_sep.split(points.strip())]
    except ValueError:
        cuts = []
    if any(x >= y for x, y in zip(cuts, cuts[1:])):
        cuts = []
    if not cuts:
        return "invalid cuts"
    return disc.Discretizer.create_discretized_var(var, cuts)


class Methods(IntEnum):
    # pylint: disable=invalid-name
    Default, Keep, MDL, EqualFreq, EqualWidth, Remove, Custom, Binning, \
        FixedWidth, FixedWidthTime = range(10)


class MethodDesc(NamedTuple):
    """
    Definitions of all methods; used for creation of interface and calling
    """
    id_: Methods  # Method id
    label: str  # Label used for radio button
    short_desc: str  # Short descriptions for list views
    tooltip: str  # Tooltip for radio button
    # Discretization function, see, e.g. fixed_width_discretization
    function: Optional[Callable[..., Union[DiscreteVariable, str]]]
    controls: Tuple[str, ...] = ()  # Widget attributes with related ux controls


Options: Dict[Methods, MethodDesc] = {
    method.id_: method
    for method in (
        MethodDesc(Methods.Default,
                   "Use default setting", "default",
                   "Treat the variable as defined in 'default setting'",
                   None,
                   ()),
        MethodDesc(Methods.Keep,
                   "Keep numeric", "keep",
                   "Keep the variable as is",
                   lambda data, var: var,
                   ()),
        MethodDesc(Methods.MDL,
                   "Entropy vs. MDL", "entropy",
                   "Split values until MDL exceeds the entropy (Fayyad-Irani)\n"
                   "(requires discrete class variable)",
                   _mdl_discretization,
                   ()),
        MethodDesc(Methods.EqualFreq,
                   "Equal frequency, intervals: ", "equal freq, k={}",
                   "Create bins with same number of instances",
                   lambda data, var, k: disc.EqualFreq(k)(data, var),
                   ("freq_spin", )),
        MethodDesc(Methods.EqualWidth,
                   "Equal width, intervals: ", "equal width, k={}",
                   "Create bins of the same width",
                   lambda data, var, k: disc.EqualWidth(k)(data, var),
                   ("width_spin", )),
        MethodDesc(Methods.Remove,
                   "Remove", "remove",
                   "Remove variable",
                   lambda *_: None,
                   ()),
        MethodDesc(Methods.Binning,
                   "Natural binning, desired bins: ", "binning, desired={}",
                   "Create bins with nice thresholds; "
                   "try matching desired number of bins",
                   lambda data, var, nbins: disc.Binning(nbins)(data, var),
                   ("binning_spin", )),
        MethodDesc(Methods.FixedWidth,
                   "Fixed width: ", "fixed width {}",
                   "Create bins with the given width (not for time variables)",
                   _fixed_width_discretization,
                   ("width_line", )),
        MethodDesc(Methods.FixedWidthTime,
                   "Time interval: ", "time interval, {} {}",
                   "Create bins with the give width (for time variables)",
                   _fixed_time_width_discretization,
                   ("width_time_line", "width_time_unit")),
        MethodDesc(Methods.Custom,
                   "Custom: ", "custom: {}",
                   "Use manually specified thresholds",
                   _custom_discretization,
                   ("threshold_line", ))
    )
}


class VarHint(NamedTuple):
    """Description for settings"""
    method_id: Methods
    args: Tuple[Union[str, float, int]]


class DiscDesc(NamedTuple):
    """Data for list view model"""
    hint: VarHint
    points: str
    values: Tuple[str]


KeyType = Optional[Tuple[str, bool]]
DefaultHint = VarHint(Methods.Keep, ())
DefaultKey = None


def variable_key(var: ContinuousVariable) -> KeyType:
    """Key for that variable in var_hints and discretized_vars"""
    return var.name, isinstance(var, TimeVariable)


class ListViewSearch(listview.ListViewSearch):
    """
    A list view with two components shown above it:
    - a listview containing a single item representing default settings
    - a filter for search

    The class is based on listview.ListViewSearch and needs to have the same
    name in order to override its private method __layout.

