feat: add FundSkiaChartRenderer (SkiaSharp price line chart)

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

CertReports.Syncfusion/Services/Implementations/FundSkiaChartRenderer.cs

@@ -0,0 +1,188 @@
+using CertReports.Syncfusion.Models;
+using SkiaSharp;
+
+namespace CertReports.Syncfusion.Services.Implementations;
+
+public static class FundSkiaChartRenderer
+{
+    private const int DefaultWidth  = 1100;
+    private const int DefaultHeight = 700;
+    private const float MarginLeft   = 70f;
+    private const float MarginRight  = 40f;
+    private const float MarginTop    = 55f;
+    private const float MarginBottom = 55f;
+
+    public static byte[] Render(List<FundChartPoint> points, string instrumentName,
+        int width = DefaultWidth, int height = DefaultHeight, bool jpeg = false)
+    {
+        using var surface = SKSurface.Create(new SKImageInfo(width, height));
+        var canvas = surface.Canvas;
+        canvas.Clear(SKColors.White);
+
+        if (points.Count < 2)
+            DrawNoDataMessage(canvas, width, height, instrumentName);
+        else
+            DrawChart(canvas, points, instrumentName, width, height);
+
+        using var image = surface.Snapshot();
+        using var data  = jpeg
+            ? image.Encode(SKEncodedImageFormat.Jpeg, 90)
+            : image.Encode(SKEncodedImageFormat.Png, 100);
+        return data.ToArray();
+    }
+
+    private static void DrawChart(SKCanvas canvas, List<FundChartPoint> points,
+        string title, int width, int height)
+    {
+        float plotX = MarginLeft;
+        float plotY = MarginTop;
+        float plotW = width  - MarginLeft - MarginRight;
+        float plotH = height - MarginTop  - MarginBottom;
+
+        decimal minPrice = points.Min(p => p.Close);
+        decimal maxPrice = points.Max(p => p.Close);
+        decimal priceRange = maxPrice - minPrice;
+        if (priceRange == 0) priceRange = 1;
+        decimal pad  = priceRange * 0.08m;
+        decimal yMin = minPrice - pad;
+        decimal yMax = maxPrice + pad;
+
+        var minDate  = points.First().Date;
+        var maxDate  = points.Last().Date;
+        double totalDays = (maxDate - minDate).TotalDays;
+
+        // Plot area background
+        using var bgPaint = new SKPaint { Color = new SKColor(250, 250, 255), Style = SKPaintStyle.Fill };
+        canvas.DrawRect(plotX, plotY, plotW, plotH, bgPaint);
+
+        DrawGrid(canvas, plotX, plotY, plotW, plotH, yMin, yMax, minDate, maxDate, totalDays);
+
+        // Price line
+        using var linePaint = new SKPaint
+        {
+            Color       = SKColors.Black,
+            StrokeWidth = 2f,
+            IsAntialias = true,
+            Style       = SKPaintStyle.Stroke
+        };
+        using var path = new SKPath();
+        bool first = true;
+        foreach (var pt in points)
+        {
+            float px = DateToX(pt.Date, minDate, maxDate, plotX, plotW);
+            float py = PriceToY(pt.Close, yMin, yMax, plotY, plotH);
+            if (first) { path.MoveTo(px, py); first = false; }
+            else path.LineTo(px, py);
+        }
+        canvas.DrawPath(path, linePaint);
+
+        // End label (last price)
+        var last   = points.Last();
+        float lastX = DateToX(last.Date, minDate, maxDate, plotX, plotW);
+        float lastY = PriceToY(last.Close, yMin, yMax, plotY, plotH);
+        var labelFont = new SKFont(SKTypeface.Default, 11f);
+        using var labelPaint = new SKPaint { Color = SKColors.Black, IsAntialias = true };
+        canvas.DrawText($"{last.Close:F2}", lastX + 4f, lastY + 4f,
+            SKTextAlign.Left, labelFont, labelPaint);
+
+        // Chart title
+        var titleFont = new SKFont(SKTypeface.Default, 14f) { Embolden = true };
+        using var titlePaint = new SKPaint
+        {
