import sys
import threading
import io
import csv
import itertools
import concurrent.futures

from collections import OrderedDict, namedtuple
from typing import List, Tuple, Iterable

from math import isnan

import numpy
from scipy.sparse import issparse

from AnyQt.QtWidgets import (
    QTableView, QHeaderView, QAbstractButton, QApplication, QStyleOptionHeader,
    QStyle, QStylePainter, QStyledItemDelegate
)
from AnyQt.QtGui import QColor, QClipboard, QMouseEvent
from AnyQt.QtCore import (
    Qt, QSize, QEvent, QByteArray, QMimeData, QObject, QMetaObject,
    QAbstractProxyModel, QIdentityProxyModel, QModelIndex,
    QItemSelectionModel, QItemSelection, QItemSelectionRange,
    Signal)
from AnyQt.QtCore import pyqtSlot as Slot

import Orange.data
from Orange.data.storage import Storage
from Orange.data.table import Table
from Orange.data.sql.table import SqlTable
from Orange.statistics import basic_stats

from Orange.widgets import gui
from Orange.widgets.settings import Setting, DomainContextHandler
from Orange.widgets.utils.widgetpreview import WidgetPreview
from Orange.widgets.widget import OWWidget, Input, Output
from Orange.widgets.utils import datacaching
from Orange.widgets.utils.annotated_data import (create_annotated_table,
                                                 ANNOTATED_DATA_SIGNAL_NAME)
from Orange.widgets.utils.itemmodels import TableModel


class RichTableModel(TableModel):
    """A TableModel with some extra bells and whistles/

    (adds support for gui.BarRole, include variable labels and icons
    in the header)
    """
    #: Rich header data flags.
    Name, Labels, Icon = 1, 2, 4

    def __init__(self, sourcedata, parent=None):
        super().__init__(sourcedata, parent)

        self._header_flags = RichTableModel.Name
        self._continuous = [var.is_continuous for var in self.vars]
        labels = []
        for var in self.vars:
            if isinstance(var, Orange.data.Variable):
                labels.extend(var.attributes.keys())
        self._labels = list(sorted(
            {label for label in labels if not label.startswith("_")}))

    def data(self, index, role=Qt.DisplayRole,
             # for faster local lookup
             _BarRole=gui.TableBarItem.BarRole):
        # pylint: disable=arguments-differ
        if role == _BarRole and self._continuous[index.column()]:
            val = super().data(index, TableModel.ValueRole)
            if val is None or isnan(val):
                return None

            dist = super().data(index, TableModel.VariableStatsRole)
            if dist is not None and dist.max > dist.min:
                return (val - dist.min) / (dist.max - dist.min)
            else:
                return None
        elif role == Qt.TextAlignmentRole and self._continuous[index.column()]:
            return Qt.AlignRight | Qt.AlignVCenter
        else:
            return super().data(index, role)

    def headerData(self, section, orientation, role):
        if orientation == Qt.Horizontal and role == Qt.DisplayRole:
            var = super().headerData(
                section, orientation, TableModel.VariableRole)
            if var is None:
                return super().headerData(
                    section, orientation, Qt.DisplayRole)

            lines = []
            if self._header_flags & RichTableModel.Name:
                lines.append(var.name)
            if self._header_flags & RichTableModel.Labels:
                lines.extend(str(var.attributes.get(label, ""))
                             for label in self._labels)
            return "\n".join(lines)
        elif orientation == Qt.Horizontal and role == Qt.DecorationRole and \
                self._header_flags & RichTableModel.Icon:
            var = super().headerData(
                section, orientation, TableModel.VariableRole)
            if var is not None:
                return gui.attributeIconDict[var]
            else:
                return None
        else:
            return super().headerData(section, orientation, role)

    def setRichHeaderFlags(self, flags):
        if flags != self._header_flags:
            self._header_flags = flags
            self.headerDataChanged.emit(
                Qt.Horizontal, 0, self.columnCount() - 1)

    def richHeaderFlags(self):
        return self._header_flags


class TableSliceProxy(QIdentityProxyModel):
    def __init__(self, parent=None, rowSlice=slice(0, -1), **kwargs):
        super().__init__(parent, **kwargs)
        self.__rowslice = rowSlice

    def setRowSlice(self, rowslice):
        if rowslice.step is not None and rowslice.step != 1:
            raise ValueError("invalid stride")

        if self.__rowslice != rowslice:
            self.beginResetModel()
            self.__rowslice = rowslice
            self.endResetModel()

