using Comal.Classes;
using Expressive;
using InABox.Core;
using InABox.Database;
using Org.BouncyCastle.Asn1.X509.Qualified;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;

namespace PRS.Shared.Events;

public interface IEventData : ISerializeBinary
{
    IEvent Event { get; }
}

public class EventData<T, TDataModel> : IEventData
    where T : IEvent<TDataModel>
    where TDataModel : IEventDataModel
{
    public T Event { get; set; }

    /// <summary>
    /// A list of triggers for this event. If any of the triggers match, the event runs.
    /// </summary>
    public List<IEventTrigger<T, TDataModel>> Triggers { get; set; }

    public List<IEventAction<T>> Actions { get; set; }

    IEvent IEventData.Event => Event;

    public EventData(T eventData)
    {
        Event = eventData;
        Triggers = new List<IEventTrigger<T, TDataModel>>();
        Actions = new List<IEventAction<T>>();
    }

    public Notification GenerateNotification(TDataModel model) => Event.GenerateNotification(model);

    public void SerializeBinary(CoreBinaryWriter writer)
    {
        Event.SerializeBinary(writer);
        writer.Write(Triggers.Count);
        foreach(var trigger in Triggers)
        {
            EventUtils.SerializeObject(trigger, writer);
        }
        writer.Write(Actions.Count);
        foreach(var action in Actions)
        {
            EventUtils.SerializeObject(action, writer);
        }
    }

    public void DeserializeBinary(CoreBinaryReader reader)
    {
        Event.DeserializeBinary(reader);
        var nTriggers = reader.ReadInt32();
        for(int i = 0; i < nTriggers; ++i)
        {
            var trigger = EventUtils.DeserializeObject<IEventTrigger<T, TDataModel>>(EventUtils.GetTriggerType, reader);
            Triggers.Add(trigger);
        }
        var nActions = reader.ReadInt32();
        for(int i = 0; i < nActions; ++i)
        {
            var action = EventUtils.DeserializeObject<IEventAction<T>>(EventUtils.GetTriggerType, reader);
            Actions.Add(action);
        }
    }
}

public static class EventUtils
{
    #region Serialisation

    public static void SerializeObject(ISerializeBinary obj, CoreBinaryWriter writer)
    {
        writer.Write(obj.GetType().Name);
        foreach(var arg in obj.GetType().GenericTypeArguments)
        {
            writer.Write(CoreUtils.EntityName(arg));
        }
        obj.SerializeBinary(writer);
    }
    public static T DeserializeObject<T>(Func<string, Type> typeSource, CoreBinaryReader reader)
        where T : class, ISerializeBinary
    {
        var eventTypeName = reader.ReadString();
        var objType = typeSource(eventTypeName);

        var typeParams = objType.GetTypeInfo().GenericTypeParameters;
        var typeArgs = new Type[typeParams.Length];
        for(int i = 0; i < typeParams.Length; ++i)
        {
            var entityType = CoreUtils.GetEntity(reader.ReadString());
            typeArgs[i] = entityType;
        }
        if(typeArgs.Length > 0)
        {
            objType = objType.MakeGenericType(typeArgs);
        }
        var obj = (Activator.CreateInstance(objType) as T)!;
        obj.DeserializeBinary(reader);

        return obj;
    }

    public static void Serialize(IEventData data, CoreBinaryWriter writer)
    {
        writer.Write(data.Event.GetType().Name);
        foreach(var arg in data.Event.GetType().GenericTypeArguments)
        {
            writer.Write(CoreUtils.EntityName(arg));
        }
        data.SerializeBinary(writer);
    }

    public static IEventData Deserialize(CoreBinaryReader reader)
    {
        var eventTypeName = reader.ReadString();
        var eventType = EventUtils.GetEventType(eventTypeName);

        var typeParams = eventType.GetTypeInfo().GenericTypeParameters;
        var typeArgs = new Type[typeParams.Length];
        for(int i = 0; i < typeParams.Length; ++i)
        {
            var entityType = CoreUtils.GetEntity(reader.ReadString());
            typeArgs[i] = entityType;
        }
        if(typeArgs.Length > 0)
        {
            eventType = eventType.MakeGenericType(typeArgs);
        }
        var ev = (Activator.CreateInstance(eventType) as IEvent)!;

        var dataModelType = ev.GetType().GetInterfaceDefinition(typeof(IEvent<>))!.GenericTypeArguments[0];

        var eventDataType = typeof(EventData<,>).MakeGenericType(ev.GetType(), dataModelType);

        var eventData = (Activator.CreateInstance(eventDataType, ev) as IEventData)!;

        eventData.DeserializeBinary(reader);

        return eventData;
    }

    #endregion

    #region Event Types

    private static Dictionary<string, Type>? _eventTypes;
    private static Dictionary<string, Type>? _triggerTypes;
    private static Dictionary<string, Type>? _actionTypes;

    private static Dictionary<Type, List<Type>>? _eventTriggerTypes;
    private static Dictionary<Type, List<Type>>? _eventActionTypes;

