MoShiro/backend/shared/MoShiro.Protocol/Raw/StreamBuilder.cs

namespace MoShiro.Protocol;

/// <summary>按 <see cref="StreamSpec"/> 逐行构造一个 <see cref="RawStream"/>（用于测试、模拟器和离线工具，不用于节点热路径）。</summary>
public sealed class StreamBuilder
{
    private readonly StreamSpec _spec;
    private readonly List<long>[] _values;
    private readonly List<bool>[] _valid;

    public StreamBuilder(StreamSpec spec)
    {
        _spec = spec;
        _values = new List<long>[spec.Columns.Count];
        _valid = new List<bool>[spec.Columns.Count];
        for (int i = 0; i < _values.Length; i++)
        {
            _values[i] = [];
            _valid[i] = [];
        }
    }

    public int Count { get; private set; }

    /// <summary>添加一行；<c>null</c> 表示缺失值（只允许用于可空列）。</summary>
    public StreamBuilder Add(params long?[] row)
    {
        if (row.Length != _values.Length)
        {
            throw new ArgumentException($"stream {_spec.Name} expects {_values.Length} values, got {row.Length}", nameof(row));
        }

        for (int i = 0; i < row.Length; i++)
        {
            if (row[i] is null && !_spec.Columns[i].Nullable)
            {
                throw new ArgumentException($"column {_spec.Columns[i].Name} is not nullable", nameof(row));
            }

            _values[i].Add(row[i] ?? 0);
            _valid[i].Add(row[i] is not null);
        }

        Count++;
        return this;
    }

    public RawStream Build()
    {
        var columns = new List<RawColumn>(_values.Length);
        for (int i = 0; i < _values.Length; i++)
        {
            ColumnSpec spec = _spec.Columns[i];
            columns.Add(new RawColumn(spec.Name, spec.Type, spec.Enc, spec.Nullable, spec.Role, [.. _values[i]], spec.Nullable ? [.. _valid[i]] : null));
        }

        return new RawStream(_spec.Name, Count, columns);
    }
}