    def mapToSource(self, proxyindex):
        model = self.sourceModel()
        if model is None or not proxyindex.isValid():
            return QModelIndex()

        row, col = proxyindex.row(), proxyindex.column()
        row = row + self.__rowslice.start
        assert 0 <= row < model.rowCount()
        return model.createIndex(row, col, proxyindex.internalPointer())

    def mapFromSource(self, sourceindex):
        model = self.sourceModel()
        if model is None or not sourceindex.isValid():
            return QModelIndex()
        row, col = sourceindex.row(), sourceindex.column()
        row = row - self.__rowslice.start
        assert 0 <= row < self.rowCount()
        return self.createIndex(row, col, sourceindex.internalPointer())

    def rowCount(self, parent=QModelIndex()):
        if parent.isValid():
            return 0
        count = super().rowCount()
        start, stop, step = self.__rowslice.indices(count)
        assert step == 1
        return stop - start


class BlockSelectionModel(QItemSelectionModel):
    """
    Item selection model ensuring the selection maintains a simple block
    like structure.

    e.g.

        [a b] c [d e]
        [f g] h [i j]

    is allowed but this is not

        [a] b  c  d e
        [f  g] h [i j]

    I.e. select the Cartesian product of row and column indices.

    """
    def __init__(self, model, parent=None, selectBlocks=True, **kwargs):
        super().__init__(model, parent, **kwargs)
        self.__selectBlocks = selectBlocks

    def select(self, selection, flags):
        """Reimplemented."""
        if isinstance(selection, QModelIndex):
            selection = QItemSelection(selection, selection)

        if not self.__selectBlocks:
            super().select(selection, flags)
            return

        model = self.model()

        def to_ranges(spans):
            return list(range(*r) for r in spans)

        if flags & QItemSelectionModel.Current:  # no current selection support
            flags &= ~QItemSelectionModel.Current
        if flags & QItemSelectionModel.Toggle:  # no toggle support either
            flags &= ~QItemSelectionModel.Toggle
            flags |= QItemSelectionModel.Select

        if flags == QItemSelectionModel.ClearAndSelect:
            # extend selection ranges in `selection` to span all row/columns
            sel_rows = selection_rows(selection)
            sel_cols = selection_columns(selection)
            selection = QItemSelection()
            for row_range, col_range in \
                    itertools.product(to_ranges(sel_rows), to_ranges(sel_cols)):
                selection.select(
                    model.index(row_range.start, col_range.start),
                    model.index(row_range.stop - 1, col_range.stop - 1)
                )
        elif flags & (QItemSelectionModel.Select |
                      QItemSelectionModel.Deselect):
            # extend all selection ranges in `selection` with the full current
            # row/col spans
            rows, cols = selection_blocks(self.selection())
            sel_rows = selection_rows(selection)
            sel_cols = selection_columns(selection)
            ext_selection = QItemSelection()
            for row_range, col_range in \
                    itertools.product(to_ranges(rows), to_ranges(sel_cols)):
                ext_selection.select(
                    model.index(row_range.start, col_range.start),
                    model.index(row_range.stop - 1, col_range.stop - 1)
                )
            for row_range, col_range in \
                    itertools.product(to_ranges(sel_rows), to_ranges(cols)):
                ext_selection.select(
                    model.index(row_range.start, col_range.start),
                    model.index(row_range.stop - 1, col_range.stop - 1)
                )
            selection.merge(ext_selection, QItemSelectionModel.Select)
        super().select(selection, flags)

    def selectBlocks(self):
        """Is the block selection in effect."""
        return self.__selectBlocks

    def setSelectBlocks(self, state):
        """Set the block selection state.

        If set to False, the selection model behaves as the base
        QItemSelectionModel

        """
        self.__selectBlocks = state


def selection_rows(selection):
    # type: (QItemSelection) -> List[Tuple[int, int]]
    """
    Return a list of ranges for all referenced rows contained in selection

    Parameters
    ----------
    selection : QItemSelection

    Returns
    -------
    rows : List[Tuple[int, int]]
    """
    spans = set(range(s.top(), s.bottom() + 1) for s in selection)
    indices = sorted(set(itertools.chain(*spans)))
    return list(ranges(indices))


def selection_columns(selection):
    # type: (QItemSelection) -> List[Tuple[int, int]]
    """
    Return a list of ranges for all referenced columns contained in selection

