//
// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
//
using System;
using System.Collections.Concurrent;
using System.IO;
using System.Threading.Tasks;
using Microsoft.SqlTools.ServiceLayer.Connection;
using Microsoft.SqlTools.ServiceLayer.Hosting;
using Microsoft.SqlTools.ServiceLayer.Hosting.Protocol;
using Microsoft.SqlTools.ServiceLayer.QueryExecution.Contracts;
using Microsoft.SqlTools.ServiceLayer.QueryExecution.Contracts.ExecuteRequests;
using Microsoft.SqlTools.ServiceLayer.QueryExecution.DataStorage;
using Microsoft.SqlTools.ServiceLayer.SqlContext;
using Microsoft.SqlTools.ServiceLayer.Utility;
using Microsoft.SqlTools.ServiceLayer.Workspace;
using Microsoft.SqlTools.ServiceLayer.Workspace.Contracts;

namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
{
    /// <summary>
    /// Service for executing queries
    /// </summary>
    public sealed class QueryExecutionService : IDisposable
    {
        #region Singleton Instance Implementation

        private static readonly Lazy<QueryExecutionService> LazyInstance = new Lazy<QueryExecutionService>(() => new QueryExecutionService());

        /// <summary>
        /// Singleton instance of the query execution service
        /// </summary>
        public static QueryExecutionService Instance => LazyInstance.Value;

        private QueryExecutionService()
        {
            ConnectionService = ConnectionService.Instance;
            WorkspaceService = WorkspaceService<SqlToolsSettings>.Instance;
            Settings = new SqlToolsSettings();
        }

        internal QueryExecutionService(ConnectionService connService, WorkspaceService<SqlToolsSettings> workspaceService)
        {
            ConnectionService = connService;
            WorkspaceService = workspaceService;
            Settings = new SqlToolsSettings();
        }

        #endregion

        #region Properties

        /// <summary>
        /// File factory to be used to create a buffer file for results.
        /// </summary>
        /// <remarks>
        /// Made internal here to allow for overriding in unit testing
        /// </remarks>
        internal IFileStreamFactory BufferFileStreamFactory;

        /// <summary>
        /// File factory to be used to create a buffer file for results
        /// </summary>
        private IFileStreamFactory BufferFileFactory
        {
            get
            {
                if (BufferFileStreamFactory == null)
                {
                    BufferFileStreamFactory = new ServiceBufferFileStreamFactory
                    {
                        ExecutionSettings = Settings.QueryExecutionSettings
                    };
                }
                return BufferFileStreamFactory;
            }
        }

        /// <summary>
        /// File factory to be used to create CSV files from result sets. Set to internal in order
        /// to allow overriding in unit testing
        /// </summary>
        internal IFileStreamFactory CsvFileFactory { get; set; }

        /// <summary>
        /// File factory to be used to create JSON files from result sets. Set to internal in order
        /// to allow overriding in unit testing
        /// </summary>
        internal IFileStreamFactory JsonFileFactory { get; set; }

        /// <summary>
        /// The collection of active queries
        /// </summary>
        internal ConcurrentDictionary<string, Query> ActiveQueries => queries.Value;

        /// <summary>
        /// Instance of the connection service, used to get the connection info for a given owner URI
        /// </summary>
        private ConnectionService ConnectionService { get; }

        private WorkspaceService<SqlToolsSettings> WorkspaceService { get; }

        /// <summary>
        /// Internal storage of active queries, lazily constructed as a threadsafe dictionary
        /// </summary>
        private readonly Lazy<ConcurrentDictionary<string, Query>> queries =
            new Lazy<ConcurrentDictionary<string, Query>>(() => new ConcurrentDictionary<string, Query>());

        /// <summary>
        /// Settings that will be used to execute queries. Internal for unit testing
        /// </summary>
        internal SqlToolsSettings Settings { get; set; }

