// SPDX-FileCopyrightText: 2026 Marco Allegretti
// SPDX-License-Identifier: EUPL-1.2
//
// SHIFT Dynamic Tiling — KWin declarative script
//
// Architecture:
//   - One persistent layout tree per output, keyed by output.name
//   - Tree nodes are split groups or window leaves; leaf rects are absolute
//     in-screen coordinates
//   - On add/remove/reorder the tree is updated and then laid out for the
//     affected screen, preserving the split structure instead of rebuilding a
//     fresh linear BSP from window count
//   - Drag detection uses interactiveMoveResizeStarted/Stepped/Finished
//   - Dragging over a tile shows the exact directional split that will be
//     created on drop
//   - Gap: outer 8px on screen edges, inner 8px between tiles (4px each side)

import QtQuick
import org.kde.kwin as KWinComponents
import org.kde.plasma.private.mobileshell.shellsettingsplugin as ShellSettings

Item {
    id: root

    // ── Configuration ───────────────────────────────────────────────────────
    readonly property int outerGap: 8
    readonly property int innerGap: 8    // half applied to each edge → 4px per tile

    // ── State ───────────────────────────────────────────────────────────────

    // Per-screen layout tree. Key: output.name. Value: split/leaf node.
    property var screenLayouts: ({})

    // Per-screen tile list derived from screenLayouts. Key: output.name.
    // Value: [{win, rect}], where rect is absolute in-screen coordinates.
    property var screenTiles: ({})

    // Windows the user has manually floated (by UUID string).
    property var floatedWindows: ({})

    // Windows whose interactive move/resize signals are already connected.
    property var dragConnectedWindows: ({})

    property int lastWindowRequestSerial: ShellSettings.Settings.dynamicTilingWindowRequestSerial

    // Drag state.
    //
    // Behaviour: dragging a tile over another tile previews the exact
    // left/right/up/down split that will be created on drop. Dropping inside
    // the work area but outside another tile restores the original slot.
    // Dropping outside the work area floats the window, giving users a visible
    // escape hatch from the tiled layout.
    property var draggingWindow: null
    property bool dragOutlineActive: false
    property string dragDropMode: "" // "insert", "restore", or "float"
    property rect dragOutlineRect: Qt.rect(0, 0, 0, 0)

    // Reorder state — kept stable while dragging so the rest of the layout
    // doesn't shuffle under the cursor.
    property string dragSourceScreen: ""
    property int    dragSourceIndex:  -1
    property rect   dragSourceRect:   Qt.rect(0, 0, 0, 0)
    property var    dragInsertTarget: null   // {screen, key, direction, rect} preview slot
    readonly property int floatEscapeMargin: 32

    // Deferred retile queue.
    // The dockSpaceReserver LayerShell exclusive zone needs one Wayland
    // roundtrip after setMaximize() before KWin updates MaximizeArea.
    // We queue output names and flush after 200 ms — same pattern as
    // convergentwindows constrainAfterRestoreTimer.
    property var pendingRetile: []

    Timer {
        id: retileTimer
        interval: 200
        repeat: false
        onTriggered: {
            const queue = root.pendingRetile.slice();
            root.pendingRetile = [];
            const done = {};
            for (let i = 0; i < queue.length; i++) {
                if (!done[queue[i]]) {
                    done[queue[i]] = true;
                    root.retileScreen(queue[i]);
                }
            }
        }
    }

    function scheduleRetile(outputName) {
        const q = root.pendingRetile.slice();
        if (q.indexOf(outputName) < 0) q.push(outputName);
        root.pendingRetile = q;
        retileTimer.restart();
    }

    // ── Tiling guard ────────────────────────────────────────────────────────

    // Active when convergence is on, gaming is off, AND the user has
    // dynamic tiling enabled in quick settings.  When this returns false
    // the script is fully inert and KWin's native quick-tile behaviour
    // owns window placement.
    function isConvergence() {
        return ShellSettings.Settings.convergenceModeEnabled &&
               !ShellSettings.Settings.gamingModeEnabled &&
               ShellSettings.Settings.dynamicTilingEnabled;
    }

