CBDD/src/CBDD.SourceGenerators/Helpers/SyntaxHelper.cs

using System.Collections.Generic;
using System.Linq;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Syntax;

namespace ZB.MOM.WW.CBDD.SourceGenerators.Helpers;

public static class SyntaxHelper
{
    /// <summary>
    ///     Determines whether a symbol inherits from a base type with the specified name.
    /// </summary>
    /// <param name="symbol">The symbol to inspect.</param>
    /// <param name="baseTypeName">The base type name to match.</param>
    /// <returns><see langword="true" /> if the symbol inherits from the base type; otherwise, <see langword="false" />.</returns>
    public static bool InheritsFrom(INamedTypeSymbol symbol, string baseTypeName)
    {
        var current = symbol.BaseType;
        while (current != null)
        {
            if (current.Name == baseTypeName)
                return true;
            current = current.BaseType;
        }

        return false;
    }

    /// <summary>
    ///     Finds method invocations with a matching method name under the provided syntax node.
    /// </summary>
    /// <param name="node">The root syntax node to search.</param>
    /// <param name="methodName">The method name to match.</param>
    /// <returns>A list of matching invocation expressions.</returns>
    public static List<InvocationExpressionSyntax> FindMethodInvocations(SyntaxNode node, string methodName)
    {
        return node.DescendantNodes()
            .OfType<InvocationExpressionSyntax>()
            .Where(invocation =>
            {
                if (invocation.Expression is MemberAccessExpressionSyntax memberAccess)
                    return memberAccess.Name.Identifier.Text == methodName;
                return false;
            })
            .ToList();
    }

    /// <summary>
    ///     Gets the first generic type argument from an invocation, if present.
    /// </summary>
    /// <param name="invocation">The invocation to inspect.</param>
    /// <returns>The generic type argument text, or <see langword="null" /> when not available.</returns>
    public static string? GetGenericTypeArgument(InvocationExpressionSyntax invocation)
    {
        if (invocation.Expression is MemberAccessExpressionSyntax memberAccess &&
            memberAccess.Name is GenericNameSyntax genericName &&
            genericName.TypeArgumentList.Arguments.Count > 0)
            return genericName.TypeArgumentList.Arguments[0].ToString();
        return null;
    }

    /// <summary>
    ///     Extracts a property name from an expression.
    /// </summary>
    /// <param name="expression">The expression to analyze.</param>
    /// <returns>The property name when resolved; otherwise, <see langword="null" />.</returns>
    public static string? GetPropertyName(ExpressionSyntax? expression)
    {
        if (expression == null) return null;
        if (expression is LambdaExpressionSyntax lambda) return GetPropertyName(lambda.Body as ExpressionSyntax);
        if (expression is MemberAccessExpressionSyntax memberAccess) return memberAccess.Name.Identifier.Text;
        if (expression is PrefixUnaryExpressionSyntax prefixUnary &&
            prefixUnary.Operand is MemberAccessExpressionSyntax prefixMember) return prefixMember.Name.Identifier.Text;
        if (expression is PostfixUnaryExpressionSyntax postfixUnary &&
            postfixUnary.Operand is MemberAccessExpressionSyntax postfixMember)
            return postfixMember.Name.Identifier.Text;
        return null;
    }

    /// <summary>
    ///     Gets the fully-qualified type name without the global prefix.
    /// </summary>
    /// <param name="symbol">The symbol to format.</param>
    /// <returns>The formatted full type name.</returns>
    public static string GetFullName(INamedTypeSymbol symbol)
    {
        return symbol.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)
            .Replace("global::", "");
    }

    /// <summary>
    ///     Gets a display name for a type symbol.
    /// </summary>
    /// <param name="type">The type symbol to format.</param>
    /// <returns>The display name.</returns>
    public static string GetTypeName(ITypeSymbol type)
    {
        if (type is INamedTypeSymbol namedType &&
            namedType.OriginalDefinition.SpecialType == SpecialType.System_Nullable_T)
        {
            var underlyingType = namedType.TypeArguments[0];
            return GetTypeName(underlyingType) + "?";
        }

        if (type is IArrayTypeSymbol arrayType) return GetTypeName(arrayType.ElementType) + "[]";

        if (type is INamedTypeSymbol nt && nt.IsTupleType) return type.ToDisplayString();

        return type.ToDisplayString();
    }

    /// <summary>
    ///     Determines whether a type is nullable.
    /// </summary>
    /// <param name="type">The type to evaluate.</param>
    /// <returns><see langword="true" /> if the type is nullable; otherwise, <see langword="false" />.</returns>
    public static bool IsNullableType(ITypeSymbol type)
    {
        if (type is INamedTypeSymbol namedType &&
            namedType.OriginalDefinition.SpecialType == SpecialType.System_Nullable_T)
            return true;
        return type.NullableAnnotation == NullableAnnotation.Annotated;
    }