        #endregion

        /// <summary>
        /// Initializes the service with the service host, registers request handlers and shutdown
        /// event handler.
        /// </summary>
        /// <param name="serviceHost">The service host instance to register with</param>
        public void InitializeService(ServiceHost serviceHost)
        {
            // Register handlers for requests
            serviceHost.SetRequestHandler(ExecuteDocumentSelectionRequest.Type, HandleExecuteRequest);
            serviceHost.SetRequestHandler(ExecuteStringRequest.Type, HandleExecuteRequest);
            serviceHost.SetRequestHandler(SubsetRequest.Type, HandleResultSubsetRequest);
            serviceHost.SetRequestHandler(QueryDisposeRequest.Type, HandleDisposeRequest);
            serviceHost.SetRequestHandler(QueryCancelRequest.Type, HandleCancelRequest);
            serviceHost.SetRequestHandler(SaveResultsAsCsvRequest.Type, HandleSaveResultsAsCsvRequest);
            serviceHost.SetRequestHandler(SaveResultsAsJsonRequest.Type, HandleSaveResultsAsJsonRequest);
            serviceHost.SetRequestHandler(QueryExecutionPlanRequest.Type, HandleExecutionPlanRequest);

            // Register handler for shutdown event
            serviceHost.RegisterShutdownTask((shutdownParams, requestContext) =>
            {
                Dispose();
                return Task.FromResult(0);
            });

            // Register a handler for when the configuration changes
            WorkspaceService.RegisterConfigChangeCallback(UpdateSettings);
        }

        #region Request Handlers

        /// <summary>
        /// Handles request to execute a selection of a document in the workspace service
        /// </summary>
        internal Task HandleExecuteRequest(ExecuteRequestParamsBase executeParams,
            RequestContext<ExecuteRequestResult> requestContext)
        {
            // Setup actions to perform upon successful start and on failure to start
            Func<Task> queryCreationAction = () => requestContext.SendResult(new ExecuteRequestResult());
            Func<string, Task> queryFailAction = requestContext.SendError;

            // Use the internal handler to launch the query
            return InterServiceExecuteQuery(executeParams, requestContext, queryCreationAction, queryFailAction);
        }

        /// <summary>
        /// Handles a request to get a subset of the results of this query
        /// </summary>
        internal async Task HandleResultSubsetRequest(SubsetParams subsetParams,
            RequestContext<SubsetResult> requestContext)
        {
            try
            {
                // Attempt to load the query
                Query query;
                if (!ActiveQueries.TryGetValue(subsetParams.OwnerUri, out query))
                {
                    await requestContext.SendResult(new SubsetResult
                    {
                        Message = SR.QueryServiceRequestsNoQuery
                    });
                    return;
                }

                // Retrieve the requested subset and return it
                var result = new SubsetResult
                {
                    Message = null,
                    ResultSubset = await query.GetSubset(subsetParams.BatchIndex,
                        subsetParams.ResultSetIndex, subsetParams.RowsStartIndex, subsetParams.RowsCount)
                };
                await requestContext.SendResult(result);
            }
            catch (InvalidOperationException ioe)
            {
                // Return the error as a result
                await requestContext.SendResult(new SubsetResult
                {
                    Message = ioe.Message
                });
            }
            catch (ArgumentOutOfRangeException aoore)
            {
                // Return the error as a result
                await requestContext.SendResult(new SubsetResult
                {
                    Message = aoore.Message
                });
            }
            catch (Exception e)
            {
                // This was unexpected, so send back as error
                await requestContext.SendError(e.Message);
            }
        }

         /// <summary>
        /// Handles a request to get an execution plan
        /// </summary>
        internal async Task HandleExecutionPlanRequest(QueryExecutionPlanParams planParams,
            RequestContext<QueryExecutionPlanResult> requestContext)
        {
            try
            {
                // Attempt to load the query
                Query query;
                if (!ActiveQueries.TryGetValue(planParams.OwnerUri, out query))
                {
                    await requestContext.SendError(SR.QueryServiceRequestsNoQuery);
                    return;
                }

                // Retrieve the requested execution plan and return it
                var result = new QueryExecutionPlanResult
                {
                    ExecutionPlan = await query.GetExecutionPlan(planParams.BatchIndex, planParams.ResultSetIndex)
                };
                await requestContext.SendResult(result);
            }
            catch (Exception e)
            {
                // This was unexpected, so send back as error
                await requestContext.SendError(e.Message);
            }
        }

        /// <summary>
        /// Handles a request to dispose of this query
        /// </summary>
        internal async Task HandleDisposeRequest(QueryDisposeParams disposeParams,
            RequestContext<QueryDisposeResult> requestContext)
        {
            // Setup action for success and failure
            Func<Task> successAction = () => requestContext.SendResult(new QueryDisposeResult());
            Func<string, Task> failureAction = requestContext.SendError;