    // Mirror the same guard used by convergentwindows: only normalWindow is
    // reliable in the KWin 6 declarative script API.  Add maximizable to
    // avoid calling setMaximize on layer-shell / panel surfaces.
    function shouldIgnore(win) {
        if (!win || win.deleted) return true;
        if (!win.normalWindow) return true;   // panels, dock, desktop, layer-shell
        if (!win.maximizable) return true;    // fixed/special surfaces
        if (win.fullScreen) return true;
        // Skip xwaylandvideobridge (same as convergentwindows)
        if (win.resourceClass === "xwaylandvideobridge") return true;
        return false;
    }

    function shouldFloat(win) {
        if (!win) return true;
        // Fixed-size windows (won't tile sensibly)
        const minW = win.minSize ? win.minSize.width  : 0;
        const maxW = win.maxSize ? win.maxSize.width  : 0;
        const minH = win.minSize ? win.minSize.height : 0;
        const maxH = win.maxSize ? win.maxSize.height : 0;
        if (minW > 0 && maxW > 0 && minW >= maxW) return true;
        if (minH > 0 && maxH > 0 && minH >= maxH) return true;
        // Manually floated
        if (floatedWindows[windowKey(win)]) return true;
        return false;
    }

    function isTileable(win) {
        if (!isConvergence()) return false;
        if (shouldIgnore(win)) return false;
        if (shouldFloat(win)) return false;
        return true;
    }

    // ── Layout engine ───────────────────────────────────────────────────────

    function workRect(win) {
        const output = win.output;
        const desktop = win.desktops[0];
        if (!output || !desktop) return null;
        return KWinComponents.Workspace.clientArea(
            KWinComponents.Workspace.MaximizeArea, output, desktop);
    }

    // Apply outer + inner gaps to a list of rects that together tile a screen.
    // outer: gap between screen edge and tile
    // inner: total gap between two adjacent tiles (split equally, so 4px each side)
    function applyGaps(rects, workArea) {
        if (!rects || rects.length === 0) return rects;
        const half = innerGap / 2;
        const result = [];
        for (let i = 0; i < rects.length; i++) {
            let r = rects[i];
            // Determine which edges touch the work area boundary
            const atLeft   = Math.abs(r.x - workArea.x) < 2;
            const atTop    = Math.abs(r.y - workArea.y) < 2;
            const atRight  = Math.abs((r.x + r.width)  - (workArea.x + workArea.width))  < 2;
            const atBottom = Math.abs((r.y + r.height) - (workArea.y + workArea.height)) < 2;

            const left   = atLeft   ? outerGap       : half;
            const top    = atTop    ? outerGap       : half;
            const right  = atRight  ? outerGap       : half;
            const bottom = atBottom ? outerGap       : half;

            result.push(Qt.rect(
                r.x + left,
                r.y + top,
                r.width  - left - right,
                r.height - top  - bottom
            ));
        }
        return result;
    }

    function setScreenLayout(outputName, layout) {
        const layouts = Object.assign({}, screenLayouts);
        if (layout) {
            layouts[outputName] = layout;
        } else {
            delete layouts[outputName];
        }
        screenLayouts = layouts;
    }

    function setScreenTiles(outputName, tiles) {
        const allTiles = Object.assign({}, screenTiles);
        if (tiles && tiles.length > 0) {
            allTiles[outputName] = tiles;
        } else {
            delete allTiles[outputName];
        }
        screenTiles = allTiles;
    }

    function makeLeaf(win) {
        return { kind: "leaf", win: win, rect: Qt.rect(0, 0, 0, 0) };
    }

    function makeSplit(orientation, first, second, ratio) {
        return {
            kind: "split",
            orientation: orientation,
            first: first,
            second: second,
            ratio: ratio || 0.5,
            rect: Qt.rect(0, 0, 0, 0)
        };
    }

    function splitOrientation(rect) {
        return rect && rect.width >= rect.height ? "vertical" : "horizontal";
    }

