function petriNetGuiDemo2
%PETRINETGUIDEMO Parallel-task Petri net tutorial GUI.
%   One job splits into two parallel tasks (A and B) and then joins again.
%   Run:
%       petriNetGuiDemo2

places = ["Ready", "TaskA", "TaskB", "ADone", "BDone", "Done"];
transitions = ["Split", "FinishA", "FinishB", "Join"];

% pre(:,j) = tokens consumed by transition j
pre = [1 0 0 0;
       0 1 0 0;
       0 0 1 0;
       0 0 0 1;
       0 0 0 1;
       0 0 0 0];

% post(:,j) = tokens produced by transition j
post = [0 0 0 0;
        1 0 0 0;
        1 0 0 0;
        0 1 0 0;
        0 0 1 0;
        0 0 0 1];

initialMarking = [1; 0; 0; 0; 0; 0];
marking = initialMarking;
stepCount = 0;
maxSteps = 30;

placePos = [1.2  0.0;
            5.2  1.4;
            5.2 -1.4;
            9.2  1.4;
            9.2 -1.4;
            13.2 0.0];

transPos = [3.2  0.0;
            7.2  1.4;
            7.2 -1.4;
            11.2 0.0];

placeR = 0.75;
transW = 0.55;
transH = 1.45;

fig = figure( ...
    'Name', 'Parallel Petri Net Tutorial', ...
    'Color', 'w', ...
    'MenuBar', 'none', ...
    'ToolBar', 'none', ...
    'NumberTitle', 'off', ...
    'Position', [100 100 1240 700]);

ax = axes('Parent', fig, 'Position', [0.04 0.20 0.92 0.74]);
hold(ax, 'on');
axis(ax, [-0.5 14.2 -2.8 2.8]);
axis(ax, 'equal');
axis(ax, 'off');

statusText = uicontrol( ...
    'Style', 'text', ...
    'Parent', fig, ...
    'Units', 'normalized', ...
    'Position', [0.04 0.04 0.92 0.08], ...
    'BackgroundColor', 'w', ...
    'HorizontalAlignment', 'left', ...
    'FontSize', 11, ...
    'String', '');

btnStep = uicontrol(fig, 'Style', 'pushbutton', 'Units', 'normalized', ...
    'Position', [0.04 0.11 0.08 0.05], 'String', 'Step', ...
    'FontSize', 10, 'Callback', @onStep);

btnSplit = uicontrol(fig, 'Style', 'pushbutton', 'Units', 'normalized', ...
    'Position', [0.14 0.11 0.10 0.05], 'String', 'Split', ...
    'FontSize', 10, 'Callback', @(~,~) fireTransition(1, true));

btnFinishA = uicontrol(fig, 'Style', 'pushbutton', 'Units', 'normalized', ...
    'Position', [0.26 0.11 0.10 0.05], 'String', 'Finish A', ...
    'FontSize', 10, 'Callback', @(~,~) fireTransition(2, true));

btnFinishB = uicontrol(fig, 'Style', 'pushbutton', 'Units', 'normalized', ...
    'Position', [0.38 0.11 0.10 0.05], 'String', 'Finish B', ...
    'FontSize', 10, 'Callback', @(~,~) fireTransition(3, true));

btnJoin = uicontrol(fig, 'Style', 'pushbutton', 'Units', 'normalized', ...
    'Position', [0.50 0.11 0.10 0.05], 'String', 'Join', ...
    'FontSize', 10, 'Callback', @(~,~) fireTransition(4, true));

btnRun = uicontrol(fig, 'Style', 'pushbutton', 'Units', 'normalized', ...
    'Position', [0.62 0.11 0.08 0.05], 'String', 'Run', ...
    'FontSize', 10, 'Callback', @onRun);

btnReset = uicontrol(fig, 'Style', 'pushbutton', 'Units', 'normalized', ...
    'Position', [0.72 0.11 0.08 0.05], 'String', 'Reset', ...
    'FontSize', 10, 'Callback', @onReset);

transitionPatch = gobjects(numel(transitions), 1);
countText = gobjects(numel(places), 1);

drawStaticNet();
renderTokens();
updateUI();

    function drawStaticNet
        % Arcs
        line(ax, [placePos(1,1) + placeR, transPos(1,1) - transW/2], ...
            [0, 0], 'Color', [0 0 0], 'LineWidth', 1.4);

