/*
 *  SPDX-FileCopyrightText: 2015 Marco Martin <mart@kde.org>
 *
 *  SPDX-License-Identifier: LGPL-2.0-or-later
 */

import QtQuick
import QtQuick.Layouts
import QtQuick.Templates as T
import QtQuick.Controls as QQC2
import org.kde.kirigami as Kirigami
import "private" as P

/**
 * Page is a container for all the app pages: everything pushed to the
 * ApplicationWindow's pageStack should be a Page.
 *
 * @see ScrollablePage
 * For content that should be scrollable, such as ListViews, use ScrollablePage instead.
 * @inherit QtQuick.Controls.Page
 */
QQC2.Page {
    id: root

//BEGIN properties
    padding: Kirigami.Units.gridUnit

    /**
     * @brief If the central element of the page is a Flickable
     * (ListView and Gridview as well) you can set it there.
     *
     * Normally, you wouldn't need to do that, but just use the
     * ScrollablePage element instead.
     *
     * Use this if your flickable has some non standard properties, such as not covering the whole Page.
     *
     * @see ScrollablePage
     */
    property Flickable flickable

    /**
     * @brief This property holds the actions for the page.
     *
     * These actions will be displayed in the toolbar on the desktop and inside
     * the ContextDrawer on mobile.
     *
     * @code
     * import org.kde.kirigami as Kirigami
     *
     * Kirigami.Page {
     *     actions: [
     *         Kirigami.Action {...},
     *         Kirigami.Action {...}
     *     }
     * }
     * @endcode
     */
    property list<T.Action> actions

    /**
     * @brief This property tells us if it is the currently active page.
     *
     * Specifies if it's the currently selected page in the window's pages row, or if layers
     * are used whether this is the topmost item on the layers stack. If the page is
     * not attached to either a column view or a stack view, expect this to be true.
     *
     * @since 2.1
     */
    //TODO KF6: remove this or at least all the assumptions about the internal tree structure of items
    // Kirigami.ColumnView.view.parent.parent is the StackView in which the ColumnView is, the condition means "is the ColumnView the current layer of the pagerow"
    readonly property bool isCurrentPage: Kirigami.ColumnView.view
            ? (Kirigami.ColumnView.index === Kirigami.ColumnView.view.currentIndex && Kirigami.ColumnView.view.parent.parent.currentItem === Kirigami.ColumnView.view.parent)
            : (parent && parent instanceof QQC2.StackView
                ? parent.currentItem === root
                : true)

    /**
     * An item which stays on top of every other item in the page,
     * if you want to make sure some elements are completely in a
     * layer on top of the whole content, parent items to this one.
     * It's a "local" version of ApplicationWindow's overlay
     *
     * @property Item overlay
     * @since 2.5
     */
    readonly property alias overlay: overlayItem

    /**
     * @brief This holds the icon that represents this page.
     * @property var icon
     */
    property P.ActionIconGroup icon: P.ActionIconGroup {}

    /**
     * @brief Progress of a task this page is doing.
     *
     * Set to undefined to indicate that there are no ongoing tasks.
     *
     * default: ``undefined``
     *
     * @property real progress
     */
    property var progress: undefined

    /**
     * @brief The delegate which will be used to draw the page title.
     *
     * It can be customized to put any kind of Item in there.
     *
     * @since 2.7
     */
    property Component titleDelegate: Component {
        id: defaultTitleDelegate
        P.DefaultPageTitleDelegate {
            text: root.title
        }
    }

    /**
     * The item used as global toolbar for the page
     * present only if we are in a PageRow as a page or as a layer,
     * and the style is either Titles or ToolBar.
     *
     * @since 2.5
     */
    readonly property Item globalToolBarItem: globalToolBar.item

    /**
     * The style for the automatically generated global toolbar: by default the Page toolbar is the one set globally in the PageRow in its globalToolBar.style property.
     * A single page can override the application toolbar style for itself.
     * It is discouraged to use this, except very specific exceptions, like a chat
     * application which can't have controls on the bottom except the text field.
     * If the Page is not in a PageRow, by default the toolbar will be invisible,
     * so has to be explicitly set to Kirigami.ApplicationHeaderStyle.ToolBar if
     * desired to be used in that case.
     */
    property int globalToolBarStyle: {
        if (globalToolBar.row && !globalToolBar.stack) {
            return globalToolBar.row.globalToolBar.actualStyle;
        } else if (globalToolBar.stack) {
            return Kirigami.Settings.isMobile ? Kirigami.ApplicationHeaderStyle.Titles : Kirigami.ApplicationHeaderStyle.ToolBar;
        } else {
            return Kirigami.ApplicationHeaderStyle.None;
        }
    }
//END properties