            // Use the inter-service dispose functionality
            await InterServiceDisposeQuery(disposeParams.OwnerUri, successAction, failureAction);
        }

        /// <summary>
        /// Handles a request to cancel this query if it is in progress
        /// </summary>
        internal async Task HandleCancelRequest(QueryCancelParams cancelParams,
            RequestContext<QueryCancelResult> requestContext)
        {
            try
            {
                // Attempt to find the query for the owner uri
                Query result;
                if (!ActiveQueries.TryGetValue(cancelParams.OwnerUri, out result))
                {
                    await requestContext.SendResult(new QueryCancelResult
                    {
                        Messages = SR.QueryServiceRequestsNoQuery
                    });
                    return;
                }

                // Cancel the query and send a success message
                result.Cancel();
                await requestContext.SendResult(new QueryCancelResult());
            }
            catch (InvalidOperationException e)
            {
                // If this exception occurred, we most likely were trying to cancel a completed query
                await requestContext.SendResult(new QueryCancelResult
                {
                    Messages = e.Message
                });
            }
            catch (Exception e)
            {
                await requestContext.SendError(e.Message);
            }
        }

        /// <summary>
        /// Process request to save a resultSet to a file in CSV format
        /// </summary>
        internal async Task HandleSaveResultsAsCsvRequest(SaveResultsAsCsvRequestParams saveParams,
            RequestContext<SaveResultRequestResult> requestContext)
        {
            // Use the default CSV file factory if we haven't overridden it
            IFileStreamFactory csvFactory = CsvFileFactory ?? new SaveAsCsvFileStreamFactory
            {
                SaveRequestParams = saveParams,
                QueryExecutionSettings = Settings.QueryExecutionSettings
            };
            await SaveResultsHelper(saveParams, requestContext, csvFactory);
        }

        /// <summary>
        /// Process request to save a resultSet to a file in JSON format
        /// </summary>
        internal async Task HandleSaveResultsAsJsonRequest(SaveResultsAsJsonRequestParams saveParams,
            RequestContext<SaveResultRequestResult> requestContext)
        {
            // Use the default JSON file factory if we haven't overridden it
            IFileStreamFactory jsonFactory = JsonFileFactory ?? new SaveAsJsonFileStreamFactory
            {
                SaveRequestParams = saveParams,
                QueryExecutionSettings = Settings.QueryExecutionSettings
            };
            await SaveResultsHelper(saveParams, requestContext, jsonFactory);
        }

        #endregion

        #region Inter-Service API Handlers

        /// <summary>
        /// Query execution meant to be called from another service. Utilizes callbacks to allow
        /// custom actions to be taken upon creation of query and failure to create query.
        /// </summary>
        /// <param name="executeParams">Params for creating the new query</param>
        /// <param name="eventSender">Object that can send events for query execution progress</param>
        /// <param name="queryCreatedAction">
        /// Action to perform when query has been successfully created, right before execution of 
        /// the query
        /// </param>
        /// <param name="failureAction">Action to perform if query was not successfully created</param>
        public async Task InterServiceExecuteQuery(ExecuteRequestParamsBase executeParams, IEventSender eventSender,
            Func<Task> queryCreatedAction, Func<string, Task> failureAction)
        {
            Validate.IsNotNull(nameof(executeParams), executeParams);
            Validate.IsNotNull(nameof(eventSender), eventSender);
            Validate.IsNotNull(nameof(queryCreatedAction), queryCreatedAction);
            Validate.IsNotNull(nameof(failureAction), failureAction);

            // Get a new active query
            Query newQuery = await CreateAndActivateNewQuery(executeParams, queryCreatedAction, failureAction);

            // Execute the query asynchronously
            ExecuteAndCompleteQuery(executeParams.OwnerUri, eventSender, newQuery);
        }

