using Comal.Classes;
using Expressive;
using InABox.Core;
using InABox.Database;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;
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
{
    IEvent Event { get; }

    IEnumerable<string> ReferencedVariables { 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 IEnumerable<string> ReferencedVariables =>
        Triggers.SelectMany(x => x.ReferencedVariables)
        .Concat(Actions.SelectMany(x => x.ReferencedVariables))
        .Distinct();

    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 static class EventUtils
{
    #region Serialisation

    private class WritablePropertiesOnlyResolver : DefaultContractResolver
    {
        protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
        {
            IList<JsonProperty> props = base.CreateProperties(type, memberSerialization);
            return props.Where(p => p.Writable).ToList();
        }
    }

    private static JsonSerializerSettings SerializationSettings()
    {
        var settings = Serialization.CreateSerializerSettings();
        settings.TypeNameHandling = TypeNameHandling.Auto;
        settings.ContractResolver = new WritablePropertiesOnlyResolver();
        return settings;
    }

    public static string Serialize(IEventData data)
    {
        return JsonConvert.SerializeObject(data, typeof(IEventData), SerializationSettings());
    }

    public static IEventData Deserialize(string json)
    {
        return JsonConvert.DeserializeObject<IEventData>(json, SerializationSettings())!;
    }

    #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 Event Cache

    private static bool _loadedCache = false;
    private static Dictionary<EventType, Dictionary<Type, List<(Event Event, IEventData EventData)>>> _entityEvents = new();
    private static Dictionary<Guid, (EventType, Type)> _entityEventMap = new();

    public static void ReloadCache(IProvider provider)
    {
        _loadedCache = true;
        _entityEvents.Clear();
        _entityEventMap.Clear();
        var events = provider.Query(
            new Filter<Event>(x => x.Enabled).IsEqualTo(true),
            Columns.None<Event>().Add(x => x.ID).Add(x => x.Code).Add(x => x.EventType).Add(x => x.Data))
            .ToObjects<Event>();
        foreach(var ev in events)
        {
            AddEvent(provider, ev);
        }
    }

    private static void AddEntityEvent(Event ev)
    {
        if(ev.Data is not null && ev.Data.Length != 0)
        {
            var data = Deserialize(ev.Data);

            var entityType = data.Event.GetType().GenericTypeArguments[0];
            var list = _entityEvents.GetValueOrAdd(ev.EventType).GetValueOrAdd(entityType);
            list.RemoveAll(x => x.Event.ID == ev.ID);
            
            list.Add((ev, data));
            _entityEventMap[ev.ID] = (ev.EventType, entityType);
        }
    }
    private static void RemoveEntityEvent(Event ev)
    {
        if(_entityEventMap.TryGetValue(ev.ID, out var item))
        {
            if(_entityEvents.TryGetValue(item.Item1, out var eventTypeEvents))
            {
                if(eventTypeEvents.TryGetValue(item.Item2, out var entityEvents))
                {
                    entityEvents.RemoveAll(x => x.Event.ID == ev.ID);
                    if(entityEvents.Count == 0)
                    {
                        eventTypeEvents.Remove(item.Item2);
                    }
                }
                if(eventTypeEvents.Count == 0)
                {
                    _entityEvents.Remove(item.Item1);
                }
            }
            _entityEventMap.Remove(ev.ID);
        }
    }

    public static void RemoveEvent(IProvider provider, Event ev)
    {
        if (!_loadedCache) ReloadCache(provider);

        switch (ev.EventType)
        {
            case EventType.AfterSave:
                RemoveEntityEvent(ev);
                break;
        }
    }
    public static void AddEvent(IProvider provider, Event ev)
    {
        if (!_loadedCache) ReloadCache(provider);

        switch (ev.EventType)
        {
            case EventType.AfterSave:
                AddEntityEvent(ev);
                break;
        }
    }

    #endregion

    #region Public Event Running Interface

    public static void AfterSave<T>(IStore store, T entity)
        where T : Entity, new()
    {
        if (!_loadedCache) ReloadCache(store.Provider);

        var events = _entityEvents.GetValueOrDefault(EventType.AfterSave)
            ?.GetValueOrDefault(typeof(T));
        if (events is null) return;

        foreach(var ev in events)
        {
            var eventData = (ev.EventData as EventData<SaveEvent<T>, SaveEventDataModel<T>>)!;
            var model = new SaveEventDataModel<T>(entity, store);

            eventData.Event.Init(store, eventData, model);

            Run(store, ev.Event, eventData, model);
        }
    }

    #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);
    }

    public void Init(IEventData data)
    {
    }
}

#endregion

public interface IEvent
{
    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?)>() };

        foreach(var variable in action.ReferencedVariables)
        {
            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);
        }
    }
}

/// <summary>
/// Indicates that this event type has properties that can be edited; <typeparamref name="TProperties"/> is used to edit these properties
/// with a dynamic editor.
/// </summary>
public interface IPropertiesEvent<TProperties>
    where TProperties : BaseObject, new()
{
    /// <summary>
    /// Create the properties object for editing.
    /// </summary>
    TProperties GetProperties();

    /// <summary>
    /// Given an edited properties object, save them again.
    /// </summary>
    void SetProperties(TProperties properties);
}

public interface IEvent<TDataModel> : IEvent
{
    void Init(IStore store, IEventData data, TDataModel model);

    Notification GenerateNotification(TDataModel model);
}

public interface IEventTrigger
{
    IEnumerable<string> ReferencedVariables { get; }

    string Description { get; }
}

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

public interface IEventTriggerParent<TEvent, TDataModel> : IEventTrigger<TEvent, TDataModel>
    where TEvent : IEvent<TDataModel>
    where TDataModel : IEventDataModel
{
    public List<IEventTrigger<TEvent, TDataModel>> ChildTriggers { get; }
}

public class AndTrigger<TEvent, TDataModel> : IEventTrigger<TEvent, TDataModel>, IEventTriggerParent<TEvent, TDataModel>
    where TEvent : IEvent<TDataModel>
    where TDataModel : IEventDataModel
{
    public List<IEventTrigger<TEvent, TDataModel>> ChildTriggers { get; set; } = new();

    public IEnumerable<string> ReferencedVariables => ChildTriggers.SelectMany(x => x.ReferencedVariables);

    public string Description => "And";

    public bool Check(TDataModel dataModel)
    {
        return ChildTriggers.All(x => x.Check(dataModel));
    }
}

public class OrTrigger<TEvent, TDataModel> : IEventTrigger<TEvent, TDataModel>, IEventTriggerParent<TEvent, TDataModel>
    where TEvent : IEvent<TDataModel>
    where TDataModel : IEventDataModel
{
    public List<IEventTrigger<TEvent, TDataModel>> ChildTriggers { get; set; } = new();

    public IEnumerable<string> ReferencedVariables => ChildTriggers.SelectMany(x => x.ReferencedVariables);

    public string Description => "Or";

    public bool Check(TDataModel dataModel)
    {
        return ChildTriggers.Any(x => x.Check(dataModel));
    }
}

public interface IEventAction
{
    IEnumerable<string> ReferencedVariables { get; }

    object? Execute(IEventDataModel dataModel);

    string Description { get; }
}

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