// GridSpaces — per-workspace flexible tiling for GNOME Shell 48 (Wayland).
//
// A "grid workspace" is a stack of rows; each row has its own column count.
// Row heights (h%) and per-row column widths (w%) are percentages of the whole
// work area (dividers live on those percentage boundaries — the 100 already
// accounts for them). Windows entering the workspace auto-fill the first free
// cell and fully occupy it. Drag a window onto another cell to swap. Drag the
// always-visible divider lines to resize adjacent rows/columns (preview line
// while dragging, applied on release). Normal workspaces get zero hooks.
// Overflow windows pop to the nearest normal workspace.
//
// SAFETY: every signal / timeout / event callback is funnelled through a guard
// that (a) no-ops after teardown and (b) swallows+logs exceptions. On Wayland
// an unhandled throw inside such a callback is uncatchable by GNOME and takes
// the whole shell down, so this is load-bearing, not defensive paranoia.

import GObject from 'gi://GObject';
import Meta from 'gi://Meta';
import GLib from 'gi://GLib';
import Gio from 'gi://Gio';
import Clutter from 'gi://Clutter';
import St from 'gi://St';

import {Extension} from 'resource:///org/gnome/shell/extensions/extension.js';
import * as Main from 'resource:///org/gnome/shell/ui/main.js';
import * as PanelMenu from 'resource:///org/gnome/shell/ui/panelMenu.js';
import * as PopupMenu from 'resource:///org/gnome/shell/ui/popupMenu.js';

const MAX_ROWS = 8;
const MAX_COLS = 8;
const DIVIDER = 8;     // px: thickness of the draggable seam
const MIN_CELL = 80;   // px: smallest a row/column may be dragged to
const TA_SCHEMA = 'org.gnome.shell.extensions.tiling-assistant';

function logErr(where, e) {
    try {
        logError(e, `GridSpaces:${where}`);
    } catch (_e) {}
}

function isManaged(win) {
    return !!win &&
        win.get_window_type() === Meta.WindowType.NORMAL &&
        !win.is_skip_taskbar() &&
        !win.is_on_all_workspaces();
}

// Owns every connection / timeout for the whole extension instance. A single
// place to wrap callbacks and to tear everything down deterministically.
class Lifetime {
    constructor() {
        this.dead = false;
        this._signals = [];          // [obj, id]
        this._timeouts = new Set();  // GLib source ids
    }

    // Wrap any callback: no-op once dead, never let an exception escape.
    guard(where, fn) {
        return (...args) => {
            if (this.dead)
                return undefined;
            try {
                return fn(...args);
            } catch (e) {
                logErr(where, e);
                return undefined;
            }
        };
    }

    connect(obj, signal, where, fn) {
        const id = obj.connect(signal, this.guard(where, fn));
        this._signals.push([obj, id]);
        return id;
    }

    // Track an arbitrary external connection so destroy() reaps it.
    track(obj, id) {
        this._signals.push([obj, id]);
        return id;
    }

    timeout(where, ms, fn) {
        let id = 0;
        const run = () => {
            this._timeouts.delete(id);
            if (this.dead)
                return GLib.SOURCE_REMOVE;
            try {
                return fn();
            } catch (e) {
                logErr(where, e);
                return GLib.SOURCE_REMOVE;
            }
        };
        id = GLib.timeout_add(GLib.PRIORITY_DEFAULT, ms, run);
        this._timeouts.add(id);
        return id;
    }

    destroy() {
        this.dead = true;
        for (const id of this._timeouts) {
            try { GLib.source_remove(id); } catch (_e) {}
        }
        this._timeouts.clear();
        for (const [obj, id] of this._signals) {
            try { obj.disconnect(id); } catch (_e) {}
        }
        this._signals = [];
    }
}