    Inherited __init__ calls __layout, so `default_view` must be constructed
    there. Construction before calling super().__init__ doesn't work because
    PyQt does not allow it.
    """
    class DiscDelegate(QStyledItemDelegate):
        """
        A delegate that shows items (variables) with specific settings in bold
        """
        def initStyleOption(self, option, index):
            super().initStyleOption(option, index)
            option.font.setBold(index.data(Qt.UserRole).hint is not None)

    def __init__(self, *args, **kwargs):
        self.default_view = None
        super().__init__(preferred_size=QSize(350, -1), *args, **kwargs)
        self.setItemDelegate(self.DiscDelegate(self))

    def select_default(self):
        """Select the item representing default settings"""
        index = self.default_view.model().index(0)
        self.default_view.selectionModel().select(
            index, QItemSelectionModel.Select)

    # pylint: disable=unused-private-member
    def __layout(self):
        if self.default_view is None:  # __layout was called from __init__
            view = self.default_view = QListView(self)
            view.setModel(DefaultDiscModel())
            view.verticalScrollBar().setDisabled(True)
            view.horizontalScrollBar().setDisabled(True)
            view.setHorizontalScrollBarPolicy(
                Qt.ScrollBarPolicy.ScrollBarAlwaysOff)
            view.setVerticalScrollBarPolicy(
                Qt.ScrollBarPolicy.ScrollBarAlwaysOff)
            font = view.font()
            font.setBold(True)
            view.setFont(font)
        else:
            view = self.default_view

        # Put the list view with default on top
        margins = self.viewportMargins()
        def_height = view.sizeHintForRow(0) + 2 * view.spacing() + 2
        view.setGeometry(0, 0, self.geometry().width(), def_height)
        view.setFixedHeight(def_height)

        # Then search
        search = self.__search
        src_height = search.sizeHint().height()
        size = self.size()
        search.setGeometry(0, def_height + 2, size.width(), src_height)

        # Then the real list view
        margins.setTop(def_height + 2 + src_height)
        self.setViewportMargins(margins)


def format_desc(hint: VarHint) -> str:
    """Describe the method and its parameters; used in list views and report"""
    if hint is None:
        return Options[Methods.Default].short_desc
    desc = Options[hint.method_id].short_desc
    if hint.method_id == Methods.FixedWidthTime:
        width, unit = hint.args
        try:
            width = int(width)
        except ValueError:
            unit = f"{time_units[unit]}(s)"
        else:
            unit = f"{pl(width, time_units[unit])}"
        return desc.format(width, unit)
    return desc.format(*hint.args)


class DiscDomainModel(DomainModel):
    """
    Domain model that adds description of discretization methods and thresholds

    Also provides a tooltip that shows bins, that is, labels of the discretized
    variable.
    """
    def data(self, index, role=Qt.DisplayRole):
        if role == Qt.ToolTipRole:
            var = self[index.row()]
            data = index.data(Qt.UserRole)
            if not isinstance(data, DiscDesc):
                return super().data(index, role)
            tip = f"<b>{var.name}: </b>"
            values = map(html.escape, data.values)
            if not data.values:
                return None
            if len(data.values) <= 3:
                return f'<p style="white-space:pre">{tip}' \
                       f'{",&nbsp;&nbsp;".join(values)}</p>'
            else:
                return tip + "<br/>" \
                    + "".join(f"- {value}<br/>" for value in values)
        value = super().data(index, role)
        if role == Qt.DisplayRole:
            try:
                hint, points, values = index.data(Qt.UserRole)
            except TypeError:
                pass  # don't have user role (yet)
            else:
                value += f" ({format_desc(hint)}){points}"
        return value


class DefaultDiscModel(QAbstractListModel):
    """
    A model used for showing "Default settings" above the list view with var
    """
    icon = None

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        if DefaultDiscModel.icon is None:
            DefaultDiscModel.icon = gui.createAttributePixmap(
                "★", QColor(0, 0, 0, 0), Qt.black)
        self.hint: VarHint = DefaultHint

    @staticmethod
    def rowCount(parent):
        return 0 if parent.isValid() else 1

    @staticmethod
    def columnCount(parent):
        return 0 if parent.isValid() else 1

    def data(self, _, role=Qt.DisplayRole):
        if role == Qt.DisplayRole:
            return "Default setting: " + format_desc(self.hint)
        elif role == Qt.DecorationRole:
            return DefaultDiscModel.icon
        elif role == Qt.ToolTipRole:
            return "Default setting for variables without specific setings"
        return None

    def setData(self, index, value, role=Qt.DisplayRole):
        if role == Qt.UserRole:
            self.hint = value
            self.dataChanged.emit(index, index)


class IncreasingNumbersListValidator(QValidator):
    """
    A validator for custom thresholds