    function directionOrientation(direction, rect) {
        if (direction === "left" || direction === "right") return "vertical";
        if (direction === "up" || direction === "down") return "horizontal";
        return splitOrientation(rect);
    }

    function splitRect(rect, orientation, ratio) {
        const splitRatio = ratio || 0.5;
        if (orientation === "vertical") {
            const firstWidth = Math.round(rect.width * splitRatio);
            return [
                Qt.rect(rect.x, rect.y, firstWidth, rect.height),
                Qt.rect(rect.x + firstWidth, rect.y, rect.width - firstWidth, rect.height)
            ];
        }

        const firstHeight = Math.round(rect.height * splitRatio);
        return [
            Qt.rect(rect.x, rect.y, rect.width, firstHeight),
            Qt.rect(rect.x, rect.y + firstHeight, rect.width, rect.height - firstHeight)
        ];
    }

    function collectLeaves(node, leaves) {
        if (!node) return;
        if (node.kind === "leaf") {
            leaves.push(node);
            return;
        }
        collectLeaves(node.first, leaves);
        collectLeaves(node.second, leaves);
    }

    function lastLeafKey(node) {
        if (!node) return "";
        if (node.kind === "leaf") return windowKey(node.win);
        return lastLeafKey(node.second) || lastLeafKey(node.first);
    }

    function containsLeaf(node, key) {
        if (!node || !key) return false;
        if (node.kind === "leaf") return windowKey(node.win) === key;
        return containsLeaf(node.first, key) || containsLeaf(node.second, key);
    }

    function splitLeaf(node, targetKey, newLeaf, direction, fallbackRect) {
        if (!node || !targetKey || !newLeaf) return node;

        if (node.kind === "leaf") {
            if (windowKey(node.win) !== targetKey) return node;

            const baseRect = validRect(node.rect) ? node.rect : fallbackRect;
            const orientation = directionOrientation(direction, baseRect);
            if (direction === "left" || direction === "up") {
                return makeSplit(orientation, newLeaf, node, 0.5);
            }
            return makeSplit(orientation, node, newLeaf, 0.5);
        }

        node.first = splitLeaf(node.first, targetKey, newLeaf, direction, fallbackRect);
        node.second = splitLeaf(node.second, targetKey, newLeaf, direction, fallbackRect);
        return node;
    }

    function removeLeaf(node, key) {
        if (!node || !key) return { node: node, leaf: null };

        if (node.kind === "leaf") {
            if (windowKey(node.win) === key) {
                return { node: null, leaf: node };
            }
            return { node: node, leaf: null };
        }

        let first = removeLeaf(node.first, key);
        if (first.leaf) {
            node.first = first.node;
            if (!node.first) return { node: node.second, leaf: first.leaf };
            return { node: node, leaf: first.leaf };
        }

        let second = removeLeaf(node.second, key);
        if (second.leaf) {
            node.second = second.node;
            if (!node.second) return { node: node.first, leaf: second.leaf };
            return { node: node, leaf: second.leaf };
        }

        return { node: node, leaf: null };
    }

    function layoutTree(node, area, leaves) {
        if (!node || !area) return;
        node.rect = Qt.rect(area.x, area.y, area.width, area.height);

        if (node.kind === "leaf") {
            leaves.push(node);
            return;
        }

        const rects = splitRect(area, node.orientation, node.ratio);
        layoutTree(node.first, rects[0], leaves);
        layoutTree(node.second, rects[1], leaves);
    }

    function insertWindowInLayout(outputName, win) {
        const rootNode = screenLayouts[outputName];
        const newLeaf = makeLeaf(win);

        if (!rootNode) {
            setScreenLayout(outputName, newLeaf);
            return;
        }

        let targetKey = "";
        const active = KWinComponents.Workspace.activeWindow;
        if (active && active.output && active.output.name === outputName && windowKey(active) !== windowKey(win)) {
            targetKey = windowKey(active);
        }
        if (!containsLeaf(rootNode, targetKey)) {
            targetKey = lastLeafKey(rootNode);
        }

