using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Linq;
using System.Reflection;
using Upsilon.BaseTypes;
using Upsilon.Binder;
using Upsilon.Binder.VariableSymbols;
using Upsilon.StandardLibraries;
using Type = Upsilon.BaseTypes.Type;

namespace Upsilon.BoundTypes
{
    public class UserDataBoundTypeDefinition : BoundTypeDefinition
    {
        public string Name { get; protected set; }
        public Dictionary<string, UserDataBoundProperty> Properties { get; protected set; }

        internal UserDataBoundTypeDefinition(System.Type backingType, string name)
            : base(new TypeContainer(name), backingType)
        {
            Name = backingType.Name;
            ValidInternalTypes = ValidInternalTypes.Concat(GetParentTypes(backingType)).ToArray();
        }

        private static IEnumerable<System.Type> GetParentTypes(System.Type type)
        {
            // is there any base type?
            if (type == null)
            {
                yield break;
            }

            // return all implemented or inherited interfaces
            foreach (var i in type.GetInterfaces())
            {
                yield return i;
            }

            // return all inherited types
            var currentBaseType = type.BaseType;
            while (currentBaseType != null)
            {
                // We don't want the global object type to be returned
                if (currentBaseType == typeof(object))
                    break;
                yield return currentBaseType;
                currentBaseType = currentBaseType.BaseType;
            }
        }

        public UserDataBoundTypeDefinition(string name, Dictionary<string, UserDataBoundProperty> backingType)
            : base(new TypeContainer(name), new System.Type[0])
        {
            Name = name;
            Properties = backingType;
        }

        public static UserDataBoundTypeDefinition Create(System.Type backingType, string name)
        {
            var obj = new UserDataBoundTypeDefinition(backingType, name)
            {
                Properties = new Dictionary<string, UserDataBoundProperty>(),
                Name = name
            };
            const BindingFlags generalBindAttributes = BindingFlags.Public | BindingFlags.Instance | BindingFlags.Static;
            var fields = backingType.GetFields(generalBindAttributes).Select(x => new UserDataBoundProperty()
            {
                Name       = x.Name,
                ActualType =  x.FieldType.Name,
                Type       = x.FieldType.GetScriptType(),
            });
            foreach (var f in fields)
            {
                obj.Properties.Add(f.Name.ToLowerInvariant(), f);
            }

            PropertyInfo[] realProperties;
            if (backingType.IsInterface)
            {
                realProperties = new[]{backingType}
                    .Concat(backingType.GetInterfaces())
                    .SelectMany(x => x.GetProperties(generalBindAttributes)).ToArray();
            }
            else
            {
                realProperties = backingType.GetProperties(generalBindAttributes);
            }
            var properties = realProperties.Select(x => new UserDataBoundProperty()
            {
                Name       = x.Name,
                ActualType =  x.PropertyType.Name,
                Type       = x.PropertyType.GetScriptType(),
            });
            foreach (var f in properties)
            {
                var lowerPropertyName = f.Name.ToLowerInvariant();
                if (!obj.Properties.ContainsKey(lowerPropertyName))
                    obj.Properties.Add(lowerPropertyName, f);
            }
            var methods = new Dictionary<string, UserDataBoundMethod>();
            var backingMethods = backingType.GetMethods(generalBindAttributes);
            foreach (var backingMethod in backingMethods)
            {
                if (backingMethod.IsSpecialName)
                    continue;
                var methodName = backingMethod.Name;
                var passScriptReference = false;
                var attribute = backingMethod.GetCustomAttribute(typeof(ScriptFunctionAttribute));
                if (attribute is ScriptFunctionAttribute sfa )
                {
                    methodName = sfa.Name;
                    passScriptReference = sfa.PassScriptReference;
                }

                var parameters = backingMethod.GetParameters().Select(parameter => new UserDataBoundFunctionParameter()
                {
                    Name       = parameter.Name,
                    ActualType = parameter.ParameterType.Name,
                    Type       = StaticScope.DeriveValidTypes(parameter.ParameterType),
                    IsOptional = parameter.IsOptional
                }).ToArray();
                var option = new UserDataBoundMethodOption(backingMethod.ReturnType.GetScriptType(), parameters, passScriptReference);
                if (methods.TryGetValue(methodName, out var func))
                {
                    func.Options.Add(option);
                }
                else
                {
                    methods.Add(methodName,
                        new UserDataBoundMethod(methodName, new List<UserDataBoundMethodOption>() {option})
                        {
                            Type = Type.Function
                        });
                }