+            Color       = new SKColor(21, 101, 192),
+            IsAntialias = true
+        };
+        canvas.DrawText(title, (float)width / 2, MarginTop - 10f,
+            SKTextAlign.Center, titleFont, titlePaint);
+
+        // Plot border
+        using var borderPaint = new SKPaint
+        {
+            Color       = new SKColor(200, 200, 200),
+            StrokeWidth = 0.8f,
+            Style       = SKPaintStyle.Stroke
+        };
+        canvas.DrawRect(plotX, plotY, plotW, plotH, borderPaint);
+    }
+
+    private static void DrawGrid(SKCanvas canvas,
+        float plotX, float plotY, float plotW, float plotH,
+        decimal yMin, decimal yMax,
+        DateTime minDate, DateTime maxDate, double totalDays)
+    {
+        using var gridPaint = new SKPaint
+        {
+            Color       = new SKColor(220, 220, 220),
+            StrokeWidth = 0.5f,
+            Style       = SKPaintStyle.Stroke
+        };
+        using var axisPaint = new SKPaint
+        {
+            Color       = new SKColor(100, 100, 100),
+            StrokeWidth = 0.8f,
+            Style       = SKPaintStyle.Stroke
+        };
+        using var axisLabelPaint = new SKPaint
+        {
+            Color       = new SKColor(100, 100, 100),
+            IsAntialias = true
+        };
+        var axisLabelFont = new SKFont(SKTypeface.Default, 10f);
+
+        // Y grid (5 horizontal lines)
+        for (int i = 0; i <= 5; i++)
+        {
+            decimal price = yMin + (yMax - yMin) * i / 5;
+            float py = PriceToY(price, yMin, yMax, plotY, plotH);
+            canvas.DrawLine(plotX, py, plotX + plotW, py, i == 0 ? axisPaint : gridPaint);
+            canvas.DrawText($"{price:F2}", plotX - 5f, py + 4f,
+                SKTextAlign.Right, axisLabelFont, axisLabelPaint);
+        }
+
+        // X grid (adaptive monthly intervals)
+        int monthInterval = totalDays > 365 * 3 ? 12 :
+                            totalDays > 365      ? 6  :
+                            totalDays > 90       ? 3  : 1;
+
+        var current = new DateTime(minDate.Year, minDate.Month, 1).AddMonths(1);
+        while (current <= maxDate)
+        {
+            if (current.Month % monthInterval == 0)
+            {
+                float px = DateToX(current, minDate, maxDate, plotX, plotW);
+                canvas.DrawLine(px, plotY, px, plotY + plotH, gridPaint);
+                var lbl = monthInterval >= 12
+                    ? current.Year.ToString()
+                    : current.ToString("MMM yy");
+                canvas.DrawText(lbl, px, plotY + plotH + 14f,
+                    SKTextAlign.Center, axisLabelFont, axisLabelPaint);
+            }
+            current = current.AddMonths(1);
+        }
+    }
+
+    private static void DrawNoDataMessage(SKCanvas canvas, int width, int height, string title)
+    {
+        var font = new SKFont(SKTypeface.Default, 14f);
+        using var paint = new SKPaint { Color = new SKColor(150, 150, 150), IsAntialias = true };
+        canvas.DrawText($"{title} — Dati insufficienti",
+            (float)width / 2, (float)height / 2, SKTextAlign.Center, font, paint);
+    }
+
+    private static float DateToX(DateTime date, DateTime minDate, DateTime maxDate,
+        float plotX, float plotW)
+    {
+        double totalDays = (maxDate - minDate).TotalDays;
+        if (totalDays == 0) return plotX;
+        double ratio = (date - minDate).TotalDays / totalDays;
+        return plotX + (float)(ratio * plotW);
+    }
+
+    private static float PriceToY(decimal price, decimal yMin, decimal yMax,
+        float plotY, float plotH)
+    {
+        if (yMax == yMin) return plotY + plotH / 2;
+        double ratio = (double)((price - yMin) / (yMax - yMin));
+        return plotY + plotH - (float)(ratio * plotH);
+    }
+}