function subG = plotSingleFileDependencies(G, targetFile)
% PLOTSINGLEFILEDEPENDENCIES Extracts and plots the dependencies for a single file.
%
% USAGE:
%   G = buildDependencyGraph(); % First, get the master graph
%   plotSingleFileDependencies(G, 'FitList.mat');
%
% =========================================================================
% SCRIPT OUTPUTS & VISUALIZATION OPTIONS
% =========================================================================
% 1. MATLAB Figure: A standard MATLAB figure window will automatically 
%    open displaying the dependency graph.
%
% 2. Static Image (PNG): A high-resolution (300 DPI) PNG file is saved to
%    your current directory (e.g., 'ProjectDependencies.png'). This is 
%    ideal for quick viewing, sharing, or inserting into reports.
%
% 3. Interactive Graph (yEd Graph Editor): For complex networks where you 
%    can drag, auto-layout, and isolate nodes:
%      a) Find the generated text file (e.g., 'Dependency_Graph.tgf').
%      b) Open the free yEd Graph Editor app (macOS/Windows/Linux).
%      c) Go to File -> Open and select the .tgf file.
%      d) To arrange the messy graph, go to the top menu: 
%         Layout -> Hierarchical (or press Cmd+Option+H).
%
% =========================================================================
% =========================================================================
% HOW TO UNTANGLE THE GRAPH IN yEd (First-time Open)
% =========================================================================
% When you first open the .tgf file, the nodes will be in a messy pile. 
% Follow these 3 steps to instantly format the dependency tree:
%
% 1. UNTANGLE: Go to Layout -> Hierarchical (or press Cmd+Option+H).
%    This arranges the scripts and data files in a logical flow.
%
% 2. FIX BOX SIZES: Press Cmd+A to select all, then go to:
%    Tools -> Fit Node to Label... -> Click OK.
%    This resizes the boxes to fit your file names perfectly.
%
% 3. VIEW ALL: Click the 'Fit Content' icon (magnifying glass with square)
%    in the top toolbar to center the graph on your screen.
%
% You can now click and drag any node; the arrows will follow automatically.
% =========================================================================

    % 1. Check if the file actually exists in the graph
    if findnode(G, targetFile) == 0
        error('File "%s" was not found in the dependency graph. Check spelling and paths.', targetFile);
    end

    % 2. Find scripts that create it (incoming edges)
    creators = predecessors(G, targetFile);

    % 3. Find scripts that use it (outgoing edges)
    consumers = successors(G, targetFile);

    % 4. Combine them into a single list of nodes to keep
    neighborhood = unique([targetFile; creators; consumers]);
    
    % 5. Extract the smaller subgraph
    subG = subgraph(G, neighborhood);

    % ---------------------------------------------------------
    % 6. Apply Colors (Highlighting the Target File)
    % ---------------------------------------------------------
    numNodes = numnodes(subG);
    nodeColors = zeros(numNodes, 3);
    
    colorScript = [0 0.4470 0.7410];      % Blue for .m scripts
    colorData   = [0.8500 0.3250 0.0980]; % Orange for .mat data
    colorOther  = [0.4660 0.6740 0.1880]; % Green for anything else
    colorTarget = [0.9290 0.6940 0.1250]; % Gold/Yellow for the TARGET file

    for n = 1:numNodes
        nodeName = subG.Nodes.Name{n};
        if strcmp(nodeName, targetFile)
            nodeColors(n, :) = colorTarget; % Apply Gold to target
        elseif endsWith(nodeName, '.m', 'IgnoreCase', true)
            nodeColors(n, :) = colorScript;
        elseif endsWith(nodeName, '.mat', 'IgnoreCase', true)
            nodeColors(n, :) = colorData;
        else
            nodeColors(n, :) = colorOther;
        end
    end
    
    % ---------------------------------------------------------
    % 7. Plot the Subgraph
    % ---------------------------------------------------------
    fig = figure('Name', ['Dependencies for ' targetFile], 'Color', 'w');
    p = plot(subG, 'Layout', 'layered', ...
        'NodeLabel', subG.Nodes.Name, ...
        'Interpreter', 'none', ...
        'NodeColor', nodeColors, ...
        'MarkerSize', 8, ... 
        'EdgeColor', [0.7 0.7 0.7], ...
        'LineWidth', 1.5, ...
        'ArrowSize', 12);
    
    % Make the target file visually stand out by making its marker larger
    highlight(p, targetFile, 'MarkerSize', 14);

    p.NodeFontSize = 10;
    p.NodeFontWeight = 'bold';
    title(['Data Flow for: ' targetFile], 'Interpreter', 'none');
    
    % ---------------------------------------------------------
    % 8. Export Data
    % ---------------------------------------------------------
    safeName = strrep(targetFile, '/', '_');
    safeName = strrep(safeName, '\', '_');
    % Use the new consistent prefix
    outputFile = sprintf('Dependency_Node_%s.png', safeName);
    

   % --- Export text for yEd Graph Editor (TGF Format) ---
    if numedges(subG) > 0
        % Extract the exact edges from the subgraph
        subSources = subG.Edges.EndNodes(:,1);
        subTargets = subG.Edges.EndNodes(:,2);
        
        % 1. Create a unique list of all nodes in this subgraph
        allNodes = unique([subSources; subTargets; targetFile]);
        
        safeName = strrep(targetFile, '/', '_');
        safeName = strrep(safeName, '\', '_');
       tgfFile = sprintf('Dependency_Node_%s.tgf', safeName);
        fid = fopen(tgfFile, 'w');
        
        % 2. Write the Node List (Format: ID Label)
        for i = 1:length(allNodes)
            fprintf(fid, '%d %s\n', i, allNodes{i});
        end
        
        % 3. Write the Separator
        fprintf(fid, '#\n');
        
        % 4. Write the Edge List (Format: SourceID TargetID)
        for i = 1:length(subSources)
            srcIdx = find(strcmp(allNodes, subSources{i}));
            tgtIdx = find(strcmp(allNodes, subTargets{i}));
            fprintf(fid, '%d %d\n', srcIdx, tgtIdx);
        end
        
        fclose(fid);
        fprintf('Generated %s for yEd Graph Editor.\n', tgfFile);
    end
    % --- Export high-res PNG ---
    exportgraphics(fig, outputFile, 'Resolution', 300, 'BackgroundColor', 'w');
    fprintf('Saved isolated dependency graph to %s\n', outputFile);
end