        setScreenLayout(outputName, splitLeaf(rootNode, targetKey, newLeaf, "", workRect(win)));
    }

    function removeWindowFromLayout(outputName, win) {
        const key = windowKey(win);
        const rootNode = screenLayouts[outputName];
        if (!key || !rootNode) return false;

        const result = removeLeaf(rootNode, key);
        if (!result.leaf) return false;
        setScreenLayout(outputName, result.node);
        return true;
    }

    function moveWindowToSplit(target) {
        if (!target || !draggingWindow || !dragSourceScreen) return;

        const sourceKey = windowKey(draggingWindow);
        if (!sourceKey || sourceKey === target.key) return;

        const sourceRoot = screenLayouts[dragSourceScreen];
        const detached = removeLeaf(sourceRoot, sourceKey);
        if (!detached.leaf) return;

        setScreenLayout(dragSourceScreen, detached.node);

        const targetRoot = screenLayouts[target.screen];
        if (!targetRoot || !containsLeaf(targetRoot, target.key)) {
            setScreenLayout(dragSourceScreen, sourceRoot);
            return;
        }

        setScreenLayout(target.screen, splitLeaf(targetRoot, target.key, detached.leaf, target.direction, target.rect));
        retileScreen(dragSourceScreen);
        if (target.screen !== dragSourceScreen) {
            retileScreen(target.screen);
        }
    }

    // Recompute and apply layout for a single screen.
    function retileScreen(outputName) {
        const rootNode = screenLayouts[outputName];
        if (!rootNode) {
            setScreenTiles(outputName, []);
            return;
        }

        const leaves = [];
        collectLeaves(rootNode, leaves);
        if (leaves.length === 0) {
            setScreenTiles(outputName, []);
            return;
        }

        // Get work area from the first window's output
        let area = null;
        for (let i = 0; i < leaves.length; i++) {
            const r = workRect(leaves[i].win);
            if (r) { area = r; break; }
        }
        if (!area) return;

        const rawLeaves = [];
        layoutTree(rootNode, area, rawLeaves);
        const rawRects = [];
        for (let i = 0; i < rawLeaves.length; i++) {
            rawRects.push(rawLeaves[i].rect);
        }
        const gappedRects = applyGaps(rawRects, area);

        for (let i = 0; i < rawLeaves.length; i++) {
            const win = rawLeaves[i].win;
            if (!win || win.deleted) continue;
            const r = gappedRects[i];
            rawLeaves[i].rect = r;
            win.frameGeometry = r;
        }
        setScreenLayout(outputName, rootNode);
        setScreenTiles(outputName, rawLeaves.slice());
    }

    // Retile all layout trees.
    function retileAll() {
        for (const name in screenLayouts) {
            retileScreen(name);
        }
    }

    function scheduleRetileAll() {
        for (const name in screenLayouts) {
            scheduleRetile(name);
        }
    }

    function screenNameForWindow(win) {
        const key = windowKey(win);
        if (!key) return "";

        for (const name in screenLayouts) {
            if (containsLeaf(screenLayouts[name], key)) {
                return name;
            }
        }
        return "";
    }

    function reconcileWindowOutput(win) {
        if (!isTileable(win)) return;

        connectDragHandlers(win);

        const output = win.output;
        if (!output) return;

        const currentName = screenNameForWindow(win);
        const targetName = output.name;

        if (currentName !== "" && currentName !== targetName) {
            removeWindowFromLayout(currentName, win);
            scheduleRetile(currentName);
        }

        if (!containsLeaf(screenLayouts[targetName], windowKey(win))) {
            insertWindowInLayout(targetName, win);
        }

        if (win.maximizable) win.setMaximize(false, false);
        win.noBorder = false;
        scheduleRetile(targetName);
    }

    // Add a window to its screen's tile list and retile.
    function addWindow(win) {
        if (!isTileable(win)) return;

        connectDragHandlers(win);

        const output = win.output;
        if (!output) return;
        const name = output.name;

