unit Myc.Fmx.Chart;

interface

uses
    System.SysUtils,
    System.Classes,
    System.Types,
    System.Generics.Collections,
    System.UITypes,
    System.UIConsts,
    System.Messaging,
    System.Math.Vectors,
    FMX.Types,
    FMX.Controls,
    FMX.Graphics,
    FMX.Forms,
    Myc.Trade.Types,
    Myc.Signals,
    Myc.Mutable,
    Myc.Data.Pipeline;

type
    TMycChart = class(TStyledControl)
    public
        type
            TPanel = class;

            // Abstract base for a drawable layer in a panel.
            TLayer = class abstract(TObject)
            protected
                function GetCount: Int64; virtual; abstract;
                function GetTotalCount: Int64; virtual; abstract;
                function GetOwner: TMycChart; virtual; abstract;
                function Update: Boolean; virtual; abstract;
            public
                procedure Repaint;
                property Count: Int64 read GetCount;
                property TotalCount: Int64 read GetTotalCount;
                property Owner: TMycChart read GetOwner;
            end;

            TDataLayer = class abstract(TLayer)
            private
                FParent: TPanel;
            protected
                function GetOwner: TMycChart; override; final;
                function GetValueRange(First, Last: Int64; out Min, Max: Double): Boolean; virtual; abstract;
                procedure Paint(
                    const Canvas: TCanvas;
                    First, Last: Int64;
                    const XForm: TFunc<Int64, Single>;
                    const YForm: TFunc<Double, Single>
                ); virtual; abstract;
            public
                constructor Create(AParent: TPanel);
            end;

            TDragPoint = record
                Point: TPointF;
                Idx: Int64;
                BarX: Single;
            end;

            TAxisLayer = class abstract(TLayer)
            private
                FOwner: TMycChart;
            protected
                function GetOwner: TMycChart; override; final;
                // Paint crosshair and other axis related overlays
                procedure Paint(const Canvas: TCanvas; const Viewport: TRectF; const MousePos: TDragPoint); virtual; abstract;
            public
                constructor Create(AOwner: TMycChart);
            end;

            TXAxisLayer = class(TAxisLayer)
            protected
                // Paint crosshair and time caption
                procedure Paint(const Canvas: TCanvas; const Viewport: TRectF; const MousePos: TDragPoint); override;
                // This function delivers the text for the caption.
                function GetCaption(Idx: Int64): String; virtual; abstract;
            end;

            // A panel is a rectangular area in the chart with its own Y-axis, which can contain multiple layers.
            TPanel = class(TObject)
            private
                FOwner: TMycChart;
                FLayers: TObjectList<TMycChart.TDataLayer>;
                FWeight: Single;
                procedure SetWeight(const Value: Single);
            protected
                procedure Paint(const Canvas: TCanvas; const Viewport: TRectF; MasterTotalCount: Int64; ViewStartIndex, ViewCount: Int64);
                function Update: Boolean;

            public
                constructor Create(AOwner: TMycChart; AWeight: Single);
                destructor Destroy; override;

                function AddOhlcSeries(
                    const Producer: TProducer<TOhlcItem>;
                    const AUpColor: TAlphaColor = TAlphaColors.Green;
                    const ADownColor: TAlphaColor = TAlphaColors.Red
                ): TMycChart.TDataLayer;

                function AddDoubleSeries(
                    const Producer: TProducer<Double>;
                    const ALineColor: TAlphaColor = TAlphaColors.Cornflowerblue;
                    const ALineWidth: Single = 1.5
                ): TMycChart.TDataLayer;

                property Owner: TMycChart read FOwner;
                property Weight: Single read FWeight write SetWeight;
            end;