// ---- Tiling Assistant coexistence (scoped, fully reversible) ---------------
class TilingAssistantGuard {
    constructor() {
        this._settings = null;
        this._origPopup = null;
        this._suppressed = false;
        try {
            const src = Gio.SettingsSchemaSource.get_default();
            if (src && src.lookup(TA_SCHEMA, true))
                this._settings = new Gio.Settings({schema_id: TA_SCHEMA});
        } catch (_e) {
            this._settings = null;
        }
    }

    sync(gridActive) {
        if (!this._settings || this._suppressed === gridActive)
            return;
        try {
            if (gridActive) {
                this._origPopup =
                    this._settings.get_boolean('enable-tiling-popup');
                this._settings.set_boolean('enable-tiling-popup', false);
                this._suppressed = true;
            } else {
                this.restore();
            }
        } catch (e) {
            logErr('ta.sync', e);
        }
    }

    restore() {
        try {
            if (this._settings && this._suppressed && this._origPopup !== null)
                this._settings.set_boolean(
                    'enable-tiling-popup', this._origPopup);
        } catch (e) {
            logErr('ta.restore', e);
        }
        this._suppressed = false;
        this._origPopup = null;
    }
}

// ---- One grid bound to one Meta.Workspace ---------------------------------
class WorkspaceGrid {
    constructor(manager, workspace) {
        this._mgr = manager;
        this._life = manager._life;
        this.ws = workspace;
        this._destroyed = false;
        // Default: 2 rows, 2 columns each.
        this.rows = [
            {h: 50, cols: [{w: 50}, {w: 50}]},
            {h: 50, cols: [{w: 50}, {w: 50}]},
        ];
        this.slots = new Array(this.capacity).fill(null);

        this._addedId = this._life.track(workspace,
            workspace.connect('window-added',
                this._life.guard('grid.added',
                    (_ws, win) => this._onWindowAdded(win))));
        this._removedId = this._life.track(workspace,
            workspace.connect('window-removed',
                this._life.guard('grid.removed',
                    (_ws, win) => this._onWindowRemoved(win))));

        for (const win of workspace.list_windows())
            this._onWindowAdded(win);
    }

    get capacity() {
        return this.rows.reduce((n, r) => n + r.cols.length, 0);
    }

    _coord(index) {
        let i = index;
        for (let r = 0; r < this.rows.length; r++) {
            const n = this.rows[r].cols.length;
            if (i < n)
                return {row: r, col: i};
            i -= n;
        }
        return null;
    }

    _workArea() {
        return this.ws.get_work_area_for_monitor(
            Main.layoutManager.primaryIndex);
    }

    // Pixel rect of a cell. Outer edges sit flush with the work area; internal
    // seams reserve DIVIDER px (carved evenly from both neighbours).
    _cellRect(row, col) {
        const a = this._workArea();
        const R = this.rows.length;
        const r = this.rows[row];
        const C = r.cols.length;

        let topPct = 0;
        for (let i = 0; i < row; i++)
            topPct += this.rows[i].h;
        const y0 = a.y + Math.round((a.height * topPct) / 100);
        const y1 = a.y + Math.round((a.height * (topPct + r.h)) / 100);

        let leftPct = 0;
        for (let i = 0; i < col; i++)
            leftPct += r.cols[i].w;
        const x0 = a.x + Math.round((a.width * leftPct) / 100);
        const x1 =
            a.x + Math.round((a.width * (leftPct + r.cols[col].w)) / 100);

        const top = y0 + (row > 0 ? DIVIDER / 2 : 0);
        const bot = y1 - (row < R - 1 ? DIVIDER / 2 : 0);
        const left = x0 + (col > 0 ? DIVIDER / 2 : 0);
        const right = x1 - (col < C - 1 ? DIVIDER / 2 : 0);
        return {
            x: Math.round(left),
            y: Math.round(top),
            w: Math.max(1, Math.round(right - left)),
            h: Math.max(1, Math.round(bot - top)),
        };
    }

    cellRectForSlot(index) {
        const c = this._coord(index);
        return c ? this._cellRect(c.row, c.col) : null;
    }