        // Avoid duplicates
        const key = windowKey(win);
        if (containsLeaf(screenLayouts[name], key)) return;

        const tiles = screenTiles[name] || [];
        for (let i = 0; i < tiles.length; i++) {
            if (windowKey(tiles[i].win) === key) return;
        }

        insertWindowInLayout(name, win);

        // Un-maximize now so the exclusive-zone Wayland roundtrip begins;
        // retileScreen runs 200 ms later when MaximizeArea has settled.
        // (Same pattern as convergentwindows constrainAfterRestoreTimer.)
        if (win.maximizable) win.setMaximize(false, false);
        win.noBorder = false;
        scheduleRetile(name);
    }

    // Remove a window from its screen's tile list and retile.
    function removeWindow(win) {
        if (!win) return;

        // Search all layout trees (window may have been moved or queued before
        // the deferred tile list has refreshed).
        for (const sName in screenLayouts) {
            if (removeWindowFromLayout(sName, win)) {
                retileScreen(sName);
                return;
            }
        }
    }

    function windowKey(win) {
        return win && win.internalId !== undefined ? String(win.internalId) : "";
    }

    function findWindowById(windowId) {
        const wanted = String(windowId);
        const wins = KWinComponents.Workspace.windows;
        for (let i = 0; i < wins.length; i++) {
            if (windowKey(wins[i]) === wanted) {
                return wins[i];
            }
        }
        return null;
    }

    function floatWindow(win) {
        const key = windowKey(win);
        if (!key) return;
        floatedWindows[key] = true;
        removeWindow(win);
    }

    function tileWindow(win) {
        const key = windowKey(win);
        if (!key) return;
        delete floatedWindows[key];
        if (isTileable(win)) {
            addWindow(win);
        }
    }

    function connectDragHandlers(win) {
        const key = windowKey(win);
        if (!key || dragConnectedWindows[key]) return;

        dragConnectedWindows[key] = true;
        win.interactiveMoveResizeStarted.connect(function() { root.onDragStart(win); });
        win.interactiveMoveResizeStepped.connect(function(geo) { root.onDragStep(win, geo); });
        win.interactiveMoveResizeFinished.connect(function() { root.onDragEnd(win); });
    }

    function handleWindowTilingRequest() {
        const serial = ShellSettings.Settings.dynamicTilingWindowRequestSerial;
        if (serial === lastWindowRequestSerial) return;
        lastWindowRequestSerial = serial;

        if (!isConvergence()) return;
        const win = findWindowById(ShellSettings.Settings.dynamicTilingWindowRequestId);
        if (!win || shouldIgnore(win)) return;

        const action = ShellSettings.Settings.dynamicTilingWindowRequestAction;
        if (action === "float") {
            floatWindow(win);
        } else if (action === "tile") {
            tileWindow(win);
        }
    }

    // ── Keyboard navigation helpers ──────────────────────────────────────────

    function centreOf(rect) {
        return { x: rect.x + rect.width / 2, y: rect.y + rect.height / 2 };
    }

    // Find the tile on-screen whose centre is most in `direction` from `fromRect`.
    // direction: "left"|"right"|"up"|"down"
    function findNeighbour(fromWin, direction) {
        const outputName = fromWin.output ? fromWin.output.name : null;
        if (!outputName) return null;
        const tiles = screenTiles[outputName];
        if (!tiles) return null;

        const from = fromWin.frameGeometry;
        const fc = centreOf(from);
        let best = null;
        let bestScore = Infinity;

        for (let i = 0; i < tiles.length; i++) {
            const t = tiles[i];
            if (windowKey(t.win) === windowKey(fromWin)) continue;
            const tc = centreOf(t.rect);
            const dx = tc.x - fc.x;
            const dy = tc.y - fc.y;

            let inDirection = false;
            let primary = 0;
            let secondary = 0;
            switch (direction) {
            case "left":  inDirection = dx < -5; primary = -dx; secondary = Math.abs(dy); break;
            case "right": inDirection = dx >  5; primary =  dx; secondary = Math.abs(dy); break;
            case "up":    inDirection = dy < -5; primary = -dy; secondary = Math.abs(dx); break;
            case "down":  inDirection = dy >  5; primary =  dy; secondary = Math.abs(dx); break;
            }
            if (!inDirection) continue;
            // Score: penalise perpendicular distance lightly
            const score = primary + secondary * 0.3;
            if (score < bestScore) { bestScore = score; best = t.win; }
        }
        return best;
    }

