// SPDX-FileCopyrightText: 2015 Marco Martin <notmart@gmail.com>
// SPDX-FileCopyrightText: 2021-2023 Devin Lin <devin@kde.org>
// SPDX-License-Identifier: GPL-2.0-or-later

import QtQuick
import QtQuick.Layouts
import Qt5Compat.GraphicalEffects

import org.kde.plasma.core as PlasmaCore
import org.kde.plasma.components 3.0 as PlasmaComponents
import org.kde.plasma.extras as PlasmaExtras
import org.kde.plasma.private.mobileshell as MobileShell
import org.kde.plasma.private.mobileshell.state as MobileShellState

import org.kde.kwin 3.0 as KWinComponents
import org.kde.kwin.private.effects 1.0

/**
 * Component that provides a task switcher.
 */
FocusScope {
    id: root
    focus: true

    readonly property QtObject effect: KWinComponents.SceneView.effect
    readonly property QtObject targetScreen: KWinComponents.SceneView.screen

    readonly property real topMargin: MobileShell.Constants.topPanelHeight
    readonly property real bottomMargin: MobileShell.Constants.bottomPanelHeight
    readonly property real leftMargin: 0
    readonly property real rightMargin: 0

    property var taskSwitcherState: TaskSwitcherState {
        taskSwitcher: root
    }

    KWinComponents.WindowModel {
        id: stackModel
    }

    KWinComponents.VirtualDesktopModel {
        id: desktopModel
    }

    property var tasksModel: KWinComponents.WindowFilterModel {
        activity: KWinComponents.Workspace.currentActivity
        desktop: KWinComponents.Workspace.currentDesktop
        screenName: root.targetScreen.name
        windowModel: stackModel
        minimizedWindows: true
        windowType: ~KWinComponents.WindowFilterModel.Dock &
                    ~KWinComponents.WindowFilterModel.Desktop &
                    ~KWinComponents.WindowFilterModel.Notification &
                    ~KWinComponents.WindowFilterModel.CriticalNotification
    }

    readonly property int tasksCount: taskList.count

    // keep track of task list events
    property int oldTasksCount: tasksCount
    onTasksCountChanged: {
        if (tasksCount === 0 && oldTasksCount !== 0) {
            hide();
        } else if (tasksCount < oldTasksCount && taskSwitcherState.currentTaskIndex >= tasksCount - 1) {
            // if the user is on the last task, and it is closed, scroll left
            taskSwitcherState.animateGoToTaskIndex(tasksCount - 1, PlasmaCore.Units.longDuration);
        }

        oldTasksCount = tasksCount;
    }

    Keys.onEscapePressed: hide();

    Component.onCompleted: {
        taskList.jumpToFirstVisibleWindow();
        taskList.minimizeAll();

        // fully open the panel (if this is a button press, not gesture)
        if (!root.effect.gestureInProgress) {
            taskSwitcherState.open();
        }
    }

    // called by c++ plugin
    function hideAnimation() {
        closeAnim.restart();
    }

    function instantHide() {
        root.effect.deactivate(true);
    }

    function hide() {
        root.effect.deactivate(false);
    }

    // scroll to delegate index, and activate it
    function activateWindow(index, window) {
        KWinComponents.Workspace.activeClient = window;
        taskSwitcherState.openApp(index, window);
    }

    Connections {
        target: root.effect

        function onPartialActivationFactorChanged() {
            taskSwitcherState.positionY = taskSwitcherState.openedYPosition * root.effect.partialActivationFactor;
        }

        function onGestureInProgressChanged() {
            if (!root.effect.gestureInProgress) {
                taskSwitcherState.updateState();
            }
        }
    }

    KWinComponents.DesktopBackground {
        id: backgroundItem
        activity: KWinComponents.Workspace.currentActivity
        desktop: KWinComponents.Workspace.currentDesktop
        outputName: targetScreen.name
    }