        line(ax, [transPos(1,1) + transW/2, placePos(2,1) - placeR], ...
            [0, placePos(2,2)], 'Color', [0 0 0], 'LineWidth', 1.4);

        line(ax, [transPos(1,1) + transW/2, placePos(3,1) - placeR], ...
            [0, placePos(3,2)], 'Color', [0 0 0], 'LineWidth', 1.4);

        line(ax, [placePos(2,1) + placeR, transPos(2,1) - transW/2], ...
            [placePos(2,2), transPos(2,2)], 'Color', [0 0 0], 'LineWidth', 1.4);

        line(ax, [transPos(2,1) + transW/2, placePos(4,1) - placeR], ...
            [transPos(2,2), placePos(4,2)], 'Color', [0 0 0], 'LineWidth', 1.4);

        line(ax, [placePos(3,1) + placeR, transPos(3,1) - transW/2], ...
            [placePos(3,2), transPos(3,2)], 'Color', [0 0 0], 'LineWidth', 1.4);

        line(ax, [transPos(3,1) + transW/2, placePos(5,1) - placeR], ...
            [transPos(3,2), placePos(5,2)], 'Color', [0 0 0], 'LineWidth', 1.4);

        line(ax, [placePos(4,1) + placeR, transPos(4,1) - transW/2], ...
            [placePos(4,2), transPos(4,2)], 'Color', [0 0 0], 'LineWidth', 1.4);

        line(ax, [placePos(5,1) + placeR, transPos(4,1) - transW/2], ...
            [placePos(5,2), transPos(4,2)], 'Color', [0 0 0], 'LineWidth', 1.4);

        line(ax, [transPos(4,1) + transW/2, placePos(6,1) - placeR], ...
            [transPos(4,2), placePos(6,2)], 'Color', [0 0 0], 'LineWidth', 1.4);

        % Places
        for i = 1:numel(places)
            rectangle(ax, ...
                'Position', [placePos(i,1) - placeR, placePos(i,2) - placeR, 2*placeR, 2*placeR], ...
                'Curvature', [1 1], ...
                'EdgeColor', 'k', ...
                'LineWidth', 2, ...
                'FaceColor', 'w');

            text(ax, placePos(i,1), placePos(i,2) - 1.20, places(i), ...
                'HorizontalAlignment', 'center', ...
                'FontSize', 11, ...
                'FontWeight', 'bold');

            countText(i) = text(ax, placePos(i,1), placePos(i,2) + 1.20, '', ...
                'HorizontalAlignment', 'center', ...
                'FontSize', 10, ...
                'FontWeight', 'bold');
        end

        % Transitions
        for i = 1:numel(transitions)
            transitionPatch(i) = rectangle(ax, ...
                'Position', [transPos(i,1) - transW/2, transPos(i,2) - transH/2, transW, transH], ...
                'EdgeColor', 'k', ...
                'LineWidth', 2, ...
                'FaceColor', [0.85 0.85 0.85]);

            text(ax, transPos(i,1), transPos(i,2) - 1.20, transitions(i), ...
                'HorizontalAlignment', 'center', ...
                'FontSize', 11, ...
                'FontWeight', 'bold');
        end

        text(ax, 7.0, 2.35, 'Parallel Petri Net Tutorial', ...
            'HorizontalAlignment', 'center', ...
            'FontSize', 14, ...
            'FontWeight', 'bold');
    end

    function renderTokens
        delete(findobj(ax, 'Tag', 'token'));

        for p = 1:numel(places)
            pts = tokenLayout(placePos(p,:), marking(p));
            for k = 1:size(pts, 1)
                plot(ax, pts(k,1), pts(k,2), 'ko', ...
                    'MarkerFaceColor', 'k', ...
                    'MarkerSize', 8, ...
                    'Tag', 'token');
            end
        end
    end

    function pts = tokenLayout(center, count)
        if count <= 0
            pts = zeros(0, 2);
        elseif count == 1
            pts = center;
        else
            r = 0.23;
            ang = linspace(0, 2*pi, count + 1);
            ang(end) = [];
            pts = center + [r*cos(ang(:)), r*sin(ang(:))];
        end
    end

    function updateUI
        enabled = all(marking >= pre, 1);
        enabledNames = transitions(enabled);

        if isempty(enabledNames)
            enabledText = "none";
        else
            enabledText = strjoin(enabledNames, ", ");
        end

