// Copyright (C) 2026 Danilo M. <danix@danix.xyz>
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License version 2 as
// published by the Free Software Foundation.
//
// 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 General Public License for more details.

import Quickshell
import Quickshell.Wayland
import QtQuick

Scope {
    id: root

    // The modules the drawer hosts, in grid order. Set from shell.qml.
    property list<QtObject> modules

    // Waybar runs on this screen and the launcher sits at its left end, so
    // the drawer belongs here. Falls back to the first screen when this
    // monitor is not connected, so the drawer is never invisible.
    property string monitor: "DP-1"

    property bool open: false

    // Which module's page is showing. Empty means the grid.
    property string page: ""

    readonly property var screenObj:
        Quickshell.screens.find(s => s.name === root.monitor) ?? Quickshell.screens[0]

    // A plain `list<QtObject>` is indexed directly; it is not an
    // ObjectModel, so there is no `.values` to go through.
    readonly property QtObject current: {
        for (let i = 0; i < root.modules.length; i++)
            if (root.modules[i].name === root.page) return root.modules[i];
        return null;
    }

    function show(name) {
        root.page = name ?? "";
        root.open = true;
    }

    function close() {
        root.open = false;
        // Reset to the grid: a panel that reopens somewhere unexpected is
        // worse than one extra click.
        root.page = "";
    }

    function toggle(name) {
        if (root.open && (name ?? "") === root.page) root.close();
        else root.show(name);
    }

    // Clicking a tile: a module with a page opens it, one without acts.
    function activate(mod) {
        if (mod.page) root.page = mod.name;
        else { mod.activate(); root.close(); }
    }

    LazyLoader {
        active: root.open

        PanelWindow {
            id: win
            screen: root.screenObj

            anchors { top: true; left: true; right: true; bottom: true }
            color: "transparent"

            // Normal, not Ignore: waybar claims an exclusive zone at the top
            // of this screen, so respecting it puts the drawer below the bar
            // without this file knowing the bar's height. The drawer is
            // reached from the bar, so the bar must stay visible and
            // clickable while it is open.
            exclusionMode: ExclusionMode.Normal

            WlrLayershell.layer: WlrLayer.Overlay
            WlrLayershell.namespace: "quickshell-desktop"
            WlrLayershell.keyboardFocus: WlrKeyboardFocus.Exclusive

            // The click-outside catcher. It covers the whole surface, and the
            // drawer sits on top of it swallowing its own clicks.
            MouseArea {
                anchors.fill: parent
                onClicked: root.close()
            }

            // Keys reach a focused item, never the window: setting
            // keyboardFocus above is necessary but not sufficient, and
            // Keys.onEscapePressed on a PanelWindow never fires. See AGENTS.md.
            Item {
                anchors.fill: parent
                focus: true
                Keys.onEscapePressed: {
                    if (root.page) root.page = "";
                    else root.close();
                }
            }

            Rectangle {
                id: panel
                anchors { top: parent.top; left: parent.left; bottom: parent.bottom }
                width: 600
                color: Qt.alpha(Theme.base, 0.72)
                topRightRadius: 14
                bottomRightRadius: 14
                border.width: 1
                border.color: Qt.alpha(Theme.text, 0.12)

                // Clicks on the panel must not reach the catcher behind it.
                MouseArea { anchors.fill: parent }

                // --- grid view ---

                Item {
                    anchors.fill: parent
                    anchors.margins: 16
                    visible: root.page === ""

                    // Reserved for the notification engine. An empty Item that
                    // claims the space rather than a placeholder graphic: the
                    // grid has to sit where it will sit once notifications
                    // arrive, or the layout is tuned against a position that
                    // does not survive.
                    Item {
                        id: notifications
                        anchors { top: parent.top; left: parent.left; right: parent.right }
                        anchors.bottom: grid.top
                        anchors.bottomMargin: 16
                    }

                    // Fixed, never scrolled. Three columns at 600px with a
                    // 180px minimum; tiles wrap and add rows, ceiling 3x3.
                    Flow {
                        id: grid
                        anchors { left: parent.left; right: parent.right; bottom: parent.bottom }
                        spacing: 10

                        Repeater {
                            model: root.modules

                            Tile {
                                required property QtObject modelData
                                // Three columns, or fewer if the panel is
                                // narrower than three 180px tiles allow.
                                width: (grid.width - 2 * grid.spacing) / 3
                                icon: modelData.icon
                                label: modelData.label
                                content: modelData.tileContent
                                onClicked: root.activate(modelData)
                            }
                        }
                    }
                }

                // --- page view ---

                Loader {
                    id: pageLoader
                    anchors.fill: parent
                    anchors.margins: 16
                    active: root.current !== null
                    sourceComponent: root.current?.page ?? null

                    // The Page's back arrow returns to the grid. Without this
                    // the header button is inert, since the page only emits
                    // `back` and does not know who hosts it.
                    onLoaded: if (item && item.back) item.back.connect(() => root.page = "")

                    // The page enters from the right: the one piece of motion
                    // in the design, and what makes the drawer read as one
                    // surface rather than a window swapping contents.
                    opacity: active ? 1 : 0
                    x: active ? 16 : 60
                    Behavior on x { NumberAnimation { duration: 160; easing.type: Easing.OutCubic } }
                    Behavior on opacity { NumberAnimation { duration: 160 } }
                }
            }
        }
    }
}