    Requires a string with increasing comma-separated values. If the string
    ends with number followed by space, it inserts a comma.
    """
    @staticmethod
    def validate(string: str, pos: int) -> Tuple[QValidator.State, str, int]:
        for i, c in enumerate(string, start=1):
            if c not in "+-., 0123456789":
                return QValidator.Invalid, string, i
        prev = None
        if pos == len(string) >= 2 \
                and string[-1] == " " and string[-2].isdigit():
            string = string[:-1] + ", "
            pos += 1
        for valuestr in re_custom_sep.split(string.strip()):
            try:
                value = float(valuestr)
            except ValueError:
                return QValidator.Intermediate, string, pos
            if prev is not None and value <= prev:
                return QValidator.Intermediate, string, pos
            prev = value
        return QValidator.Acceptable, string, pos

    @staticmethod
    def show_tip(
            widget: QWidget, pos: QPoint, text: str, timeout=-1,
            textFormat=Qt.AutoText, wordWrap=None):
        """Show a tooltip; used for invalid custom thresholds"""
        propname = __name__ + "::show_tip_qlabel"
        if timeout < 0:
            timeout = widget.toolTipDuration()
        if timeout < 0:
            timeout = 5000 + 40 * max(0, len(text) - 100)
        tip = widget.property(propname)
        if not text and tip is None:
            return

        def hide():
            w = tip.parent()
            w.setProperty(propname, None)
            tip.timer.stop()
            tip.close()
            tip.deleteLater()

        if not isinstance(tip, QLabel):
            tip = QLabel(objectName="tip-label", focusPolicy=Qt.NoFocus)
            tip.setBackgroundRole(QPalette.ToolTipBase)
            tip.setForegroundRole(QPalette.ToolTipText)
            tip.setPalette(QToolTip.palette())
            tip.setFont(QApplication.font("QTipLabel"))
            tip.setContentsMargins(2, 2, 2, 2)
            tip.timer = QTimer(tip, singleShot=True, objectName="hide-timer")
            tip.timer.timeout.connect(hide)
            widget.setProperty(propname, tip)
            tip.setParent(widget, Qt.ToolTip)

        tip.setText(text)
        tip.setTextFormat(textFormat)
        if wordWrap is None:
            wordWrap = textFormat != Qt.PlainText
        tip.setWordWrap(wordWrap)

        if not text:
            hide()
        else:
            tip.timer.start(timeout)
            tip.show()
            tip.move(pos)


# These are no longer used, but needed for loading and migrating old pickles.
# We insert them into namespace instead of normally defining them, in order
# to hide it from IDE's and avoid mistakenly using them.
# pylint: disable=wrong-import-position,wrong-import-order
from collections import namedtuple
globals().update(dict(
    DState=namedtuple(
        "DState",
        ["method",  # discretization method
         "points",  # induced cut points
         "disc_var"],
        defaults=(None, None)  # induced discretized variable
    ),
    Default=namedtuple("Default", ["method"]),
    Leave=namedtuple("Leave", []),
    MDL=namedtuple("MDL", []),
    EqualFreq=namedtuple("EqualFreq", ["k"]),
    EqualWidth=namedtuple("EqualWidth", ["k"]),
    Remove=namedtuple("Remove", []),
    Custom=namedtuple("Custom", ["points"])
))


class OWDiscretize(widget.OWWidget):
    # pylint: disable=too-many-instance-attributes
    name = "Discretize"
    description = "Discretize numeric variables"
    category = "Transform"
    icon = "icons/Discretize.svg"
    keywords = "discretize, bin, categorical, nominal, ordinal"
    priority = 2130

    class Inputs:
        data = Input("Data", Table, doc="Input data table")

    class Outputs:
        data = Output("Data", Table, doc="Table with categorical features")

    settings_version = 3

    #: Default setting (key DefaultKey) and specific settings for variables;
    # if variable is not in the dict, it uses default
    var_hints: Dict[KeyType, VarHint] = Setting(
        {DefaultKey: DefaultHint}, schema_only=True)
    autosend = Setting(True)

    want_main_area = False

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

        #: input data
        self.data = None
        #: Cached discretized variables
        self.discretized_vars: Dict[KeyType, DiscreteVariable] = {}

