TheVVaS-Assets/RPGCoreCommon/DynamicValues/Runtime/MarkerParser.cs

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

namespace RPGCoreCommon.DynamicValues
{
    public class MarkerParser
    {
        private static readonly BindingFlags BindingFlags = BindingFlags.Instance | BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.DeclaredOnly;
        
        public string wholeMarker { get; private set; }
        public string sourceMarker { get; private set; }

        internal Type sourceType;
        private MemberInfo[] _members;
        private object[] _membersParameters;
        private string[] _markers;
        private string[] _parameters;
        
        internal MarkerParser(string wholeMarker)
        {
            this.wholeMarker = wholeMarker;
            var tempMarker = wholeMarker.Trim('{', '}').Split('.'); 
            
            // Source marker should be always present (even if not it will be as empty string)
            sourceMarker = tempMarker[0];
            
            if (tempMarker.Length <= 1) return;

            _markers = new string[tempMarker.Length - 1];
            _parameters = new string[tempMarker.Length - 1];

            for (var i = 1; i < tempMarker.Length; i++)
            {
                var valueMarker = tempMarker[i];
                var tempValueMarker = valueMarker.TrimEnd(']').Split('[');
                _markers[i - 1] = tempValueMarker[0];
                if (tempValueMarker.Length > 1) _parameters[i - 1] = tempValueMarker[1];
            }
        }

        /// <param name="type">Type that will be scanned</param>
        /// <param name="attribute">Attribute with settings for this instance of <see cref="DynamicValue"/></param>
        /// <returns>List of members that can be used as value providers for <see cref="DynamicValue"/>'s formula</returns>
        internal static List<MemberInfo> GetMembersForType(Type type, DynamicValueAttribute attribute)
        {
            return type.GetAllTypes()
                .SelectMany(t => t.GetMembers(BindingFlags))
                .Where(member =>
                {
                    if (attribute.ignoredDeclaringTypes.Contains(member.DeclaringType)) return false;
                    if (member is not MethodInfo and not PropertyInfo and not FieldInfo) return false;
                    var isProvider = member.GetCustomAttribute<DynamicValueProviderAttribute>() != null;
                    return isProvider || (member.IsMemberReadPublic() && member is not MethodInfo);
                }).ToList();
        }

        /// <param name="member">Member to check if it can provide any subtypes besides itself</param>
        /// <param name="isProvider">TRUE whenever given member is provider for <see cref="DynamicValue"/>'s formula</param>
        /// <param name="isDynamic">TRUE if this member has parameter, but not specified with type, only by user's string</param>
        /// <returns>All subtypes that this member can provide. If type can't be specified then it is dynamic.</returns>
        internal static List<Type> GetSubTypesInProvider(MemberInfo member, out bool isProvider, out bool isDynamic)
        {
            isProvider = true;
            isDynamic = false;
            var providerAttribute = member.GetCustomAttribute<DynamicValueProviderAttribute>();
            var methodInfo = member as MethodInfo;
            
            // Only Methods support parameters, but only when attribute is also given
            if (methodInfo == null || providerAttribute == null)
            {
                isProvider = false;
                return new List<Type>();
            }
                
            var parameter = methodInfo.GetParameters().FirstOrDefault();
            var isStringParameter = parameter?.ParameterType == typeof(string);
            var isTypeParameter = parameter?.ParameterType == typeof(Type);
            
            // BAD - invalid parameter definition in method!
            if ((!isStringParameter && !isTypeParameter) || methodInfo.GetParameters().Length != 1)
            {
                Debug.LogError($"<b>{member.Name}</b> has invalid definition!<br>" +
                               $"[{nameof(DynamicValueProviderAttribute)}] Supports only methods with ONE parameter that is <b>string</b> or <b>type</b>!");
                return new List<Type>();
            }
            
            // BAD - return type is required!
            if (methodInfo.ReturnType == typeof(void))
            {
                Debug.LogError($"<b>{member.Name}</b> has invalid definition!<br>" +
                               $"[{nameof(DynamicValueProviderAttribute)}] Supports only methods with defined return type!");
                return new List<Type>();
            }

            // GOOD by string - polymorphism not supported - parameter is dynamic, which means text can have anything
            if (isStringParameter)
            {
                isDynamic = true;
                return new List<Type> { methodInfo.ReturnType };
            }

            // GOOD by type - polymorphism supported
            return UnityEditor.TypeCache.GetTypesDerivedFrom(methodInfo.ReturnType)
                .Where(type => !type.IsAbstract && !type.IsGenericType)
                .ToList();
        }