    slotAtPoint(px, py) {
        for (let i = 0; i < this.capacity; i++) {
            const rc = this.cellRectForSlot(i);
            if (rc && px >= rc.x && px < rc.x + rc.w &&
                py >= rc.y && py < rc.y + rc.h)
                return i;
        }
        let best = -1, bd = Infinity;
        for (let i = 0; i < this.capacity; i++) {
            const rc = this.cellRectForSlot(i);
            if (!rc)
                continue;
            const dx = px - (rc.x + rc.w / 2);
            const dy = py - (rc.y + rc.h / 2);
            const d = dx * dx + dy * dy;
            if (d < bd) {
                bd = d;
                best = i;
            }
        }
        return best;
    }

    slotOf(win) {
        return this.slots.indexOf(win);
    }

    _place(win, index) {
        const rect = this.cellRectForSlot(index);
        if (!rect)
            return;
        const apply = () => {
            if (this._destroyed || !win || !win.get_compositor_private())
                return GLib.SOURCE_REMOVE;
            if (win.get_maximized())
                win.unmaximize(Meta.MaximizeFlags.BOTH);
            win.move_resize_frame(true, rect.x, rect.y, rect.w, rect.h);
            return GLib.SOURCE_REMOVE;
        };
        apply();
        this._life.timeout('grid.place', 60, apply);
    }

    relayout() {
        if (this._destroyed)
            return;
        for (let i = 0; i < this.slots.length; i++) {
            if (this.slots[i])
                this._place(this.slots[i], i);
        }
        this._mgr.refreshOverlay();
    }

    _onWindowAdded(win) {
        if (this._destroyed || !isManaged(win) ||
            this._mgr.isRelocating(win))
            return;
        if (this.slotOf(win) !== -1)
            return;
        const free = this.slots.indexOf(null);
        if (free === -1) {
            this._mgr.bounce(win, this.ws);
            return;
        }
        this.slots[free] = win;
        this._place(win, free);
        this._mgr.refreshOverlay();
    }

    _onWindowRemoved(win) {
        if (this._destroyed)
            return;
        const i = this.slotOf(win);
        if (i !== -1) {
            this.slots[i] = null;
            this._mgr.refreshOverlay();
        }
    }

    handleDragEnd(win) {
        if (this._destroyed)
            return;
        const from = this.slotOf(win);
        if (from === -1)
            return;
        const [px, py] = global.get_pointer();
        const to = this.slotAtPoint(px, py);
        if (to !== -1 && to !== from) {
            const other = this.slots[to];
            this.slots[from] = other;   // swap (other may be null)
            this.slots[to] = win;
        }
        this.relayout();
        for (const delay of [50, 180]) {
            this._life.timeout('grid.dragEnd', delay, () => {
                if (!this._destroyed)
                    this.relayout();
                return GLib.SOURCE_REMOVE;
            });
        }
    }

    _reseat() {
        const live = this.slots.filter(w => w !== null);
        const cap = this.capacity;
        this.slots = new Array(cap).fill(null);
        live.slice(0, cap).forEach((w, i) => (this.slots[i] = w));
        for (const w of live.slice(cap))
            this._mgr.popToNormal(w, this.ws);
        this.relayout();
    }

    addRow() {
        if (this._destroyed || this.rows.length >= MAX_ROWS)
            return;
        this.rows.push({h: 0, cols: [{w: 100}]});
        const eq = 100 / this.rows.length;
        this.rows.forEach(r => (r.h = eq));
        this._reseat();
    }

    removeRow(idx) {
        if (this._destroyed || this.rows.length <= 1 ||
            idx < 0 || idx >= this.rows.length)
            return;
        this.rows.splice(idx, 1);
        const eq = 100 / this.rows.length;
        this.rows.forEach(r => (r.h = eq));
        this._reseat();
    }

    setRowColumns(idx, n) {
        if (this._destroyed)
            return;
        const r = this.rows[idx];
        if (!r)
            return;
        n = Math.max(1, Math.min(MAX_COLS, n));
        if (n === r.cols.length)
            return;
        r.cols = Array.from({length: n}, () => ({w: 100 / n}));
        this._reseat();
    }

