using System.Globalization;
using System.Text;

namespace General_Ledger_Service.Services.CsvDocuments
{
    // Shared row-building/escaping helper for every report's CSV writer (05_LKAS_Report_PDF_Templates.md
    // Section 10) - parallel to Services/PdfDocuments/ReportPageHeader.cs, one small shared piece
    // reused by seven otherwise-independent writer classes, not a base class (CLAUDE.md Rule 2).
    public class CsvBuilder
    {
        private readonly StringBuilder _sb = new();

        public CsvBuilder AddRow(params object?[] values)
        {
            _sb.AppendLine(string.Join(",", values.Select(Escape)));
            return this;
        }

        public byte[] Build()
        {
            // UTF-8 BOM so Excel (the realistic consumer of a downloaded .csv) recognizes the
            // encoding instead of guessing at a locale-default codepage.
            var preamble = Encoding.UTF8.GetPreamble();
            var body = Encoding.UTF8.GetBytes(_sb.ToString());
            var result = new byte[preamble.Length + body.Length];
            preamble.CopyTo(result, 0);
            body.CopyTo(result, preamble.Length);
            return result;
        }

        private static string Escape(object? value)
        {
            var text = value switch
            {
                null => "",
                decimal d => d.ToString(CultureInfo.InvariantCulture),
                DateOnly d => d.ToString("yyyy-MM-dd"),
                _ => value.ToString() ?? ""
            };

            return text.Contains(',') || text.Contains('"') || text.Contains('\n')
                ? $"\"{text.Replace("\"", "\"\"")}\""
                : text;
        }
    }
}