        /// <summary>
        /// Query disposal meant to be called from another service. Utilizes callbacks to allow
        /// custom actions to be performed on success or failure.
        /// </summary>
        /// <param name="ownerUri">The identifier of the query to be disposed</param>
        /// <param name="successAction">Action to perform on success</param>
        /// <param name="failureAction">Action to perform on failure</param>
        /// <returns></returns>
        public async Task InterServiceDisposeQuery(string ownerUri, Func<Task> successAction,
            Func<string, Task> failureAction)
        {
            Validate.IsNotNull(nameof(successAction), successAction);
            Validate.IsNotNull(nameof(failureAction), failureAction);

            try
            {
                // Attempt to remove the query for the owner uri
                Query result;
                if (!ActiveQueries.TryRemove(ownerUri, out result))
                {
                    await failureAction(SR.QueryServiceRequestsNoQuery);
                    return;
                }

                // Cleanup the query
                result.Dispose();

                // Success
                await successAction();
            }
            catch (Exception e)
            {
                await failureAction(e.Message);
            }
        }

        #endregion

        #region Private Helpers

        private async Task<Query> CreateAndActivateNewQuery(ExecuteRequestParamsBase executeParams, Func<Task> successAction, Func<string, Task> failureAction)
        {
            try
            {
                // Attempt to get the connection for the editor
                ConnectionInfo connectionInfo;
                if (!ConnectionService.TryFindConnection(executeParams.OwnerUri, out connectionInfo))
                {
                    await failureAction(SR.QueryServiceQueryInvalidOwnerUri);
                    return null;
                }

                // Attempt to clean out any old query on the owner URI
                Query oldQuery;
                if (ActiveQueries.TryGetValue(executeParams.OwnerUri, out oldQuery) && oldQuery.HasExecuted)
                {
                    oldQuery.Dispose();
                    ActiveQueries.TryRemove(executeParams.OwnerUri, out oldQuery);
                }

                // Retrieve the current settings for executing the query with
                QueryExecutionSettings querySettings = Settings.QueryExecutionSettings;

                // Apply execution parameter settings 
                querySettings.ExecutionPlanOptions = executeParams.ExecutionPlanOptions;

                // If we can't add the query now, it's assumed the query is in progress
                Query newQuery = new Query(GetSqlText(executeParams), connectionInfo, querySettings, BufferFileFactory);
                if (!ActiveQueries.TryAdd(executeParams.OwnerUri, newQuery))
                {
                    await failureAction(SR.QueryServiceQueryInProgress);
                    newQuery.Dispose();
                    return null;
                }

                // Successfully created query
                await successAction();

                return newQuery;
            }
            catch (Exception e)
            {
                await failureAction(e.Message);
                return null;
            }
        }

        private static void ExecuteAndCompleteQuery(string ownerUri, IEventSender eventSender, Query query)
        {
            // Skip processing if the query is null
            if (query == null)
            {
                return;
            }

            // Setup the query completion/failure callbacks
            Query.QueryAsyncEventHandler callback = async q =>
            {
                // Send back the results
                QueryCompleteParams eventParams = new QueryCompleteParams
                {
                    OwnerUri = ownerUri,
                    BatchSummaries = q.BatchSummaries
                };

                await eventSender.SendEvent(QueryCompleteEvent.Type, eventParams);
            };

            query.QueryCompleted += callback;
            query.QueryFailed += callback;

            // Setup the batch callbacks
            Batch.BatchAsyncEventHandler batchStartCallback = async b =>
            {
                BatchEventParams eventParams = new BatchEventParams
                {
                    BatchSummary = b.Summary,
                    OwnerUri = ownerUri
                };

                await eventSender.SendEvent(BatchStartEvent.Type, eventParams);
            };
            query.BatchStarted += batchStartCallback;

            Batch.BatchAsyncEventHandler batchCompleteCallback = async b =>
            {
                BatchEventParams eventParams = new BatchEventParams
                {
                    BatchSummary = b.Summary,
                    OwnerUri = ownerUri
                };

                await eventSender.SendEvent(BatchCompleteEvent.Type, eventParams);
            };
            query.BatchCompleted += batchCompleteCallback;

            Batch.BatchAsyncMessageHandler batchMessageCallback = async m =>
            {
                MessageParams eventParams = new MessageParams
                {
                    Message = m,
                    OwnerUri = ownerUri
                };
                await eventSender.SendEvent(MessageEvent.Type, eventParams);
            };
            query.BatchMessageSent += batchMessageCallback;