    Parameters
    ----------
    selection : QItemSelection

    Returns
    -------
    rows : List[Tuple[int, int]]
    """
    spans = {range(s.left(), s.right() + 1) for s in selection}
    indices = sorted(set(itertools.chain(*spans)))
    return list(ranges(indices))


def selection_blocks(selection):
    # type: (QItemSelection) -> Tuple[List[Tuple[int, int]], List[Tuple[int, int]]]
    if selection.count() > 0:
        rowranges = {range(span.top(), span.bottom() + 1)
                     for span in selection}
        colranges = {range(span.left(), span.right() + 1)
                     for span in selection}
    else:
        return [], []

    rows = sorted(set(itertools.chain(*rowranges)))
    cols = sorted(set(itertools.chain(*colranges)))
    return list(ranges(rows)), list(ranges(cols))


def ranges(indices):
    # type: (Iterable[int]) -> Iterable[Tuple[int, int]]
    """
    Group consecutive indices into `(start, stop)` tuple 'ranges'.

    >>> list(ranges([1, 2, 3, 5, 3, 4]))
    >>> [(1, 4), (5, 6), (3, 5)]

    """
    g = itertools.groupby(enumerate(indices),
                          key=lambda t: t[1] - t[0])
    for _, range_ind in g:
        range_ind = list(range_ind)
        _, start = range_ind[0]
        _, end = range_ind[-1]
        yield start, end + 1


def table_selection_to_mime_data(table):
    """Copy the current selection in a QTableView to the clipboard.
    """
    lines = table_selection_to_list(table)

    as_csv = lines_to_csv_string(lines, dialect="excel").encode("utf-8")
    as_tsv = lines_to_csv_string(lines, dialect="excel-tab").encode("utf-8")

    mime = QMimeData()
    mime.setData("text/csv", QByteArray(as_csv))
    mime.setData("text/tab-separated-values", QByteArray(as_tsv))
    mime.setData("text/plain", QByteArray(as_tsv))
    return mime


def lines_to_csv_string(lines, dialect="excel"):
    stream = io.StringIO()
    writer = csv.writer(stream, dialect=dialect)
    writer.writerows(lines)
    return stream.getvalue()


def table_selection_to_list(table):
    model = table.model()
    indexes = table.selectedIndexes()

    rows = sorted(set(index.row() for index in indexes))
    columns = sorted(set(index.column() for index in indexes))

    lines = []
    for row in rows:
        line = []
        for col in columns:
            val = model.index(row, col).data(Qt.DisplayRole)
            # TODO: use style item delegate displayText?
            line.append(str(val))
        lines.append(line)

    return lines


TableSlot = namedtuple("TableSlot", ["input_id", "table", "summary", "view"])


class TableView(QTableView):
    #: Signal emitted when selection finished. It is not emitted during
    #: mouse drag selection updates.
    selectionFinished = Signal()

    __mouseDown = False
    __selectionDidChange = False

    def setSelectionModel(self, selectionModel: QItemSelectionModel) -> None:
        sm = self.selectionModel()
        if sm is not None:
            sm.selectionChanged.disconnect(self.__on_selectionChanged)
        super().setSelectionModel(selectionModel)
        if selectionModel is not None:
            selectionModel.selectionChanged.connect(self.__on_selectionChanged)

    def __on_selectionChanged(self):
        if self.__mouseDown:
            self.__selectionDidChange = True
        else:
            self.selectionFinished.emit()

    def mousePressEvent(self, event: QMouseEvent) -> None:
        self.__mouseDown = event.button() == Qt.LeftButton
        super().mousePressEvent(event)

    def mouseReleaseEvent(self, event: QMouseEvent) -> None:
        super().mouseReleaseEvent(event)
        if self.__mouseDown and event.button() == Qt.LeftButton:
            self.__mouseDown = False
        if self.__selectionDidChange:
            self.__selectionDidChange = False
            self.selectionFinished.emit()


class DataTableView(TableView):
    dataset: Table
    input_slot: TableSlot


class OWDataTable(OWWidget):
    name = "Data Table"
    description = "View the dataset in a spreadsheet."
    icon = "icons/Table.svg"
    priority = 50
    keywords = []

    buttons_area_orientation = Qt.Vertical

    class Inputs:
        data = Input("Data", Table, multiple=True)

    class Outputs:
        selected_data = Output("Selected Data", Table, default=True)
        annotated_data = Output(ANNOTATED_DATA_SIGNAL_NAME, Table)

    show_distributions = Setting(False)
    dist_color_RGB = Setting((220, 220, 220, 255))
    show_attribute_labels = Setting(True)
    select_rows = Setting(True)
    auto_commit = Setting(True)

    color_by_class = Setting(True)
    settingsHandler = DomainContextHandler(
        match_values=DomainContextHandler.MATCH_VALUES_ALL)
    selected_rows = Setting([], schema_only=True)
    selected_cols = Setting([], schema_only=True)

