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using System;
using System.Net;
using System.Web;
using ServiceStack.CacheAccess;
using ServiceStack.CacheAccess.Providers;
using ServiceStack.Common;
using ServiceStack.Common.Utils;
using ServiceStack.Common.Web;
using ServiceStack.Logging;
using ServiceStack.Messaging;
using ServiceStack.Redis;
using ServiceStack.ServiceHost;
using ServiceStack.ServiceInterface.ServiceModel;
using ServiceStack.Text;
using ServiceStack.WebHost.Endpoints;
using ServiceStack.WebHost.Endpoints.Extensions;

namespace ServiceStack.ServiceInterface
{
/// <summary>
/// A Useful ServiceBase for all services with support for automatically serializing
/// Exceptions into a common ResponseError DTO so errors can be handled generically by clients.
///
/// If an 'IRedisClientsManager' is configured in your AppHost, service errors will
/// also be maintained into a service specific and combined rolling error log.
/// </summary>
/// <typeparam name="TRequest"></typeparam>
public abstract class ServiceBase<TRequest>
: IService<TRequest>, IRequiresRequestContext, IServiceBase
{
private static readonly ILog Log = LogManager.GetLogger(typeof(ServiceBase<>));

/// <summary>
/// Naming convention for the request's Response DTO
/// </summary>
public const string ResponseDtoSuffix = "Response";

/// <summary>
/// Naming convention for the ResponseStatus property name on the response DTO
/// </summary>
public const string ResponseStatusPropertyName = "ResponseStatus";

/// <summary>
/// Service error logs are kept in 'urn:ServiceErrors:{ServiceName}'
/// </summary>
public const string UrnServiceErrorType = "ServiceErrors";

/// <summary>
/// Combined service error logs are maintained in 'urn:ServiceErrors:All'
/// </summary>
public const string CombinedServiceLogId = "All";


/// <summary>
/// Can be overriden to supply Custom 'ServiceName' error logs
/// </summary>
public virtual string ServiceName
{
get { return typeof(TRequest).Name; }
}

/// <summary>
/// Access to the Applications ServiceStack AppHost Instance
/// </summary>
private IAppHost appHost;
public virtual IAppHost AppHost
{
get
{
return appHost ?? EndpointHost.AppHost;
}
set
{
this.appHost = value;
}
}

public IRequestContext RequestContext { get; set; }

public ISessionFactory SessionFactory { get; set; }

private ISession session;
public ISession Session
{
get
{
if (SessionFactory == null)
SessionFactory = new SessionFactory(this.GetCacheClient());

return session ?? (session =
SessionFactory.GetOrCreateSession(
RequestContext.Get<IHttpRequest>(),
RequestContext.Get<IHttpResponse>()
));
}
}

/// <summary>
/// Resolve an alternate Web Service from ServiceStack's IOC container.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public T ResolveService<T>()
{
var service = this.AppHost.TryResolve<T>();
var requiresContext = service as IRequiresRequestContext;
if (requiresContext != null)
{
requiresContext.RequestContext = this.RequestContext;
}
return service;
}

/// <summary>
/// Maintains the current request DTO in this property
/// </summary>
protected TRequest CurrentRequestDto;

/// <summary>
/// Override to provide additional/less context about the Service Exception.
/// By default the request is serialized and appended to the ResponseStatus StackTrace.
/// </summary>
public virtual string GetRequestErrorBody()
{
var requestString = "";
try
{
requestString = TypeSerializer.SerializeToString(CurrentRequestDto);
}
catch /*(Exception ignoreSerializationException)*/
{
//Serializing request successfully is not critical and only provides added error info
}

return string.Format("[{0}: {1}]:\n[REQUEST: {2}]", GetType().Name, DateTime.UtcNow, requestString);
}

public T TryResolve<T>()
{
return this.AppHost == null
? default(T)
: this.AppHost.TryResolve<T>();
}

/// <summary>
/// Single method sub classes should implement to execute the request
/// </summary>
/// <param name="request"></param>
/// <returns></returns>
protected abstract object Run(TRequest request);

/// <summary>
/// Called before the request is Executed. Override to enforce generic validation logic.
/// </summary>
/// <param name="request"></param>
protected virtual void OnBeforeExecute(TRequest request) { }