    private
        FPanelList: TObjectList<TPanel>;
        FXAxisSeries: TMycChart.TXAxisLayer;
        FLookback: TWriteable<Int64>;
        FIdleSubscrId: TMessageSubscriptionId;
        FViewStartIndex: Int64;
        FViewCount: Int64;
        FIsDragging: Boolean;
        FMousePos: TDragPoint;
        FDragStartPoint: TDragPoint;
        FIsMouseInControl: Boolean;
        FJumpButtonRect: TRectF;
        FJumpButtonHot: Boolean;
        FJumpButtonPressed: Boolean;
        FNeedRepaint: TFlag;
        FIsResizing: Boolean;
        FResizePanelIndex: Integer;
        FHotResizePanelIndex: Integer;
        function GetPanel(Index: Integer): TPanel;
        function GetPanelCount: Integer;
        function CreateDragPoint(X, Y: Single): TDragPoint;
    protected
        procedure Paint; override;
        procedure DoIdle;
        function Update: Boolean;
        procedure DoMouseLeave; override;
        procedure MouseWheel(Shift: TShiftState; WheelDelta: Integer; var Handled: Boolean); override;
        procedure MouseDown(Button: TMouseButton; Shift: TShiftState; X, Y: Single); override;
        procedure MouseMove(Shift: TShiftState; X, Y: Single); override;
        procedure MouseUp(Button: TMouseButton; Shift: TShiftState; X, Y: Single); override;
    public
        constructor Create(AOwner: TComponent); override;
        destructor Destroy; override;

        // Adds a new, empty panel to the bottom of the chart.
        function AddPanel: TPanel;

        // Sets the master series that defines the time scale (X-axis).
        function SetXAxisSeries(Timeframe: TTimeframe; const Producer: TProducer<TDateTime>): TMycChart.TXAxisLayer; overload;
        function SetXAxisCounter<T>(const Producer: TProducer<T>): TMycChart.TXAxisLayer; overload;

        property Lookback: TWriteable<Int64> read FLookback write FLookback;
        property NeedRepaint: TFlag read FNeedRepaint;
        property PanelCount: Integer read GetPanelCount;
        property Panels[Index: Integer]: TPanel read GetPanel; default;
        // The rectangle occupied by the jump-to-latest button, used for hit testing.
        property JumpButtonRect: TRectF read FJumpButtonRect;
        property ViewCount: Int64 read FViewCount;
        property ViewStartIndex: Int64 read FViewStartIndex;
        property XAxisSeries: TMycChart.TXAxisLayer read FXAxisSeries;
    end;

implementation

uses
    System.Math,
    Myc.FMX.Chart.Series;

const
    RESIZE_HOT_ZONE = 4;
    MIN_PANEL_HEIGHT = 30;
    MIN_PANEL_WEIGHT = 0.05;

{ TMycChart }

constructor TMycChart.Create(AOwner: TComponent);
begin
    inherited Create(AOwner);
    FPanelList := TObjectList<TPanel>.Create(true);
    FXAxisSeries := nil;

    FLookback := TWriteable<Int64>.CreateWriteable(1000);
    FViewStartIndex := 0;
    FViewCount := 100;

    FIsDragging := false;
    FIsResizing := false;
    FResizePanelIndex := -1;
    FHotResizePanelIndex := -1;
    FIsMouseInControl := false;

    FNeedRepaint := TFlag.CreateFlag();

    FIdleSubscrId :=
        TMessageManager
            .DefaultManager
            .SubscribeToMessage(TIdleMessage, procedure(const Sender: TObject; const M: TMessage) begin DoIdle; end);
end;

destructor TMycChart.Destroy;
begin
    TMessageManager.DefaultManager.Unsubscribe(TIdleMessage, FIdleSubscrId);

    FXAxisSeries.Free;
    FPanelList.Free;
    inherited;
end;

function TMycChart.AddPanel: TPanel;
begin
    Result := TPanel.Create(Self, IfThen(FPanelList.Count = 0, 1, 0.2));
    FPanelList.Add(Result);
    Repaint;
end;

function TMycChart.CreateDragPoint(X, Y: Single): TDragPoint;
begin
    var rect := LocalRect;

    Result.Point.X := X;
    Result.Point.Y := Y;
    Result.Idx := Round((rect.Right - X) * (FViewCount - 1) / rect.Width);
    if (Result.Idx < 0) or (Result.Idx >= FXAxisSeries.Count) then
        Result.Idx := -1;
    Result.BarX := NaN;
    if Result.Idx >= 0 then
        Result.BarX := rect.Right - (Result.Idx * (FViewCount - 1)) / (FViewCount - 1) * (rect.Width / (FViewCount - 1));
end;

function TMycChart.GetPanel(Index: Integer): TPanel;
begin
    Result := FPanelList[Index];
end;

function TMycChart.GetPanelCount: Integer;
begin
    Result := FPanelList.Count;
end;

procedure TMycChart.DoIdle;
begin
    if Update then
        Repaint;
end;

function TMycChart.Update: Boolean;
begin
    if not Assigned(FXAxisSeries) then
        exit(false);

    var prevTotalCount := FXAxisSeries.TotalCount;
    var seriesChanged := false;

    if FXAxisSeries.Update then
        seriesChanged := (FViewStartIndex = 0);

    for var panel in FPanelList do
    begin
        if panel.Update then
            seriesChanged := true;
    end;