        # Indicates that buttons, spins, edit and combos are being changed
        # programmatically (when interface is changed due to selection change),
        # so this should not trigger update of hints and invalidation of
        # discretization in `self.discretized_vars`.
        self.__interface_update = False

        box = gui.hBox(self.controlArea, True, spacing=8)
        self._create_var_list(box)
        self._create_buttons(box)
        gui.auto_apply(self.buttonsArea, self, "autosend")
        gui.rubber(self.buttonsArea)
        self.varview.select_default()

    def _create_var_list(self, box):
        """Create list view with variables"""
        # If we decide to not elide, remove the `uniformItemSize` argument
        self.varview = ListViewSearch(
            selectionMode=QListView.ExtendedSelection, uniformItemSizes=True)
        self.varview.setModel(
            DiscDomainModel(
                valid_types=(ContinuousVariable, TimeVariable),
                order=DiscDomainModel.MIXED
            ))
        self.varview.selectionModel().selectionChanged.connect(
            self._var_selection_changed)
        self.varview.default_view.selectionModel().selectionChanged.connect(
            self._default_selected)
        self._update_default_model()
        box.layout().addWidget(self.varview)

    def _create_buttons(self, box):
        """Create radio buttons"""
        def intspin():
            s = QSpinBox(self)
            s.setMinimum(2)
            s.setMaximum(10)
            s.setFixedWidth(60)
            s.setAlignment(Qt.AlignRight)
            s.setContentsMargins(0, 0, 0, 0)
            return s, s.valueChanged

        def widthline(validator):
            s = QLineEdit(self)
            s.setFixedWidth(60)
            s.setAlignment(Qt.AlignRight)
            s.setValidator(validator)
            s.setContentsMargins(0, 0, 0, 0)
            return s, s.textChanged

        def manual_cut_editline(text="", enabled=True) -> QLineEdit:
            edit = QLineEdit(
                text=text,
                placeholderText="e.g. 0.0, 0.5, 1.0",
                toolTip='<p style="white-space:pre">' +
                        'Enter cut points as a comma-separate list of \n'
                        'strictly increasing numbers e.g. 0.0, 0.5, 1.0).</p>',
                enabled=enabled,
            )
            edit.setValidator(IncreasingNumbersListValidator())
            edit.setSizePolicy(QSizePolicy.MinimumExpanding, QSizePolicy.Fixed)

            @edit.textChanged.connect
            def update():
                validator = edit.validator()
                if validator is not None and edit.text().strip():
                    state, _, _ = validator.validate(edit.text(), 0)
                else:
                    state = QValidator.Acceptable
                palette = edit.palette()
                colors = {
                    QValidator.Intermediate: (Qt.yellow, Qt.black),
                    QValidator.Invalid: (Qt.red, Qt.black),
                }.get(state, None)
                if colors is None:
                    palette = QPalette()
                else:
                    palette.setColor(QPalette.Base, colors[0])
                    palette.setColor(QPalette.Text, colors[1])

                cr = edit.cursorRect()
                p = edit.mapToGlobal(cr.bottomRight())
                edit.setPalette(palette)
                if state != QValidator.Acceptable and edit.isVisible():
                    validator.show_tip(edit, p, edit.toolTip(),
                                       textFormat=Qt.RichText)
                else:
                    validator.show_tip(edit, p, "")
            return edit, edit.textChanged

        children = []

        def button(id_, *controls, stretch=True):
            layout = QHBoxLayout()
            desc = Options[id_]
            button = QRadioButton(desc.label)
            button.setToolTip(desc.tooltip)
            self.button_group.addButton(button, id_)
            layout.addWidget(button)
            if controls:
                if stretch:
                    layout.addStretch(1)
                for c, signal in controls:
                    layout.addWidget(c)
                    if signal is not None:
                        @signal.connect
                        def arg_changed():
                            self.button_group.button(id_).setChecked(True)
                            self.update_hints(id_)

            children.append(layout)
            button_box.layout().addLayout(layout)
            return (*controls, (None, ))[0][0]

        button_box = gui.vBox(box)
        button_box.layout().setSpacing(0)
        button_box.setSizePolicy(QSizePolicy(QSizePolicy.Fixed, QSizePolicy.Preferred))
        self.button_group = QButtonGroup(self)
        self.button_group.idClicked.connect(self.update_hints)