        /// <returns>Type of value that this marker leads to</returns>
        /// <exception cref="MemberNotFoundException">When member at path could not be found</exception>
        public Type GetValueType()
        {
            return GetMembers().Last().GetMemberValueType();
        }

        public string GetValue(object source)
        {
            // This will also refill _members and _membersParameters
            GetMembers();
            
            var tempObject = source;
            for (var i = 0; i < _members.Length; i++)
            {
                if (_members[i] is FieldInfo or PropertyInfo)
                    tempObject = _members[i].GetMemberValue(tempObject);
                else if (_members[i] is MethodInfo methodInfo)
                    tempObject = methodInfo.Invoke(tempObject, new[] { _membersParameters[i] });
            }

            return tempObject.ToString();
        }
        
        /// <summary>
        /// Returns chain of <see cref="MemberInfo"/> that will be used to get value for this marker.
        /// </summary>
        /// <returns>Array of <see cref="MemberInfo"/> used by this marker.</returns>
        /// <exception cref="MemberNotFoundException">When given path from marker doesn't exist in source.</exception>
        public MemberInfo[] GetMembers()
        {
            if (Application.isPlaying && _members != null) return _members.ToArray();

            _members = new MemberInfo[_markers.Length];
            _membersParameters = new object[_markers.Length];
            
            var tempType = sourceType;
            for (var i = 0; i < _markers.Length; i++)
            {
                var member = tempType.GetAllTypes()
                    .SelectMany(t => t.GetMember(_markers[i], BindingFlags)).FirstOrDefault();
                
                // BAD - whole member doesn't exist
                if (member == null)
                    throw new MemberNotFoundException($"Member [{_markers[i]}] is not found!", tempType);
                
                var attribute = member.GetCustomAttribute<DynamicValueProviderAttribute>();
                
                // BAD - non-public member without attribute
                if (!member.IsMemberReadPublic() && attribute is null)
                    throw new MemberNotFoundException($"Member [{_markers[i]}] found, but its non-public without {nameof(DynamicValueProviderAttribute)}!", tempType);

                // BAD - member is collection, collections aren't supported
                if (typeof(Enumerable).IsAssignableFrom(member.GetMemberValueType()))
                    throw new MemberNotFoundException($"Member [{_markers[i]}] found, but it is collection. Collections aren't supported!", tempType);
                
                tempType = member.GetMemberValueType();
                
                if (member is not MethodInfo methodInfo)
                {
                    // BAD - simple non-collection found, but marker has parameter
                    if (_parameters[i] != null)
                        throw new MemberNotFoundException($"Member [{_markers[i]}] found, but marker has parameter. Only methods can have parameters!", tempType);
                    
                    // GOOD - simple non-collection field or property
                    _members[i] = member;
                    continue;
                }
                
                // BAD - is method, but without required attribute
                if (attribute is null)
                    throw new MemberNotFoundException($"Member [{_markers[i]}] found, but without required {nameof(DynamicValueProviderAttribute)}!", tempType);
                
                var validReturnType = methodInfo.ReturnType != typeof(void);
                var parameter = methodInfo.GetParameters().FirstOrDefault();
                var isStringParameter = parameter?.ParameterType == typeof(string);
                var isTypeParameter = parameter?.ParameterType == typeof(Type);

                // BAD - provider method has invalid definition
                if (!validReturnType || (!isStringParameter && !isTypeParameter))
                    throw new MemberNotFoundException($"Member [{_markers[i]}] found, but definition is invalid! Must contain only one parameter <b>string</b> or <b>Type</b> and also must return something.", tempType);

                _members[i] = methodInfo;
                
                // GOOD - parameter is string, which means it is dynamic, only body of method can use it.
                //        Polymorphism is NOT supported here, return value is always method's return type 
                if (isStringParameter)
                {
                    _membersParameters[i] = _parameters[i];
                    tempType = methodInfo.ReturnType;
                    continue;
                }
                
                // GOOD - parameter is Type, which we can match by its name.
                //        Polymorphism is supported here, dynamic value know type referenced by marker.
                tempType = UnityEditor.TypeCache.GetTypesDerivedFrom(methodInfo.ReturnType)
                    .FirstOrDefault(t => t.Name.Equals(_parameters[i], StringComparison.OrdinalIgnoreCase));
                _membersParameters[i] = tempType;
            }

            return _members.ToArray();
        }

        /// <summary>
        /// <inheritdoc cref="GetMembers()"/>
        /// </summary>
        /// <param name="membersParameters">
        /// <b>[Only when MethodInfo]</b> List of parameters that will be used for specific member.
        /// Can be <b>string</b> or <b>Type</b>.
        /// </param>
        /// <inheritdoc cref="GetMembers()"/>
        public MemberInfo[] GetMembers(out object[] membersParameters)
        {
            var members = GetMembers();
            membersParameters = _membersParameters.ToArray();
            return members;
        }
    }
}