Plot to PNG

  ok: chart has two data series and one trend line
  ok: a trend line has exactly two points
Exporting to ...\plot-output
  ok: PNG file has content
  ok: PNG is 800 x 500
  ok: SVG root has the requested size
  ok: SVG contains the title
  ok: SVG shows category ticks from the point text
  ok: SVG clips the series to the plot area
  ok: CSV header is series,kind,x,y,text
  ok: CSV has one row per point
  ok: first row is the first order bar
  ok: numbers use a decimal point regardless of locale
  ok: the trend line is exported as a series
  ok: CSV import recreates all three series
  ok: series kinds survive the round trip
  ok: import and export are symmetric
  ok: a value beyond 1E100 is rejected and nothing changes
  ok: no partial files are left behind
PlotToPng: all checks passed

program PlotToPng;

// Atlas Plot quick start: build a chart in code, export it as PNG, SVG and CSV
// without showing a window, then verify the files.

{$APPTYPE CONSOLE}

uses
  System.SysUtils, System.Classes, System.IOUtils, Vcl.Graphics, Vcl.Imaging.pngimage,
  Atlas.Plot, Atlas.PlotSeries, Atlas.PlotAxis;

const
  Months: array[0..11] of string = ('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
    'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec');
  OrderCounts: array[0..11] of Double = (42, 38, 51, 47, 55, 61, 58, 64, 70, 66, 73, 81);
  Revenue: array[0..11] of Double = (12.5, 11.2, 15.8, 14.1, 17.3, 19.0, 18.2, 20.6, 22.9, 21.4, 24.0, 27.5);

procedure Check(Condition: Boolean; const What: string);
begin
  if not Condition then raise Exception.Create('Check failed: ' + What);
  Writeln('  ok: ', What);
end;

procedure BuildChart(Plot: TAtlasPlot);
var
  Orders, Sales: TAtlasPlotSeries;
  I: Integer;
begin
  Plot.BeginUpdate;
  try
    Plot.Title := 'Orders and revenue, 2026';
    Plot.Footnote := 'Revenue in thousands';
    Plot.LegendPosition := lpBottom;
    Plot.ArgumentAxis.Title := 'Month';
    Plot.ValueAxis.Title := 'Count / thousands';
    Plot.ValueAxis.Grid := True;
    Orders := Plot.AddSeries('Orders', pkBar);
    Sales := Plot.AddSeries('Revenue', pkLine, clMaroon);
    Sales.LineWidth := 3;
    Sales.ShowPoints := True;
    Sales.Marks := pmValue;
    for I := 0 to High(Months) do
    begin
      // AddY numbers the argument 0, 1, 2, ... and the text becomes a category tick.
      Orders.AddY(OrderCounts[I], Months[I]);
      Sales.AddY(Revenue[I]);
    end;
    // A least-squares fit of the revenue; a snapshot that does not follow later edits.
    Plot.AddTrendLine(Sales).LineWidth := 1;
  finally
    Plot.EndUpdate;
  end;
end;

procedure VerifyPng(const FileName: string);
var Png: TPngImage;
begin
  Check(TFile.GetSize(FileName) > 1000, 'PNG file has content');
  Png := TPngImage.Create;
  try
    Png.LoadFromFile(FileName);
    Check((Png.Width = 800) and (Png.Height = 500), 'PNG is 800 x 500');
  finally
    Png.Free;
  end;
end;

procedure VerifySvg(const FileName: string);
var Svg: string;
begin
  Svg := TFile.ReadAllText(FileName, TEncoding.UTF8);
  Check(Pos('<svg xmlns="http://www.w3.org/2000/svg" width="800" height="500"', Svg) > 0, 'SVG root has the requested size');
  Check(Pos('>Orders and revenue, 2026<', Svg) > 0, 'SVG contains the title');
  Check((Pos('>Jan<', Svg) > 0) and (Pos('>Dec<', Svg) > 0), 'SVG shows category ticks from the point text');
  Check(Pos('<clipPath', Svg) > 0, 'SVG clips the series to the plot area');
end;

procedure VerifyCsv(const FileName: string; Plot: TAtlasPlot);
var
  Lines: TArray<string>;
  Copy: TAtlasPlot;
begin
  Lines := TFile.ReadAllLines(FileName, TEncoding.UTF8);
  Check(Lines[0] = 'series,kind,x,y,text', 'CSV header is series,kind,x,y,text');
  // 12 order rows, 12 revenue rows and the two-point trend line.
  Check(Length(Lines) = 1 + 12 + 12 + 2, 'CSV has one row per point');
  Check(Lines[1] = 'Orders,bar,0,42,Jan', 'first row is the first order bar');
  Check(Lines[13] = 'Revenue,line,0,12.5,', 'numbers use a decimal point regardless of locale');
  Check(Pos('Revenue trend,line,', Lines[25]) = 1, 'the trend line is exported as a series');
  Copy := TAtlasPlot.Create(nil);
  try
    Copy.DataFromCSV(TFile.ReadAllText(FileName, TEncoding.UTF8));
    Check(Copy.Series.Count = 3, 'CSV import recreates all three series');
    Check(Copy.Series.Find('orders').Kind = pkBar, 'series kinds survive the round trip');
    Check(Copy.DataToCSV = Plot.DataToCSV, 'import and export are symmetric');
  finally
    Copy.Free;
  end;
end;

procedure Run;
var
  Plot: TAtlasPlot;
  Folder: string;
begin
  Folder := TPath.Combine(GetCurrentDir, 'plot-output');
  TDirectory.CreateDirectory(Folder);
  Plot := TAtlasPlot.Create(nil);
  try
    BuildChart(Plot);
    Check(Plot.Series.Count = 3, 'chart has two data series and one trend line');
    Check(Plot.Series[2].Count = 2, 'a trend line has exactly two points');
    Writeln('Exporting to ', Folder);
    // The extension selects the format; width and height are in pixels.
    Plot.SaveToFile(TPath.Combine(Folder, 'orders.png'), 800, 500);
    Plot.SaveToFile(TPath.Combine(Folder, 'orders.svg'), 800, 500);
    Plot.SaveToFile(TPath.Combine(Folder, 'orders.csv'));
    VerifyPng(TPath.Combine(Folder, 'orders.png'));
    VerifySvg(TPath.Combine(Folder, 'orders.svg'));
    VerifyCsv(TPath.Combine(Folder, 'orders.csv'), Plot);
    // Invalid input raises EAtlasPlotError and leaves the chart unchanged.
    try
      Plot.Series[0].Add(12, 1E101);
      Check(False, 'a value beyond 1E100 must be rejected');
    except
      on EAtlasPlotError do Check(Plot.Series[0].Count = 12, 'a value beyond 1E100 is rejected and nothing changes');
    end;
    Check(Length(TDirectory.GetFiles(Folder, '*.part')) = 0, 'no partial files are left behind');
  finally
    Plot.Free;
  end;
end;

begin
  try
    Run;
    Writeln('PlotToPng: all checks passed');
  except
    on E: Exception do
    begin
      Writeln(E.ClassName, ': ', E.Message);
      ExitCode := 1;
    end;
  end;
end.