    // When we are not displaying live data, adjust start index accordingly
    if FViewStartIndex > 0 then
    begin
        var newTotalCount := FXAxisSeries.TotalCount;
        var countDelta := newTotalCount - prevTotalCount;
        if countDelta > 0 then
        begin
            FViewStartIndex := FViewStartIndex + countDelta;
            if (FViewStartIndex + FViewCount > newTotalCount) then
                FViewStartIndex := newTotalCount - FViewCount;
        end;
    end;

    var repaintSignal := FNeedRepaint.Reset;

    Result := repaintSignal or seriesChanged;
end;

procedure TMycChart.DoMouseLeave;
begin
    inherited;
    if FIsMouseInControl then
    begin
        FIsMouseInControl := false;
        Repaint;
    end;
end;

procedure TMycChart.Paint;
var
    rect, panelRect: TRectF;
    isButtonVisible: Boolean;
    buttonColor: TAlphaColor;
    path: TPathData;
    masterTotalCount: Int64;
    panelHeight, totalWeight: Double;
    currentY: Single;
begin
    inherited;
    rect := Self.LocalRect;

    if (not Assigned(FXAxisSeries)) or (FXAxisSeries.Count <= 1) or (FViewCount <= 1) or (PanelCount = 0) then
    begin
        Canvas.Fill.Color := TAlphaColors.Gray;
        Canvas.FillText(rect, 'No Data', false, 1, [], TTextAlign.Center, TTextAlign.Center);
        Exit;
    end;

    masterTotalCount := FXAxisSeries.TotalCount;

    // Calculate total weight for proportional panel height
    totalWeight := 0;
    for var panel in FPanelList do
        totalWeight := totalWeight + panel.Weight;
    if (totalWeight <= 0) then
        totalWeight := PanelCount; // Fallback to equal distribution

    currentY := rect.Top;
    for var i := 0 to PanelCount - 1 do
    begin
        var panel := Panels[i];

        panelHeight := panel.Weight * rect.Height / totalWeight;
        panelRect := TRectF.Create(rect.Left, currentY, rect.Right, currentY + panelHeight);

        // Draw panel content
        panel.Paint(Self.Canvas, panelRect, masterTotalCount, FViewStartIndex, FViewCount);

        // Draw separator line
        if (i > 0) then
        begin
            Canvas.Stroke.Color := TAlphaColors.Gray;
            Canvas.Stroke.Thickness := 1;
            Canvas.DrawLine(PointF(panelRect.Left, panelRect.Top), PointF(panelRect.Right, panelRect.Top), 1);
        end;

        currentY := currentY + panelHeight;
    end;

    // Draw crosshair if mouse is in control
    if FIsMouseInControl and Assigned(FXAxisSeries) and (FMousePos.Idx >= 0) then
    begin
        // Do not draw crosshair if mouse is over the jump button
        if not FJumpButtonRect.Contains(FMousePos.Point) then
            FXAxisSeries.Paint(Self.Canvas, rect, FMousePos);
    end;

    // --- Draw the "jump to latest" button (code unchanged) ---
    isButtonVisible := (FViewStartIndex > 0);

    if isButtonVisible then
    begin
        FJumpButtonRect := TRectF.Create(Self.Width - 44, Self.Height - 44, Self.Width - 10, Self.Height - 10);

        if FJumpButtonPressed then
            buttonColor := $FF707070
        else if FJumpButtonHot then
            buttonColor := $FF505050
        else
            buttonColor := $FF303030;

        Canvas.Fill.Color := buttonColor;
        Canvas.FillRect(FJumpButtonRect, 4, 4, AllCorners, 0.7);