    [MemberNotNullWhen(true, nameof(_eventTypes), nameof(_triggerTypes), nameof(_actionTypes), nameof(_eventTriggerTypes), nameof(_eventActionTypes))]
    private static bool _loadedTypes { get; set; }

    [MemberNotNull(nameof(_eventTypes), nameof(_triggerTypes), nameof(_actionTypes), nameof(_eventTriggerTypes), nameof(_eventActionTypes))]
    private static void LoadTypes()
    {
        if (_loadedTypes) return;

        _loadedTypes = true;
        _eventTypes = new();
        _triggerTypes = new();
        _actionTypes = new();
        _eventTriggerTypes = new();
        _eventActionTypes = new();
        foreach(var type in CoreUtils.TypeList(x => true))
        {
            if (type.HasInterface(typeof(IEvent<>)))
            {
                if (type.GetConstructor([]) is not null)
                {
                    _eventTypes[type.Name] = type;
                }
            }
            else if (type.GetInterfaceDefinition(typeof(IEventTrigger<,>)) is Type eventTriggerInterface)
            {
                if (type.GetConstructor([]) is not null)
                {
                    _triggerTypes[type.Name] = type;

                    var eventType = eventTriggerInterface.GenericTypeArguments[0];
                    eventType = eventType.IsGenericType ? eventType.GetGenericTypeDefinition() : eventType;
                    _eventTriggerTypes.GetValueOrAdd(eventType).Add(type);
                }
            }
            else if (type.GetInterfaceDefinition(typeof(IEventAction<>)) is Type eventActionInterface)
            {
                if (type.GetConstructor([]) is not null)
                {
                    _actionTypes[type.Name] = type;

                    var eventType = eventActionInterface.GenericTypeArguments[0];
                    eventType = eventType.IsGenericType ? eventType.GetGenericTypeDefinition() : eventType;
                    _eventActionTypes.GetValueOrAdd(eventType).Add(type);
                }
            }
        }
    }

    public static IEnumerable<Type> GetEventTriggerTypes(Type eventType)
    {
        LoadTypes();
        eventType = eventType.IsGenericType ? eventType.GetGenericTypeDefinition() : eventType;
        return _eventTriggerTypes.GetValueOrDefault(eventType) ?? Enumerable.Empty<Type>();
    }

    public static IEnumerable<Type> GetEventActionTypes(Type eventType)
    {
        LoadTypes();
        eventType = eventType.IsGenericType ? eventType.GetGenericTypeDefinition() : eventType;
        return _eventActionTypes.GetValueOrDefault(eventType) ?? Enumerable.Empty<Type>();
    }

    public static Type GetEventType(string type)
    {
        LoadTypes();
        return _eventTypes[type]; // Force exception if not a valid type name.
    }

    public static Type GetTriggerType(string type)
    {
        LoadTypes();
        return _triggerTypes[type]; // Force exception if not a valid type name.
    }

    public static Type GetActionType(string type)
    {
        LoadTypes();
        return _actionTypes[type]; // Force exception if not a valid type name.
    }

    #endregion

    #region Execution

    private static bool Check<T, TDataModel>(EventData<T, TDataModel> ev, TDataModel dataModel)
        where T : IEvent<TDataModel>
        where TDataModel : IEventDataModel
    {
        return ev.Triggers.Any(x => x.Check(dataModel));
    }

    public static void Run<T, TDataModel>(IStore store, Event ev, EventData<T, TDataModel> evData, TDataModel dataModel)
        where T : IEvent<TDataModel>
        where TDataModel : IEventDataModel
    {
        if (!Check(evData, dataModel)) return;

        foreach(var action in evData.Actions)
        {
            IEvent.RunAction(evData.Event, dataModel, action);
        }

        NotifySubscribers(store, ev, evData, dataModel);
    }

    private static void NotifySubscribers<T, TDataModel>(IStore store, Event ev, EventData<T, TDataModel> evData, TDataModel dataModel)
        where T : IEvent<TDataModel>
        where TDataModel : IEventDataModel
    {
        string? description;
        if (ev.NotificationExpression.IsNullOrWhiteSpace())
        {
            description = null;
        }
        else
        {
            var descriptionExpr = new CoreExpression(ev.NotificationExpression, typeof(string));
            if(!descriptionExpr.TryEvaluate<string>(dataModel).Get(out description, out var error))
            {
                CoreUtils.LogException(store.UserID, error, extra: "Error notifying subscribers", store.Logger);
                return;
            }
        }

        var subscribers = store.Provider.Query(
            new Filter<EventSubscriber>(x => x.Event.ID).IsEqualTo(ev.ID),
            Columns.None<EventSubscriber>().Add(x => x.Employee.ID))
            .ToArray<EventSubscriber>();

        var notifications = new List<Notification>();
        foreach(var subscriber in subscribers)
        {
            var notification = evData.GenerateNotification(dataModel);
            notification.Employee.CopyFrom(subscriber.Employee);
            if(description is not null)
            {
                notification.Description = description;
            }
            notifications.Add(notification);
        }
        store.Provider.Save(notifications);
    }