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

        self._inputs = OrderedDict()

        self.__pending_selected_rows = self.selected_rows
        self.selected_rows = None
        self.__pending_selected_cols = self.selected_cols
        self.selected_cols = None

        self.dist_color = QColor(*self.dist_color_RGB)

        info_box = gui.vBox(self.controlArea, "Info")
        self.info_ex = gui.widgetLabel(info_box, 'No data on input.', )
        self.info_ex.setWordWrap(True)
        self.info_attr = gui.widgetLabel(info_box, ' ')
        self.info_attr.setWordWrap(True)
        self.info_class = gui.widgetLabel(info_box, ' ')
        self.info_class.setWordWrap(True)
        self.info_meta = gui.widgetLabel(info_box, ' ')
        self.info_meta.setWordWrap(True)
        info_box.setMinimumWidth(200)
        gui.separator(self.controlArea)

        box = gui.vBox(self.controlArea, "Variables")
        self.c_show_attribute_labels = gui.checkBox(
            box, self, "show_attribute_labels",
            "Show variable labels (if present)",
            callback=self._on_show_variable_labels_changed)

        gui.checkBox(box, self, "show_distributions",
                     'Visualize numeric values',
                     callback=self._on_distribution_color_changed)
        gui.checkBox(box, self, "color_by_class", 'Color by instance classes',
                     callback=self._on_distribution_color_changed)

        box = gui.vBox(self.controlArea, "Selection")

        gui.checkBox(box, self, "select_rows", "Select full rows",
                     callback=self._on_select_rows_changed)

        gui.rubber(self.controlArea)

        reset = gui.button(
            None, self, "Restore Original Order", callback=self.restore_order,
            tooltip="Show rows in the original order", autoDefault=False)
        self.buttonsArea.layout().insertWidget(0, reset)
        gui.auto_send(self.buttonsArea, self, "auto_commit")

        # GUI with tabs
        self.tabs = gui.tabWidget(self.mainArea)
        self.tabs.currentChanged.connect(self._on_current_tab_changed)

    def copy_to_clipboard(self):
        self.copy()

    @staticmethod
    def sizeHint():
        return QSize(800, 500)

    @Inputs.data
    def set_dataset(self, data, tid=None):
        """Set the input dataset."""
        self.closeContext()
        if data is not None:
            datasetname = getattr(data, "name", "Data")
            if tid in self._inputs:
                # update existing input slot
                slot = self._inputs[tid]
                view = slot.view
                # reset the (header) view state.
                view.setModel(None)
                view.horizontalHeader().setSortIndicator(-1, Qt.AscendingOrder)
                assert self.tabs.indexOf(view) != -1
                self.tabs.setTabText(self.tabs.indexOf(view), datasetname)
            else:
                view = DataTableView()
                view.setSortingEnabled(True)
                view.setHorizontalScrollMode(QTableView.ScrollPerPixel)

                if self.select_rows:
                    view.setSelectionBehavior(QTableView.SelectRows)

                header = view.horizontalHeader()
                header.setSectionsMovable(True)
                header.setSectionsClickable(True)
                header.setSortIndicatorShown(True)
                header.setSortIndicator(-1, Qt.AscendingOrder)

                # QHeaderView does not 'reset' the model sort column,
                # because there is no guaranty (requirement) that the
                # models understand the -1 sort column.
                def sort_reset(index, order):
                    if view.model() is not None and index == -1:
                        view.model().sort(index, order)

                header.sortIndicatorChanged.connect(sort_reset)
                self.tabs.addTab(view, datasetname)

            view.dataset = data
            self.tabs.setCurrentWidget(view)

            self._setup_table_view(view, data)
            slot = TableSlot(tid, data, table_summary(data), view)
            view.input_slot = slot
            self._inputs[tid] = slot

            self.tabs.setCurrentIndex(self.tabs.indexOf(view))

            self.set_info(slot.summary)

            if isinstance(slot.summary.len, concurrent.futures.Future):
                def update(_):
                    QMetaObject.invokeMethod(
                        self, "_update_info", Qt.QueuedConnection)

                slot.summary.len.add_done_callback(update)

        elif tid in self._inputs:
            slot = self._inputs.pop(tid)
            view = slot.view
            view.hide()
            view.deleteLater()
            self.tabs.removeTab(self.tabs.indexOf(view))

            current = self.tabs.currentWidget()
            if current is not None:
                self.set_info(current.input_slot.summary)

