sharplib/ser/CodeGen.cs

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//
//  S H A R P L I B
//
/// // (c) 2003..2025

using System;
using System.IO;
using System.Xml;
using System.Collections;
using System.Collections.Generic;
using System.Reflection;
using System.Linq;
using System.Collections.Immutable;
using System.Collections.Concurrent;
using System.Collections.Immutable;

namespace ser;

public record CodeGenConfig : imm.Recorded<CodeGenConfig>
{
    // Whitelists (if needed, otherwise rely on attributes/defaults)
    public ImmutableDictionary<string, ImmutableList<string>> WLProps { get; init; } = ImmutableDictionary<string, ImmutableList<string>>.Empty;
    public ImmutableDictionary<string, ImmutableList<string>> WLFields { get; init; } = ImmutableDictionary<string, ImmutableList<string>>.Empty;

    // Default member types to process
    public lib.Types TypesDefault { get; init; } = lib.Types.Fields | lib.Types.Props;

    // How to handle backing fields (might be less relevant for code gen)
    public BackingFieldNaming Naming { get; init; } = BackingFieldNaming.Regular;

    public static CodeGenConfig Default { get; } = new CodeGenConfig();
}

public record GenMemberMeta(
		MemberInfo Info,
		Type Type,
		string Name, // Name for code generation (usually original)
		bool IsPrimitive,
		bool IsCollection,
		Type? CollectionElementType,
		bool HasDo,
		bool HasDont
);

public record TypeStructureInfo(
    Type Type,
    List<GenMemberMeta> Members,
    bool IsValueType,
    bool IsCollection
);

public class TypeStructureAnalyzer
{
    private readonly ConcurrentDictionary<Type, TypeStructureInfo> _cache = new();
    private readonly CodeGenConfig _cfg;

    public TypeStructureAnalyzer(CodeGenConfig cfg) => _cfg = cfg;

    public TypeStructureInfo Get(Type type) => _cache.GetOrAdd(type, BuildTypeInfo);

    private TypeStructureInfo BuildTypeInfo(Type type)
    {
        var members = new List<GenMemberMeta>();
        var typesTodo = type.GetCustomAttribute<lib.Ser>(true)?.Types ?? _cfg.TypesDefault;
        bool doFields = typesTodo.HasFlag(lib.Types.Fields);
        bool doProps = typesTodo.HasFlag(lib.Types.Props);

        // Track processed names to avoid duplicates (e.g., field + prop)
        var processedNames = new HashSet<string>();

        // Process Properties First (often preferred interface)
        if (doProps)
        {
            foreach (var pi in refl.GetAllProperties(type))
            {
                if (ProcessMember(pi, false, false, new HashSet<string>(), false, members))
                {
                    processedNames.Add(pi.Name);
                }
            }
        }

        // Process Fields, avoiding those already covered by properties
        if (doFields)
        {
            foreach (var fi in refl.GetAllFields(type))
            {
                var (isBacking, propName) = IsBackingField(fi);
                string nameToTest = isBacking ? propName : fi.Name;

                if (!processedNames.Contains(nameToTest))
                {
                     if(ProcessMember(fi, false, false, new HashSet<string>(), false, members))
                     {
                         processedNames.Add(nameToTest);
                     }
                }
            }
        }

        return new TypeStructureInfo(
            type,
            members,
            type.IsValueType,
            typeof(IEnumerable).IsAssignableFrom(type) && type != typeof(string)
        );
    }

    private bool ProcessMember(MemberInfo mi, bool filter, bool doImpls, HashSet<string> whitelist, bool isImm, List<GenMemberMeta> members)
    {
        var (hasDo, hasDont, propName) = GetMemberAttributes(mi, out var actualMiForAtts);

        if (hasDont) return false;
        if (mi.GetCustomAttribute<NonSerializedAttribute>(true) != null) return false;
        if (mi.Name.Contains("k__BackingField") && !propName.Any()) return false; // Skip if backing but no prop found

        string name = string.IsNullOrEmpty(propName) ? mi.Name : propName;

        // Add filtering logic if needed (based on whitelist, etc.)

        var type = (mi is FieldInfo fi) ? fi.FieldType : ((PropertyInfo)mi).PropertyType;
        bool isCollection = typeof(IEnumerable).IsAssignableFrom(type) && type != typeof(string);
        Type? elementType = isCollection ? GetElementType(type) : null;
        bool isPrimitive = Type.GetTypeCode(type) != TypeCode.Object && !isCollection;

        members.Add(new GenMemberMeta(
            mi, type, name, isPrimitive, isCollection, elementType, hasDo, hasDont
        ));
        return true;
    }

    private (bool, string) IsBackingField(FieldInfo fi)
    {
         if (fi.Name.StartsWith("<") && fi.Name.EndsWith("BackingField"))
         {
            var gtIndex = fi.Name.IndexOf('>');
            if (gtIndex > 1) {
                return (true, fi.Name.Substring(1, gtIndex - 1));
            }
         }
         return (false, "");
    }

    private (bool hasDo, bool hasDont, string propName) GetMemberAttributes(MemberInfo mi, out MemberInfo actualMi)
    {
        actualMi = mi;
        string propName = "";
        if (mi is FieldInfo fi && IsBackingField(fi).Item1)
        {
            propName = IsBackingField(fi).Item2;
            var propInfo = mi.DeclaringType?.GetProperty(propName, BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
            if (propInfo != null) actualMi = propInfo;
        } else if (mi is PropertyInfo) {
             propName = mi.Name;
        }

        return (
            actualMi.GetCustomAttribute<lib.Do>() != null,
            actualMi.GetCustomAttribute<lib.Dont>() != null,
            propName
        );
    }

    private Type GetElementType(Type collectionType)
    {
        if (collectionType.IsArray) return collectionType.GetElementType()!;
        if (collectionType.IsGenericType) return collectionType.GetGenericArguments().Last(); // Usually last (e.g., List<T>, Dict<K,V>)
        return typeof(object); // Fallback
    }

    // Add GetFilters and FilterField if needed, or simplify as above
}