TheVVaS-Assets/RPGCoreCommon/Helpers/Runtime/ReflectionExtensions.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using RPGCoreCommon.Helpers.Exceptions;

namespace RPGCoreCommon.Helpers
{
    public static class ReflectionExtensions
    {
        public const BindingFlags DefaultBindingFlags = BindingFlags.Public | BindingFlags.Instance | BindingFlags.IgnoreCase;
        
        /// <summary>Works with any member (type, field, property, method)</summary>
        /// <returns>type of this member's value</returns>
        public static Type GetMemberValueType(this MemberInfo memberInfo)
        {
            return memberInfo switch
            {
                Type type => type,
                FieldInfo fieldInfo => fieldInfo.FieldType,
                PropertyInfo propertyInfo => propertyInfo.PropertyType,
                MethodInfo methodInfo => methodInfo.ReturnType,
                _ => null
            };
        }

        /// <summary>Works with any member (type, field, property, method)</summary>
        /// <param name="memberInfo">this member</param>
        /// <param name="obj">Object to use for this reflection</param>
        /// <returns>member's value</returns>
        public static object GetMemberValue(this MemberInfo memberInfo, object obj)
        {
            return memberInfo switch
            {
                Type => obj,
                FieldInfo fi => fi.GetValue(obj),
                PropertyInfo pi => pi.GetValue(obj, null),
                MethodInfo mi => mi.Invoke(obj, null),
                _ => null
            };
        }

        /// <summary>Works with any member (type, field, property, method)</summary>
        /// <param name="memberInfo">this member</param>
        /// <param name="path">path from current member with dot "." as delimiter</param>
        /// <param name="bindingFlags">Custom binding flags to use</param>
        /// <returns>TYPE of member's value from given path</returns>
        /// <exception cref="MemberNotFoundException">when member is not found</exception>
        public static Type GetMemberValueTypeByPath(this MemberInfo memberInfo, string path, BindingFlags bindingFlags = DefaultBindingFlags)
        {
            var pathParts = path.Split('.');
            var memberType = memberInfo.GetMemberValueType();

            foreach (var pathPart in pathParts)
            {
                var member = memberType.GetMember(pathPart, bindingFlags).FirstOrDefault();
                if (member == null) throw new MemberNotFoundException(path, memberType.GetMemberValueType());
                memberType = member.GetMemberValueType();
            }
            
            return memberType;
        }

        /// <summary>This function supports all members: type, property, field, method</summary>
        /// <param name="memberInfo">Type (or any memberInfo) that will be used to get result value. When not provided memberInfo will be taken from obj type</param>
        /// <param name="obj">Object from which finding will be performed</param>
        /// <param name="path">path from current member with dot "." as delimiter</param>
        /// <param name="bindingFlags">Custom binding flags to use</param>
        /// <returns>member's value from given path</returns>
        /// <exception cref="MemberNotFoundException">When property at given path doesn't exist</exception>
        public static object GetMemberValueByPath(this MemberInfo memberInfo, object obj, string path, BindingFlags bindingFlags = DefaultBindingFlags)
        {
            var pathParts = path.Split('.');
            var memberType = memberInfo.GetMemberValueType();
            var memberObj = obj;

            foreach (var pathPart in pathParts)
            {
                var member = memberType.GetMember(pathPart, bindingFlags).FirstOrDefault();
                if (member == null) throw new MemberNotFoundException(path, memberType.GetMemberValueType());
                memberType = member.GetMemberValueType();
                memberObj = memberType.GetMemberValue(memberObj);
            }

            return memberObj;
        }

        /// <inheritdoc cref="GetMemberValueByPath(MemberInfo, object, string, BindingFlags)"/>
        /// <exception cref="MemberValueWrongTypeException">When result is not desired type</exception>
        /// <typeparam name="T">Result type</typeparam>
        public static T GetMemberValueByPath<T>(this MemberInfo memberInfo, object obj, string path, BindingFlags bindingFlags = DefaultBindingFlags)
        {
            var result = GetMemberValueByPath(memberInfo, obj, path, bindingFlags);
            
            if (result is T typedResult) return typedResult;

            throw new MemberValueWrongTypeException(path, obj.GetType(), typeof(T), result.GetType());
        }

        /// <inheritdoc cref="GetMemberValueByPath(MemberInfo, object, string, BindingFlags)"/>
        public static object GetMemberValueByPath(object obj, string path, BindingFlags bindingFlags = DefaultBindingFlags)
        {
            return GetMemberValueByPath(obj.GetType(), obj, path, bindingFlags);
        }

        /// <summary>
        /// Tries to find specific generic type in currently implementation.
        /// </summary>
        /// <param name="type">This type</param>
        /// <param name="genericTypeDefinition">Generic type to find</param>
        /// <returns>Found generic type with parameters</returns>
        /// <exception cref="Exception">Generic type to find isn't generic.</exception>
        public static Type FindGenericDefinitionType(this Type type, Type genericTypeDefinition)
        {
            if (!genericTypeDefinition.IsGenericTypeDefinition) throw new Exception("The generic argument must be a generic type definition.");
            
            var tempType = type;
            while (tempType != null && tempType != typeof(object))
            {
                if (tempType.IsGenericType && tempType.GetGenericTypeDefinition() == genericTypeDefinition) return tempType;
                tempType = tempType.BaseType;
            }

            return null;
        }

        /// <summary>
        /// Checks if specific generic type in currently implementation has type as argument at index.
        /// </summary>
        /// <param name="type">this type</param>
        /// <param name="genericTypeDefinition">Generic type to find</param>
        /// <param name="argIndex">index to check</param>
        /// <param name="argType">type in generic implementation</param>
        /// <returns></returns>
        public static bool IsArgTypeInGenericDefinitionType(this Type type, Type genericTypeDefinition, int argIndex, Type argType)
        {
            return type.FindGenericDefinitionType(genericTypeDefinition).GenericTypeArguments.ElementAtOrDefault(argIndex) == argType;
        }

        /// <summary>
        /// Checks if this member has public read accessor.
        /// </summary>
        /// <param name="memberInfo">this member</param>
        /// <returns>TRUE if member exists and is public</returns>
        public static bool IsMemberReadPublic(this MemberInfo memberInfo)
        {
            return memberInfo switch
            {
                Type type => type.IsPublic,
                PropertyInfo pi => pi.GetGetMethod() != null,
                MethodInfo mi => mi.IsPublic,
                FieldInfo fi => fi.IsPublic,
                _ => false
            };
        }

        public static IEnumerable<Type> GetAllTypes(this Type forType, bool withObject = false)
        {
            var tempType = forType;
            while (tempType is not null)
            {
                yield return tempType;
                tempType = tempType.BaseType;
                if (!withObject && tempType == typeof(object)) yield break;
            }
        }
    }
}