    setRowHeights(a, b, hA, hB) {
        if (this._destroyed)
            return;
        this.rows[a].h = hA;
        this.rows[b].h = hB;
        this.relayout();
    }

    setColWidths(row, a, b, wA, wB) {
        if (this._destroyed)
            return;
        this.rows[row].cols[a].w = wA;
        this.rows[row].cols[b].w = wB;
        this.relayout();
    }

    destroy() {
        this._destroyed = true;
        try {
            this.ws.disconnect(this._addedId);
            this.ws.disconnect(this._removedId);
        } catch (_e) {}
        this.slots = [];
    }
}

// ---- Always-visible draggable divider overlay -----------------------------
class DividerOverlay {
    constructor(manager) {
        this._mgr = manager;
        this._life = manager._life;
        this._strips = [];
        this._preview = null;
        this._dragCtx = null;
        this._grab = null;
        this._grabber = null;
        this._watchdog = 0;
    }

    _clearStrips() {
        for (const s of this._strips) {
            try {
                Main.layoutManager.removeChrome(s);
                s.destroy();
            } catch (_e) {}
        }
        this._strips = [];
    }

    _addStrip(rect, vertical, onPress) {
        const strip = new St.Widget({
            reactive: true,
            track_hover: true,
            style_class: vertical
                ? 'gridspaces-divider-v' : 'gridspaces-divider-h',
        });
        strip.set_position(rect.x, rect.y);
        strip.set_size(Math.max(1, rect.w), Math.max(1, rect.h));
        // Only Alt+click starts a resize drag; a plain click on the seam is
        // ignored (the 8px strip sits in the empty gutter between windows, so
        // letting it through changes nothing) — this prevents accidental drags.
        strip.connect('button-press-event',
            this._life.guard('ovl.press', (_a, ev) => {
                if (!(ev.get_state() & Clutter.ModifierType.MOD1_MASK))
                    return Clutter.EVENT_PROPAGATE;
                onPress(ev);
                return Clutter.EVENT_STOP;
            }));
        Main.layoutManager.addChrome(strip, {affectsInputRegion: true});
        this._strips.push(strip);
    }

    rebuild() {
        this._clearStrips();
        if (this._life.dead || this._dragCtx)
            return;

        const grid = this._mgr.gridForActiveIfGrid();
        if (!grid || Main.overview.visible)
            return;

        const a = grid._workArea();
        let topPct = 0;
        for (let r = 0; r < grid.rows.length; r++) {
            const row = grid.rows[r];
            const rowTop = a.y + Math.round((a.height * topPct) / 100);
            const rowBot =
                a.y + Math.round((a.height * (topPct + row.h)) / 100);

            let leftPct = 0;
            for (let c = 0; c < row.cols.length - 1; c++) {
                leftPct += row.cols[c].w;
                const x = a.x + Math.round((a.width * leftPct) / 100);
                const cc = c, rr = r;
                this._addStrip(
                    {x: x - DIVIDER / 2, y: rowTop + DIVIDER / 2,
                     w: DIVIDER, h: rowBot - rowTop - DIVIDER},
                    true,
                    ev => this._beginDrag(ev, {
                        kind: 'v', grid, row: rr, seam: cc,
                        area: a, rowTop, rowBot}));
            }

            if (r < grid.rows.length - 1) {
                const rr = r;
                this._addStrip(
                    {x: a.x, y: rowBot - DIVIDER / 2, w: a.width, h: DIVIDER},
                    false,
                    ev => this._beginDrag(ev, {
                        kind: 'h', grid, seam: rr, area: a}));
            }
            topPct += row.h;
        }
    }

    _beginDrag(ev, ctx) {
        if (this._dragCtx || this._life.dead)
            return;
        try {
            const a = ctx.area;