    // ── Workspace connections ─────────────────────────────────────────────

    Connections {
        target: KWinComponents.Workspace

        function onWindowAdded(win) {
            if (isTileable(win)) {
                addWindow(win);
            }
        }

        function onWindowRemoved(win) {
            const key = root.windowKey(win);
            if (key) delete root.dragConnectedWindows[key];
            root.removeWindow(win);
        }

        function onScreensChanged() {
            if (!root.isConvergence()) {
                return;
            }

            const wins = KWinComponents.Workspace.windows;
            for (let i = 0; i < wins.length; i++) {
                root.reconcileWindowOutput(wins[i]);
            }

            root.scheduleRetileAll();
        }
    }

    Connections {
        target: ShellSettings.Settings

        function onConvergenceModeEnabledChanged() {
            if (isConvergence()) {
                // Tile all existing normal windows
                const wins = KWinComponents.Workspace.windows;
                for (let i = 0; i < wins.length; i++) {
                    addWindow(wins[i]);
                }
            } else {
                // Clear all tiles — the convergentwindows script will re-maximize
                screenLayouts = {};
                screenTiles = {};
            }
        }

        function onGamingModeEnabledChanged() {
            if (ShellSettings.Settings.gamingModeEnabled) {
                screenLayouts = {};
                screenTiles = {};
            } else if (isConvergence()) {
                const wins = KWinComponents.Workspace.windows;
                for (let i = 0; i < wins.length; i++) {
                    addWindow(wins[i]);
                }
            }
        }

        function onDynamicTilingEnabledChanged() {
            if (isConvergence()) {
                const wins = KWinComponents.Workspace.windows;
                for (let i = 0; i < wins.length; i++) {
                    addWindow(wins[i]);
                }
            } else {
                // Tiling turned off — leave windows where they are.
                screenLayouts = {};
                screenTiles = {};
            }
        }

        function onDynamicTilingWindowRequestChanged() {
            root.handleWindowTilingRequest();
        }
    }

    // ── Drag handlers ─────────────────────────────────────────────────────

    // Find the (screen, index) of an existing tile holding this window.
    function findTileSlot(win) {
        for (const sName in screenTiles) {
            const tiles = screenTiles[sName];
            for (let i = 0; i < tiles.length; i++) {
                if (tiles[i].win && windowKey(tiles[i].win) === windowKey(win)) {
                    return { screen: sName, index: i };
                }
            }
        }
        return null;
    }

    // Find the tile under a cursor position, ignoring the dragged window.
    function findTileAtCursor(cursor, ignoreWin) {
        for (const sName in screenTiles) {
            const tiles = screenTiles[sName];
            for (let i = 0; i < tiles.length; i++) {
                const t = tiles[i];
                if (ignoreWin && t.win && windowKey(t.win) === windowKey(ignoreWin)) continue;
                const r = t.rect;
                if (!r || r.width <= 0 || r.height <= 0) continue;
                if (cursor.x >= r.x && cursor.x <= r.x + r.width &&
                    cursor.y >= r.y && cursor.y <= r.y + r.height) {
                    return { screen: sName, index: i, rect: r, key: windowKey(t.win), win: t.win };
                }
            }
        }
        return null;
    }

    function tileInsertDirection(cursor, rect) {
        if (!validRect(rect)) return "";

        const left = Math.abs(cursor.x - rect.x);
        const right = Math.abs((rect.x + rect.width) - cursor.x);
        const top = Math.abs(cursor.y - rect.y);
        const bottom = Math.abs((rect.y + rect.height) - cursor.y);
        const nearest = Math.min(left, right, top, bottom);