        Canvas.Stroke.Color := TAlphaColors.White;
        Canvas.Stroke.Thickness := 1.5;

        path := TPathData.Create;
        try
            var cx := FJumpButtonRect.CenterPoint.X;
            var cy := FJumpButtonRect.CenterPoint.Y;
            path.MoveTo(PointF(cx - 5, cy - 6));
            path.LineTo(PointF(cx, cy));
            path.LineTo(PointF(cx - 5, cy + 6));
            path.MoveTo(PointF(cx + 2, cy - 6));
            path.LineTo(PointF(cx + 7, cy));
            path.LineTo(PointF(cx + 2, cy + 6));
            Canvas.DrawPath(path, 1);
        finally
            path.Free;
        end;
    end
    else
    begin
        FJumpButtonRect := TRectF.Empty;
        FJumpButtonPressed := false;
    end;
end;

procedure TMycChart.MouseDown(Button: TMouseButton; Shift: TShiftState; X, Y: Single);
begin
    inherited MouseDown(Button, Shift, X, Y);

    // Check for button press first
    if (Button = TMouseButton.mbLeft) and (FViewStartIndex > 0) and FJumpButtonRect.Contains(PointF(X, Y)) then
    begin
        FJumpButtonPressed := true;
        Repaint;
        exit;
    end;

    // Check for starting a resize
    if (Button = TMouseButton.mbLeft) and (FHotResizePanelIndex >= 0) then
    begin
        FIsResizing := true;
        FResizePanelIndex := FHotResizePanelIndex;
        FDragStartPoint := CreateDragPoint(X, Y);
        Capture;
        exit;
    end;

    if (Button = TMouseButton.mbLeft) then
    begin
        FIsDragging := true;
        FDragStartPoint := CreateDragPoint(X, Y);
        Capture;
    end;
end;

procedure TMycChart.MouseUp(Button: TMouseButton; Shift: TShiftState; X, Y: Single);
begin
    inherited MouseUp(Button, Shift, X, Y);

    if (Button = TMouseButton.mbLeft) then
    begin
        // Stop resizing
        if FIsResizing then
        begin
            FIsResizing := false;
            FResizePanelIndex := -1;
            // Force cursor update on next move by resetting hot index
            if (FHotResizePanelIndex <> -1) then
            begin
                FHotResizePanelIndex := -1;
                Self.Cursor := crDefault;
            end;
        end;

        // Stop panning
        FIsDragging := false;

        // Stop button press
        if FJumpButtonPressed then
        begin
            FJumpButtonPressed := false;
            // If mouse is released over the button, trigger the action
            if (FViewStartIndex > 0) and FJumpButtonRect.Contains(PointF(X, Y)) then
            begin
                FViewStartIndex := 0; // Jump to the latest candle
            end;
            Repaint;
        end;

        // Release mouse capture if it was held by this control
        ReleaseCapture;
    end;
end;

procedure TMycChart.MouseMove(Shift: TShiftState; X, Y: Single);
var
    indexDelta: Int64;
    maxIndex: Int64;
begin
    inherited MouseMove(Shift, X, Y);

    if not FIsMouseInControl then
        FIsMouseInControl := true;
    FMousePos := CreateDragPoint(X, Y);

    // --- Panel Resizing Logic ---
    if FIsResizing then
    begin
        var dy := FMousePos.Point.Y - FDragStartPoint.Point.Y;
        if Abs(dy) < 2 then // Threshold to avoid jitter
            exit;

        var panel1 := Panels[FResizePanelIndex];
        var panel2 := Panels[FResizePanelIndex + 1];

        // Get total weight and height of the two panels being resized
        var totalWeight := 0.0;
        for var panel in FPanelList do
            totalWeight := totalWeight + panel.Weight;
        if (totalWeight <= 0) then
            totalWeight := PanelCount;

        var h1 := (panel1.Weight / totalWeight) * Self.Height;
        var h2 := (panel2.Weight / totalWeight) * Self.Height;
        var twoPanelWeight := panel1.Weight + panel2.Weight;

        var newH1 := h1 + dy;
        var newH2 := h2 - dy;

        // Clamp to minimum height
        if (newH1 < MIN_PANEL_HEIGHT) then
        begin
            newH2 := newH2 + (newH1 - MIN_PANEL_HEIGHT);
            newH1 := MIN_PANEL_HEIGHT;
        end;
        if (newH2 < MIN_PANEL_HEIGHT) then
        begin
            newH1 := newH1 + (newH2 - MIN_PANEL_HEIGHT);
            newH2 := MIN_PANEL_HEIGHT;
        end;

