function petriNetGuiDemo
%PETRINETGUIDEMO Simple GUI tutorial for a Petri net.
%   Run:
%       petriNetGuiDemo

places = ["Ready", "InService", "Done"];
transitions = ["Start", "Finish"];

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

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

initialMarking = [3; 0; 0];
marking = initialMarking;
stepCount = 0;
maxSteps = 20;

placePos = [1 0;
            5 0;
            9 0];

transPos = [3 0;
            7 0];

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

fig = figure( ...
    'Name', 'Petri Net Tutorial', ...
    'Color', 'w', ...
    'MenuBar', 'none', ...
    'ToolBar', 'none', ...
    'NumberTitle', 'off', ...
    'Position', [100 100 1120 640]);

ax = axes('Parent', fig, 'Position', [0.04 0.18 0.92 0.78]);
hold(ax, 'on');
axis(ax, [-0.5 10.5 -2.4 2.4]);
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 0.10 0.05], 'String', 'Step', ...
    'FontSize', 10, 'Callback', @onStep);

btnStart = uicontrol(fig, 'Style', 'pushbutton', 'Units', 'normalized', ...
    'Position', [0.16 0.11 0.10 0.05], 'String', 'Fire Start', ...
    'FontSize', 10, 'Callback', @(~,~) fireTransition(1, true));

btnFinish = uicontrol(fig, 'Style', 'pushbutton', 'Units', 'normalized', ...
    'Position', [0.28 0.11 0.10 0.05], 'String', 'Fire Finish', ...
    'FontSize', 10, 'Callback', @(~,~) fireTransition(2, true));

btnRun = uicontrol(fig, 'Style', 'pushbutton', 'Units', 'normalized', ...
    'Position', [0.40 0.11 0.10 0.05], 'String', 'Run', ...
    'FontSize', 10, 'Callback', @onRun);

btnReset = uicontrol(fig, 'Style', 'pushbutton', 'Units', 'normalized', ...
    'Position', [0.52 0.11 0.10 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', 1.5);
        line(ax, [transPos(1,1) + transW/2, placePos(2,1) - placeR], [0 0], ...
            'Color', [0 0 0], 'LineWidth', 1.5);
        line(ax, [placePos(2,1) + placeR, transPos(2,1) - transW/2], [0 0], ...
            'Color', [0 0 0], 'LineWidth', 1.5);
        line(ax, [transPos(2,1) + transW/2, placePos(3,1) - placeR], [0 0], ...
            'Color', [0 0 0], 'LineWidth', 1.5);

        % 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), -1.20, places(i), ...
                'HorizontalAlignment', 'center', ...
                'FontSize', 11, ...
                'FontWeight', 'bold');

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

        text(ax, 5, 1.95, 'Simple 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(btnStart,  'Enable', onOff(enabled(1)));
        set(btnFinish, 'Enable', onOff(enabled(2)));

        msg = sprintf('Step: %d/%d    Marking: Ready=%d, InService=%d, Done=%d    Enabled: %s', ...
            stepCount, maxSteps, marking(1), marking(2), marking(3), enabledText);
        set(statusText, 'String', msg);

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

    function onStep(~, ~)
        enabled = all(marking >= pre, 1);

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

        if enabled(2)
            chosen = 2;
        else
            chosen = 1;
        end

        fireTransition(chosen, true);
    end

    function onRun(~, ~)
        while stepCount < maxSteps && isvalid(fig)
            enabled = all(marking >= pre, 1);

            if ~any(enabled)
                break
            end

            if enabled(2)
                chosen = 2;
            else
                chosen = 1;
            end

            fireTransition(chosen, true);
            pause(0.5);
        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 && ~isempty(inPlaces) && ~isempty(outPlaces)
            src = inPlaces(1);
            dst = outPlaces(1);

            token = plot(ax, placePos(src,1), placePos(src,2), 'ro', ...
                'MarkerFaceColor', [0.90 0.20 0.20], ...
                'MarkerSize', 10, ...
                'Tag', 'token');

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

            nFrames = 24;
            for s = 1:nFrames
                alpha = s / nFrames;
                x = (1 - alpha) * placePos(src,1) + alpha * placePos(dst,1);
                y = (1 - alpha) * placePos(src,2) + alpha * placePos(dst,2);
                set(token, 'XData', x, 'YData', y);
                drawnow
                pause(0.02);
            end

            delete(token);
        end

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

        renderTokens();
        updateUI();
    end

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