using Flee.InternalTypes;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Reflection;

namespace Flee.PublicTypes
{
    /// <summary>
    ///
    /// </summary>
    public sealed class VariableCollection : IDictionary<string, object>
    {
        private IDictionary<string, IVariable> _myVariables;
        private readonly ExpressionContext _myContext;

        public event EventHandler<ResolveVariableTypeEventArgs> ResolveVariableType;

        public event EventHandler<ResolveVariableValueEventArgs> ResolveVariableValue;

        public event EventHandler<ResolveFunctionEventArgs> ResolveFunction;

        public event EventHandler<InvokeFunctionEventArgs> InvokeFunction;

        internal VariableCollection(ExpressionContext context)
        {
            _myContext = context;
            this.CreateDictionary();
            this.HookOptions();
        }

        #region "Methods - Non Public"

        private void HookOptions()
        {
            _myContext.Options.CaseSensitiveChanged += OnOptionsCaseSensitiveChanged;
        }

        private void CreateDictionary()
        {
            _myVariables = new Dictionary<string, IVariable>(_myContext.Options.StringComparer);
        }

        private void OnOptionsCaseSensitiveChanged(object sender, EventArgs e)
        {
            this.CreateDictionary();
        }

        internal void Copy(VariableCollection dest)
        {
            dest.CreateDictionary();
            dest.HookOptions();

            foreach (KeyValuePair<string, IVariable> pair in _myVariables)
            {
                IVariable copyVariable = pair.Value.Clone();
                dest._myVariables.Add(pair.Key, copyVariable);
            }
        }

        internal void DefineVariableInternal(string name, Type variableType, object variableValue)
        {
            Utility.AssertNotNull(variableType, "variableType");

            if (_myVariables.ContainsKey(name) == true)
            {
                string msg = Utility.GetGeneralErrorMessage("VariableWithNameAlreadyDefined", name);
                throw new ArgumentException(msg);
            }

            IVariable v = this.CreateVariable(variableType, variableValue);
            _myVariables.Add(name, v);
        }

        internal Type GetVariableTypeInternal(string name)
        {
            IVariable value = null;
            bool success = _myVariables.TryGetValue(name, out value);

            if (success == true)
            {
                return value.VariableType;
            }

            ResolveVariableTypeEventArgs args = new ResolveVariableTypeEventArgs(name);
            ResolveVariableType?.Invoke(this, args);

            return args.VariableType;
        }

        private IVariable GetVariable(string name, bool throwOnNotFound)
        {
            IVariable value = null;
            bool success = _myVariables.TryGetValue(name, out value);

            if (success == false & throwOnNotFound == true)
            {
                string msg = Utility.GetGeneralErrorMessage("UndefinedVariable", name);
                throw new ArgumentException(msg);
            }
            else
            {
                return value;
            }
        }

        private IVariable CreateVariable(Type variableValueType, object variableValue)
        {
            Type variableType = default(Type);

            // Is the variable value an expression?
            IExpression expression = variableValue as IExpression;
            ExpressionOptions options = null;

            if (expression != null)
            {
                options = expression.Context.Options;
                // Get its result type
                variableValueType = options.ResultType;

                // Create a variable that wraps the expression

                if (options.IsGeneric == false)
                {
                    variableType = typeof(DynamicExpressionVariable<>);
                }
                else
                {
                    variableType = typeof(GenericExpressionVariable<>);
                }
            }
            else
            {
                // Create a variable for a regular value
                _myContext.AssertTypeIsAccessible(variableValueType);
                variableType = typeof(GenericVariable<>);
            }

            // Create the generic variable instance
            variableType = variableType.MakeGenericType(variableValueType);
            IVariable v = (IVariable)Activator.CreateInstance(variableType);

            return v;
        }

        internal Type ResolveOnDemandFunction(string name, Type[] argumentTypes)
        {
            ResolveFunctionEventArgs args = new ResolveFunctionEventArgs(name, argumentTypes);
            ResolveFunction?.Invoke(this, args);
            return args.ReturnType;
        }

        private static T ReturnGenericValue<T>(object value)
        {
            if (value == null)
            {
                return default(T);
            }
            else
            {
                return (T)value;
            }
        }

        private static void ValidateSetValueType(Type requiredType, object value)
        {
            if (value == null)
            {
                // Can always assign null value
                return;
            }

            Type valueType = value.GetType();

            if (requiredType.IsAssignableFrom(valueType) == false)
            {
                string msg = Utility.GetGeneralErrorMessage("VariableValueNotAssignableToType", valueType.Name, requiredType.Name);
                throw new ArgumentException(msg);
            }
        }

        internal static MethodInfo GetVariableLoadMethod(Type variableType)
        {
            MethodInfo mi = typeof(VariableCollection).GetMethod("GetVariableValueInternal", BindingFlags.Public | BindingFlags.Instance);
            mi = mi.MakeGenericMethod(variableType);
            return mi;
        }

        internal static MethodInfo GetFunctionInvokeMethod(Type returnType)
        {
            MethodInfo mi = typeof(VariableCollection).GetMethod("GetFunctionResultInternal", BindingFlags.Public | BindingFlags.Instance);
            mi = mi.MakeGenericMethod(returnType);
            return mi;
        }

        internal static MethodInfo GetVirtualPropertyLoadMethod(Type returnType)
        {
            MethodInfo mi = typeof(VariableCollection).GetMethod("GetVirtualPropertyValueInternal", BindingFlags.Public | BindingFlags.Instance);
            mi = mi.MakeGenericMethod(returnType);
            return mi;
        }

        private Dictionary<string, object> GetNameValueDictionary()
        {
            Dictionary<string, object> dict = new Dictionary<string, object>();

            foreach (KeyValuePair<string, IVariable> pair in _myVariables)
            {
                dict.Add(pair.Key, pair.Value.ValueAsObject);
            }

            return dict;
        }

        #endregion "Methods - Non Public"