        // Recalculate weights based on new clamped heights
        if (newH1 + newH2 > 0) then
        begin
            panel1.Weight := (newH1 / (newH1 + newH2)) * twoPanelWeight;
            panel2.Weight := (newH2 / (newH1 + newH2)) * twoPanelWeight;
        end;

        FDragStartPoint := CreateDragPoint(FDragStartPoint.Point.X, Y); // Update start point for next move
        Repaint;
        exit; // Do not continue with other mouse move logic
    end;

    // --- Chart Panning Logic ---
    if FIsDragging then
    begin
        if Abs(FMousePos.Point.X - FDragStartPoint.Point.X) < 2 then // Threshold to avoid jitter
            exit;

        if not Assigned(FXAxisSeries) or (FViewCount <= 0) then
            exit;

        indexDelta := FMousePos.Idx - FDragStartPoint.Idx;
        FDragStartPoint.Idx := FDragStartPoint.Idx + indexDelta;

        FViewStartIndex := FViewStartIndex - indexDelta;

        // Clamp values
        maxIndex := FXAxisSeries.Count - FViewCount;
        if (maxIndex < 0) then
            maxIndex := 0;
        if (FViewStartIndex < 0) then
            FViewStartIndex := 0;
        if (FViewStartIndex > maxIndex) then
            FViewStartIndex := maxIndex;

        Repaint;
        exit;
    end;

    // --- Separator Hit-Testing and Cursor Change ---
    var currentHotIndex := -1;
    if (PanelCount > 1) then
    begin
        var totalWeight := 0.0;
        for var panel in FPanelList do
            totalWeight := totalWeight + panel.Weight;
        if (totalWeight <= 0) then
            totalWeight := PanelCount;

        var currentY: Single := 0;
        for var i := 0 to PanelCount - 2 do
        begin
            currentY := currentY + (Panels[i].Weight / totalWeight) * Self.Height;
            if (Abs(Y - currentY) < RESIZE_HOT_ZONE) then
            begin
                currentHotIndex := i;
                break;
            end;
        end;
    end;

    if (currentHotIndex <> FHotResizePanelIndex) then
    begin
        FHotResizePanelIndex := currentHotIndex;
        if (FHotResizePanelIndex <> -1) then
            Self.Cursor := crVSplit
        else
            Self.Cursor := crDefault;
    end;

    // --- Jump Button Hot State Logic and final repaint for crosshair ---
    Repaint;
end;

procedure TMycChart.MouseWheel(Shift: TShiftState; WheelDelta: Integer; var Handled: Boolean);
var
    zoomFactor: Double;
    newViewCount: Int64;
begin
    inherited MouseWheel(Shift, WheelDelta, Handled);

    Handled := true;

    // An X-axis series is required for zooming
    if not Assigned(FXAxisSeries) then
        exit;

    var xAxisCount := FXAxisSeries.Count;
    if (xAxisCount = 0) or (Width <= 0) then
        exit;

    if (WheelDelta > 0) then
        zoomFactor := 0.8 // Zoom In
    else
        zoomFactor := 1.25; // Zoom Out

    newViewCount := Round(FViewCount * zoomFactor);

    // Clamp zoom level
    if (newViewCount < 10) then
        newViewCount := 10;
    if (newViewCount > xAxisCount) then
        newViewCount := xAxisCount;
    if (newViewCount = FViewCount) then
        exit;

    FViewCount := newViewCount;

    var oldIdx := FViewStartIndex + FMousePos.Idx;
    FMousePos := CreateDragPoint(FMousePos.Point.X, FMousePos.Point.Y);
    FViewStartIndex := oldIdx - FMousePos.Idx;

    // Clamp start index
    if (FViewStartIndex < 0) then
        FViewStartIndex := 0;
    if (FViewStartIndex + FViewCount > xAxisCount) then
    begin
        FViewStartIndex := xAxisCount - FViewCount;
    end;

    Repaint;
end;

function TMycChart.SetXAxisCounter<T>(const Producer: TProducer<T>): TMycChart.TXAxisLayer;
begin
    FXAxisSeries.Free;