        button(Methods.Keep)
        button(Methods.Remove)

        self.binning_spin = button(Methods.Binning, intspin())
        validator = QDoubleValidator()
        validator.setBottom(0)
        self.width_line = button(Methods.FixedWidth, widthline(validator))

        self.width_time_unit = u = QComboBox(self)
        u.setContentsMargins(0, 0, 0, 0)
        u.addItems([f"{unit}(s)" for unit in time_units])
        validator = QIntValidator()
        validator.setBottom(1)
        self.width_time_line = button(Methods.FixedWidthTime,
                                      widthline(validator),
                                      (u, u.currentTextChanged))

        self.freq_spin = button(Methods.EqualFreq, intspin())
        self.width_spin = button(Methods.EqualWidth, intspin())
        button(Methods.MDL)

        self.copy_to_custom = FixedSizeButton(
            text="CC", toolTip="Copy the current cut points to manual mode")
        self.copy_to_custom.clicked.connect(self._copy_to_manual)
        self.threshold_line = button(Methods.Custom,
                                     manual_cut_editline(),
                                     (self.copy_to_custom, None),
                                     stretch=False)
        button(Methods.Default)
        maxheight = max(w.sizeHint().height() for w in children)
        for w in children:
            w.itemAt(0).widget().setFixedHeight(maxheight)
        button_box.layout().addStretch(1)

    def _update_default_model(self):
        """Update data in the model showing default settings"""
        model = self.varview.default_view.model()
        model.setData(model.index(0), self.var_hints[DefaultKey], Qt.UserRole)

    def _set_mdl_button(self):
        """Disable MDL discretization for data with non-discrete class"""
        mdl_button = self.button_group.button(Methods.MDL)
        if self.data is None or self.data.domain.has_discrete_class:
            mdl_button.setEnabled(True)
        else:
            if mdl_button.isChecked():
                self._check_button(Methods.Keep, True)
            mdl_button.setEnabled(False)

    def _check_button(self, method_id: Methods, checked: bool):
        """Checks the given button"""
        self.button_group.button(method_id).setChecked(checked)

    def _uncheck_all_buttons(self):
        """Uncheck all radio buttons"""
        group = self.button_group
        button = group.checkedButton()
        if button is not None:
            group.setExclusive(False)
            button.setChecked(False)
            group.setExclusive(True)

    def _set_radio_enabled(self, method_id: Methods, value: bool):
        """Enable/disable radio button and related controls"""
        if self.button_group.button(method_id).isChecked() and not value:
            self._uncheck_all_buttons()
        self.button_group.button(method_id).setEnabled(value)
        for control_name in Options[method_id].controls:
            getattr(self, control_name).setEnabled(value)

    def _get_values(self, method_id: Methods) -> Tuple[Union[int, float, str]]:
        """Return parameters from controls pertaining to the given method"""
        controls = Options[method_id].controls
        values = []
        for control_name in controls:
            control = getattr(self, control_name)
            if isinstance(control, QSpinBox):
                values.append(control.value())
            elif isinstance(control, QComboBox):
                values.append(control.currentIndex())
            else:
                values.append(control.text())
        return tuple(values)

    def _set_values(self, method_id: Methods,
                    values: Tuple[Union[str, int, float]]):
        """
        Set controls pertaining to the given method to parameters from hint
        """
        controls = Options[method_id].controls
        for control_name, value in zip(controls, values):
            control = getattr(self, control_name)
            if isinstance(control, QSpinBox):
                control.setValue(value)
            elif isinstance(control, QComboBox):
                control.setCurrentIndex(value)
            else:
                control.setText(value)

    def varkeys_for_selection(self) -> List[KeyType]:
        """
        Return list of KeyType's for selected variables (for indexing var_hints)

        If 'Default settings' are selected, this returns DefaultKey
        """
        model = self.varview.model()
        varkeys = [variable_key(model[index.row()])
                   for index in self.varview.selectionModel().selectedRows()]
        return varkeys or [DefaultKey]  # default settings are selected

    def update_hints(self, method_id: Methods):
        """
        Callback for radio buttons and for controls regulating parameters

        This function:
        - updates `var_hints` for all selected methods
        - invalidates (removes) `discretized_vars` for affected variables
        - calls _update_discretizations to compute and commit new discretization
        - calls deferred commit

