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

"""
Dock widgets for plugins
"""

from qtpy.QtCore import QEvent, QObject, Qt, QSize, Signal
from qtpy.QtWidgets import (QDockWidget, QHBoxLayout, QSizePolicy, QTabBar,
                            QToolButton, QWidget)
import qstylizer.style

from spyder.api.translations import get_translation
from spyder.utils.icon_manager import ima
from spyder.utils.palette import QStylePalette
from spyder.utils.stylesheet import PanesToolbarStyleSheet


# For translations
_ = get_translation('spyder')


# =============================================================================
# Tab filter
# =============================================================================
class TabFilter(QObject):
    """Filter event attached to each DockWidget QTabBar."""
    def __init__(self, dock_tabbar, main):
        QObject.__init__(self)
        self.dock_tabbar = dock_tabbar
        self.main = main
        self.from_index = None
        self.dock_tabbar.setStyleSheet(self._tabbar_stylesheet)

    def eventFilter(self, obj, event):
        """Filter mouse press events.

        Events that are captured and not propagated return True. Events that
        are not captured and are propagated return False.
        """
        event_type = event.type()
        if event_type == QEvent.MouseButtonPress:
            self.tab_pressed(event)
            return False
        return False

    def tab_pressed(self, event):
        """Method called when a tab from a QTabBar has been pressed."""
        self.from_index = self.dock_tabbar.tabAt(event.pos())
        self.dock_tabbar.setCurrentIndex(self.from_index)

        try:
            if event.button() == Qt.RightButton:
                if self.from_index == -1:
                    self.show_nontab_menu(event)
                else:
                    self.show_tab_menu(event)
        except AttributeError:
            # Needed to avoid an error when generating the
            # context menu on top of the tab.
            # See spyder-ide/spyder#11226
            pass

    def show_tab_menu(self, event):
        """Show the context menu assigned to tabs."""
        self.show_nontab_menu(event)

    def show_nontab_menu(self, event):
        """Show the context menu assigned to nontabs section."""
        menu = self.main.createPopupMenu()
        menu.exec_(self.dock_tabbar.mapToGlobal(event.pos()))

    @property
    def _tabbar_stylesheet(self):
        css = qstylizer.style.StyleSheet()

        # Center tabs to differentiate them from plugin ones.
        # See spyder-ide/spyder#9763
        css.QTabBar.setValues(
            alignment='center'
        )

        # Also add a border below selected tabs so they don't touch either the
        # window separator or the status bar.
        css['QTabBar::tab:bottom:selected'].setValues(
            borderBottom=f'2px solid {QStylePalette.COLOR_BACKGROUND_1}'
        )

        return css.toString()


# =============================================================================
# Title bar
# =============================================================================
class DragButton(QToolButton):
    """
    Drag button for the title bar.

    This button pass all its mouse events to its parent.
    """

    def __init__(self, parent, button_size):
        super().__init__(parent)
        self.parent = parent

        # Style
        self.setIconSize(button_size)
        self.setAutoRaise(True)
        self.setIcon(ima.icon('drag_dock_widget'))
        self.setToolTip(_("Drag and drop pane to a different position"))
        self.setStyleSheet(self._stylesheet)

    def mouseReleaseEvent(self, event):
        self.parent.mouseReleaseEvent(event)

    def mousePressEvent(self, event):
        self.parent.mousePressEvent(event)

    @property
    def _stylesheet(self):
        css = qstylizer.style.StyleSheet()
        css.QToolButton.setValues(
            borderRadius='0px',
            border='0px'
        )
        return css.toString()


class CloseButton(QToolButton):
    """Close button for the title bar."""

    def __init__(self, parent, button_size):
        super().__init__(parent)
        self.parent = parent

        # Style
        self.setIconSize(button_size)
        self.setAutoRaise(True)
        self.setIcon(ima.icon('lock_open'))
        self.setToolTip(_("Lock pane"))
        self._apply_stylesheet(QStylePalette.COLOR_BACKGROUND_3, 0)

    def _apply_stylesheet(self, bgcolor, bradius):
        css = qstylizer.style.StyleSheet()
        css.QToolButton.setValues(
            width=PanesToolbarStyleSheet.BUTTON_WIDTH,
            borderRadius=f'{bradius}px',
            border='0px',
            backgroundColor=bgcolor,
        )

        self.setStyleSheet(css.toString())

    def enterEvent(self, event):
        self.setCursor(Qt.ArrowCursor)
        self._apply_stylesheet(QStylePalette.COLOR_BACKGROUND_5, 3)
        self.parent._apply_stylesheet(QStylePalette.COLOR_BACKGROUND_3)
        self.setIcon(ima.icon('lock'))
        super().enterEvent(event)

    def mousePressEvent(self, event):
        self._apply_stylesheet(QStylePalette.COLOR_BACKGROUND_6, 3)
        super().mousePressEvent(event)

    def leaveEvent(self, event):
        self._apply_stylesheet(QStylePalette.COLOR_BACKGROUND_3, 0)
        self.parent._apply_stylesheet(QStylePalette.COLOR_BACKGROUND_5)
        self.setIcon(ima.icon('lock_open'))
        super().leaveEvent(event)


class DockTitleBar(QWidget):
    """
    Custom title bar for our dock widgets.

