using System.Reflection;
using GenHTTP.Api.Content;
using GenHTTP.Api.Protocol;
using GenHTTP.Modules.IO;
using GenHTTP.Modules.IO.FileSystem;
using GenHTTP.Modules.IO.Streaming;
using InABox.Clients;
using InABox.Core;
using InABox.Database;
using InABox.Server;
using RequestMethod = GenHTTP.Api.Protocol.RequestMethod;

namespace InABox.API
{
    public class RestHandler : IHandler
    {
        private readonly List<string> endpoints;
        private readonly List<string> operations;

        public RestHandler(IHandler parent)
        {
            Parent = parent;

            endpoints = new();
            operations = new();

            var types = CoreUtils.TypeList(
                x => x.IsSubclassOf(typeof(Entity))
                     && x.GetInterfaces().Contains(typeof(IRemotable))
            );
            var DBTypes = DbFactory.SupportedTypes();

            foreach (var t in types)
                if (DBTypes.Contains(t.EntityName().Replace(".", "_")))
                {
                    operations.Add(t.EntityName().Replace(".", "_"));

                    endpoints.Add(string.Format("List{0}", t.Name));
                    endpoints.Add(string.Format("Load{0}", t.Name));
                    endpoints.Add(string.Format("Save{0}", t.Name));
                    endpoints.Add(string.Format("MultiSave{0}", t.Name));
                    endpoints.Add(string.Format("Delete{0}", t.Name));
                    endpoints.Add(string.Format("MultiDelete{0}", t.Name));
                }

            endpoints.Add("QueryMultiple");
        }
        
        private RequestData GetRequestData(IRequest request)
        {
            BinarySerializationSettings settings = BinarySerializationSettings.V1_0;
            if (request.Query.TryGetValue("serializationVersion", out var versionString))
            {
                settings = BinarySerializationSettings.ConvertVersionString(versionString);
            }

            var data = new RequestData(settings);
            if (request.Query.TryGetValue("format", out var formatString) && Enum.TryParse<SerializationFormat>(formatString, out var format))
            {
                data.RequestFormat = format;
            }
            data.ResponseFormat = SerializationFormat.Json;
            if (request.Query.TryGetValue("responseFormat", out formatString) && Enum.TryParse<SerializationFormat>(formatString, out format))
            {
                data.ResponseFormat = format;
            }

            return data;
        }

        /// <summary>
        /// The main handler for the server; an HTTP request comes in, an HTTP response goes out.
        /// </summary>
        /// <param name="request"></param>
        /// <returns></returns>
        public ValueTask<IResponse?> HandleAsync(IRequest request)
        {
            try
            {
                switch (request.Method.KnownMethod)
                {
                    case RequestMethod.GET:
                    case RequestMethod.HEAD:
                        var current = request.Target.Current?.Value;
                        if (String.Equals(current,"update"))
                        {
                            request.Target.Advance();
                            current = request.Target.Current?.Value;
                        }
                        switch (current)
                        {
                            case "operations" or "supported_operations":
                                return new ValueTask<IResponse?>(GetSupportedOperations(request).Build());
                            case "classes" or "supported_classes":
                                return new ValueTask<IResponse?>(GetSupportedClasses(request).Build());
                            case "version" or "releasenotes" or "release_notes" or "install" or "install_desktop":
                                return new ValueTask<IResponse?>(GetUpdateFile(request).Build());
                            case "info":
                                return new ValueTask<IResponse?>(GetServerInfo(request).Build());
                            case "ping":
                                return new ValueTask<IResponse?>(request.Respond().Status(ResponseStatus.OK).Build());
                        }

                        Logger.Send(LogType.Error, request.Client.IPAddress.ToString(),
                            string.Format("GET/HEAD request to endpoint '{0}' is unresolved, because it does not exist", current));
                        return new ValueTask<IResponse?>(request.Respond().Status(ResponseStatus.NotFound).Build());
                    case RequestMethod.POST:
                        var target = request.Target.Current;
                        if (target is not null)
                        {
                            var data = GetRequestData(request);
                            return target.Value switch
                            {
                                "validate" => new ValueTask<IResponse?>(Validate(request, data).Build()),
                                "check_2fa" => new ValueTask<IResponse?>(Check2FA(request, data).Build()),
                                _ => HandleDatabaseRequest(request, data),
                            };
                        }
                        return new ValueTask<IResponse?>(request.Respond().Status(ResponseStatus.NotFound).Build());
                }

                return new ValueTask<IResponse?>(request.Respond().Status(ResponseStatus.MethodNotAllowed).Header("Allow", "GET, POST, HEAD").Build());
            }
            catch(Exception e)
            {
                Logger.Send(LogType.Error, "", CoreUtils.FormatException(e));
                return new ValueTask<IResponse?>(request.Respond().Status(ResponseStatus.InternalServerError).Build());
            }
        }
        
