function petriNetBatchPackagingDemo
% PETRINETBATCHPACKAGINGDEMO  GUI demo for a weighted-arc Petri net.
% P1 accumulates parts. T1 fires only when M(P1) >= 4 and 
% produces 1 box.

fig = figure( ...
    'Name', 'Factory Batch Packaging Petri Net', ...
    'Color', 'w', ...
    'NumberTitle', 'off', ...
    'MenuBar', 'none', ...
    'ToolBar', 'none', ...
    'Resize', 'off', ...
    'Position', [100 100 1080 620]);

ax = axes( ...
    'Parent', fig, ...
    'Position', [0.04 0.24 0.92 0.67]);
hold(ax, 'on');
axis(ax, [0 10 0 6]);
axis(ax, 'equal');
axis(ax, 'off');

% -------------------------------------------------------------------------
% State
% -------------------------------------------------------------------------
state.partCount = 0;
state.boxCount = 0;
state.message = 'Add parts to the Produced Parts Buffer. T1 needs 4 tokens to fire.';

% -------------------------------------------------------------------------
% Layout
% -------------------------------------------------------------------------
bufferPos = [0.8 1.55 2.3 2.3];
t1Pos = [4.4 2.35 1.0 1.3];
boxPos = [7.0 1.55 2.3 2.3];

bufferCenter = [bufferPos(1) + bufferPos(3)/2, bufferPos(2) + bufferPos(4)/2];
t1Center = [t1Pos(1) + t1Pos(3)/2, t1Pos(2) + t1Pos(4)/2];
boxCenter = [boxPos(1) + boxPos(3)/2, boxPos(2) + boxPos(4)/2];

% Header text
text(ax, 5.0, 5.78, ...
    'Weighted arc example: T1 needs 4 parts before it can fire', ...
    'HorizontalAlignment', 'center', 'FontSize', 12, 'FontWeight', 'bold', ...
    'Interpreter', 'none');
text(ax, 5.0, 5.48, ...
    'P1 = Produced Parts Buffer   |   T1 = Pack Box   |   P2 = Packed Boxes', ...
    'HorizontalAlignment', 'center', 'FontSize', 10, 'Interpreter', 'none');

% Arcs
h.arcIn = drawArrow([3.15 3.0], [4.4 3.0]);
h.arcOut = drawArrow([5.4 3.0], [7.0 3.0]);

% Places and transition
h.p1 = rectangle(ax, 'Position', bufferPos, 'Curvature', [1 1], ...
    'FaceColor', [1.0 0.98 0.88], 'EdgeColor', [0.25 0.25 0.25], 'LineWidth', 2);

h.t1 = rectangle(ax, 'Position', t1Pos, ...
    'FaceColor', [0.25 0.25 0.25], 'EdgeColor', [0.15 0.15 0.15], 'LineWidth', 1.5);

h.p2 = rectangle(ax, 'Position', boxPos, 'Curvature', [1 1], ...
    'FaceColor', [0.92 0.96 1.0], 'EdgeColor', [0.25 0.25 0.25], 'LineWidth', 2);

% Weight label
text(ax, 3.85, 3.28, '4', 'Color', [0.85 0.2 0.2], 'FontSize', 13, ...
    'FontWeight', 'bold', 'HorizontalAlignment', 'center');
text(ax, 6.25, 3.28, '1', 'Color', [0.2 0.2 0.7], 'FontSize', 13, ...
    'FontWeight', 'bold', 'HorizontalAlignment', 'center');

% Labels
text(ax, bufferCenter(1), bufferCenter(2) + 1.45, 'P1: Produced Parts Buffer', ...
    'HorizontalAlignment', 'center', 'FontSize', 11, 'Interpreter', 'none');
text(ax, t1Center(1), t1Center(2) + 1.55, 'T1: Pack Box', ...
    'HorizontalAlignment', 'center', 'FontSize', 11, 'Interpreter', 'none');
text(ax, boxCenter(1), boxCenter(2) + 1.45, 'P2: Packed Boxes', ...
    'HorizontalAlignment', 'center', 'FontSize', 11, 'Interpreter', 'none');

text(ax, 5.0, 2.05, 'T1 is enabled only when M(P1) >= 4', ...
    'HorizontalAlignment', 'center', 'FontSize', 10, 'Color', [0.35 0.35 0.35]);

% Count displays
h.p1Count = text(ax, bufferCenter(1), 1.08, 'M(P1) = 0', ...
    'HorizontalAlignment', 'center', 'FontSize', 11, 'FontWeight', 'bold');
h.p2Count = text(ax, boxCenter(1), 1.08, 'M(P2) = 0', ...
    'HorizontalAlignment', 'center', 'FontSize', 11, 'FontWeight', 'bold');

% Token holders
h.partTokens = gobjects(0);
h.boxTokens = gobjects(0);

