using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Dapper;
using DataModel.Helpers;
using DataModel.Models;
using DataModel.Process;
using Newtonsoft.Json;
using NLog;
using WorkerService.Models;

namespace WorkerService.Process
{
    /// <summary>
    /// Data update processor
    /// </summary>
    public partial class UpdateProcessor
    {
        /// <summary>
        /// Shared logger instance
        /// </summary>
        private static readonly Logger logger = LogManager.GetCurrentClassLogger();

        /// <summary>
        /// Collection of configured data source update configurations
        /// </summary>
        public static readonly List<DataSourceConfig> configs = new List<DataSourceConfig>();

        /// <summary>
        /// Static class initializer
        /// </summary>
        static UpdateProcessor()
        {
            foreach (string configFileName in Directory.GetFiles("dsconfig"))
            {
                //continue;
                DataSourceConfig config = JsonConvert.DeserializeObject<DataSourceConfig>(File.ReadAllText(configFileName));

                if (config.IsEnabled) { configs.Add(config); }
            }
        }

        public static void DoUpdate(string tableName, UpdateTypes updateType = UpdateTypes.Mass)
        {
            DataSourceConfig dataSourceConfig = configs.FirstOrDefault(c => c.TableName.Equals(tableName, StringComparison.CurrentCultureIgnoreCase));

            //Get last data updates
            List<LastDataUpdate> lastDataUpdates = null;
            using (SqlConnection connection = LotFinderDB.GetConnection())
            {
                lastDataUpdates = GetLastDataUpdates(connection);
            }

            LastDataUpdate lastDataUpdate = lastDataUpdates.FirstOrDefault(ldu => ldu.TableName.Equals(dataSourceConfig.TableName));
            DateTime? minDT = null;
            switch (updateType)
            {
                case UpdateTypes.Mass:
                    minDT = null;
                    break;
                case UpdateTypes.Daily:
                    minDT = lastDataUpdate.DailyUpdateDT.AddMinutes(-3 * dataSourceConfig.DailyUpdateConfig.Interval);
                    break;
                case UpdateTypes.Hourly:
                    minDT = lastDataUpdate.HourlyUpdateDT.AddMinutes(-3 * dataSourceConfig.HourlyUpdateConfig.Interval);
                    break;
            }

            DoUpdate(dataSourceConfig, updateType, minDT);
        }

        /// <summary>
        /// Gets list of pending data update tasks
        /// </summary>
        /// <returns>Pending data update tasks</returns>
        public static List<DataUpdateTask> GetPendingUpdateTasks()
        {
            List<DataUpdateTask> pending = new List<DataUpdateTask>();

            using (SqlConnection connection = LotFinderDB.GetConnection())
            {
                //Get last data updates
                List<LastDataUpdate> lastDataUpdates = GetLastDataUpdates(connection);

                foreach (DataSourceConfig dataSourceConfig in configs)
                {
                    LastDataUpdate lastDataUpdate = lastDataUpdates.FirstOrDefault(ldu => ldu.TableName.Equals(dataSourceConfig.TableName));

                    if (lastDataUpdate == null || (dataSourceConfig.MassUpdateConfig.Enabled && DateTime.Now > lastDataUpdate.MassUpdateDT.AddMinutes(dataSourceConfig.MassUpdateConfig.Interval)))
                    {
                        pending.Add(new DataUpdateTask() { Configuration = dataSourceConfig, UpdateType = UpdateTypes.Mass });
                    }
                    else if (dataSourceConfig.DailyUpdateConfig.Enabled && DateTime.Now > lastDataUpdate.DailyUpdateDT.AddMinutes(dataSourceConfig.DailyUpdateConfig.Interval))
                    {
                        pending.Add(new DataUpdateTask() { Configuration = dataSourceConfig, UpdateType = UpdateTypes.Daily, MinimumDT = lastDataUpdate.DailyUpdateDT.AddMinutes(-3 * dataSourceConfig.DailyUpdateConfig.Interval) });
                    }
                    else if (dataSourceConfig.HourlyUpdateConfig.Enabled && DateTime.Now > lastDataUpdate.HourlyUpdateDT.AddMinutes(dataSourceConfig.HourlyUpdateConfig.Interval))
                    {
                        pending.Add(new DataUpdateTask() { Configuration = dataSourceConfig, UpdateType = UpdateTypes.Hourly, MinimumDT = lastDataUpdate.DailyUpdateDT.AddMinutes(-3 * dataSourceConfig.DailyUpdateConfig.Interval) });
                    }
                }
            }