            // Full-work-area transparent input catcher. We take an explicit
            // Clutter grab on it so motion/release/Esc reach us reliably even
            // when the pointer leaves the thin seam (the old global
            // captured-event approach lost events after ~10px on Wayland).
            this._grabber = new St.Widget({reactive: true});
            this._grabber.set_position(a.x, a.y);
            this._grabber.set_size(a.width, a.height);
            Main.layoutManager.addChrome(this._grabber);

            this._preview = new St.Widget({
                style_class: 'gridspaces-preview',
                reactive: false,
            });
            if (ctx.kind === 'h') {
                const [, py] = ev.get_coords();
                this._preview.set_position(a.x, Math.round(py - DIVIDER / 2));
                this._preview.set_size(a.width, DIVIDER);
            } else {
                const [px] = ev.get_coords();
                this._preview.set_position(
                    Math.round(px - DIVIDER / 2), ctx.rowTop);
                this._preview.set_size(DIVIDER, ctx.rowBot - ctx.rowTop);
            }
            Main.layoutManager.addChrome(this._preview);

            this._dragCtx = ctx;
            this._grabber.connect('motion-event',
                this._life.guard('ovl.motion',
                    (_a, e) => this._onMotion(e)));
            this._grabber.connect('button-release-event',
                this._life.guard('ovl.release', (_a, e) => {
                    this._finishDrag(e);
                    return Clutter.EVENT_STOP;
                }));
            this._grabber.connect('key-press-event',
                this._life.guard('ovl.key', (_a, e) => {
                    if (e.get_key_symbol() === Clutter.KEY_Escape)
                        this._cancelDrag();
                    return Clutter.EVENT_STOP;
                }));

            this._grab = global.stage.grab(this._grabber);

            // Watchdog: never let a drag outlive a sane interaction window.
            this._watchdog = this._life.timeout('ovl.watchdog', 8000, () => {
                this._cancelDrag();
                return GLib.SOURCE_REMOVE;
            });
        } catch (e) {
            logErr('ovl.beginDrag', e);
            this._cancelDrag();
        }
    }

    _clamp(v, lo, hi) {
        return Math.max(lo, Math.min(hi, v));
    }

    _onMotion(e) {
        const ctx = this._dragCtx;
        if (!ctx || !this._preview)
            return Clutter.EVENT_PROPAGATE;
        const [px, py] = e.get_coords();
        const a = ctx.area;
        if (ctx.kind === 'h') {
            const y = this._clamp(py,
                a.y + MIN_CELL, a.y + a.height - MIN_CELL);
            this._preview.set_position(a.x, Math.round(y - DIVIDER / 2));
        } else {
            const row = ctx.grid.rows[ctx.row];
            let leftPx = a.x;
            for (let i = 0; i < ctx.seam; i++)
                leftPx += (a.width * row.cols[i].w) / 100;
            const rightPx = leftPx +
                (a.width * (row.cols[ctx.seam].w +
                    row.cols[ctx.seam + 1].w)) / 100;
            const x = this._clamp(px,
                leftPx + MIN_CELL, rightPx - MIN_CELL);
            this._preview.set_position(
                Math.round(x - DIVIDER / 2), ctx.rowTop);
        }
        return Clutter.EVENT_STOP;
    }

    _finishDrag(e) {
        try {
            this._applyDrag(e);
        } catch (err) {
            logErr('ovl.finishDrag', err);
        } finally {
            this._endDrag();
        }
    }

    _applyDrag(e) {
        const ctx = this._dragCtx;
        if (!ctx)
            return;
        const a = ctx.area;
        const [px, py] = e.get_coords();