    FXAxisSeries := TChartXAxisLayer<Int64>.Create(Self, Producer.Chain<Int64>(TConverter.CreateCounter<T>));
    Result := FXAxisSeries;
end;

function TMycChart.SetXAxisSeries(Timeframe: TTimeframe; const Producer: TProducer<TDateTime>): TMycChart.TXAxisLayer;
begin
    FXAxisSeries.Free;

    FXAxisSeries := TChartXAxisTimestampLayer.Create(Self, Timeframe, Producer);
    Result := FXAxisSeries;
end;

procedure TMycChart.TLayer.Repaint;
begin
    Owner.Repaint;
end;

{ TMycChart.TPanel }

constructor TMycChart.TPanel.Create(AOwner: TMycChart; AWeight: Single);
begin
    inherited Create;
    FOwner := AOwner;
    FLayers := TObjectList<TMycChart.TDataLayer>.Create(true);
    FWeight := AWeight;
end;

destructor TMycChart.TPanel.Destroy;
begin
    FLayers.Free;
    inherited Destroy;
end;

function TMycChart.TPanel.AddDoubleSeries(
    const Producer: TProducer<Double>;
    const ALineColor: TAlphaColor = TAlphaColors.Cornflowerblue;
    const ALineWidth: Single = 1.5
): TMycChart.TDataLayer;
begin
    Result := TChartLineLayer.Create(Self, Producer, ALineColor, ALineWidth);
    FLayers.Add(Result);
end;

function TMycChart.TPanel.AddOhlcSeries(
    const Producer: TProducer<TOhlcItem>;
    const AUpColor: TAlphaColor = TAlphaColors.Green;
    const ADownColor: TAlphaColor = TAlphaColors.Red
): TMycChart.TDataLayer;
begin
    Result := TChartOhlcLayer.Create(Self, Producer, TMutable<TAlphaColor>.Constant(AUpColor), TMutable<TAlphaColor>.Constant(ADownColor));
    FLayers.Add(Result);
end;

procedure TMycChart.TPanel.Paint(const Canvas: TCanvas; const Viewport: TRectF; MasterTotalCount, ViewStartIndex, ViewCount: Int64);
var
    localMin, localMax, seriesMin, seriesMax: Double;
    rangeInitialized: Boolean;
    seriesFirst, seriesLast: Int64;
    xTransform: TFunc<Int64, Single>;
    yTransform: TFunc<Double, Single>;

    function CalcView(Layer: TMycChart.TDataLayer; out First, Last: Int64): Boolean;
    var
        seriesTotalCount, offset, startIdx: Int64;
    begin
        seriesTotalCount := Layer.TotalCount;
        offset := MasterTotalCount - seriesTotalCount;
        startIdx := ViewStartIndex - offset;

        First := Max(0, startIdx);
        Last := Min(Layer.Count, startIdx + ViewCount) - 1;
        Result := First <= Last;
    end;

begin
    rangeInitialized := false;
    localMin := 0;
    localMax := 0;

    // Update data state
    for var layer in FLayers do
        layer.Update;

    // 1. Calculate value range (Y-Axis) for this panel only
    for var layer in FLayers do
    begin
        if CalcView(layer, seriesFirst, seriesLast) then
        begin
            if layer.GetValueRange(seriesFirst, seriesLast, seriesMin, seriesMax) then
            begin
                if not rangeInitialized then
                begin
                    localMin := seriesMin;
                    localMax := seriesMax;
                    rangeInitialized := true;
                end
                else
                begin
                    localMin := Min(localMin, seriesMin);
                    localMax := Max(localMax, seriesMax);
                end;
            end;
        end;
    end;

    if not rangeInitialized then
        Exit; // Nothing to draw in this panel

    if (localMax - localMin) = 0 then
        localMax := localMin + 1; // Avoid division by zero

    // 2. Create transforms for this panel
    const padding = 2;
    var top: Double := Viewport.Top + padding;
    var height: Double := Viewport.Height - (2 * padding);
    var range: Double := localMax - localMin;
    yTransform := function(value: Double): Single begin Result := top + (1 - (value - localMin) / range) * height; end;