    #endregion
}

#region DataModel Definition

public interface IEventVariable
{
    string Name { get; set; }

    Type Type { get; set; }
}

public class StandardEventVariable : IEventVariable
{
    public string Name { get; set; }

    public Type Type { get; set; }

    public StandardEventVariable(string name, Type type)
    {
        Name = name;
        Type = type;
    }
}

public class ListEventVariable : IEventVariable
{
    public string Name { get; set; }

    public Type Type { get; set; }

    public ListEventVariable(string name, Type type)
    {
        Name = name;
        Type = type;
    }
}

public interface IEventDataModelDefinition
{
    IEnumerable<IEventVariable> GetVariables();

    IEventVariable? GetVariable(string name);
}

#endregion

#region DataModel

public interface IEventDataModel : IVariableProvider
{
    bool TryGetVariable(string name, out object? value);

    bool IVariableProvider.TryGetValue(string variableName, out object? value)
    {
        return TryGetVariable(variableName, out value);
    }

    T RootModel<T>()
        where T : IEventDataModel
    {
        if(this is IChildEventDataModel child)
        {
            return child.Parent.RootModel<T>();
        }
        else if(this is T root)
        {
            return root;
        }
        else
        {
            throw new Exception($"Root model of wrong type; expected {typeof(T).FullName}; got {GetType().FullName}");
        }
    }
}

public interface ITypedEventDataModel : IEventDataModel
{
    public Type EntityType { get; }
}

public interface IChildEventDataModel : IEventDataModel
{
    IEventDataModel Parent { get; }
}

public class ChildEventDataModel : IChildEventDataModel
{
    public IEventDataModel Parent { get; set; }

    public Dictionary<string, object?> Values { get; set; } = new Dictionary<string, object?>();

    public ChildEventDataModel(IEventDataModel parent)
    {
        Parent = parent;
    }

    public bool TryGetVariable(string name, out object? value)
    {
        return Values.TryGetValue(name, out value)
            || Parent.TryGetVariable(name, out value);
    }
}

#endregion

public interface IEvent : ISerializeBinary
{
    IEventDataModelDefinition DataModelDefinition();

    public static void RunAction(IEvent ev, IEventDataModel model, IEventAction action)
    {
        var dataModelDef = ev.DataModelDefinition();

        var values = new List<(string name, object? value)[]>() { Array.Empty<(string, object?)>() };

        var vars = action.ReferencedVariables();
        foreach(var variable in vars)
        {
            var varDef = dataModelDef.GetVariable(variable);
            if(varDef is ListEventVariable)
            {
                if (model.TryGetVariable(varDef.Name, out var list) && list is IEnumerable enumerable)
                {
                    var oldValues = values;
                    values = new List<(string name, object? value)[]>();
                    foreach(var item in enumerable)
                    {
                        foreach(var valueList in oldValues)
                        {
                            values.Add(valueList.Concatenate(new (string name, object? value)[]
                            {
                                (varDef.Name, item)
                            }));
                        }
                    }
                }
                else
                {
                    values.Clear();
                    break;
                }
            }
        }

        if(values.Count > 0 && (values.Count > 1 || values[0].Length > 0))
        {
            var subModel = new ChildEventDataModel(model);
            foreach(var valueSet in values)
            {
                subModel.Values.Clear();
                foreach(var (name, value) in valueSet)
                {
                    subModel.Values[name] = value;
                }
                action.Execute(subModel);
            }
        }
        else
        {
            action.Execute(model);
        }
    }
}

public interface IEvent<TDataModel> : IEvent
{
    Notification GenerateNotification(TDataModel model);
}

public interface IEventTrigger
{
    string GetDescription();
}

public interface IEventTrigger<TEvent, TDataModel> : ISerializeBinary, IEventTrigger
    where TEvent : IEvent<TDataModel>
    where TDataModel : IEventDataModel
{
    bool Check(TDataModel dataModel);
}

public interface IEventAction : ISerializeBinary
{
    IEnumerable<string> ReferencedVariables();

    object? Execute(IEventDataModel dataModel);

    string GetDescription();
}

public interface IEventAction<TEvent> : IEventAction
    where TEvent : IEvent
{
}