/// <summary>
/// Execute the request with the protected abstract Run() method in a managed scope by
/// provide default handling of Service Exceptions by serializing exceptions in the response
/// DTO and maintaining all service errors in a managed service-specific and combined rolling error logs
/// </summary>
/// <param name="request"></param>
/// <returns></returns>
public object Execute(TRequest request)
{
try
{
OnBeforeExecute(request);
return Run(request);
}
catch (Exception ex)
{
var result = HandleException(request, ex);

if (result == null) throw;

return result;
}
}

protected virtual object HandleException(TRequest request, Exception ex)
{
var responseStatus = ResponseStatusTranslator.Instance.Parse(ex);

if (EndpointHost.UserConfig.DebugMode)
{
// View stack trace in tests and on the client
responseStatus.StackTrace = GetRequestErrorBody() + ex;
}

Log.Error("ServiceBase<TRequest>::Service Exception", ex);

//If Redis is configured, maintain rolling service error logs in Redis (an in-memory datastore)
var redisManager = TryResolve<IRedisClientsManager>();
if (redisManager != null)
{
try
{
//Get a thread-safe redis client from the client manager pool
using (var client = redisManager.GetClient())
{
//Get a client with a native interface for storing 'ResponseStatus' objects
var redis = client.GetTypedClient<ResponseStatus>();

//Store the errors in predictable Redis-named lists i.e.
//'urn:ServiceErrors:{ServiceName}' and 'urn:ServiceErrors:All'
var redisSeriviceErrorList = redis.Lists[UrnId.Create(UrnServiceErrorType, ServiceName)];
var redisCombinedErrorList = redis.Lists[UrnId.Create(UrnServiceErrorType, CombinedServiceLogId)];

//Append the error at the start of the service-specific and combined error logs.
redisSeriviceErrorList.Prepend(responseStatus);
redisCombinedErrorList.Prepend(responseStatus);

//Clip old error logs from the managed logs
const int rollingErrorCount = 1000;
redisSeriviceErrorList.Trim(0, rollingErrorCount);
redisCombinedErrorList.Trim(0, rollingErrorCount);
}
}
catch (Exception suppressRedisException)
{
Log.Error("Could not append exception to redis service error logs", suppressRedisException);
}
}

var responseDto = CreateResponseDto(request, responseStatus);

if (responseDto == null)
{
return null;
}

var httpError = ex as IHttpError;
if (httpError != null)
{
httpError.Response = responseDto;
return httpError;
}

var statusCode = HttpStatusCode.InternalServerError;
if (ex is NotImplementedException) statusCode = HttpStatusCode.MethodNotAllowed;
else if (ex is ArgumentException) statusCode = HttpStatusCode.BadRequest;

return new HttpResult(responseDto, null, statusCode);
}

/// <summary>
/// Create an instance of the service response dto type and inject it with the supplied responseStatus
/// </summary>
/// <param name="request"></param>
/// <param name="responseStatus"></param>
/// <returns></returns>
protected static object CreateResponseDto(TRequest request, ResponseStatus responseStatus)
{
// Predict the Response message type name
// Get the type
var responseDtoType = AssemblyUtils.FindType(GetResponseDtoName(request));
var responseDto = CreateResponseDto(request);

if (responseDto == null)
return null;

// For faster serialization of exceptions, services should implement IHasResponseStatus
var hasResponseStatus = responseDto as IHasResponseStatus;
if (hasResponseStatus != null)
{
hasResponseStatus.ResponseStatus = responseStatus;
}
else
{
// Get the ResponseStatus property
var responseStatusProperty = responseDtoType.GetProperty(ResponseStatusPropertyName);

if (responseStatusProperty != null)
{
// Set the ResponseStatus
ReflectionUtils.SetProperty(responseDto, responseStatusProperty, responseStatus);
}
}

// Return an Error DTO with the exception populated
return responseDto;
}

/// <summary>
/// Create an instance of the response dto based on the requestDto type and default naming convention
/// </summary>
/// <param name="request"></param>
/// <returns></returns>
protected static object CreateResponseDto(TRequest request)
{
// Get the type
var responseDtoType = AssemblyUtils.FindType(GetResponseDtoName(request));

if (responseDtoType == null)
{
// We don't support creation of response messages without a predictable type name
return null;
}

// Create an instance of the response message for this request
var responseDto = ReflectionUtils.CreateInstance(responseDtoType);
return responseDto;
}

protected static string GetResponseDtoName(TRequest request)
{
return typeof(TRequest).FullName + ResponseDtoSuffix;
}

protected HttpResult View(string viewName, object response)
{
return new HttpResult(response) {
TemplateName = viewName
};
}

/// <summary>
/// The Deferred execution of ExecuteAsync(request)'s.
/// This request is typically invoked from a messaging queue service host.
/// </summary>
/// <param name="request"></param>
public virtual object Execute(IMessage<TRequest> request)
{
return Execute(request.GetBody());
}
}

}
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