    // 3. Paint all layers in this panel
    for var layer in FLayers do
    begin
        if CalcView(layer, seriesFirst, seriesLast) then
        begin
            var offset := MasterTotalCount - layer.TotalCount;
            xTransform :=
                function(index: Int64): Single
                begin
                    Result := Viewport.Right - (((index + offset - ViewStartIndex) / (ViewCount - 1)) * Viewport.Width);
                end;

            layer.Paint(Canvas, seriesFirst, seriesLast, xTransform, yTransform);
        end;
    end;
end;

procedure TMycChart.TPanel.SetWeight(const Value: Single);
begin
    // Ensure weight does not become too small or negative
    var clampedValue := Max(MIN_PANEL_WEIGHT, Value);
    if FWeight <> clampedValue then
    begin
        FWeight := clampedValue;
        // Do not call Repaint here, it will be handled by the mouse move logic
        if Assigned(FOwner) and (not FOwner.FIsResizing) then
            FOwner.Repaint;
    end;
end;

function TMycChart.TPanel.Update: Boolean;
begin
    Result := false;
    for var layer in FLayers do
    begin
        if layer.Update then
            if (Owner.ViewStartIndex <= Owner.FXAxisSeries.TotalCount - layer.TotalCount) then
                Result := true;
    end;
end;

{ TMycChart.TDataLayer }

constructor TMycChart.TDataLayer.Create(AParent: TPanel);
begin
    inherited Create;
    FParent := AParent;
end;

function TMycChart.TDataLayer.GetOwner: TMycChart;
begin
    Result := FParent.Owner;
end;

{ TMycChart.TAxisLayer }

constructor TMycChart.TAxisLayer.Create(AOwner: TMycChart);
begin
    inherited Create;
    FOwner := AOwner;
end;

function TMycChart.TAxisLayer.GetOwner: TMycChart;
begin
    Result := FOwner;
end;

{ TMycChart.TXAxisLayer }

procedure TMycChart.TXAxisLayer.Paint(const Canvas: TCanvas; const Viewport: TRectF; const MousePos: TDragPoint);
var
    caption: string;
    captionRect: TRectF;
    padding: Single;
    candleX: Single;
    textSize: TRectF;
begin
    // Do not draw if no data or view is invalid
    if GetCount = 0 then
        exit;

    // 1. Snap X to the candle's center
    candleX := MousePos.BarX;

    // 2. Draw the vertical line at the snapped position
    Canvas.Stroke.Kind := TBrushKind.Solid;
    Canvas.Stroke.Color := TAlphaColors.Gray;
    Canvas.Stroke.Thickness := 1;
    Canvas.DrawLine(PointF(candleX, Viewport.Top), PointF(candleX, Viewport.Bottom), 1.0);

    // 3. Get the caption for the index
    caption := GetCaption(FOwner.ViewStartIndex + MousePos.Idx);
    if caption.IsEmpty then
        exit;

    // 4. Draw the caption with a background
    padding := 1;
    Canvas.Font.Size := 9;

    // Measure text size
    textSize := TRectF.Create(0, 0, 10000, 10000);
    Canvas.MeasureText(textSize, caption, False, [], TTextAlign.Leading);

    // Position the caption box, centered on the snapped candle X
    captionRect.Left := candleX - (textSize.Width / 2) - padding;
    captionRect.Width := textSize.Width + (padding * 2);
    captionRect.Top := Viewport.Bottom - textSize.Height - (padding * 2);
    captionRect.Height := textSize.Height + (padding * 2);

    // Adjust position to not go outside the viewport
    if captionRect.Left < Viewport.Left then
        captionRect.SetLocation(Viewport.Left, captionRect.Top);
    if captionRect.Right > Viewport.Right then
        captionRect.SetLocation(Viewport.Right - captionRect.Width, captionRect.Top);

    // Draw the styled box
    Canvas.Fill.Color := TAlphaColors.White;
    Canvas.Fill.Kind := TBrushKind.Solid;
    Canvas.Stroke.Kind := TBrushKind.Solid;
    Canvas.Stroke.Color := TAlphaColors.Gray;
    Canvas.Stroke.Thickness := 1;
    Canvas.FillRect(captionRect, 2, 2, AllCorners, 0.7);
    Canvas.DrawRect(captionRect, 2, 2, AllCorners, 1.0);

    // Draw the text
    Canvas.Fill.Color := TAlphaColors.Black;
    Canvas.FillText(captionRect, caption, false, 1.0, [], TTextAlign.Center, TTextAlign.Center);
end;

end.