        #region "Methods - Public"

        public Type GetVariableType(string name)
        {
            IVariable v = this.GetVariable(name, true);
            return v.VariableType;
        }

        public void DefineVariable(string name, Type variableType)
        {
            this.DefineVariableInternal(name, variableType, null);
        }

        public T GetVariableValueInternal<T>(string name)
        {
            if (_myVariables.TryGetValue(name, out IVariable variable))
            {
                if (variable is IGenericVariable<T> generic)
                {
                    return (T)generic.GetValue();
                }
            }

            GenericVariable<T> result = new GenericVariable<T>();
            GenericVariable<T> vTemp = new GenericVariable<T>();
            ResolveVariableValueEventArgs args = new ResolveVariableValueEventArgs(name, typeof(T));
            ResolveVariableValue?.Invoke(this, args);

            ValidateSetValueType(typeof(T), args.VariableValue);
            vTemp.ValueAsObject = args.VariableValue;
            result = vTemp;
            return (T)result.GetValue();
        }

        public T GetVirtualPropertyValueInternal<T>(string name, object component)
        {
            PropertyDescriptorCollection coll = TypeDescriptor.GetProperties(component);
            PropertyDescriptor pd = coll.Find(name, true);

            object value = pd.GetValue(component);
            ValidateSetValueType(typeof(T), value);
            return ReturnGenericValue<T>(value);
        }

        public T GetFunctionResultInternal<T>(string name, object[] arguments)
        {
            InvokeFunctionEventArgs args = new InvokeFunctionEventArgs(name, arguments);
            if (InvokeFunction != null)
            {
                InvokeFunction(this, args);
            }

            object result = args.Result;
            ValidateSetValueType(typeof(T), result);

            return ReturnGenericValue<T>(result);
        }

        #endregion "Methods - Public"

        #region "IDictionary Implementation"

        private void Add1(System.Collections.Generic.KeyValuePair<string, object> item)
        {
            this.Add(item.Key, item.Value);
        }

        void System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<string, object>>.Add(System.Collections.Generic.KeyValuePair<string, object> item)
        {
            Add1(item);
        }

        public void Clear()
        {
            _myVariables.Clear();
        }

        private bool Contains1(System.Collections.Generic.KeyValuePair<string, object> item)
        {
            return this.ContainsKey(item.Key);
        }

        bool System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<string, object>>.Contains(System.Collections.Generic.KeyValuePair<string, object> item)
        {
            return Contains1(item);
        }

        private void CopyTo(System.Collections.Generic.KeyValuePair<string, object>[] array, int arrayIndex)
        {
            Dictionary<string, object> dict = this.GetNameValueDictionary();
            ICollection<KeyValuePair<string, object>> coll = dict;
            coll.CopyTo(array, arrayIndex);
        }

        private bool Remove1(System.Collections.Generic.KeyValuePair<string, object> item)
        {
            return this.Remove(item.Key);
        }

        bool System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<string, object>>.Remove(System.Collections.Generic.KeyValuePair<string, object> item)
        {
            return Remove1(item);
        }

        public void Add(string name, object value)
        {
            Utility.AssertNotNull(value, "value");
            this.DefineVariableInternal(name, value.GetType(), value);
            this[name] = value;
        }

        public bool ContainsKey(string name)
        {
            return _myVariables.ContainsKey(name);
        }

        public bool Remove(string name)
        {
            return _myVariables.Remove(name);
        }

        public bool TryGetValue(string key, out object value)
        {
            IVariable v = this.GetVariable(key, false);
            value = v?.ValueAsObject;
            return v != null;
        }

        public System.Collections.Generic.IEnumerator<System.Collections.Generic.KeyValuePair<string, object>> GetEnumerator()
        {
            Dictionary<string, object> dict = this.GetNameValueDictionary();
            return dict.GetEnumerator();
        }

        private System.Collections.IEnumerator GetEnumerator1()
        {
            return this.GetEnumerator();
        }

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return GetEnumerator1();
        }

        public int Count => _myVariables.Count;

        public bool IsReadOnly => false;

        public object this[string name]
        {
            get
            {
                IVariable v = this.GetVariable(name, true);
                return v.ValueAsObject;
            }
            set
            {
                IVariable v = null;

                if (_myVariables.TryGetValue(name, out v) == true)
                {
                    v.ValueAsObject = value;
                }
                else
                {
                    this.Add(name, value);
                }
            }
        }

        public System.Collections.Generic.ICollection<string> Keys => _myVariables.Keys;

        public System.Collections.Generic.ICollection<object> Values
        {
            get
            {
                Dictionary<string, object> dict = this.GetNameValueDictionary();
                return dict.Values;
            }
        }

        void ICollection<KeyValuePair<string, object>>.CopyTo(KeyValuePair<string, object>[] array, int arrayIndex)
        {
            CopyTo(array, arrayIndex);
        }

        #endregion "IDictionary Implementation"
    }
}