        if (ctx.kind === 'h') {
            const g = ctx.grid;
            const A = ctx.seam, B = ctx.seam + 1;
            let topPct = 0;
            for (let i = 0; i < A; i++)
                topPct += g.rows[i].h;
            const sum = g.rows[A].h + g.rows[B].h;
            const minPct = (MIN_CELL / a.height) * 100;
            let hA = ((this._clamp(py, a.y + MIN_CELL,
                a.y + a.height - MIN_CELL) - a.y) / a.height) * 100 - topPct;
            hA = this._clamp(hA, minPct, sum - minPct);
            g.setRowHeights(A, B, hA, sum - hA);
        } else {
            const g = ctx.grid;
            const row = g.rows[ctx.row];
            const A = ctx.seam, B = ctx.seam + 1;
            let leftPct = 0;
            for (let i = 0; i < A; i++)
                leftPct += row.cols[i].w;
            const sum = row.cols[A].w + row.cols[B].w;
            const minPct = (MIN_CELL / a.width) * 100;
            const leftPx = a.x + (a.width * leftPct) / 100;
            const rightPx = leftPx + (a.width * sum) / 100;
            let wA = ((this._clamp(px, leftPx + MIN_CELL,
                rightPx - MIN_CELL) - a.x) / a.width) * 100 - leftPct;
            wA = this._clamp(wA, minPct, sum - minPct);
            g.setColWidths(ctx.row, A, B, wA, sum - wA);
        }
    }

    _cancelDrag() {
        this._endDrag();
    }

    // Idempotent: safe to call multiple times / from teardown.
    _endDrag() {
        if (this._watchdog) {
            try { GLib.source_remove(this._watchdog); } catch (_e) {}
            this._watchdog = 0;
        }
        if (this._grab) {
            try { this._grab.dismiss(); } catch (_e) {}
            this._grab = null;
        }
        if (this._grabber) {
            try {
                Main.layoutManager.removeChrome(this._grabber);
                this._grabber.destroy();
            } catch (_e) {}
            this._grabber = null;
        }
        if (this._preview) {
            try {
                Main.layoutManager.removeChrome(this._preview);
                this._preview.destroy();
            } catch (_e) {}
            this._preview = null;
        }
        const wasDragging = this._dragCtx !== null;
        this._dragCtx = null;
        if (wasDragging && !this._life.dead)
            this.rebuild();
    }

    destroy() {
        this._endDrag();
        this._clearStrips();
    }
}

// ---- Manager ---------------------------------------------------------------
class GridManager {
    constructor(life) {
        this._life = life;
        this._grids = new Map();
        this._relocating = new Set();
        this._taGuard = new TilingAssistantGuard();
        this._overlay = new DividerOverlay(this);
        this._onChange = null;
        this._prevWorkspace = new Map();   // win -> last ws index
        this._winSignals = new Map();      // win -> [ids]

        const wm = global.workspace_manager;
        this._life.connect(wm, 'workspace-removed', 'wm.removed',
            () => this._reconcile());
        this._life.connect(wm, 'active-workspace-changed', 'wm.active',
            () => this._notify());

        this._life.connect(global.display, 'grab-op-end', 'disp.grabEnd',
            (_d, win) => this._onGrabEnd(win));
        this._life.connect(global.display, 'window-created', 'disp.winNew',
            (_d, win) => this._trackWindow(win));

        this._life.connect(Main.overview, 'showing', 'ovr.show',
            () => this.refreshOverlay());
        this._life.connect(Main.overview, 'hidden', 'ovr.hide',
            () => this.refreshOverlay());
        this._life.connect(Main.layoutManager, 'monitors-changed', 'mon.chg',
            () => this.refreshOverlay());

        // Seed already-existing windows so bounce() knows their origin.
        for (const a of global.get_window_actors()) {
            const w = a.meta_window;
            if (w)
                this._trackWindow(w);
        }
    }

    _trackWindow(win) {
        if (!win || this._winSignals.has(win))
            return;
        const ws = win.get_workspace();
        if (ws)
            this._prevWorkspace.set(win, ws.index());

        const wcId = win.connect('workspace-changed',
            this._life.guard('win.wsChg', () => {
                const cur = win.get_workspace();
                win._gridPrevWs = this._prevWorkspace.get(win);
                if (cur)
                    this._prevWorkspace.set(win, cur.index());
            }));
        const unId = win.connect('unmanaged',
            this._life.guard('win.unmanaged', () => this._untrackWindow(win)));
        this._winSignals.set(win, [wcId, unId]);
    }

