/*
 *  SPDX-FileCopyrightText: 2018 Marco Martin <mart@kde.org>
 *  SPDX-FileCopyrightText: 2023 ivan tkachenko <me@ratijas.tk>
 *
 *  SPDX-License-Identifier: LGPL-2.0-or-later
 */

import QtQuick
import QtQuick.Layouts
import org.kde.kirigami as Kirigami

ListView {
    id: root

    readonly property Kirigami.PageRow pageRow: {
        // This is fetched from breadcrumbLoader in PageRowGlobalToolBarUI.qml
        const pr = parent?.pageRow ?? null;
        return pr as Kirigami.PageRow;
    }

    currentIndex: {
        if (!pageRow) {
            return -1;
        }
        // This ListView is eventually consistent with PageRow, so it has to
        // force-refresh currentIndex when its count finally catches up,
        // otherwise currentIndex might get reset and stuck at -1.
        void count;
        // TODO: This "eventual consistency" causes Behavior on contentX to
        // scroll from the start each time a page is added. Besides, simple
        // number is not the most efficient model, because ListView
        // recreates all delegates when number changes.

        if (pageRow.layers.depth > 1) {
            // First layer (index 0) is the main columnView.
            // Since it is ignored, depth has to be adjusted by 1.
            // In case of layers, current index is always the last one,
            // which is one less than their count, thus minus another 1.
            return pageRow.layers.depth - 2;
        } else {
            return pageRow.currentIndex;
        }
    }

    // This function exists outside of delegate, so that when popping layers
    // the JavaScript execution context won't be destroyed along with delegate.
    function selectIndex(index: int) {
        if (!pageRow) {
            return;
        }
        if (pageRow.layers.depth > 1) {
            // First layer (index 0) is the main columnView.
            // Since it is ignored, index has to be adjusted by 1.
            // We want to pop anything after selected index,
            // turning selected layer into current one, thus plus another 1.
            while (pageRow.layers.depth > index + 2) {
                pageRow.layers.pop();
            }
        } else {
            pageRow.currentIndex = index;
        }
    }

    contentHeight: height
    clip: true
    orientation: ListView.Horizontal
    boundsBehavior: Flickable.StopAtBounds
    interactive: Kirigami.Settings.hasTransientTouchInput

    contentX: {
        if (!currentItem) {
            return 0;
        }
        // preferred position: current item is centered within viewport
        const preferredPosition = currentItem.x + (currentItem.width - width) / 2;

        // Note: Order of min/max is important. Make sure to test on all sorts
        // and sizes before committing changes to this formula.
        if (LayoutMirroring.enabled) {
            // In a mirrored ListView contentX starts from left edge and increases to the left.
            const maxLeftPosition = -contentWidth;
            const minRightPosition = -width;
            return Math.round(Math.min(minRightPosition, Math.max(preferredPosition, maxLeftPosition)));
        } else {
            const minLeftPosition = 0;
            const maxRightPosition = contentWidth - width;
            return Math.round(Math.max(minLeftPosition, Math.min(preferredPosition, maxRightPosition)));
        }
    }

    Behavior on contentX {
        NumberAnimation {
            duration: Kirigami.Units.longDuration
            easing.type: Easing.InOutQuad
        }
    }

    model: {
        if (!root.pageRow) {
            return null;
        }
        if (root.pageRow.layers.depth > 1) {
            // First layer (index 0) is the main columnView; ignore it.
            return root.pageRow.layers.depth - 1;
        } else {
            return root.pageRow.depth;
        }
    }

    delegate: MouseArea {
        id: delegate

        required property int index

        // We can't use Kirigami.Page here instead of Item since we now accept
        // pushing PageRow to a new layer.
        readonly property Item page: {
            if (!root.pageRow) {
                return null;
            }
            if (root.pageRow.layers.depth > 1) {
                // First layer (index 0) is the main columnView.
                // Since it is ignored, index has to be adjusted by 1.
                return pageRow.layers.get(index + 1);
            } else {
                return pageRow.get(index);
            }
        }


        width: Math.ceil(layout.implicitWidth)
        height: ListView.view?.height ?? 0

        hoverEnabled: !Kirigami.Settings.tabletMode

        onClicked: mouse => {
            root.selectIndex(index);
        }

        // background
        Rectangle {
            color: Kirigami.Theme.highlightColor
            anchors.fill: parent
            radius: Kirigami.Units.cornerRadius
            opacity: root.count > 1 && parent.containsMouse ? 0.1 : 0
        }

        // content
        RowLayout {
            id: layout
            anchors.fill: parent
            spacing: 0

            Kirigami.Icon {
                visible: delegate.index > 0
                Layout.alignment: Qt.AlignVCenter
                Layout.preferredHeight: Kirigami.Units.iconSizes.small
                Layout.preferredWidth: Kirigami.Units.iconSizes.small
                isMask: true
                color: Kirigami.Theme.textColor
                source: LayoutMirroring.enabled ? "go-next-symbolic-rtl" : "go-next-symbolic"
            }
            Kirigami.Heading {
                Layout.leftMargin: Kirigami.Units.largeSpacing
                Layout.rightMargin: Kirigami.Units.largeSpacing
                color: Kirigami.Theme.textColor
                verticalAlignment: Text.AlignVCenter
                wrapMode: Text.NoWrap
                text: delegate.page?.title ?? ""
                opacity: delegate.ListView.isCurrentItem ? 1 : 0.4
            }
        }
    }
}