            // Setup the ResultSet completion callback
            ResultSet.ResultSetAsyncEventHandler resultCallback = async r =>
            {
                ResultSetEventParams eventParams = new ResultSetEventParams
                {
                    ResultSetSummary = r.Summary,
                    OwnerUri = ownerUri
                };
                await eventSender.SendEvent(ResultSetCompleteEvent.Type, eventParams);
            };
            query.ResultSetCompleted += resultCallback;

            // Launch this as an asynchronous task
            query.Execute();
        }

        private async Task SaveResultsHelper(SaveResultsRequestParams saveParams,
            RequestContext<SaveResultRequestResult> requestContext, IFileStreamFactory fileFactory)
        {
            // retrieve query for OwnerUri
            Query query;
            if (!ActiveQueries.TryGetValue(saveParams.OwnerUri, out query))
            {
                await requestContext.SendError(new SaveResultRequestError
                {
                    message = SR.QueryServiceQueryInvalidOwnerUri
                });
                return;
            }

            //Setup the callback for completion of the save task
            ResultSet.SaveAsAsyncEventHandler successHandler = async parameters =>
            {
                await requestContext.SendResult(new SaveResultRequestResult());
            };
            ResultSet.SaveAsFailureAsyncEventHandler errorHandler = async (parameters, reason) =>
            {
                string message = SR.QueryServiceSaveAsFail(Path.GetFileName(parameters.FilePath), reason);
                await requestContext.SendError(new SaveResultRequestError { message = message });
            };

            try
            {
                // Launch the task
                query.SaveAs(saveParams, fileFactory, successHandler, errorHandler);
            }
            catch (Exception e)
            {
                await errorHandler(saveParams, e.Message);
            }
        }

        // Internal for testing purposes
        internal string GetSqlText(ExecuteRequestParamsBase request)
        {
            // If it is a document selection, we'll retrieve the text from the document
            ExecuteDocumentSelectionParams docRequest = request as ExecuteDocumentSelectionParams;
            if (docRequest != null)
            {
                // Get the document from the parameters
                ScriptFile queryFile = WorkspaceService.Workspace.GetFile(docRequest.OwnerUri);

                // If a selection was not provided, use the entire document
                if (docRequest.QuerySelection == null)
                {
                    return queryFile.Contents;
                }

                // A selection was provided, so get the lines in the selected range
                string[] queryTextArray = queryFile.GetLinesInRange(
                    new BufferRange(
                        new BufferPosition(
                            docRequest.QuerySelection.StartLine + 1,
                            docRequest.QuerySelection.StartColumn + 1
                        ),
                        new BufferPosition(
                            docRequest.QuerySelection.EndLine + 1,
                            docRequest.QuerySelection.EndColumn + 1
                        )
                    )
                );
                return string.Join(Environment.NewLine, queryTextArray);
            }

            // If it is an ExecuteStringParams, return the text as is
            ExecuteStringParams stringRequest = request as ExecuteStringParams;
            if (stringRequest != null)
            {
                return stringRequest.Query;
            }

            // Note, this shouldn't be possible due to inheritance rules
            throw new InvalidCastException("Invalid request type");
        }

        /// Internal for testing purposes
        internal Task UpdateSettings(SqlToolsSettings newSettings, SqlToolsSettings oldSettings, EventContext eventContext)
        {
            Settings.QueryExecutionSettings.Update(newSettings.QueryExecutionSettings);
            return Task.FromResult(0);
        }

        #endregion

        #region IDisposable Implementation

        private bool disposed;

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        private void Dispose(bool disposing)
        {
            if (disposed)
            {
                return;
            }

            if (disposing)
            {
                foreach (var query in ActiveQueries)
                {
                    if (!query.Value.HasExecuted)
                    {
                        try
                        {
                            query.Value.Cancel();
                        }
                        catch (Exception e)
                        {
                            // We don't particularly care if we fail to cancel during shutdown
                            string message = string.Format("Failed to cancel query {0} during query service disposal: {1}", query.Key, e);
                            Logger.Write(LogLevel.Warning, message);
                        }
                    }
                    query.Value.Dispose();
                }
                ActiveQueries.Clear();
            }

            disposed = true;
        }

        ~QueryExecutionService()
        {
            Dispose(false);
        }

        #endregion
    }
}