AyCode.Core/AyCode.Core.Tests/GeneratedWriters/TestOrderWriter.cs

using System.Runtime.CompilerServices;
using AyCode.Core.Serializers.Binaries;
using AyCode.Core.Tests.TestModels;

namespace AyCode.Core.Tests.GeneratedWriters;

/// <summary>
/// Hand-written generated binary writer for TestOrder.
/// Demonstrates the pattern that the source generator will produce.
/// 
/// Bypasses the runtime switch/delegate property loop:
/// - Direct obj.Property access instead of Func&lt;&gt;.Invoke()
/// - No switch dispatch per property
/// - No boxing for value types
/// - Small method (~500B native) vs 27KB WriteObject — better ICache
/// 
/// Properties are written in alphabetical order to match the runtime serializer.
/// Complex/Collection properties fall back to the runtime serializer via WriteValue.
/// </summary>
internal sealed class TestOrderWriter : IGeneratedBinaryWriter
{
    internal static readonly TestOrderWriter Instance = new();

    public void WriteProperties<TOutput>(
        object value,
        AcBinarySerializer.BinarySerializationContext<TOutput> context,
        int depth)
        where TOutput : struct, IBinaryOutputBase
    {
        var obj = Unsafe.As<TestOrder>(value);
        var nextDepth = depth;

        // Properties in alphabetical order (matching runtime serializer):

        // AuditMetadata: MetadataInfo? (complex, nullable)
        WriteComplexOrNull(obj.AuditMetadata, context, nextDepth);

        // Category: SharedCategory? (complex, nullable)
        WriteComplexOrNull(obj.Category, context, nextDepth);

        // CreatedAt: DateTime
        context.WriteByte(BinaryTypeCode.DateTime);
        context.WriteDateTimeBits(obj.CreatedAt);

        // Id: int
        WriteInt32OrSkip(obj.Id, context);

        // Items: List<TestOrderItem> (collection)
        WriteComplexOrNull(obj.Items, context, nextDepth);

        // MetadataList: List<MetadataInfo> (collection)
        WriteComplexOrNull(obj.MetadataList, context, nextDepth);

        // NoMergeItems: List<TestOrderItem> (collection)
        WriteComplexOrNull(obj.NoMergeItems, context, nextDepth);

        // OrderMetadata: MetadataInfo? (complex, nullable)
        WriteComplexOrNull(obj.OrderMetadata, context, nextDepth);

        // OrderNumber: string
        AcBinarySerializer.WriteStringGenerated(obj.OrderNumber, context);

        // Owner: SharedUser? (complex, nullable)
        WriteComplexOrNull(obj.Owner, context, nextDepth);

        // PaidDateUtc: DateTime? (nullable)
        var paidDate = obj.PaidDateUtc;
        if (paidDate.HasValue)
        {
            context.WriteByte(BinaryTypeCode.DateTime);
            context.WriteDateTimeBits(paidDate.Value);
        }
        else
        {
            context.WriteByte(BinaryTypeCode.Null);
        }

        // PrimaryTag: SharedTag? (complex, nullable)
        WriteComplexOrNull(obj.PrimaryTag, context, nextDepth);

        // SecondaryTag: SharedTag? (complex, nullable)
        WriteComplexOrNull(obj.SecondaryTag, context, nextDepth);

        // Status: TestStatus (enum)
        context.WriteByte(BinaryTypeCode.Enum);
        var enumVal = (int)obj.Status;
        if (BinaryTypeCode.TryEncodeTinyInt(enumVal, out var tinyEnum))
            context.WriteByte(tinyEnum);
        else
        {
            context.WriteByte(BinaryTypeCode.Int32);
            context.WriteVarInt(enumVal);
        }

        // Tags: List<SharedTag> (collection)
        WriteComplexOrNull(obj.Tags, context, nextDepth);

        // TotalAmount: decimal
        if (obj.TotalAmount == 0m)
            context.WriteByte(BinaryTypeCode.PropertySkip);
        else
        {
            context.WriteByte(BinaryTypeCode.Decimal);
            context.WriteDecimalBits(obj.TotalAmount);
        }
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private static void WriteInt32OrSkip<TOutput>(int value, AcBinarySerializer.BinarySerializationContext<TOutput> context)
        where TOutput : struct, IBinaryOutputBase
    {
        if (value == 0)
        {
            context.WriteByte(BinaryTypeCode.PropertySkip);
            return;
        }

        if (BinaryTypeCode.TryEncodeTinyInt(value, out var tiny))
        {
            context.WriteByte(BinaryTypeCode.Int32);
            context.WriteByte(tiny);
            return;
        }

        context.WriteByte(BinaryTypeCode.Int32);
        context.WriteVarInt(value);
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private static void WriteComplexOrNull<TOutput>(object? value, AcBinarySerializer.BinarySerializationContext<TOutput> context, int depth)
        where TOutput : struct, IBinaryOutputBase
    {
        if (value == null)
        {
            context.WriteByte(BinaryTypeCode.PropertySkip);
            return;
        }

        AcBinarySerializer.WriteValueGenerated(value, value.GetType(), context, depth);
    }
}