        if (nearest === left) return "left";
        if (nearest === right) return "right";
        if (nearest === top) return "up";
        return "down";
    }

    function previewInsertRect(win, target, position) {
        if (!target || !validRect(target.rect) || dragSourceIndex < 0) return null;

        const orientation = directionOrientation(position, target.rect);
        const rects = splitRect(target.rect, orientation, 0.5);
        if (position === "left" || position === "up") return rects[0];
        return rects[1];
    }

    function insertDraggedWindow(target) {
        moveWindowToSplit(target);
    }

    function validRect(rect) {
        return rect && rect.width > 0 && rect.height > 0;
    }

    function rectContainsPoint(rect, point) {
        return validRect(rect) &&
               point.x >= rect.x && point.x <= rect.x + rect.width &&
               point.y >= rect.y && point.y <= rect.y + rect.height;
    }

    function rectsClose(a, b) {
        return Math.abs(a.x - b.x) < 2 &&
               Math.abs(a.y - b.y) < 2 &&
               Math.abs(a.width - b.width) < 2 &&
               Math.abs(a.height - b.height) < 2;
    }

    function outsideWorkArea(win, cursor) {
        const area = workRect(win);
        if (!area) return false;
        const expanded = Qt.rect(
            area.x - floatEscapeMargin,
            area.y - floatEscapeMargin,
            area.width + floatEscapeMargin * 2,
            area.height + floatEscapeMargin * 2
        );
        return !rectContainsPoint(expanded, cursor);
    }

    function showDragOutline(mode, rect) {
        if (!validRect(rect)) {
            clearDragOutline();
            return;
        }
        if (dragOutlineActive && dragDropMode === mode && rectsClose(dragOutlineRect, rect)) {
            return;
        }
        dragDropMode = mode;
        dragOutlineRect = Qt.rect(rect.x, rect.y, rect.width, rect.height);
        dragOutlineActive = true;
    }

    function clearDragOutline() {
        dragOutlineActive = false;
        dragDropMode = "";
        dragOutlineRect = Qt.rect(0, 0, 0, 0);
    }

    function resetDragState() {
        clearDragOutline();
        dragInsertTarget = null;
        dragSourceScreen = "";
        dragSourceIndex = -1;
        dragSourceRect = Qt.rect(0, 0, 0, 0);
        draggingWindow = null;
    }

    function updateDragIntent(win, geo) {
        const cursor = KWinComponents.Workspace.cursorPos;
        const target = findTileAtCursor(cursor, win);

        if (target) {
            const position = tileInsertDirection(cursor, target.rect);
            const insertRect = previewInsertRect(win, target, position);
            if (validRect(insertRect)) {
                dragInsertTarget = {
                    screen: target.screen,
                    key: target.key,
                    direction: position,
                    rect: insertRect,
                    position: position
                };
                showDragOutline("insert", insertRect);
                return;
            }
        }

        dragInsertTarget = null;
        if (outsideWorkArea(win, cursor)) {
            showDragOutline("float", validRect(geo) ? geo : win.frameGeometry);
        } else {
            showDragOutline("restore", dragSourceRect);
        }
    }

    function onDragStart(win) {
        if (!isConvergence()) return;
        draggingWindow = win;
        clearDragOutline();
        dragInsertTarget = null;
        dragSourceRect = Qt.rect(0, 0, 0, 0);

