using GB5Shared.DTO.Report;
using GB5Shared.Export.HybridReport;
using HandlebarsDotNet;
using PuppeteerSharp;
using PuppeteerSharp.Media;

namespace GB5Shared.Export.Pivot
{
    public sealed class PivotPdfExport : IPivotPdfExport
    {
        public async Task<byte[]> ExportAsync(
            PivotResultDTO    pivotResult,
            ReportStandardDTO reportStandard,
            string            templatePath,
            CancellationToken ct = default)
        {
            var allColumnHeaders = pivotResult.RowHeaders.Concat(pivotResult.PivotColumns).ToList();

            var context = new
            {
                Report       = reportStandard,
                ColumnHeaders = allColumnHeaders,
                RowHeaders   = pivotResult.RowHeaders,
                PivotColumns = pivotResult.PivotColumns,
                Rows         = pivotResult.Rows,
                GrandTotal   = pivotResult.GrandTotal,
                GeneratedOn  = DateTime.UtcNow
            };

            string html;
            if (System.IO.File.Exists(templatePath))
            {
                var source = await System.IO.File.ReadAllTextAsync(templatePath, ct).ConfigureAwait(false);
                var hb = Handlebars.Create();
                hb.RegisterHelper("formatN2", (writer, _, parameters) =>
                {
                    if (parameters.Length >= 1 && decimal.TryParse(parameters[0]?.ToString(),
                        System.Globalization.NumberStyles.Any,
                        System.Globalization.CultureInfo.InvariantCulture, out var d))
                        writer.WriteSafeString(d.ToString("N2"));
                    else
                        writer.WriteSafeString(parameters.FirstOrDefault()?.ToString() ?? "");
                });
                var template = hb.Compile(source);
                html = template(context);
            }
            else
            {
                html = BuildFallbackHtml(pivotResult, allColumnHeaders, reportStandard);
            }

            return await RenderToPdfAsync(html, ct).ConfigureAwait(false);
        }

        private static string BuildFallbackHtml(
            PivotResultDTO    pivot,
            List<string>      allHeaders,
            ReportStandardDTO report)
        {
            var sb = new System.Text.StringBuilder();
            sb.Append("<!DOCTYPE html><html><head><meta charset='utf-8'>");
            sb.Append("<style>body{font-family:Arial,sans-serif;font-size:10px;}");
            sb.Append("table{border-collapse:collapse;width:100%;}");
            sb.Append("th,td{border:1px solid #ccc;padding:3px 6px;white-space:nowrap;}");
            sb.Append("th{background:#ddd;font-weight:bold;}");
            sb.Append(".grand-total{background:#fffacd;font-weight:bold;}");
            sb.Append("</style></head><body>");

            sb.Append($"<h2>{System.Net.WebUtility.HtmlEncode(report.ReportTitle ?? "Pivot Report")}</h2>");

            sb.Append("<table><thead><tr>");
            foreach (var h in allHeaders)
                sb.Append($"<th>{System.Net.WebUtility.HtmlEncode(h)}</th>");
            sb.Append("</tr></thead><tbody>");

            foreach (var row in pivot.Rows)
            {
                sb.Append("<tr>");
                foreach (var h in allHeaders)
                {
                    row.TryGetValue(h, out var val);
                    sb.Append($"<td>{System.Net.WebUtility.HtmlEncode(val?.ToString() ?? "")}</td>");
                }
                sb.Append("</tr>");
            }

            if (pivot.GrandTotal != null)
            {
                sb.Append("<tr class='grand-total'>");
                for (int i = 0; i < allHeaders.Count; i++)
                {
                    if (i == 0)
                    {
                        sb.Append("<td>Grand Total</td>");
                    }
                    else
                    {
                        pivot.GrandTotal.TryGetValue(allHeaders[i], out var val);
                        sb.Append($"<td>{System.Net.WebUtility.HtmlEncode(val?.ToString() ?? "")}</td>");
                    }
                }
                sb.Append("</tr>");
            }

            sb.Append("</tbody></table></body></html>");
            return sb.ToString();
        }

        private static async Task<byte[]> RenderToPdfAsync(string html, CancellationToken ct)
        {
            var browser = await GlobalBrowser.GetAsync().ConfigureAwait(false);
            await using var page = await browser.NewPageAsync().ConfigureAwait(false);

            await page.SetContentAsync(html, new NavigationOptions
            {
                WaitUntil = [WaitUntilNavigation.Networkidle0],
                Timeout = 0
            }).ConfigureAwait(false);

            ct.ThrowIfCancellationRequested();

            return await page.PdfDataAsync(new PdfOptions
            {
                Format = PaperFormat.A4,
                Landscape = true,
                PrintBackground = true,
                MarginOptions = new MarginOptions
                {
                    Top = "40px", Left = "10px", Right = "10px", Bottom = "40px"
                }
            }).ConfigureAwait(false);
        }
    }
}