        Data for list view models is updated in _update_discretizations
        """
        if self.__interface_update:
            return

        method_id = Methods(method_id)
        args = self._get_values(method_id)
        keys = self.varkeys_for_selection()
        if method_id == Methods.Default:
            for key in keys:
                if key in self.var_hints:
                    del self.var_hints[key]
        else:
            self.var_hints.update(dict.fromkeys(keys, VarHint(method_id, args)))
        if keys == [DefaultKey]:
            invalidate = set(self.discretized_vars) - set(self.var_hints)
        else:
            invalidate = keys
        for key in invalidate:
            del self.discretized_vars[key]

        if keys == [DefaultKey]:
            self._update_default_model()
        self._update_discretizations()
        self.commit.deferred()

    def _update_discretizations(self):
        """
        Compute invalidated (missing) discretizations

        Also set data for list view models for all invalidated variables
        """
        if self.data is None:
            return

        default_hint = self.var_hints[DefaultKey]
        model = self.varview.model()
        for index, var in enumerate(model):
            key = variable_key(var)
            if key in self.discretized_vars:
                continue  # still valid
            var_hint = self.var_hints.get(key)
            points, dvar = self._discretize_var(var, var_hint or default_hint)
            self.discretized_vars[key] = dvar
            values = getattr(dvar, "values", ())
            model.setData(model.index(index),
                          DiscDesc(var_hint, points, values),
                          Qt.UserRole)

    def _discretize_var(self, var: ContinuousVariable, hint: VarHint) \
        -> Tuple[str, Optional[Variable]]:
        """
        Discretize using method and data in the hint.

        Returns a description (list of points or error/warning) and a
        - discrete variable
        - same variable (if kept numeric)
        - None (if removed or errored)
        """
        if isinstance(var, TimeVariable):
            if hint.method_id in (Methods.FixedWidth, Methods.Custom):
                return ": <keep, time var>", var
        else:
            if hint.method_id == Methods.FixedWidthTime:
                return ": <keep, not time>", var

        function = Options[hint.method_id].function
        dvar = function(self.data, var, *hint.args)
        if isinstance(dvar, str):
            return f" <{dvar}>", None  # error
        if dvar is None:
            return "", None  # removed
        elif dvar is var:
            return "", var  # no transformation
        thresholds = dvar.compute_value.points
        if len(thresholds) == 0:
            return " <removed>", None
        return ": " + ", ".join(map(var.repr_val, thresholds)), dvar

    def _copy_to_manual(self):
        """
        Callback for 'CC' button

        Sets selected variables' method to "Custom" and copies thresholds
        to their VarHints. Variables that are not discretized (for any reason)
        are skipped.

        Discretizations are invalidated and then updated
        (`_update_discretizations`).

        If all selected variables have the same thresholds, it copies it to
        the line edit. Otherwise it unchecks all radio buttons to keep the
        interface consistent.
        """
        varkeys = self.varkeys_for_selection()
        texts = set()
        for key in varkeys:
            dvar = self.discretized_vars.get(key)
            fmt = self.data.domain[key[0]].repr_val
            if isinstance(dvar, DiscreteVariable):
                text = ", ".join(map(fmt, dvar.compute_value.points))
                texts.add(text)
                self.var_hints[key] = VarHint(Methods.Custom, (text, ))
                del self.discretized_vars[key]
        try:
            self.__interface_update = True
            if len(texts) == 1:
                self.threshold_line.setText(texts.pop())
            else:
                self._uncheck_all_buttons()
        finally:
            self.__interface_update = False
        self._update_discretizations()
        self.commit.deferred()

    def _default_selected(self, selected):
        """Callback for selecting 'Default setting'"""
        if not selected:
            # Prevent infinite recursion (with _var_selection_changed)
            return
        self.varview.selectionModel().clearSelection()
        self._update_interface()

        set_enabled = self._set_radio_enabled
        set_enabled(Methods.Default, False)
        set_enabled(Methods.FixedWidth, True)
        set_enabled(Methods.FixedWidthTime, True)
        set_enabled(Methods.Custom, True)
        self.copy_to_custom.setEnabled(False)

    def _var_selection_changed(self, _):
        """Callback for changed selection in listview with variables"""
        selected = self.varview.selectionModel().selectedIndexes()
        if not selected:
            # Prevent infinite recursion (with _default_selected)
            return
        self.varview.default_view.selectionModel().clearSelection()
        self._update_interface()

        set_enabled = self._set_radio_enabled
        vars_ = [self.data.domain[name]
                 for name, _ in self.varkeys_for_selection()]
        no_time = not any(isinstance(var, TimeVariable) for var in vars_)
        all_time = all(isinstance(var, TimeVariable) for var in vars_)
        set_enabled(Methods.Default, True)
        set_enabled(Methods.FixedWidth, no_time)
        set_enabled(Methods.Custom, no_time)
        self.copy_to_custom.setEnabled(no_time)
        set_enabled(Methods.FixedWidthTime, all_time)

    def _update_interface(self):
        """
        Update the user interface according to selection

