/*
    SPDX-FileCopyrightText: 2012-2013 Eike Hein <hein@kde.org>

    SPDX-License-Identifier: GPL-2.0-or-later
*/

import QtQuick 2.4
import QtQuick.Window 2.2

import org.kde.plasma.core 2.0 as PlasmaCore
import org.kde.plasma.extras 2.0 as PlasmaExtras
import org.kde.draganddrop 2.0

import "code/layout.js" as LayoutManager

PlasmaCore.Dialog {
    id: groupDialog
    visible: false

    type: PlasmaCore.Dialog.PopupMenu
    flags: Qt.WindowStaysOnTopHint
    hideOnWindowDeactivate: true
    location: plasmoid.location

    readonly property int preferredWidth: Screen.width / (3 * Screen.devicePixelRatio)
    readonly property int preferredHeight: Screen.height / (2 * Screen.devicePixelRatio)
    readonly property int contentWidth: scrollArea.overflowing ? mainItem.width - (PlasmaCore.Units.smallSpacing * 3) : mainItem.width
    readonly property TextMetrics textMetrics: TextMetrics {}
    property alias overflowing: scrollArea.overflowing
    property alias activeTask: focusActiveTaskTimer.targetIndex
    property var _oldAppletStatus: PlasmaCore.Types.UnknownStatus

    function selectTask(task) {
        if (!task) {
            return;
        }

        task.forceActiveFocus();
        scrollArea.ensureItemVisible(task);
    }

    mainItem: MouseHandler {
        id: mouseHandler

        target: taskList
        handleWheelEvents: !scrollArea.overflowing

        Timer {
            id: focusActiveTaskTimer

            property var targetIndex: null

            interval: 0
            repeat: false

            onTriggered: {
                // Now we can home in on the previously active task
                // collected in groupDialog.onVisibleChanged.

                if (targetIndex != null) {
                    for (var i = 0; i < groupRepeater.count; ++i) {
                        var task = groupRepeater.itemAt(i);

                        if (task.modelIndex() === targetIndex) {
                            selectTask(task);
                            return;
                        }
                    }
                }
            }
        }

        PlasmaExtras.ScrollArea {
            id: scrollArea

            anchors.fill: parent

            readonly property bool overflowing: (viewport.height < contentItem.height)

            horizontalScrollBarPolicy: Qt.ScrollBarAlwaysOff
            
            /*ScrollBar.horizontal.visible: false;
            ScrollBar.vertical.visible: false;*/

            function ensureItemVisible(item) {
                var itemTop = item.y;
                var itemBottom = (item.y + item.height);

                if (itemTop < flickableItem.contentY) {
                    flickableItem.contentY = itemTop;
                }

                if ((itemBottom - flickableItem.contentY) > viewport.height) {
                    flickableItem.contentY = Math.abs(viewport.height - itemBottom);
                }
            }

            TaskList {
                id: taskList

                width: parent.width

                add: Transition {
                    // We trigger a null-interval timer in the first add
                    // transition after setting the model so onTriggered
                    // will run after the Flow has positioned items.

                    ScriptAction {
                        script: {
                            if (groupRepeater.aboutToPopulate) {
                                focusActiveTaskTimer.restart();
                                groupRepeater.aboutToPopulate = false;
                            }
                        }
                    }
                }

                onAnimatingChanged: {
                    if (!animating) {
                        Qt.callLater(updateSize);
                    }
                }

                Repeater {
                    id: groupRepeater

                    property bool aboutToPopulate: false

                    function currentIndex() {
                        for (var i = 0; i < count; ++i) {
                            if (itemAt(i).activeFocus) {
                                return i;
                            }
                        }

                        return -1;
                    }

                    onItemAdded: {
                        item.labelTextChanged.connect(updateSize);
                        Qt.callLater(updateSize)
                    }

                    onItemRemoved: {
                        if (groupDialog.visible && index > 0 && index == count) {
                            Qt.callLater(updateSize);
                        }
                    }
                }
            }

