using GB5Shared.Export.NativePdf;
using GB5Shared.QRCode;
using PdfSharpCore.Drawing;
using PdfSharpCore.Fonts;
using PdfSharpCore.Pdf;

namespace GB5Shared.ScanIdentifier
{
    // One PDF page per selected code, page-sized exactly to the chosen label's real physical
    // dimensions (MLABELTEMPLATE) — not a report layout, so this is its own small renderer
    // rather than reusing GB5Shared/Export/NativePdf/NativePdfRenderer.cs (built for tabular
    // reports). Reuses that same module's LatoFontResolver/PdfSharpCore stack (the actual live
    // PDF pipeline in this codebase — see NativePdfRenderer's own doc comment) rather than
    // pulling in a second PDF library. LabelsPerSheet is metadata only here — WidthMm/HeightMm
    // in MLABELTEMPLATE are already per-label, so each PDF page is exactly one physical label
    // regardless of how many sit on one physical sheet/roll.
    public static class ScanLabelPdfRenderer
    {
        private const double MmToPoints = 72.0 / 25.4;

        // Global, process-wide PdfSharpCore state — GlobalFontSettings.FontResolver can only be
        // set once per process ("must not change font resolver after it was once used"), so this
        // checks the actual shared property rather than a private flag, to coexist correctly with
        // NativePdfRenderer's own registration regardless of which one runs first.
        private static readonly object FontResolverLock = new();

        private static void EnsureFontResolverRegistered()
        {
            if (GlobalFontSettings.FontResolver is not null) return;
            lock (FontResolverLock)
            {
                GlobalFontSettings.FontResolver ??= new LatoFontResolver();
            }
        }

        public static byte[] RenderBatch(
            IReadOnlyList<(GeneratedScanIdentifierDTO Identifier, string DisplayCode, string DisplayName)> rows,
            LabelTemplateDTO template)
        {
            EnsureFontResolverRegistered();

            var widthPt = (double)template.WidthMm * MmToPoints;
            var heightPt = (double)template.HeightMm * MmToPoints;
            var margin = Math.Min(widthPt, heightPt) * 0.08;
            var qrSize = Math.Min(heightPt - margin * 2, widthPt * 0.4);

            using var doc = new PdfDocument();
            var titleFont = new XFont("Lato", Math.Max(6, heightPt * 0.14), XFontStyle.Bold);
            var bodyFont = new XFont("Lato", Math.Max(5, heightPt * 0.10), XFontStyle.Regular);

            foreach (var (identifier, displayCode, displayName) in rows)
            {
                var page = doc.AddPage();
                page.Width = XUnit.FromPoint(widthPt);
                page.Height = XUnit.FromPoint(heightPt);

                using var gfx = XGraphics.FromPdfPage(page);

                var qrBytes = QrCodeGenerator.GenerateQrPng(identifier.IdentifierValue, 10);
                using var qrImage = XImage.FromStream(() => new MemoryStream(qrBytes));
                gfx.DrawImage(qrImage, margin, margin, qrSize, qrSize);

                var textX = margin * 2 + qrSize;
                var textWidth = widthPt - textX - margin;
                var textRect1 = new XRect(textX, margin, textWidth, heightPt * 0.4);
                var textRect2 = new XRect(textX, margin + heightPt * 0.4, textWidth, heightPt * 0.3);
                var textRect3 = new XRect(textX, margin + heightPt * 0.65, textWidth, heightPt * 0.3);

                gfx.DrawString(displayCode, titleFont, XBrushes.Black, textRect1, XStringFormats.TopLeft);
                gfx.DrawString(displayName, bodyFont, XBrushes.Black, textRect2, XStringFormats.TopLeft);
                gfx.DrawString(identifier.IdentifierValue, bodyFont, XBrushes.Black, textRect3, XStringFormats.TopLeft);
            }

            using var ms = new MemoryStream();
            doc.Save(ms, false);
            return ms.ToArray();
        }
    }
}