/*
 *   Copyright 2015 Marco Martin <notmart@gmail.com>
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Library General Public License as
 *   published by the Free Software Foundation; either version 2, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU Library General Public License for more details
 *
 *   You should have received a copy of the GNU Library General Public
 *   License along with this program; if not, write to the
 *   Free Software Foundation, Inc.,
 *   51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

import QtQuick 2.0
import QtQuick.Layouts 1.1
import QtQuick.Window 2.2
import org.kde.taskmanager 0.1 as TaskManager
import org.kde.plasma.core 2.1 as PlasmaCore
import org.kde.plasma.components 2.0 as PlasmaComponents
import org.kde.plasma.mobilecomponents 0.2
import org.kde.plasma.private.mobileshell 2.0

FullScreenPanel {
    id: window

    visible: false
    width: Screen.width
    height: Screen.height
    property int offset: 0
    property int overShoot: units.gridUnit * 2
    property int tasksCount: tasksModel.count
    property int currentTaskIndex: -1
    property alias model: tasksModel

    color: Qt.rgba(0, 0, 0, 0.8 * Math.min(
        (Math.min(tasksView.contentY + tasksView.height, tasksView.height) / tasksView.height),
        ((tasksView.contentHeight - tasksView.contentY - tasksView.headerItem.height - tasksView.footerItem.height)/tasksView.height)))

    function show() {
        if (tasksModel.count == 0) {
            return;
        }
        if (!visible) {
            tasksView.contentY = -tasksView.headerItem.height;
        }
        visible = true;
        scrollAnim.from = tasksView.contentY;
        scrollAnim.to = 0;
        scrollAnim.running = true;
        setSingleActiveWindow(-1);
    }
    function hide() {
        scrollAnim.from = tasksView.contentY;
        if (tasksView.contentY + tasksView.headerItem.height < tasksView.contentHeight/2) {
            scrollAnim.to = -tasksView.headerItem.height;
        } else {
            scrollAnim.to = tasksView.contentHeight - tasksView.headerItem.height;
        }
        scrollAnim.running = true;
    }

    function setSingleActiveWindow(id) {
        var task;
        for (var i = 0; i < tasksModel.count; ++i) {
            task = filterModel.get(i);

            if (i == id) {
                tasksModel.requestActivate(tasksModel.index(i, 0));
                currentTaskIndex = id;
            } else if (i != id && !task.IsMinimized) {
                tasksModel.requestToggleMinimized(tasksModel.index(i, 0));
            }
        }
    }

    onOffsetChanged: tasksView.contentY = offset

    SequentialAnimation {
        id: scrollAnim
        property alias to: internalAnim.to
        property alias from: internalAnim.from
        ScriptAction {
            script: window.visible = true;
        }
        NumberAnimation {
            id: internalAnim
            target: tasksView
            properties: "contentY"
            duration: units.longDuration
            easing.type: Easing.InOutQuad
        }
        ScriptAction {
            script: {
                if (tasksView.contentY <= -tasksView.headerItem.height || tasksView.contentY >= tasksView.contentHeight - tasksView.headerItem.height) {
                    window.visible = false;
                }
            }
        }
    }

    GridView {
        id: tasksView
        width: window.width
        height: window.height
        cellWidth: window.width/2
        cellHeight: window.height/2
        onFlickingChanged: {
            if (!draggingVertically && contentY < -headerItem.height + window.height ||
                (contentY + footerItem.height) > (contentHeight - footerItem.height - window.height/6*5)) {
                window.hide();
            }
        }

        onDraggingVerticallyChanged: {
            if (draggingVertically) {
                return;
            }

            //manage separately the first page, the lockscreen
            //scrolling down
            if (verticalVelocity > 0 && contentY < -headerItem.height + window.height &&
                contentY > (-headerItem.height + window.height/6)) {
                show();
                return;

            //scrolling up
            } else if (verticalVelocity < 0 && contentY < -headerItem.height + window.height &&
                contentY < (-headerItem.height + window.height/6*5)) {
                hide();
                return;

            //hide by scrolling down
            } else if ((contentY + footerItem.height) > (contentHeight - footerItem.height - window.height/6*5)) {
                hide();
                return;
            //show
            } else if ((contentY + tasksView.height) > (contentHeight - headerItem.height - footerItem.height) &&
                (contentY + tasksView.height) < (contentHeight - headerItem.height - footerItem.height + window.height/6*5)) {
                scrollAnim.from = tasksView.contentY;
                visible = true;
                
                scrollAnim.to = contentHeight - footerItem.height - tasksView.height*2;
                scrollAnim.running = true;
                return;
            } else if (contentY < 0) {
                show();
            }
        }

        TaskManager.TasksModel {
            id: tasksModel
        }
        //This proxy is only used for "get"
        PlasmaCore.SortFilterModel {
            id: filterModel
            sourceModel: TaskManager.TasksModel {}
            onCountChanged: {
                if (count == 0) {
                    window.hide();
                }
            }
        }

        model: tasksModel
        header: Item {
            width: window.width
            height: window.height
        }
        footer: Item {
            width: window.width
            height: window.height
        }
        delegate: Task {}
        displaced: Transition {
            NumberAnimation {
                properties: "x,y"
                duration: units.longDuration
                easing.type: Easing.InOutQuad
            }
        }
    }

    Rectangle {
        color: theme.textColor
        anchors {
            fill: showDesktopButton
            margins: -showDesktopButton.width/4
        }
        radius: width
    }
    Button {
        id: showDesktopButton
        height: units.iconSizes.medium
        width: height
        anchors {
            horizontalCenter: parent.horizontalCenter
            bottom: parent.bottom
        }
        iconSource: "go-home"
        onClicked: {
            currentTaskIndex = -1;
            setSingleActiveWindow(-1);
            window.hide();
        }
    }
}