            Component.onCompleted: {
                flickableItem.boundsBehavior = Flickable.StopAtBounds;
            }
        }

        Keys.onUpPressed: {
            var currentIndex = groupRepeater.currentIndex();
            // In doubt focus the last item, so we start at the bottom when user
            // initially presses up.
            if (currentIndex === -1) {
                selectTask(groupRepeater.itemAt(groupRepeater.count - 1));
                return;
            }

            var previousIndex = currentIndex - 1;
            if (previousIndex < 0) {
                previousIndex = groupRepeater.count - 1;
            }

            selectTask(groupRepeater.itemAt(previousIndex));
        }

        Keys.onDownPressed: {
            var currentIndex = groupRepeater.currentIndex();
            // In doubt focus the first item, also wrap around.
            if (currentIndex === -1 || currentIndex + 1 >= groupRepeater.count) {
                selectTask(groupRepeater.itemAt(0));
                return;
            }

            selectTask(groupRepeater.itemAt(currentIndex + 1));
        }

        Keys.onEscapePressed: groupDialog.visible = false;
    }

    data: [
        VisualDataModel {
            id: groupFilter

            delegate: Task {
                visible: true
                inPopup: true
            }
        }
    ]

    onVisualParentChanged: {
        if (visible && visualParent) {
            attachModel();
        } else {
            visible = false;
        }
    }

    onVisibleChanged: {
        if (visible && visualParent) {
            _oldAppletStatus = plasmoid.status;
            plasmoid.status = PlasmaCore.Types.RequiresAttentionStatus;

            attachModel();

            groupDialog.requestActivate();
            mouseHandler.forceActiveFocus();
        } else {
            plasmoid.status = _oldAppletStatus;
            visualParent = null;
            groupRepeater.model = undefined;
            groupFilter.model = undefined;
            groupFilter.rootIndex = undefined;
        }
    }

    function attachModel() {
        if (!visualParent) {
            return;
        }

        if (!groupFilter.model) {
            groupFilter.model = tasksModel;
        }

        groupRepeater.aboutToPopulate = true;

        groupFilter.rootIndex = tasksModel.makeModelIndex(visualParent.itemIndex);

        if (!groupRepeater.model) {
            groupRepeater.model = groupFilter;
        }
    }

    function updateSize() {
        if (!visible) {
            return;
        }

        if (!visualParent) {
            visible = false;
            return;
        }

        if (!visualParent.childCount) {
            visible = false;
        // Setting VisualDataModel.rootIndex drops groupRepeater.count to 0
        // before the actual row count. updateSize is therefore invoked twice;
        // only update size once the repeater count matches the model role.
        } else if (!groupRepeater.aboutToPopulate || visualParent.childCount === groupRepeater.count) {
            var task;
            var maxWidth = 0;
            var maxHeight = 0;

            backend.cancelHighlightWindows();

            for (var i = 0; i < taskList.children.length - 1; ++i) {
                task = taskList.children[i];

                textMetrics.text = task.labelText;
                var textWidth = textMetrics.boundingRect.width;

                if (textWidth > maxWidth) {
                    maxWidth = textWidth;
                }
            }

            maxHeight = groupRepeater.count * (LayoutManager.verticalMargins() + Math.max(theme.mSize(theme.defaultFont).height, PlasmaCore.Units.iconSizes.medium));

            maxWidth += LayoutManager.horizontalMargins() + PlasmaCore.Units.iconSizes.medium + 2 * PlasmaCore.Units.smallSpacing;

            // Add horizontal space for scrollbar if needed.
            // FIXME TODO HACK: Use actual scrollbar width instead of a good guess.
            if (maxHeight > preferredHeight) {
                maxWidth += (PlasmaCore.Units.smallSpacing * 3);
            }

            mainItem.height = Math.min(preferredHeight, maxHeight);
            mainItem.width = Math.min(preferredWidth, (tasks.vertical ? Math.max(maxWidth, tasks.width) : Math.min(maxWidth, tasks.width)));
        }
    }
}