        self.tabs.tabBar().setVisible(self.tabs.count() > 1)
        self.openContext(data)

        if data and self.__pending_selected_rows is not None:
            self.selected_rows = self.__pending_selected_rows
            self.__pending_selected_rows = None
        else:
            self.selected_rows = []

        if data and self.__pending_selected_cols is not None:
            self.selected_cols = self.__pending_selected_cols
            self.__pending_selected_cols = None
        else:
            self.selected_cols = []

        self.set_selection()
        self.unconditional_commit()

    def _setup_table_view(self, view, data):
        """Setup the `view` (QTableView) with `data` (Orange.data.Table)
        """
        if data is None:
            view.setModel(None)
            return

        datamodel = RichTableModel(data)

        rowcount = data.approx_len()

        if self.color_by_class and data.domain.has_discrete_class:
            color_schema = [
                QColor(*c) for c in data.domain.class_var.colors]
        else:
            color_schema = None
        if self.show_distributions:
            view.setItemDelegate(
                gui.TableBarItem(
                    self, color=self.dist_color, color_schema=color_schema)
            )
        else:
            view.setItemDelegate(QStyledItemDelegate(self))

        # Enable/disable view sorting based on data's type
        view.setSortingEnabled(is_sortable(data))
        header = view.horizontalHeader()
        header.setSectionsClickable(is_sortable(data))
        header.setSortIndicatorShown(is_sortable(data))

        view.setModel(datamodel)

        vheader = view.verticalHeader()
        option = view.viewOptions()
        size = view.style().sizeFromContents(
            QStyle.CT_ItemViewItem, option,
            QSize(20, 20), view)

        vheader.setDefaultSectionSize(size.height() + 2)
        vheader.setMinimumSectionSize(5)
        vheader.setSectionResizeMode(QHeaderView.Fixed)

        # Limit the number of rows displayed in the QTableView
        # (workaround for QTBUG-18490 / QTBUG-28631)
        maxrows = (2 ** 31 - 1) // (vheader.defaultSectionSize() + 2)
        if rowcount > maxrows:
            sliceproxy = TableSliceProxy(
                parent=view, rowSlice=slice(0, maxrows))
            sliceproxy.setSourceModel(datamodel)
            # First reset the view (without this the header view retains
            # it's state - at this point invalid/broken)
            view.setModel(None)
            view.setModel(sliceproxy)

        assert view.model().rowCount() <= maxrows
        assert vheader.sectionSize(0) > 1 or datamodel.rowCount() == 0

        # update the header (attribute names)
        self._update_variable_labels(view)

        selmodel = BlockSelectionModel(
            view.model(), parent=view, selectBlocks=not self.select_rows)
        view.setSelectionModel(selmodel)
        view.selectionFinished.connect(self.update_selection)

    #noinspection PyBroadException
    def set_corner_text(self, table, text):
        """Set table corner text."""
        # As this is an ugly hack, do everything in
        # try - except blocks, as it may stop working in newer Qt.
        # pylint: disable=broad-except
        if not hasattr(table, "btn") and not hasattr(table, "btnfailed"):
            try:
                btn = table.findChild(QAbstractButton)

                class Efc(QObject):
                    @staticmethod
                    def eventFilter(o, e):
                        if (isinstance(o, QAbstractButton) and
                                e.type() == QEvent.Paint):
                            # paint by hand (borrowed from QTableCornerButton)
                            btn = o
                            opt = QStyleOptionHeader()
                            opt.initFrom(btn)
                            state = QStyle.State_None
                            if btn.isEnabled():
                                state |= QStyle.State_Enabled
                            if btn.isActiveWindow():
                                state |= QStyle.State_Active
                            if btn.isDown():
                                state |= QStyle.State_Sunken
                            opt.state = state
                            opt.rect = btn.rect()
                            opt.text = btn.text()
                            opt.position = QStyleOptionHeader.OnlyOneSection
                            painter = QStylePainter(btn)
                            painter.drawControl(QStyle.CE_Header, opt)
                            return True     # eat event
                        return False
                table.efc = Efc()
                # disconnect default handler for clicks and connect a new one, which supports
                # both selection and deselection of all data
                btn.clicked.disconnect()
                btn.installEventFilter(table.efc)
                btn.clicked.connect(self._on_select_all)
                table.btn = btn

                if sys.platform == "darwin":
                    btn.setAttribute(Qt.WA_MacSmallSize)