//BEGIN signal and signal handlers
    /**
     * @brief Emitted when the application requests a Back action.
     *
     * For instance a global "back" shortcut or the Android
     * Back button has been pressed.
     * The page can manage the back event by itself,
     * and if it set event.accepted = true, it will stop the main
     * application to manage the back event.
     */
    signal backRequested(var event);

    background: Rectangle {
        color: Kirigami.Theme.backgroundColor
    }

    // FIXME: on material the shadow would bleed over
    clip: root.header !== null;

    Component.onCompleted: {
        headerChanged();
        parentChanged(root.parent);
        globalToolBar.syncSource();
        bottomToolBar.pageComplete = true
    }

    onParentChanged: {
        if (!parent) {
            return;
        }
        globalToolBar.stack = null;
        globalToolBar.row = null;

        if (root.Kirigami.ColumnView.view) {
            globalToolBar.row = root.Kirigami.ColumnView.view.__pageRow;
        }
        if (root.T.StackView.view) {
            globalToolBar.stack = root.T.StackView.view;
            globalToolBar.row = root.T.StackView.view.parent instanceof Kirigami.PageRow ? root.T.StackView.view.parent : null;
        }
        if (globalToolBar.row) {
            root.globalToolBarStyleChanged.connect(globalToolBar.syncSource);
            globalToolBar.syncSource();
        }
    }
//END signals and signal handlers

    // in data in order for them to not be considered for contentItem, contentChildren, contentData
    data: [
        Item {
            id: overlayItem
            parent: root
            z: 9997
            anchors {
                fill: parent
                topMargin: globalToolBar.height
            }
        }
    ]
    // global top toolbar if we are in a PageRow (in the row or as a layer)
    Kirigami.ColumnView.globalHeader: Loader {
        id: globalToolBar
        z: 9999
        height: item ? item.implicitHeight : 0

        width: root.width
        property Kirigami.PageRow row
        property T.StackView stack

        // don't load async so that on slower devices we don't have the page content height changing while loading in
        // otherwise, it looks unpolished and jumpy
        asynchronous: false

        visible: active
        active: (root.titleDelegate !== defaultTitleDelegate || root.globalToolBarStyle === Kirigami.ApplicationHeaderStyle.ToolBar || root.globalToolBarStyle === Kirigami.ApplicationHeaderStyle.Titles)
        onActiveChanged: {
            if (active) {
                syncSource();
            }
        }

        function syncSource() {
            if (root.globalToolBarStyle !== Kirigami.ApplicationHeaderStyle.ToolBar &&
                root.globalToolBarStyle !== Kirigami.ApplicationHeaderStyle.Titles &&
                root.titleDelegate !== defaultTitleDelegate) {
                sourceComponent = root.titleDelegate;
            } else if (active) {
                const url = root.globalToolBarStyle === Kirigami.ApplicationHeaderStyle.ToolBar
                    ? "private/globaltoolbar/ToolBarPageHeader.qml"
                    : "private/globaltoolbar/TitlesPageHeader.qml";
                // TODO: find container reliably, remove assumption
                setSource(Qt.resolvedUrl(url), {
                    pageRow: Qt.binding(() => row),
                    page: root,
                    current: Qt.binding(() => {
                        if (!row && !stack) {
                            return true;
                        } else if (stack) {
                            return stack;
                        } else {
                            return row.currentIndex === root.Kirigami.ColumnView.level;
                        }
                    }),
                });
            }
        }
    }
    // bottom action buttons
    Kirigami.ColumnView.globalFooter: Loader {
        id: bottomToolBar

        property T.Page page: root
        property bool pageComplete: false

        visible: active

        active: {
            // Important! Do not do anything until the page has been
            // completed, so we are sure what the globalToolBarStyle is,
            // otherwise we risk creating the content and then discarding it.
            if (!pageComplete) {
                return false;
            }

            if ((globalToolBar.row && globalToolBar.row.globalToolBar.actualStyle === Kirigami.ApplicationHeaderStyle.ToolBar)
                || root.globalToolBarStyle === Kirigami.ApplicationHeaderStyle.ToolBar
                || root.globalToolBarStyle === Kirigami.ApplicationHeaderStyle.None) {
                return false;
            }

            if (root.actions.length === 0) {
                return false;
            }

            // Legacy
            if (typeof applicationWindow === "undefined") {
                return true;
            }

            const drawer = applicationWindow() ? applicationWindow()['contextDrawer'] : undefined;
            if (Boolean(drawer) && drawer.enabled && drawer.handleVisible) {
                return false;
            }

            return true;
        }

        source: Qt.resolvedUrl("./private/globaltoolbar/ToolBarPageFooter.qml")
    }

    Layout.fillWidth: true
}