        /// <summary>
        /// Returns a JSON list of operation names; used for checking support of operations client side
        /// </summary>
        /// <param name="request"></param>
        /// <returns></returns>
        private IResponseBuilder GetSupportedOperations(IRequest request)
        {
            var serialized = Core.Serialization.Serialize(endpoints, true) ?? "";
            return request.Respond()
                .Type(new FlexibleContentType(ContentType.ApplicationJson))
                .Content(new ResourceContent(Resource.FromString(serialized).Build()));
        }

        /// <summary>
        /// Returns a JSON list of class names; used for checking support of operations client side
        /// </summary>
        /// <param name="request"></param>
        /// <returns></returns>
        private IResponseBuilder GetSupportedClasses(IRequest request)
        {
            var serialized = Serialization.Serialize(operations) ?? "";
            return request.Respond()
                .Type(new FlexibleContentType(ContentType.ApplicationJson))
                .Content(new ResourceContent(Resource.FromString(serialized).Build()));
        }
        
        /// <summary>
        /// Returns the Splash Logo and Color Scheme for this Database
        /// </summary>
        /// <param name="request"></param>
        /// <returns></returns>
        private IResponseBuilder GetServerInfo(IRequest request)
        {
            var data = GetRequestData(request);
            InfoResponse response = RestService.Info(new InfoRequest());
            return SerializeResponse(request, data.ResponseFormat, data.BinarySerializationSettings, response);
        }

        #region Authentication

        private IResponseBuilder Validate(IRequest request, RequestData data)
        {
            var requestObj = Deserialize<ValidateRequest>(request.Content, data.RequestFormat, data.BinarySerializationSettings, true);
            var response = RestService.Validate(requestObj);

            return SerializeResponse(request, data.ResponseFormat, data.BinarySerializationSettings, response);
        }

        private IResponseBuilder Check2FA(IRequest request, RequestData data)
        {
            var requestObj = Deserialize<Check2FARequest>(request.Content, data.RequestFormat, data.BinarySerializationSettings, true);
            var response = RestService.Check2FA(requestObj);

            return SerializeResponse(request, data.ResponseFormat, data.BinarySerializationSettings, response);
        }

        #endregion

        #region Database

        private static MethodInfo GetMethod(string name) =>
            typeof(RestHandler).GetMethod(name, BindingFlags.NonPublic | BindingFlags.Static)
            ?? throw new Exception($"Invalid method '{name}'");

        private static readonly List<Tuple<string, MethodInfo>> methodMap = new()
        {
            new("List", GetMethod(nameof(List))),
            new("Save", GetMethod(nameof(Save))),
            new("Delete", GetMethod(nameof(Delete))),
            new("MultiSave", GetMethod(nameof(MultiSave))),
            new("MultiDelete", GetMethod(nameof(MultiDelete)))
        };

        private class RequestData
        {
            public SerializationFormat RequestFormat { get; set; }
            public SerializationFormat ResponseFormat { get; set; }

            public BinarySerializationSettings BinarySerializationSettings { get; set; }

            public RequestData(BinarySerializationSettings binarySerializationSettings)
            {
                BinarySerializationSettings = binarySerializationSettings;
            }
        }

        private static QueryResponse<T> List<T>(IRequest request, RequestData data) where T : Entity, new()
        {
            var requestObject = Deserialize<QueryRequest<T>>(request.Content, data.RequestFormat, data.BinarySerializationSettings, true);
            return RestService<T>.List(requestObject);
        }
        private static SaveResponse<T> Save<T>(IRequest request, RequestData data) where T : Entity, new()
        {
            var requestObject = Deserialize<SaveRequest<T>>(request.Content, data.RequestFormat, data.BinarySerializationSettings, true);
            return RestService<T>.Save(requestObject);
        }
        private static DeleteResponse<T> Delete<T>(IRequest request, RequestData data) where T : Entity, new()
        {
            var requestObject = Deserialize<DeleteRequest<T>>(request.Content, data.RequestFormat, data.BinarySerializationSettings, true);
            return RestService<T>.Delete(requestObject);
        }
        private static MultiSaveResponse<T> MultiSave<T>(IRequest request, RequestData data) where T : Entity, new()
        {
            var requestObject = Deserialize<MultiSaveRequest<T>>(request.Content, data.RequestFormat, data.BinarySerializationSettings, true);
            return RestService<T>.MultiSave(requestObject);
        }
        private static MultiDeleteResponse<T> MultiDelete<T>(IRequest request, RequestData data) where T : Entity, new()
        {
            var requestObject = Deserialize<MultiDeleteRequest<T>>(request.Content, data.RequestFormat, data.BinarySerializationSettings, true);
            return RestService<T>.MultiDelete(requestObject);
        }
        private static MultiQueryResponse QueryMultiple(IRequest request, RequestData data)
        {
            var requestObject = Deserialize<MultiQueryRequest>(request.Content, data.RequestFormat, data.BinarySerializationSettings, true);

            return RestService.QueryMultiple(requestObject, false);
        }

        private static T Deserialize<T>(Stream? stream, SerializationFormat requestFormat, BinarySerializationSettings binarySettings, bool strict = false)
        {
            if (stream is null)
                throw new Exception("Stream is null");
            if (requestFormat == SerializationFormat.Binary && typeof(T).IsAssignableTo(typeof(ISerializeBinary)))
            {
                return (T)Serialization.ReadBinary(typeof(T), stream, binarySettings);
            }
            else
            {
                var str = new StreamReader(stream).ReadToEnd();
                return Serialization.Deserialize<T>(str, strict)
                       ?? throw new Exception("Deserialization failed");
            }
        }