            except Exception:
                table.btnfailed = True

        if hasattr(table, "btn"):
            try:
                btn = table.btn
                btn.setText(text)
                opt = QStyleOptionHeader()
                opt.text = btn.text()
                s = btn.style().sizeFromContents(
                    QStyle.CT_HeaderSection,
                    opt, QSize(),
                    btn).expandedTo(QApplication.globalStrut())
                if s.isValid():
                    table.verticalHeader().setMinimumWidth(s.width())
            except Exception:
                pass

    def _on_select_all(self, _):
        data_info = self.tabs.currentWidget().input_slot.summary
        if len(self.selected_rows) == data_info.len \
                and len(self.selected_cols) == len(data_info.domain):
            self.tabs.currentWidget().clearSelection()
        else:
            self.tabs.currentWidget().selectAll()

    def _on_current_tab_changed(self, index):
        """Update the info box on current tab change"""
        view = self.tabs.widget(index)
        if view is not None and view.model() is not None:
            self.set_info(view.input_slot.summary)
            self.update_selection()
        else:
            self.set_info(None)

    def _update_variable_labels(self, view):
        "Update the variable labels visibility for `view`"
        model = view.model()
        if isinstance(model, TableSliceProxy):
            model = model.sourceModel()

        if self.show_attribute_labels:
            model.setRichHeaderFlags(
                RichTableModel.Labels | RichTableModel.Name)

            labelnames = set()
            domain = model.source.domain
            for a in itertools.chain(domain.metas, domain.variables):
                labelnames.update(a.attributes.keys())
            labelnames = sorted(
                [label for label in labelnames if not label.startswith("_")])
            self.set_corner_text(view, "\n".join([""] + labelnames))
        else:
            model.setRichHeaderFlags(RichTableModel.Name)
            self.set_corner_text(view, "")

    def _on_show_variable_labels_changed(self):
        """The variable labels (var.attribues) visibility was changed."""
        for slot in self._inputs.values():
            self._update_variable_labels(slot.view)

    def _on_distribution_color_changed(self):
        for ti in range(self.tabs.count()):
            widget = self.tabs.widget(ti)
            model = widget.model()
            while isinstance(model, QAbstractProxyModel):
                model = model.sourceModel()
            data = model.source
            class_var = data.domain.class_var
            if self.color_by_class and class_var and class_var.is_discrete:
                color_schema = [QColor(*c) for c in class_var.colors]
            else:
                color_schema = None
            if self.show_distributions:
                delegate = gui.TableBarItem(self, color=self.dist_color,
                                            color_schema=color_schema)
            else:
                delegate = QStyledItemDelegate(self)
            widget.setItemDelegate(delegate)
        tab = self.tabs.currentWidget()
        if tab:
            tab.reset()

    def _on_select_rows_changed(self):
        for slot in self._inputs.values():
            selection_model = slot.view.selectionModel()
            selection_model.setSelectBlocks(not self.select_rows)
            if self.select_rows:
                slot.view.setSelectionBehavior(QTableView.SelectRows)
                # Expand the current selection to full row selection.
                selection_model.select(
                    selection_model.selection(),
                    QItemSelectionModel.Select | QItemSelectionModel.Rows
                )
            else:
                slot.view.setSelectionBehavior(QTableView.SelectItems)

    def restore_order(self):
        """Restore the original data order of the current view."""
        table = self.tabs.currentWidget()
        if table is not None:
            table.horizontalHeader().setSortIndicator(-1, Qt.AscendingOrder)

    def set_info(self, summary):
        if summary is None:
            self.info_ex.setText("No data on input.")
            self.info_attr.setText("")
            self.info_class.setText("")
            self.info_meta.setText("")
        else:
            info_len, info_attr, info_class, info_meta = \
                format_summary(summary)

            self.info_ex.setText(info_len)
            self.info_attr.setText(info_attr)
            self.info_class.setText(info_class)
            self.info_meta.setText(info_meta)

    @Slot()
    def _update_info(self):
        current = self.tabs.currentWidget()
        if current is not None and current.model() is not None:
            self.set_info(current.input_slot.summary)

    def update_selection(self, *_):
        self.commit()

    def set_selection(self):
        if self.selected_rows and self.selected_cols:
            view = self.tabs.currentWidget()
            model = view.model()
            if model.rowCount() <= self.selected_rows[-1] or \
                    model.columnCount() <= self.selected_cols[-1]:
                return

            selection = QItemSelection()
            rowranges = list(ranges(self.selected_rows))
            colranges = list(ranges(self.selected_cols))

            for rowstart, rowend in rowranges:
                for colstart, colend in colranges:
                    selection.append(
                        QItemSelectionRange(
                            view.model().index(rowstart, colstart),
                            view.model().index(rowend - 1, colend - 1)
                        )
                    )
            view.selectionModel().select(
                selection, QItemSelectionModel.ClearAndSelect)

