satellite-provider/SatelliteProvider.Common/Utils/TileCsvWriter.cs

namespace SatelliteProvider.Common.Utils;

// AZ-368 / C15: shared CSV writer for tile rows.
// Both region and route pipelines previously emitted the same CSV (header
// "latitude,longitude,file_path", same OrderByDescending(Latitude).ThenBy(Longitude)
// ordering, same F6 numeric format). Two near-identical writers are now one.
//
// The class is instance-based (no static, per coderule.mdc — file I/O has side
// effects). It carries no dependencies, so callers can `new TileCsvWriter()`
// at use sites without DI bloat.
public sealed class TileCsvWriter
{
    public const string Header = "latitude,longitude,file_path";

    public async Task WriteAsync(string filePath, IEnumerable<TileCsvRow> rows, CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(filePath);
        ArgumentNullException.ThrowIfNull(rows);

        var ordered = rows.OrderByDescending(r => r.Latitude).ThenBy(r => r.Longitude).ToList();

        await using var writer = new StreamWriter(filePath);
        await writer.WriteLineAsync(Header.AsMemory(), cancellationToken);

        foreach (var row in ordered)
        {
            cancellationToken.ThrowIfCancellationRequested();
            var line = $"{row.Latitude:F6},{row.Longitude:F6},{row.FilePath}";
            await writer.WriteLineAsync(line.AsMemory(), cancellationToken);
        }
    }
}

public sealed record TileCsvRow(double Latitude, double Longitude, string FilePath);