/*
 *  SPDX-FileCopyrightText: 2016 Marco Martin <mart@kde.org>
 *
 *  SPDX-License-Identifier: LGPL-2.0-or-later
 */

import QtQuick
import QtQml
import QtQuick.Templates as T
import org.kde.kirigami as Kirigami

/**
 * An action used to load Pages coming from a common PagePool
 * in a PageRow or QtQuickControls2 StackView.
 *
 * @see PagePool
 */
Kirigami.Action {
    id: root

//BEGIN properties
    /**
     * @brief This property holds the url or filename of the page that this action will load.
     */
    property string page

    /**
     * @brief This property holds the PagePool object used by this PagePoolAction.
     *
     * PagePool will make sure only one instance of the page identified by the page url will be created and reused.
     * PagePool's lastLoaderUrl property will be used to control the mutual exclusivity of the checked
     * state of the PagePoolAction instances sharing the same PagePool.
     */
    property Kirigami.PagePool pagePool

    /**
     * The pageStack property accepts either a Kirigami.PageRow or a QtQuickControls2 StackView.
     * The component that will instantiate the pages, which has to work with a stack logic.
     * Kirigami.PageRow is recommended, but will work with QtQuicControls2 StackView as well.
     *
     * default: `bound to ApplicationWindow's global pageStack, which is a PageRow by default`
     */
    property Item pageStack: typeof applicationWindow !== 'undefined' ? applicationWindow().pageStack : null

    /**
     * @brief This property sets the page in the pageStack after which
     * new pages will be pushed.
     *
     * All pages present after the given basePage will be removed from the pageStack
     */
    property T.Page basePage

    /**
     * This property holds a function that generate the property values for the created page
     * when it is pushed onto the Kirigami.PagePool.
     *
     * Example usage:
     * @code{.qml}
     * Kirigami.PagePoolAction {
     *     text: i18n("Security")
     *     icon.name: "security-low"
     *     page: Qt.resolvedUrl("Security.qml")
     *     initialProperties: {
     *         return {
     *             room: root.room
     *         }
     *     }
     * }
     * @endcode
     * @property QVariantMap initialProperties
     */
    property var initialProperties

    /**
     * @brief This property sets whether PagePoolAction will use the layers property
     * implemented by the pageStack.
     *
     * This is intended for use with PageRow layers to allow PagePoolActions to
     * push context-specific pages onto the layers stack.
     *
     * default: ``false``
     *
     * @since 5.70
     * @since org.kde.kirigami 2.12
     */
    property bool useLayers: false
//END properties

    /**
     * @returns the page item held in the PagePool or null if it has not been loaded yet.
     */
    function pageItem(): Item {
        return pagePool.pageForUrl(page)
    }

    /**
     * @returns true if the page has been loaded and placed on pageStack.layers
     * and useLayers is true, otherwise returns null.
     */
    function layerContainsPage(): bool {
        if (!useLayers || !pageStack.hasOwnProperty("layers")) {
            return false;
        }

        const pageItem = this.pageItem();
        const item = pageStack.layers.find(item => item === pageItem);
        return item !== null;
    }

    /**
     * @returns true if the page has been loaded and placed on the pageStack,
     * otherwise returns null.
     */
    function stackContainsPage(): bool {
        if (useLayers) {
            return false;
        }
        return pageStack.columnView.containsItem(pagePool.pageForUrl(page));
    }

    checkable: true

    onTriggered: {
        if (page.length === 0 || !pagePool || !pageStack) {
            return;
        }

        // User intends to "go back" to this layer.
        const pageItem = this.pageItem();
        if (layerContainsPage() && pageItem !== pageStack.layers.currentItem) {
            pageStack.layers.replace(pageItem, pageItem); // force pop above
            return;
        }

        // User intends to "go back" to this page.
        if (stackContainsPage()) {
            if (pageStack.hasOwnProperty("layers")) {
                pageStack.layers.clear();
            }
        }

        const stack = useLayers ? pageStack.layers : pageStack

        if (pageItem != null && stack.currentItem == pageItem) {
            return;
        }

        if (initialProperties && typeof(initialProperties) !== "object") {
            console.warn("initialProperties must be of type object");
            return;
        }

        if (!stack.hasOwnProperty("pop") || typeof stack.pop !== "function" || !stack.hasOwnProperty("push") || typeof stack.push !== "function") {
            return;
        }

        if (pagePool.isLocalUrl(page)) {
            if (basePage) {
                stack.pop(basePage);

            } else if (!useLayers) {
                stack.clear();
            }

            stack.push(initialProperties
                ? pagePool.loadPageWithProperties(page, initialProperties)
                : pagePool.loadPage(page));
        } else {
            const callback = item => {
                if (basePage) {
                    stack.pop(basePage);

                } else if (!useLayers) {
                    stack.clear();
                }

                stack.push(item);
            };

            if (initialProperties) {
                pagePool.loadPage(page, initialProperties, callback);

            } else {
                pagePool.loadPage(page, callback);
            }
        }
    }

    // Exposing this as a property is required as Action does not have a default property
    property QtObject _private: QtObject {
        id: _private

        function setChecked(checked) {
            root.checked = checked;
        }

        function clearLayers() {
            root.pageStack.layers.clear();
        }

        property list<Connections> connections: [
            Connections {
                target: root.pageStack

                function onCurrentItemChanged() {
                    if (root.useLayers) {
                        if (root.layerContainsPage()) {
                            _private.clearLayers();
                        }
                        if (root.checkable) {
                            _private.setChecked(false);
                        }

                    } else {
                        if (root.checkable) {
                            _private.setChecked(root.stackContainsPage());
                        }
                    }
                }
            },
            Connections {
                enabled: root.pageStack.hasOwnProperty("layers")
                target: root.pageStack.layers

                function onCurrentItemChanged() {
                    if (root.useLayers && root.checkable) {
                        _private.setChecked(root.layerContainsPage());

                    } else {
                        if (root.pageStack.layers.depth === 1 && root.stackContainsPage()) {
                            _private.setChecked(true);
                        }
                    }
                }
            }
        ]
    }
}