        for i = 1:numel(places)
            set(countText(i), 'String', sprintf('Tokens: %d', marking(i)));
        end

        set(btnSplit,   'Enable', onOff(enabled(1)));
        set(btnFinishA, 'Enable', onOff(enabled(2)));
        set(btnFinishB, 'Enable', onOff(enabled(3)));
        set(btnJoin,    'Enable', onOff(enabled(4)));

        msg = sprintf([ ...
            'Step: %d/%d    ', ...
            'Ready=%d  TaskA=%d  TaskB=%d  ADone=%d  BDone=%d  Done=%d    ', ...
            'Enabled: %s'], ...
            stepCount, maxSteps, ...
            marking(1), marking(2), marking(3), marking(4), marking(5), marking(6), ...
            enabledText);

        set(statusText, 'String', msg);

        for i = 1:numel(transitions)
            if enabled(i)
                set(transitionPatch(i), 'FaceColor', [0.75 0.93 0.75]);
            else
                set(transitionPatch(i), 'FaceColor', [0.85 0.85 0.85]);
            end
        end
    end

    function idx = pickTransition
        enabled = all(marking >= pre, 1);
        idx = find(enabled, 1, 'first');
        if isempty(idx)
            idx = 0;
        end
    end

    function onStep(~, ~)
        idx = pickTransition();
        if idx == 0
            updateUI();
            return
        end
        fireTransition(idx, true);
    end

    function onRun(~, ~)
        while stepCount < maxSteps && isvalid(fig)
            idx = pickTransition();
            if idx == 0
                break
            end
            fireTransition(idx, true);
            pause(0.45);
        end
    end

    function onReset(~, ~)
        marking = initialMarking;
        stepCount = 0;
        renderTokens();
        updateUI();
    end

    function fireTransition(tIdx, animateFlag)
        enabled = all(marking >= pre, 1);

        if ~enabled(tIdx)
            updateUI();
            return
        end

        inPlaces = find(pre(:, tIdx) > 0);
        outPlaces = find(post(:, tIdx) > 0);

        if animateFlag
            animateTransition(tIdx, inPlaces, outPlaces);
        end

        marking = marking - pre(:, tIdx) + post(:, tIdx);
        stepCount = stepCount + 1;

        renderTokens();
        updateUI();
    end

    function animateTransition(tIdx, inPlaces, outPlaces)
        if isempty(inPlaces) || isempty(outPlaces)
            return
        end

        set(transitionPatch(tIdx), 'FaceColor', [0.98 0.85 0.55]);
        drawnow;

        nAnim = max(numel(inPlaces), numel(outPlaces));
        srcIdx = expandIndices(inPlaces, nAnim);
        dstIdx = expandIndices(outPlaces, nAnim);

        tokenH = gobjects(nAnim, 1);
        for i = 1:nAnim
            tokenH(i) = plot(ax, placePos(srcIdx(i),1), placePos(srcIdx(i),2), 'o', ...
                'MarkerFaceColor', [0.90 0.20 0.20], ...
                'MarkerEdgeColor', 'k', ...
                'MarkerSize', 10, ...
                'Tag', 'token');
        end

        nFrames = 24;
        for s = 1:nFrames
            alpha = s / nFrames;
            for i = 1:nAnim
                x0 = placePos(srcIdx(i),1);
                y0 = placePos(srcIdx(i),2);
                x1 = placePos(dstIdx(i),1);
                y1 = placePos(dstIdx(i),2);

                x = (1 - alpha) * x0 + alpha * x1;
                y = (1 - alpha) * y0 + alpha * y1;

                set(tokenH(i), 'XData', x, 'YData', y);
            end
            drawnow;
            pause(0.02);
        end

        delete(tokenH);
        set(transitionPatch(tIdx), 'FaceColor', [0.75 0.93 0.75]);
    end

    function idx = expandIndices(idx0, n)
        idx0 = idx0(:);

        if isempty(idx0)
            idx = ones(n, 1);
            return
        end

        if numel(idx0) >= n
            idx = idx0(1:n);
            return
        end

        idx = zeros(n, 1);
        idx(1:numel(idx0)) = idx0;
        idx(numel(idx0)+1:end) = idx0(end);
    end

    function s = onOff(tf)
        if tf
            s = 'on';
        else
            s = 'off';
        end
    end
end