    // background colour
    Rectangle {
        id: backgroundRect
        anchors.fill: parent

        opacity: container.opacity
        color: {
            // animate background colour only if we are *not* opening from the homescreen
            if (taskSwitcherState.wasInActiveTask || !taskSwitcherState.currentlyBeingOpened) {
                return Qt.rgba(0, 0, 0, 0.6);
            } else {
                return Qt.rgba(0, 0, 0, 0.6 * Math.min(1, taskSwitcherState.yPosition / taskSwitcherState.openedYPosition));
            }
        }
    }

    Item {
        id: container

        // provide shell margins
        anchors.fill: parent
        anchors.leftMargin: root.leftMargin
        anchors.rightMargin: root.rightMargin
        anchors.bottomMargin: root.bottomMargin
        anchors.topMargin: root.topMargin

        NumberAnimation on opacity {
            id: closeAnim
            running: false
            to: 0
            duration: 200
            easing.type: Easing.InOutQuad

            onFinished: {
                closeAllButton.closeRequested = false;
            }
        }

        // placeholder message
        ColumnLayout {
            id: placeholder
            spacing: PlasmaCore.Units.gridUnit
            opacity: (root.tasksCount === 0 && !taskSwitcherState.currentlyBeingClosed) ? 0.9 : 0
            Behavior on opacity { NumberAnimation { duration: 500 } }

            anchors.centerIn: parent

            PlasmaCore.IconItem {
                id: icon
                Layout.alignment: Qt.AlignHCenter
                implicitWidth: PlasmaCore.Units.iconSizes.large
                implicitHeight: PlasmaCore.Units.iconSizes.large
                source: "window"
                // color: "white"
            }

            PlasmaExtras.Heading {
                Layout.fillWidth: true
                Layout.maximumWidth: root.width * 0.75
                Layout.alignment: Qt.AlignHCenter
                color: "white"
                level: 3
                wrapMode: Text.Wrap
                horizontalAlignment: Text.AlignHCenter
                text: i18n("No applications are running.")
            }
        }

        // flicking area for task switcher
        FlickContainer {
            id: flickable
            anchors.fill: parent

            taskSwitcherState: root.taskSwitcherState

            // the item is effectively anchored to the flickable bounds
            TaskList {
                id: taskList
                taskSwitcher: root
                shellTopMargin: root.topMargin
                shellBottomMargin: root.bottomMargin

                opacity: {
                    // animate opacity only if we are *not* opening from the homescreen
                    if (taskSwitcherState.wasInActiveTask || !taskSwitcherState.currentlyBeingOpened) {
                        return 1;
                    } else {
                        return Math.min(1, taskSwitcherState.yPosition / taskSwitcherState.openedYPosition);
                    }
                }

                x: flickable.contentX
                width: flickable.width
                height: flickable.height

                PlasmaComponents.ToolButton {
                    id: closeAllButton
                    property bool closeRequested: false
                    visible: root.tasksCount !== 0

                    anchors {
                        bottom: parent.bottom
                        bottomMargin: taskList.taskY / 2
                        horizontalCenter: parent.horizontalCenter
                    }

                    PlasmaCore.ColorScope.colorGroup: PlasmaCore.Theme.ComplementaryColorGroup
                    PlasmaCore.ColorScope.inherit: false

                    opacity: (taskSwitcherState.currentlyBeingOpened || taskSwitcherState.currentlyBeingClosed) ? 0.0 : 1.0
                    Behavior on opacity { NumberAnimation { duration: PlasmaCore.Units.shortDuration } }

                    icon.name: "edit-clear-history"
                    font.bold: true

                    text: closeRequested ? i18n("Confirm Close All") : i18n("Close All")

                    onClicked: {
                        if (closeRequested) {
                            taskList.closeAll();
                        } else {
                            closeRequested = true;
                        }
                    }
                }
            }
        }
    }
}