    _untrackWindow(win) {
        const ids = this._winSignals.get(win);
        if (ids) {
            for (const id of ids) {
                try { win.disconnect(id); } catch (_e) {}
            }
            this._winSignals.delete(win);
        }
        this._prevWorkspace.delete(win);
    }

    isRelocating(win) {
        return this._relocating.has(win);
    }

    activeWorkspace() {
        return global.workspace_manager.get_active_workspace();
    }

    gridFor(ws) {
        return this._grids.get(ws) ?? null;
    }

    isGrid(ws) {
        return this._grids.has(ws);
    }

    gridForActiveIfGrid() {
        return this._grids.get(this.activeWorkspace()) ?? null;
    }

    refreshOverlay() {
        if (!this._life.dead)
            this._overlay.rebuild();
    }

    _notify() {
        this._taGuard.sync(this.isGrid(this.activeWorkspace()));
        this.refreshOverlay();
        if (this._onChange) {
            try { this._onChange(); } catch (e) { logErr('onChange', e); }
        }
    }

    makeGrid(ws) {
        if (!this._grids.has(ws))
            this._grids.set(ws, new WorkspaceGrid(this, ws));
        this._notify();
    }

    unmakeGrid(ws) {
        const g = this._grids.get(ws);
        if (!g)
            return;
        g.destroy();
        this._grids.delete(ws);
        this._notify();
    }

    _onGrabEnd(win) {
        if (!win)
            return;
        const ws = win.get_workspace();
        const g = ws ? this._grids.get(ws) : null;
        if (g)
            g.handleDragEnd(win);
    }

    _nearestNormal(fromWs) {
        const wm = global.workspace_manager;
        const n = wm.get_n_workspaces();
        const base = fromWs ? fromWs.index() : 0;
        for (let d = 1; d <= n; d++) {
            for (const idx of [base + d, base - d]) {
                if (idx < 0 || idx >= n)
                    continue;
                const ws = wm.get_workspace_by_index(idx);
                if (ws && !this._grids.has(ws))
                    return ws;
            }
        }
        wm.append_new_workspace(false, global.get_current_time());
        return wm.get_workspace_by_index(wm.get_n_workspaces() - 1);
    }

    _move(win, ws) {
        if (!ws)
            return;
        this._relocating.add(win);
        win.change_workspace(ws);
        this._life.timeout('mgr.move', 0, () => {
            this._relocating.delete(win);
            return GLib.SOURCE_REMOVE;
        });
    }

    bounce(win, fullWs) {
        const back = win._gridPrevWs;
        if (back != null) {
            const ws = global.workspace_manager.get_workspace_by_index(back);
            if (ws && ws !== fullWs && !this._grids.has(ws)) {
                this._move(win, ws);
                return;
            }
        }
        this._move(win, this._nearestNormal(fullWs));
    }

    popToNormal(win, fromWs) {
        this._move(win, this._nearestNormal(fromWs));
    }

    _reconcile() {
        const wm = global.workspace_manager;
        const live = new Set();
        for (let i = 0; i < wm.get_n_workspaces(); i++)
            live.add(wm.get_workspace_by_index(i));
        for (const [ws, g] of [...this._grids]) {
            if (!live.has(ws)) {
                g.destroy();
                this._grids.delete(ws);
            }
        }
        this._notify();
    }

    destroy() {
        this._onChange = null;
        for (const [, g] of this._grids) {
            try { g.destroy(); } catch (_e) {}
        }
        this._grids.clear();
        for (const win of [...this._winSignals.keys()])
            this._untrackWindow(win);
        try { this._overlay.destroy(); } catch (_e) {}
        this._relocating.clear();
        this._taGuard.restore();
    }
}