            return pending;
        }

        /// <summary>
        /// Performs the data update
        /// </summary>
        /// <param name="dataUpdateTask">Data update task to execute</param>
        /// <returns>Data update results</returns>
        public static DataUpdate DoUpdate(DataUpdateTask dataUpdateTask)
        {
            logger.Info($"Starting [{dataUpdateTask.UpdateType}] data update for {dataUpdateTask.Configuration.TableName}...");
            return DoUpdate(dataUpdateTask.Configuration, dataUpdateTask.UpdateType, dataUpdateTask.MinimumDT);
        }

        /// <summary>
        /// Performs the data update
        /// </summary>
        /// <param name="config">Data source configuration</param>
        /// <param name="updateType">Type of update to perform</param>
        /// <param name="minDT">Minimum timestamp to update data from</param>
        /// <returns>Data update results</returns>
        public static DataUpdate DoUpdate(DataSourceConfig config, UpdateTypes updateType, DateTime? minDT)
        {
            //Log start of data update
            DataUpdate dataUpdate = new DataUpdate()
            {
                SourceSystem = config.SourceSystem,
                SourceData = config.SourceData,
                TableName = config.TableName,
                UpdateType = updateType,
                StartDT = DateTime.Now,
                NumberRecords = 0
            };

            //Get data update configuration details
            DataUpdateConfig updateConfig;
            switch (updateType)
            {
                case UpdateTypes.Hourly:
                    updateConfig = config.HourlyUpdateConfig;
                    break;
                case UpdateTypes.Daily:
                    updateConfig = config.DailyUpdateConfig;
                    break;
                case UpdateTypes.Mass:
                    updateConfig = config.MassUpdateConfig;
                    break;
                default:
                    throw new ArgumentOutOfRangeException(nameof(updateType), updateType, null);
            }

            using (SqlConnection connection = LotFinderDB.GetConnection())
            {
                LogDataUpdateStart(connection, dataUpdate);

                //Clear destination table if needed
                if (updateConfig.PrepurgeData)
                {
                    TruncateTable(connection, config.TableName);
                }

                Type sourceType = config.DataFetchFunction.Method.ReturnType.GenericTypeArguments[0];

                //Fetch data
                IEnumerable<dynamic> data = config.DataFetchFunction(minDT);

                //Generate SQL to merge temp data to destination table
                string mergeSQL = GenerateMerge(connection, config.TableName);

                foreach (var batch in data.BatchGroup(1000000))
                {
                    //Setup temp table
                    string stagingTableName = CreateStagingTable(connection, config.TableName);

                    //Copy data to temp table
                    SqlBulkCopy bulkCopy = GenerateBulkCopy(connection, config.TableName, sourceType);
                    IDataReader reader = new GenericListDataReader(batch, sourceType);
                    bulkCopy.WriteToServer(reader);
                    dataUpdate.NumberRecords += batch.Count;

                    //Index temp table
                    RebuildIndicies(connection, stagingTableName);

                    //Copy to temp table
                    string tempTableName = CreateTempTable(connection, config.TableName);

                    //Merge data from temp table to destination table
                    connection.Execute(mergeSQL, commandTimeout: 6000);

                    logger.Debug("DoUpdate: {0:n0} rows merged to {1}", dataUpdate.NumberRecords, config.TableName);
                }

                //Run post processing action if configured
                if (config.PostProcessingAction != null)
                {
                    config.PostProcessingAction();
                }

                //Re-index destination table if needed
                if (updateConfig.ReIndexData)
                {
                    RebuildIndicies(connection, dataUpdate.TableName);
                }

                //Update data update entry
                dataUpdate.WasSuccessful = true;
                LogDataUpdateEnd(connection, dataUpdate);
            }

            return dataUpdate;
        }
    }
}