    Inspired from
    https://stackoverflow.com/a/40894225/438386
    """

    def __init__(self, parent):
        super(DockTitleBar, self).__init__(parent)

        button_size = QSize(20, 20)

        drag_button = DragButton(self, button_size)

        left_spacer = QWidget(self)
        left_spacer.setToolTip(drag_button.toolTip())
        left_spacer.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Minimum)

        right_spacer = QWidget(self)
        right_spacer.setToolTip(drag_button.toolTip())
        right_spacer.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Minimum)

        close_button = CloseButton(self, button_size)
        close_button.clicked.connect(parent.remove_title_bar)

        hlayout = QHBoxLayout(self)
        hlayout.setSpacing(0)
        hlayout.setContentsMargins(0, 0, 0, 0)
        hlayout.addWidget(left_spacer)
        hlayout.addWidget(drag_button)
        hlayout.addWidget(right_spacer)
        hlayout.addWidget(close_button)

        self._apply_stylesheet(QStylePalette.COLOR_BACKGROUND_3)

    def mouseReleaseEvent(self, event):
        self.setCursor(Qt.OpenHandCursor)
        self._apply_stylesheet(QStylePalette.COLOR_BACKGROUND_5)
        QWidget.mouseReleaseEvent(self, event)

    def mousePressEvent(self, event):
        self.setCursor(Qt.ClosedHandCursor)
        self._apply_stylesheet(QStylePalette.COLOR_BACKGROUND_6)
        QWidget.mousePressEvent(self, event)

    def enterEvent(self, event):
        # To signal that dock widgets can be dragged from here
        self.setCursor(Qt.OpenHandCursor)
        self._apply_stylesheet(QStylePalette.COLOR_BACKGROUND_5)
        super().enterEvent(event)

    def leaveEvent(self, event):
        """Remove customizations when leaving widget."""
        self.unsetCursor()
        self._apply_stylesheet(QStylePalette.COLOR_BACKGROUND_3)
        super().leaveEvent(event)

    def _apply_stylesheet(self, bgcolor):
        css = qstylizer.style.StyleSheet()
        css.QWidget.setValues(
            height=PanesToolbarStyleSheet.BUTTON_HEIGHT,
            backgroundColor=bgcolor
        )
        self.setStyleSheet(css.toString())


class SpyderDockWidget(QDockWidget):
    """Subclass to override needed methods"""

    # Attributes
    ALLOWED_AREAS = Qt.AllDockWidgetAreas
    LOCATION = Qt.LeftDockWidgetArea
    FEATURES = QDockWidget.DockWidgetClosable | QDockWidget.DockWidgetMovable

    # Signals
    sig_plugin_closed = Signal()
    sig_title_bar_shown = Signal(bool)

    def __init__(self, title, parent):
        super(SpyderDockWidget, self).__init__(title, parent)
        self.title = title

        self.setFeatures(self.FEATURES)

        # Widgets
        self.main = parent
        self.empty_titlebar = QWidget(self)
        self.titlebar = DockTitleBar(self)
        self.dock_tabbar = None  # Needed for event filter

        # Layout
        # Prevent message on internal console
        # See: https://bugreports.qt.io/browse/QTBUG-42986
        layout = QHBoxLayout(self.empty_titlebar)
        layout.setContentsMargins(0, 0, 0, 0)
        layout.setSpacing(0)
        self.empty_titlebar.setLayout(layout)
        self.empty_titlebar.setMinimumSize(0, 0)
        self.empty_titlebar.setMaximumSize(0, 0)

        # Setup
        self.set_title_bar()
        self.remove_title_bar()

        # Signals
        # To track dockwidget changes the filter is installed when dockwidget
        # visibility changes. This installs the filter on startup and also
        # on dockwidgets that are undocked and then docked to a new location.
        self.visibilityChanged.connect(self.install_tab_event_filter)

    def closeEvent(self, event):
        """
        Reimplement Qt method to send a signal on close so that "Panes" main
        window menu can be updated correctly
        """
        self.sig_plugin_closed.emit()

    def install_tab_event_filter(self, value):
        """
        Install an event filter to capture mouse events in the tabs of a
        QTabBar holding tabified dockwidgets.
        """
        dock_tabbar = None

        # This is necessary to catch an error when closing the app
        # in macOS with PyQt 5.15
        try:
            tabbars = self.main.findChildren(QTabBar)
        except RuntimeError:
            tabbars = []

        for tabbar in tabbars:
            for tab in range(tabbar.count()):
                title = tabbar.tabText(tab)
                if title == self.title:
                    dock_tabbar = tabbar
                    break

        if dock_tabbar is not None:
            self.dock_tabbar = dock_tabbar
            # Install filter only once per QTabBar
            if getattr(self.dock_tabbar, 'filter', None) is None:
                self.dock_tabbar.filter = TabFilter(self.dock_tabbar,
                                                    self.main)
                self.dock_tabbar.installEventFilter(self.dock_tabbar.filter)

    def remove_title_bar(self):
        """Set empty qwidget on title bar."""
        self.sig_title_bar_shown.emit(False)
        self.setTitleBarWidget(self.empty_titlebar)

    def set_title_bar(self):
        """Set custom title bar."""
        self.sig_title_bar_shown.emit(True)
        self.setTitleBarWidget(self.titlebar)