        // Remember the source slot so we can insert on drop.
        // The tile stays in screenTiles[] during the drag so the rest of
        // the layout doesn't shuffle.
        const slot = findTileSlot(win);
        if (slot) {
            dragSourceScreen = slot.screen;
            dragSourceIndex  = slot.index;
            const tiles = screenTiles[slot.screen];
            if (tiles && tiles[slot.index]) {
                const rect = tiles[slot.index].rect;
                dragSourceRect = Qt.rect(rect.x, rect.y, rect.width, rect.height);
            }
        } else {
            dragSourceScreen = "";
            dragSourceIndex  = -1;
        }

        showDragOutline("restore", dragSourceRect);
    }

    function onDragStep(win, geo) {
        if (!isConvergence()) {
            resetDragState();
            return;
        }
        if (draggingWindow !== win) return;
        updateDragIntent(win, geo);
    }

    function onDragEnd(win) {
        if (!isConvergence()) {
            resetDragState();
            return;
        }

        const finalDropMode = dragDropMode;
        clearDragOutline();

        if (finalDropMode === "float") {
            floatWindow(win);
        }

        else if (finalDropMode === "insert" && dragInsertTarget) {
            insertDraggedWindow(dragInsertTarget);
        }

        // Dropped elsewhere → restore the source tile to its original slot.
        // (KWin's native quick-tile may have moved the window; retileScreen
        // sets frameGeometry back to the BSP rect so the layout stays intact.)
        else if (dragSourceScreen && dragSourceIndex >= 0) {
            retileScreen(dragSourceScreen);
        }

        resetDragState();
    }

    // ── Keyboard shortcuts ─────────────────────────────────────────────────

    // Focus navigation
    KWinComponents.ShortcutHandler {
        name: "SHIFT Tiling Focus Left"
        text: "SHIFT Tiling: Focus window to the left"
        sequence: "Meta+H"
        onActivated: {
            const win = KWinComponents.Workspace.activeWindow;
            if (!win) return;
            const target = root.findNeighbour(win, "left");
            if (target) KWinComponents.Workspace.activeWindow = target;
        }
    }
    KWinComponents.ShortcutHandler {
        name: "SHIFT Tiling Focus Right"
        text: "SHIFT Tiling: Focus window to the right"
        sequence: "Meta+L"
        onActivated: {
            const win = KWinComponents.Workspace.activeWindow;
            if (!win) return;
            const target = root.findNeighbour(win, "right");
            if (target) KWinComponents.Workspace.activeWindow = target;
        }
    }
    KWinComponents.ShortcutHandler {
        name: "SHIFT Tiling Focus Up"
        text: "SHIFT Tiling: Focus window above"
        sequence: "Meta+K"
        onActivated: {
            const win = KWinComponents.Workspace.activeWindow;
            if (!win) return;
            const target = root.findNeighbour(win, "up");
            if (target) KWinComponents.Workspace.activeWindow = target;
        }
    }
    KWinComponents.ShortcutHandler {
        name: "SHIFT Tiling Focus Down"
        text: "SHIFT Tiling: Focus window below"
        sequence: "Meta+J"
        onActivated: {
            const win = KWinComponents.Workspace.activeWindow;
            if (!win) return;
            const target = root.findNeighbour(win, "down");
            if (target) KWinComponents.Workspace.activeWindow = target;
        }
    }

    // Float toggle
    KWinComponents.ShortcutHandler {
        name: "SHIFT Tiling Float Toggle"
        text: "SHIFT Tiling: Toggle float for active window"
        sequence: "Meta+F"
        onActivated: {
            const win = KWinComponents.Workspace.activeWindow;
            if (!win) return;
            const id = root.windowKey(win);
            if (root.floatedWindows[id]) {
                root.tileWindow(win);
            } else {
                root.floatWindow(win);
            }
        }
    }

    // Tiling on/off
    KWinComponents.ShortcutHandler {
        name: "SHIFT Tiling Toggle"
        text: "SHIFT Tiling: Toggle tiling on/off"
        sequence: "Meta+T"
        onActivated: {
            ShellSettings.Settings.dynamicTilingEnabled = !ShellSettings.Settings.dynamicTilingEnabled;
        }
    }

    // ── Component setup ───────────────────────────────────────────────────

    Component.onCompleted: {
        // Connect to existing windows
        const wins = KWinComponents.Workspace.windows;
        for (let i = 0; i < wins.length; i++) {
            const win = wins[i];
            if (isTileable(win)) {
                addWindow(win);
            }
        }
    }
}