% Buttons
uicontrol(fig, 'Style', 'pushbutton', 'String', 'Produce Part', ...
    'Position', [75 70 120 34], 'Callback', @(~, ~) producePart());
uicontrol(fig, 'Style', 'pushbutton', 'String', 'Pack Box', ...
    'Position', [210 70 120 34], 'Callback', @(~, ~) packBox());
uicontrol(fig, 'Style', 'pushbutton', 'String', 'Reset', ...
    'Position', [345 70 100 34], 'Callback', @(~, ~) resetDemo());

status = uicontrol(fig, 'Style', 'text', ...
    'Position', [35 18 1000 30], ...
    'BackgroundColor', 'w', ...
    'HorizontalAlignment', 'left', ...
    'FontSize', 11);

updateView();

    function producePart()
        state.partCount = state.partCount + 1;
        state.message = sprintf('One part entered P1. Now M(P1) = %d.', state.partCount);
        updateView();
    end

    function packBox()
        if state.partCount < 4
            state.message = sprintf('T1 is DISABLED: M(P1) = %d, but the arc weight is 4.', state.partCount);
            updateView();
            return;
        end

        state.message = 'T1 fires: it consumes 4 parts and produces 1 box.';
        updateView();

        pause(0.25);

        state.partCount = state.partCount - 4;
        state.boxCount = state.boxCount + 1;
        state.message = sprintf('Box packed. M(P1) = %d, M(P2) = %d.', state.partCount, state.boxCount);
        updateView();
    end

    function resetDemo()
        state.partCount = 0;
        state.boxCount = 0;
        state.message = 'Reset complete. Add parts to P1. T1 needs 4 tokens to fire.';
        updateView();
    end

    function updateView()
        enabled = state.partCount >= 4;

        if enabled
            set(h.t1, 'FaceColor', [1.0 0.85 0.25]);
            setArrowStyle(h.arcIn, [1.0 0.55 0.0], 3.0);
            setArrowStyle(h.arcOut, [1.0 0.55 0.0], 3.0);
        else
            set(h.t1, 'FaceColor', [0.30 0.30 0.30]);
            setArrowStyle(h.arcIn, [0.65 0.65 0.65], 1.3);
            setArrowStyle(h.arcOut, [0.65 0.65 0.65], 1.3);
        end

        set(h.p1Count, 'String', sprintf('M(P1) = %d', state.partCount));
        set(h.p2Count, 'String', sprintf('M(P2) = %d', state.boxCount));
        set(status, 'String', state.message);

        deleteValidHandles(h.partTokens);
        deleteValidHandles(h.boxTokens);

        h.partTokens = drawPartTokens(state.partCount, bufferCenter);
        h.boxTokens = drawBoxTokens(state.boxCount, boxCenter);

        drawnow;
    end

    function handles = drawPartTokens(n, center)
        handles = gobjects(0);
        if n <= 0
            return;
        end

        cols = min(4, max(1, ceil(sqrt(n))));
        rows = ceil(n / cols);
        dx = 0.33;
        dy = 0.33;
        startX = center(1) - (cols - 1) * dx / 2;
        startY = center(2) + (rows - 1) * dy / 2;
        r = 0.085;

        for k = 1:n
            c = mod(k - 1, cols);
            rIdx = floor((k - 1) / cols);
            x = startX + c * dx;
            y = startY - rIdx * dy;

            handles(end + 1) = rectangle(ax, ... %#ok<AGROW>
                'Position', [x - r, y - r, 2 * r, 2 * r], ...
                'Curvature', [1 1], ...
                'FaceColor', [1.0 0.75 0.15], ...
                'EdgeColor', [0.8 0.5 0.0], ...
                'LineWidth', 0.8);
        end
    end

    function handles = drawBoxTokens(n, center)
        handles = gobjects(0);
        if n <= 0
            return;
        end

        cols = min(3, max(1, ceil(sqrt(n))));
        rows = ceil(n / cols);
        dx = 0.42;
        dy = 0.42;
        startX = center(1) - (cols - 1) * dx / 2;
        startY = center(2) + (rows - 1) * dy / 2;
        s = 0.18;

        for k = 1:n
            c = mod(k - 1, cols);
            rIdx = floor((k - 1) / cols);
            x = startX + c * dx;
            y = startY - rIdx * dy;

            handles(end + 1) = rectangle(ax, ... %#ok<AGROW>
                'Position', [x - s, y - s, 2 * s, 2 * s], ...
                'FaceColor', [0.35 0.65 1.0], ...
                'EdgeColor', [0.15 0.35 0.7], ...
                'LineWidth', 1.0);
        end
    end

    function deleteValidHandles(handles)
        if isempty(handles)
            return;
        end
        handles = handles(isgraphics(handles));
        if ~isempty(handles)
            delete(handles);
        end
    end

    function setArrowStyle(hArrow, color, width)
        set(hArrow.line, 'Color', color, 'LineWidth', width);
        set(hArrow.head, 'FaceColor', color, 'EdgeColor', color);
    end

    function hArrow = drawArrow(p1, p2)
        hArrow.line = plot(ax, [p1(1) p2(1)], [p1(2) p2(2)], 'k-', 'LineWidth', 1.5);

        v = p2 - p1;
        u = v / norm(v);
        n = [-u(2) u(1)];

        tip = p2;
        base = p2 - 0.18 * u;
        left = base + 0.08 * n;
        right = base - 0.08 * n;

        hArrow.head = patch(ax, [tip(1) left(1) right(1)], ...
            [tip(2) left(2) right(2)], 'k', 'EdgeColor', 'k');
    end
end