    @staticmethod
    def get_selection(view):
        """
        Return the selected row and column indices of the selection in view.
        """
        selmodel = view.selectionModel()

        selection = selmodel.selection()
        model = view.model()
        # map through the proxies into input table.
        while isinstance(model, QAbstractProxyModel):
            selection = model.mapSelectionToSource(selection)
            model = model.sourceModel()

        assert isinstance(selmodel, BlockSelectionModel)
        assert isinstance(model, TableModel)

        row_spans, col_spans = selection_blocks(selection)
        rows = list(itertools.chain.from_iterable(itertools.starmap(range, row_spans)))
        cols = list(itertools.chain.from_iterable(itertools.starmap(range, col_spans)))
        rows = numpy.array(rows, dtype=numpy.intp)
        # map the rows through the applied sorting (if any)
        rows = model.mapToSourceRows(rows)
        rows.sort()
        rows = rows.tolist()
        return rows, cols

    @staticmethod
    def _get_model(view):
        model = view.model()
        while isinstance(model, QAbstractProxyModel):
            model = model.sourceModel()
        return model

    def commit(self):
        """
        Commit/send the current selected row/column selection.
        """
        selected_data = table = rowsel = None
        view = self.tabs.currentWidget()
        if view and view.model() is not None:
            model = self._get_model(view)
            table = model.source  # The input data table

            # Selections of individual instances are not implemented
            # for SqlTables
            if isinstance(table, SqlTable):
                self.Outputs.selected_data.send(selected_data)
                self.Outputs.annotated_data.send(None)
                return

            rowsel, colsel = self.get_selection(view)
            self.selected_rows, self.selected_cols = rowsel, colsel

            def select(data, rows, domain):
                """
                Select the data subset with specified rows and domain subsets.

                If either rows or domain is None they mean select all.
                """
                if rows is not None and domain is not None:
                    return data.from_table(domain, data, rows)
                elif rows is not None:
                    return data.from_table(data.domain, rows)
                elif domain is not None:
                    return data.from_table(domain, data)
                else:
                    return data

            domain = table.domain

            if len(colsel) < len(domain) + len(domain.metas):
                # only a subset of the columns is selected
                allvars = domain.class_vars + domain.metas + domain.attributes
                columns = [(c, model.headerData(c, Qt.Horizontal,
                                                TableModel.DomainRole))
                           for c in colsel]
                assert all(role is not None for _, role in columns)

                def select_vars(role):
                    """select variables for role (TableModel.DomainRole)"""
                    return [allvars[c] for c, r in columns if r == role]

                attrs = select_vars(TableModel.Attribute)
                if attrs and issparse(table.X):
                    # for sparse data you can only select all attributes
                    attrs = table.domain.attributes
                class_vars = select_vars(TableModel.ClassVar)
                metas = select_vars(TableModel.Meta)
                domain = Orange.data.Domain(attrs, class_vars, metas)

            # Avoid a copy if all/none rows are selected.
            if not rowsel:
                selected_data = None
            elif len(rowsel) == len(table):
                selected_data = select(table, None, domain)
            else:
                selected_data = select(table, rowsel, domain)

        self.Outputs.selected_data.send(selected_data)
        self.Outputs.annotated_data.send(create_annotated_table(table, rowsel))

    def copy(self):
        """
        Copy current table selection to the clipboard.
        """
        view = self.tabs.currentWidget()
        if view is not None:
            mime = table_selection_to_mime_data(view)
            QApplication.clipboard().setMimeData(
                mime, QClipboard.Clipboard
            )

    def send_report(self):
        view = self.tabs.currentWidget()
        if not view or not view.model():
            return
        model = self._get_model(view)
        self.report_data_brief(model.source)
        self.report_table(view)


# Table Summary

# Basic statistics for X/Y/metas arrays
DenseArray = namedtuple(
    "DenseArray", ["nans", "non_nans", "stats"])
SparseArray = namedtuple(
    "SparseArray", ["nans", "non_nans", "stats"])
SparseBoolArray = namedtuple(
    "SparseBoolArray", ["nans", "non_nans", "stats"])
NotAvailable = namedtuple("NotAvailable", [])

#: Orange.data.Table summary
Summary = namedtuple(
    "Summary",
    ["len", "domain", "X", "Y", "M"])