// ---- Panel button: structure editor ---------------------------------------
const GridIndicator = GObject.registerClass(
class GridIndicator extends PanelMenu.Button {
    _init(manager) {
        super._init(0.0, 'GridSpaces');
        this._mgr = manager;
        this.add_child(new St.Icon({
            icon_name: 'view-grid-symbolic',
            style_class: 'system-status-icon',
        }));
        // Keep the menu eagerly current. Rebuilding during the open
        // transition makes GNOME 48 collapse the popup, so we never do that —
        // we rebuild on state changes (toggle, workspace switch, in-menu
        // edits) while the menu is closed or already fully open, both safe.
        manager._onChange = () => {
            try {
                this._rebuildMenu();
            } catch (e) {
                logErr('menu.rebuild', e);
            }
        };
        this._rebuildMenu();
    }

    _rebuildMenu() {
        this.menu.removeAll();
        const ws = this._mgr.activeWorkspace();
        const on = this._mgr.isGrid(ws);

        const toggle = new PopupMenu.PopupSwitchMenuItem(
            'Grid workspace', on);
        toggle.connect('toggled', (_i, state) => {
            try {
                if (state)
                    this._mgr.makeGrid(ws);
                else
                    this._mgr.unmakeGrid(ws);
            } catch (e) {
                logErr('menu.toggle', e);
            }
        });
        this.menu.addMenuItem(toggle);
        if (!on)
            return;

        this.menu.addMenuItem(new PopupMenu.PopupSeparatorMenuItem());
        const grid = this._mgr.gridFor(ws);
        grid.rows.forEach((row, r) => {
            const item = new PopupMenu.PopupBaseMenuItem({reactive: false});
            item.add_child(new St.Label({
                text: `Row ${r + 1}`,
                x_expand: true,
                y_align: Clutter.ActorAlign.CENTER,
            }));
            const minus = this._btn('−', () => {
                this._mgr.gridFor(ws)?.setRowColumns(r, row.cols.length - 1);
                this._rebuildMenu();
            });
            const val = new St.Label({
                text: String(row.cols.length),
                y_align: Clutter.ActorAlign.CENTER,
                style: 'min-width: 22px; text-align: center;',
            });
            const plus = this._btn('+', () => {
                this._mgr.gridFor(ws)?.setRowColumns(r, row.cols.length + 1);
                this._rebuildMenu();
            });
            const del = this._btn('✕', () => {
                this._mgr.gridFor(ws)?.removeRow(r);
                this._rebuildMenu();
            });
            del.set_style('margin-left: 10px;');
            item.add_child(minus);
            item.add_child(val);
            item.add_child(plus);
            item.add_child(del);
            this.menu.addMenuItem(item);
        });

        this.menu.addMenuItem(new PopupMenu.PopupSeparatorMenuItem());
        const add = new PopupMenu.PopupMenuItem('＋ Add row');
        add.connect('activate', () => {
            try {
                this._mgr.gridFor(ws)?.addRow();
                this._rebuildMenu();
            } catch (e) {
                logErr('menu.addRow', e);
            }
        });
        this.menu.addMenuItem(add);
    }

    _btn(label, onClick) {
        const b = new St.Button({
            label,
            style_class: 'button',
            x_align: Clutter.ActorAlign.CENTER,
            style: 'min-width: 28px; margin: 0 2px;',
        });
        b.connect('clicked', () => {
            try { onClick(); } catch (e) { logErr('menu.btn', e); }
        });
        return b;
    }
});

export default class GridSpacesExtension extends Extension {
    enable() {
        this._life = new Lifetime();
        try {
            this._mgr = new GridManager(this._life);
            this._indicator = new GridIndicator(this._mgr);
            Main.panel.addToStatusArea('gridspaces', this._indicator);
        } catch (e) {
            // Never leave half-initialised callbacks wired into the shell.
            logErr('enable', e);
            this.disable();
            throw e;
        }
    }

    disable() {
        try { this._indicator?.destroy(); } catch (_e) {}
        this._indicator = null;
        try { this._mgr?.destroy(); } catch (_e) {}
        this._mgr = null;
        try { this._life?.destroy(); } catch (_e) {}
        this._life = null;
    }
}