        - If VarHints for all selected variables are the same, check the
          corresponding radio button and fill the corresponding controls;
        - otherwise, uncheck all radios.
        """
        if self.__interface_update:
            return

        try:
            self.__interface_update = True
            keys = self.varkeys_for_selection()
            mset = list(unique_everseen(map(self.var_hints.get, keys)))
            if len(mset) != 1:
                self._uncheck_all_buttons()
                return

            if mset == [None]:
                method_id, args = Methods.Default, ()
            else:
                method_id, args = mset.pop()
            self._check_button(method_id, True)
            self._set_values(method_id, args)
        finally:
            self.__interface_update = False

    @Inputs.data
    def set_data(self, data: Optional[Table]):
        self.discretized_vars = {}
        self.data = data
        self.varview.model().set_domain(None if data is None else data.domain)
        self._update_discretizations()
        self._update_default_model()
        self.varview.select_default()
        self._set_mdl_button()
        self.commit.now()

    @gui.deferred
    def commit(self):
        if self.data is None:
            self.Outputs.data.send(None)
            return

        def part(variables: List[Variable]) -> List[Variable]:
            return [dvar
                    for dvar in (self.discretized_vars.get(variable_key(v), v)
                                 for v in variables)
                    if dvar]

        d = self.data.domain
        domain = Domain(part(d.attributes), part(d.class_vars), part(d.metas))
        output = self.data.transform(domain)
        self.Outputs.data.send(output)

    def send_report(self):
        dmodel = self.varview.default_view.model()
        desc = dmodel.data(dmodel.index(0))
        self.report_items((tuple(desc.split(": ", maxsplit=1)), ))
        model = self.varview.model()
        reported = []
        for row in range(model.rowCount()):
            name = model[row].name
            desc = model.data(model.index(row), Qt.UserRole)
            if desc.hint is not None:
                name = f"{name} ({format_desc(desc.hint)})"
            reported.append((name, ', '.join(desc.values)))
        self.report_items("Variables", reported)

    @classmethod
    def migrate_settings(cls, settings, version):
        if version is None or version < 2:
            # was stored as int indexing Methods (but offset by 1)
            default = settings.pop("default_method", 0)
            default = Methods(default + 1)
            settings["default_method_name"] = default.name

        if version is None or version < 3:
            method_name = settings.pop("default_method_name",
                                       DefaultHint.method_id.name)
            k = settings.pop("default_k", 3)
            cut_points = settings.pop("default_cutpoints", ())

            method_id = getattr(Methods, method_name)
            if method_id in (Methods.EqualFreq, Methods.EqualWidth):
                args = (k, )
            elif method_id == Methods.Custom:
                args = (cut_points, )
            else:
                args = ()
            default_hint = VarHint(method_id, args)
            var_hints = {DefaultKey: default_hint}
            for context in settings.pop("context_settings", []):
                values = context.values
                if "saved_var_states" not in values:
                    continue
                var_states, _ = values.pop("saved_var_states")
                for (tpe, name), dstate in var_states.items():
                    key = (name, tpe == 4)  # time variable == 4
                    method = dstate.method
                    method_name = type(method).__name__.replace("Leave", "Keep")
                    if method_name == "Default":
                        continue
                    if method_name == "Custom":
                        args = (", ".join(f"{x:g}" for x in method.points), )
                    else:
                        args = tuple(method)
                    var_hints[key] = VarHint(getattr(Methods, method_name), args)
            settings["var_hints"] = var_hints


if __name__ == "__main__":  # pragma: no cover
    #WidgetPreview(OWDiscretize).run(Table("/Users/janez/Downloads/banking-crises.tab"))
    WidgetPreview(OWDiscretize).run(Table("heart_disease"))