        private IResponseBuilder SerializeResponse(IRequest request, SerializationFormat responseFormat, BinarySerializationSettings binarySettings, Response? result)
        {
            if (responseFormat == SerializationFormat.Binary && result is ISerializeBinary binary)
            {
                var stream = new MemoryStream();
                binary.SerializeBinary(new CoreBinaryWriter(stream, binarySettings));

                var response = request.Respond()
                    .Type(new FlexibleContentType(ContentType.ApplicationOctetStream))
                    .Content(stream, (ulong?)stream.Length, () => new ValueTask<ulong?>((ulong)stream.GetHashCode()));
                return response;
            }
            else
            {
                var serialized = Serialization.Serialize(result);

                var response = request.Respond()
                    .Type(new FlexibleContentType(ContentType.ApplicationJson))
                    .Content(new ResourceContent(Resource.FromString(serialized).Build()));
                return response;
            }
        }

        /// <summary>
        /// Handler for all database requests
        /// </summary>
        /// <param name="request"></param>
        /// <returns></returns>
        private ValueTask<IResponse?> HandleDatabaseRequest(IRequest request, RequestData requestData)
        {
            var endpoint = request.Target.Current?.Value ?? "";
            if (endpoint.StartsWith("QueryMultiple"))
            {
                var result = QueryMultiple(request, requestData);
                return new ValueTask<IResponse?>(SerializeResponse(request, requestData.ResponseFormat, requestData.BinarySerializationSettings, result).Build());
            }

            foreach (var (name, method) in methodMap)
                if (endpoint.Length > name.Length && endpoint.StartsWith(name))
                {
                    var entityName = endpoint[name.Length..];

                    var entityType = GetEntity(entityName);
                    if (entityType != null)
                    {
                        if (entityType.IsAssignableTo(typeof(ISecure)))
                        {
                            Logger.Send(LogType.Error, "", $"{entityType} is a secure entity. Request failed from IP {request.Client.IPAddress}");
                            return new ValueTask<IResponse?>(request.Respond().Status(ResponseStatus.NotFound).Build());
                        }

                        var resolvedMethod = method.MakeGenericMethod(entityType);
                        var result = resolvedMethod.Invoke(null, new object[] { request, requestData }) as Response;

                        return new ValueTask<IResponse?>(SerializeResponse(request, requestData.ResponseFormat, requestData.BinarySerializationSettings, result).Build());
                    }

                    Logger.Send(LogType.Error, request.Client.IPAddress.ToString(),
                        $"Request to endpoint '{endpoint}' unresolved, because '{entityName}' is not a valid entity");
                    return new ValueTask<IResponse?>(request.Respond().Status(ResponseStatus.NotFound).Build());
                }

            Logger.Send(LogType.Error, request.Client.IPAddress.ToString(), $"Request to endpoint '{endpoint}' unresolved, because the method does not exist");
            return new ValueTask<IResponse?>(request.Respond().Status(ResponseStatus.NotFound).Build());
        }

        private Dictionary<string, Type>? _persistentRemotable;

        private Type? GetEntity(string entityName)
        {
            _persistentRemotable ??= CoreUtils.TypeList(
                e => e.IsSubclassOf(typeof(Entity)) &&
                     e.GetInterfaces().Contains(typeof(IRemotable)) &&
                     e.GetInterfaces().Contains(typeof(IPersistent))).ToDictionary(x => x.Name, x => x);
            return _persistentRemotable.GetValueOrDefault(entityName);
        }

        #endregion

        #region Installer

        
        private IResponseBuilder GetUpdateFile(IRequest request)
        {
            var endpoint = request.Target.Current;
            string? filename = null;
            switch (endpoint?.Value)
            {
                case "version":
                    filename = UpdateData.GetUpdateVersionFile();
                    break;
                case "releasenotes" or "release_notes":
                    filename = UpdateData.GetReleaseNotesFile();
                    break;
                case "install" or "install_desktop":
                    filename = UpdateData.GetUpdateInstallerFile();
                    break;
            }

            if (filename is null) return request.Respond().Status(ResponseStatus.NotFound);

            if (File.Exists(filename))
            {
                return request.Respond()
                    .Header("Content-Disposition", $"attachment; filename={Path.GetFileName(filename)}")
                    .Content(new ResourceContent(
                        new FileResource(new FileInfo(filename), null, null)));
            }
            return request.Respond().Status(ResponseStatus.NotFound);
        }

        #endregion

        #region GenHTTP stuff
        public IHandler Parent { get; }

        public ValueTask PrepareAsync()
        {
            return new ValueTask();
        }

        public IEnumerable<ContentElement> GetContent(IRequest request)
        {
            return Enumerable.Empty<ContentElement>();
        }

        #endregion
    }
}