            }
            foreach (var f in methods)
            {
                var cleanedName = f.Value.Name.ToLowerInvariant();
                // TODO: handle this better, considering overloads
                if (obj.Properties.ContainsKey(cleanedName))
                    continue;
                obj.Properties.Add(cleanedName, f.Value);
            }

            return obj;
        }
    }

    public class UserDataBoundEnumDefinition : UserDataBoundTypeDefinition
    {
        public UserDataBoundEnumDefinition(System.Type enumType, string name) : base(enumType, name)
        {
            if (!enumType.IsEnum)
                throw new Exception("Trying to bind an enum with a type that's not an enum");

            Properties = new Dictionary<string, UserDataBoundProperty>();
            var enumValues         = Enum.GetValues(enumType);

            Name = name;

            for (var i=0; i < enumValues.Length; i++)
            {
                var value = enumValues.GetValue(i);

                var valueName = value.ToString().ToLowerInvariant();
                Properties.Add(valueName, new UserDataBoundProperty()
                {
                    Name = valueName,
                    ActualType = enumType.ToString(),
                    Type = new TypeContainer(name)
                });
            }
        }

        public UserDataBoundEnumDefinition(IEnumerable<string> values, string name) : base(name, new Dictionary<string, UserDataBoundProperty>())
        {
            Properties = new Dictionary<string, UserDataBoundProperty>();
            Name = name;

            foreach (var value in values)
            {
                var valueName = value.ToLowerInvariant();
                Properties.Add(valueName, new UserDataBoundProperty()
                {
                    Name = valueName,
                    Type = new TypeContainer(name),
                    ActualType = name
                });
            }
        }
    }

    public class UserDataBoundProperty
    {
        public string Name { get; set; }
        public TypeContainer Type { get; set; }
        public virtual string ActualType { get; set; }
        public string Comment { get; set; }
    }

    public class UserDataBoundFunctionParameter : UserDataBoundProperty
    {
        public bool IsOptional { get; set; }
    }

    public class UserDataBoundMethod: UserDataBoundProperty
    {
        public override string ActualType => "Function";
        public List<UserDataBoundMethodOption> Options;

        public UserDataBoundMethod(string name, List<UserDataBoundMethodOption> options)
        {
            Name = name;
            Options = options;
        }

        public UserDataBoundMethodOption Validate(ImmutableArray<BoundExpression> callingParameters)
        {
            return Options.FirstOrDefault(x => x.ValidateParameters(callingParameters));
        }
    }

    public class UserDataBoundMethodOption
    {
        public UserDataBoundMethodOption(TypeContainer resultType, UserDataBoundFunctionParameter[] parameters,
            bool passScriptReference)
        {
            ResultType = resultType;
            Parameters = parameters;
            PassScriptReference = passScriptReference;
            NonOptionalParameterCount = Parameters.Count(x => !x.IsOptional);
        }

        public TypeContainer                    ResultType { get; }
        public UserDataBoundFunctionParameter[] Parameters { get; }
        public bool PassScriptReference { get; }
        private int NonOptionalParameterCount { get; }

        public bool ValidateParameters(ImmutableArray<BoundExpression> callingParameters)
        {
            var effectiveLength = callingParameters.Length;
            if (PassScriptReference)
                effectiveLength++;

            if (effectiveLength < NonOptionalParameterCount
                || effectiveLength > Parameters.Length)
            {
                return false;
            }

            var callingIndexOffset = 0;
            for (var i = 0; i < callingParameters.Length; i++)
            {
                var functionParameter = Parameters[i];
                if (i == 0 && PassScriptReference)
                {
                    callingIndexOffset++;
                    continue;
                }

                var callingParameter  = callingParameters[i + callingIndexOffset];
                if (callingParameter.ValueType == Type.Unknown || callingParameter.ValueType == Type.Nil ||
                    functionParameter.Type == Type.Unknown)
                    continue;

                if (!functionParameter.Type.Type.HasFlag(callingParameter.ValueType))
                {
                    return false;
                }

                if (functionParameter.Type.Type.HasFlag(Type.UserData))
                {
                    var variable = Binder.Binder.ResolveVariable(callingParameter, null) as UserDataVariableSymbol;
                    var parent =
                        (UserDataBoundTypeDefinition) variable?.BoundTypeDefinition;
                    if (variable != null && variable.TypeContainer == Type.UserData)
                    {
                        if (parent.ValidInternalTypes.Length != 0)
                        {
                            if (functionParameter.ActualType != null)
                            {
                                if (!parent.ValidInternalTypes.Any(x =>
                                    string.Equals(x.Name, functionParameter.ActualType)))
                                {
                                    return false;
                                }
                            }
                            else if (!string.Equals(parent.Name, functionParameter.ActualType, StringComparison.InvariantCultureIgnoreCase))
                            {
                                return false;
                            }
                        }
                    }
                }
            }

            return true;
        }

    }

}