#: Orange.data.sql.table.SqlTable summary
ApproxSummary = namedtuple(
    "ApproxSummary",
    ["approx_len", "len", "domain", "X", "Y", "M"])


def table_summary(table):
    if isinstance(table, SqlTable):
        approx_len = table.approx_len()
        len_future = concurrent.futures.Future()

        def _len():
            len_future.set_result(len(table))
        threading.Thread(target=_len).start()  # KILL ME !!!

        return ApproxSummary(approx_len, len_future, table.domain,
                             NotAvailable(), NotAvailable(), NotAvailable())
    else:
        domain = table.domain
        n_instances = len(table)
        # dist = basic_stats.DomainBasicStats(table, include_metas=True)
        bstats = datacaching.getCached(
            table, basic_stats.DomainBasicStats, (table, True)
        )

        dist = bstats.stats
        # pylint: disable=unbalanced-tuple-unpacking
        X_dist, Y_dist, M_dist = numpy.split(
            dist, numpy.cumsum([len(domain.attributes),
                                len(domain.class_vars)]))

        def parts(array, density, col_dist):
            array = numpy.atleast_2d(array)
            nans = sum([dist.nans for dist in col_dist])
            non_nans = sum([dist.non_nans for dist in col_dist])
            if density == Storage.DENSE:
                return DenseArray(nans, non_nans, col_dist)
            elif density == Storage.SPARSE:
                return SparseArray(nans, non_nans, col_dist)
            elif density == Storage.SPARSE_BOOL:
                return SparseBoolArray(nans, non_nans, col_dist)
            elif density == Storage.MISSING:
                return NotAvailable()
            else:
                assert False
                return None

        X_part = parts(table.X, table.X_density(), X_dist)
        Y_part = parts(table.Y, table.Y_density(), Y_dist)
        M_part = parts(table.metas, table.metas_density(), M_dist)
        return Summary(n_instances, domain, X_part, Y_part, M_part)


def format_summary(summary):
    text = []
    if isinstance(summary, ApproxSummary):
        if summary.len.done():
            text += ["{} instances".format(summary.len.result())]
        else:
            text += ["~{} instances".format(summary.approx_len)]

    elif isinstance(summary, Summary):
        text += ["{} instances".format(summary.len)]

        if sum(p.nans for p in [summary.X, summary.Y, summary.M]) == 0:
            text[-1] += " (no missing values)"

    def format_part(part):
        if isinstance(part, NotAvailable):
            return ""
        elif part.nans + part.non_nans == 0:
            return ""

        if isinstance(part, DenseArray):
            total = part.nans + part.non_nans
            miss = ("%.1f%%" % (100 * part.nans / total) if part.nans > 0
                    else "no")
            return " (%s missing values)" % miss
        elif isinstance(part, (SparseArray, SparseBoolArray)):
            text = " ({}, density {:.2f}%)"
            tag = "sparse" if isinstance(part, SparseArray) else "tags"
            total = part.nans + part.non_nans
            return text.format(tag, 100 * part.non_nans / total)
        else:
            # MISSING, N/A
            return ""

    def sp(n):
        if n == 0:
            return "No", "s"
        elif n == 1:
            return str(n), ''
        else:
            return str(n), 's'

    text += [("%s feature%s" % sp(len(summary.domain.attributes)))
             + format_part(summary.X)]

    if not summary.domain.class_vars:
        text += ["No target variable."]
    else:
        if len(summary.domain.class_vars) > 1:
            c_text = "%s outcome%s" % sp(len(summary.domain.class_vars))
        elif summary.domain.has_continuous_class:
            c_text = "Continuous target variable"
        else:
            c_text = "Discrete class with %s value%s" % sp(
                len(summary.domain.class_var.values))
        c_text += format_part(summary.Y)
        text += [c_text]

    text += [("%s meta attribute%s" % sp(len(summary.domain.metas)))
             + format_part(summary.M)]

    return text


def is_sortable(table):
    if isinstance(table, SqlTable):
        return False
    elif isinstance(table, Orange.data.Table):
        return True
    else:
        return False


def test_model():
    app = QApplication([])
    view = QTableView(
        sortingEnabled=True
    )
    data = Orange.data.Table("lenses")
    model = TableModel(data)

    view.setModel(model)

    view.show()
    view.raise_()
    return app.exec()


if __name__ == "__main__":  # pragma: no cover
    WidgetPreview(OWDataTable).run(
        [(Table("iris"), "iris"),
         (Table("brown-selected"), "brown-selected"),
         (Table("housing"), "housing")])