    /// <summary>
    ///     Determines whether a type is a collection and returns its item type when available.
    /// </summary>
    /// <param name="type">The type to evaluate.</param>
    /// <param name="itemType">When this method returns, contains the collection item type if the type is a collection.</param>
    /// <returns><see langword="true" /> if the type is a collection; otherwise, <see langword="false" />.</returns>
    public static bool IsCollectionType(ITypeSymbol type, out ITypeSymbol? itemType)
    {
        itemType = null;

        // Exclude string (it's IEnumerable<char> but not a collection for our purposes)
        if (type.SpecialType == SpecialType.System_String)
            return false;

        // Handle arrays
        if (type is IArrayTypeSymbol arrayType)
        {
            itemType = arrayType.ElementType;
            return true;
        }

        // Check if the type itself is IEnumerable<T>
        if (type is INamedTypeSymbol namedType && namedType.IsGenericType)
        {
            string typeDefName = namedType.OriginalDefinition.ToDisplayString();
            if (typeDefName == "System.Collections.Generic.IEnumerable<T>" && namedType.TypeArguments.Length == 1)
            {
                itemType = namedType.TypeArguments[0];
                return true;
            }
        }

        // Check if the type implements IEnumerable<T> by walking all interfaces
        var enumerableInterface = type.AllInterfaces
            .FirstOrDefault(i => i.IsGenericType &&
                                 i.OriginalDefinition.ToDisplayString() == "System.Collections.Generic.IEnumerable<T>");

        if (enumerableInterface != null && enumerableInterface.TypeArguments.Length == 1)
        {
            itemType = enumerableInterface.TypeArguments[0];
            return true;
        }

        return false;
    }

    /// <summary>
    ///     Determines whether a type should be treated as a primitive value.
    /// </summary>
    /// <param name="type">The type to evaluate.</param>
    /// <returns><see langword="true" /> if the type is primitive-like; otherwise, <see langword="false" />.</returns>
    public static bool IsPrimitiveType(ITypeSymbol type)
    {
        if (type is INamedTypeSymbol namedType &&
            namedType.OriginalDefinition.SpecialType == SpecialType.System_Nullable_T)
            type = namedType.TypeArguments[0];

        if (type.SpecialType != SpecialType.None && type.SpecialType != SpecialType.System_Object)
            return true;

        string typeName = type.Name;
        if (typeName == "Guid" || typeName == "DateTime" || typeName == "DateTimeOffset" ||
            typeName == "TimeSpan" || typeName == "DateOnly" || typeName == "TimeOnly" ||
            typeName == "Decimal" || typeName == "ObjectId")
            return true;

        if (type.TypeKind == TypeKind.Enum)
            return true;

        if (type is INamedTypeSymbol nt && nt.IsTupleType)
            return true;

        return false;
    }

    /// <summary>
    ///     Determines whether a type should be treated as a nested object.
    /// </summary>
    /// <param name="type">The type to evaluate.</param>
    /// <returns><see langword="true" /> if the type is a nested object; otherwise, <see langword="false" />.</returns>
    public static bool IsNestedObjectType(ITypeSymbol type)
    {
        if (IsPrimitiveType(type)) return false;
        if (type.SpecialType == SpecialType.System_String) return false;
        if (IsCollectionType(type, out _)) return false;
        if (type.SpecialType == SpecialType.System_Object) return false;
        if (type is INamedTypeSymbol nt && nt.IsTupleType) return false;

        return type.TypeKind == TypeKind.Class || type.TypeKind == TypeKind.Struct;
    }

    /// <summary>
    ///     Determines whether a property has an associated backing field.
    /// </summary>
    /// <param name="property">The property to inspect.</param>
    /// <returns><see langword="true" /> if a backing field is found; otherwise, <see langword="false" />.</returns>
    public static bool HasBackingField(IPropertySymbol property)
    {
        // Auto-properties have compiler-generated backing fields
        // Check if there's a field with the pattern <PropertyName>k__BackingField
        return property.ContainingType.GetMembers()
            .OfType<IFieldSymbol>()
            .Any(f => f.AssociatedSymbol?.Equals(property, SymbolEqualityComparer.Default) == true);
    }
}