using System.Threading.Tasks;
using AyaNova.Util;
using AyaNova.Api.ControllerHelpers;
using AyaNova.Models;
using Microsoft.Extensions.Logging;
using System;
using Microsoft.EntityFrameworkCore;
using System.Linq;


namespace AyaNova.Biz
{


    /// <summary>
    /// Handle attachment file related cleanup and checking
    /// </summary>
    internal class AttachmentBiz : BizObject, IJobObject
    {
        internal AttachmentBiz(AyContext dbcontext, long currentUserId, AuthorizationRoles userRoles)
        {
            ct = dbcontext;
            UserId = currentUserId;
            CurrentUserRoles = userRoles;
            BizType = AyaType.FileAttachment;
        }

        ////////////////////////////////////////////////////////////////////////////////////////////////
        //JOB / OPERATIONS
        //
        public async Task HandleJobAsync(OpsJob job)
        {
            //Hand off the particular job to the corresponding processing code
            //NOTE: If this code throws an exception the caller (JobsBiz::ProcessJobsAsync) will automatically set the job to failed and log the exeption so 
            //basically any error condition during job processing should throw up an exception if it can't be handled

            //There might be future other job types so doing it like this for all biz job handlers for now
            switch (job.JobType)
            {
                case JobType.AttachmentMaintenance:
                    await ProcessAttachmentMaintenanceAsync(job);
                    break;
                default:
                    throw new System.ArgumentOutOfRangeException($"AttachmentBiz.HandleJobAsync -> Invalid job type{job.JobType.ToString()}");
            }
        }


        /// <summary>
        /// Handle the job
        /// </summary>
        /// <param name="job"></param>
        private async Task ProcessAttachmentMaintenanceAsync(OpsJob job)
        {
            ILogger log = AyaNova.Util.ApplicationLogging.CreateLogger("AttachmentMaintenanceJob");
            ApiServerState apiServerState = (ApiServerState)ServiceProviderProvider.Provider.GetService(typeof(ApiServerState));

            //get the current server state so can set back to it later
            ApiServerState.ServerState wasServerState = apiServerState.GetState();
            string wasReason = apiServerState.Reason;
            try
            {
                await JobsBiz.UpdateJobStatusAsync(job.GId, JobStatus.Running);
                await JobsBiz.LogJobAsync(job.GId, $"Starting...");
                apiServerState.SetOpsOnly("Attachment file maintenance");




                // EXISTENCE CHECK
                //iterate all records in chunks
                bool moreRecords = true;
                int skip = 0;
                int chunkSize = 100;
                do
                {
                    var chunk = await ct.FileAttachment.AsNoTracking().OrderBy(z => z.Id).Skip(skip).Take(chunkSize).Select(z => new NameIdItem { Id = z.Id, Name = z.StoredFileName }).ToListAsync();
                    if (chunk.Count < chunkSize)
                    {
                        //we've reached the end
                        moreRecords = false;
                    }
                    skip += chunkSize;
                    foreach (NameIdItem i in chunk)
                    {
                        //Does file exists where it's supposed to be?
                        if (!FileUtil.AttachmentFileExists(i.Name))
                        {
                            var f = await ct.FileAttachment.FirstOrDefaultAsync(z => z.Id == i.Id);
                            if (f != null)
                            {
                                f.Exists = false;
                                await ct.SaveChangesAsync();
                            }
                        }
                    }

                } while (moreRecords);
                // long totalRecs = await ct.FileAttachment.LongCountAsync();

                var allAttachments = FileUtil.GetAllAttachmentFilePaths();

                // 	iterate FileAttachment records, if physically present then flag as such
                // 	make sure it has a short circuit that if there are NO files physically then all are out of sync
                // 		this scenario is someone moving a db and not moving physical files
                // ORPHANED FILES CHECK
                // 	These should never be out of sync due to timing issues, the file would be deleted before teh db record
                // 	iterate physical files, if not in db then make a FileAttachment record for it AyaType nothing id 0
                // 		if user want's to move them, they can download and then attach and then remove the generated attachment (Nothing id 0) the holder of orphaned files
                // 			(Or move feature)
                // DE-ORPHANIZE ACTION
                // 	iterate orphaned file attachments to NOTHING type, if found to be attached to any other object remove the orphaned object attachement



                await JobsBiz.LogJobAsync(job.GId, "Finished.");
                await JobsBiz.UpdateJobStatusAsync(job.GId, JobStatus.Completed);
            }
            catch (Exception ex)
            {
                log.LogError(ex, "AttachmentMaintenanceJob error during ops");

                await JobsBiz.LogJobAsync(job.GId, $"AttachmentMaintenanceJob error during ops\r\n{ex.Message}");
                throw ex;
            }
            finally
            {
                log.LogInformation($"AttachmentMaintenanceJob: setting server state back to {wasServerState.ToString()}");
                apiServerState.SetState(wasServerState, wasReason);
            }
        }



        //Other job handlers here...



        /////////////////////////////////////////////////////////////////////

    }//eoc


}//eons