using System.Threading.Tasks;
using Sockeye.Util;
using Sockeye.Api.ControllerHelpers;
using Sockeye.Models;
using Microsoft.Extensions.Logging;
using System;
using Microsoft.EntityFrameworkCore;
using System.Linq;
using System.Collections.Generic;


namespace Sockeye.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 = SockType.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 = Sockeye.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, $"LT:StartJob ");
                apiServerState.SetOpsOnly("Attachment file maintenance");

                //get a list of all attachment files currently on disk
                var AllAttachmentFilesOnDisk = FileUtil.GetAllAttachmentFilePaths();

                List<string> AllDBFileFullPath = new List<string>();


                // EXISTENCE CHECK
                //iterate all records in chunks, update the existence bool field if it's incorrect only
                bool moreRecords = true;
                int skip = 0;
                int chunkSize = 100;
                do
                {
                    var chunk = await ct.FileAttachment.AsNoTracking().OrderBy(z => z.Id).Skip(skip).Take(chunkSize).ToListAsync();
                    if (chunk.Count < chunkSize)
                    {
                        //we've reached the end
                        moreRecords = false;
                    }
                    skip += chunkSize;
                    foreach (var i in chunk)
                    {
                        var FullPathName = FileUtil.GetPermanentAttachmentFilePath(i.StoredFileName);
                        AllDBFileFullPath.Add(FullPathName);
                        var FileExistsInReality = AllAttachmentFilesOnDisk.Contains(FullPathName);
                        var ParentBizObjectExistsInReality = await BizObjectExistsInDatabase.ExistsAsync(i.AttachToAType, i.AttachToObjectId, ct);
                        //does the db record reflect the same status as reality?
                        if (FileExistsInReality != i.Exists || !ParentBizObjectExistsInReality)
                        {
                            var f = await ct.FileAttachment.FirstOrDefaultAsync(z => z.Id == i.Id);
                            if (f != null)
                            {
                                f.Exists = FileExistsInReality;
                                if (!ParentBizObjectExistsInReality)
                                {
                                    //switch it to notype
                                    f.AttachToAType = SockType.NoType;
                                    f.AttachToObjectId = 0;
                                }
                                await ct.SaveChangesAsync();
                            }
                        }

                        //DOES THE PARENT OBJECT EXIST?

                    }

                } while (moreRecords);

                //I kept this block because I did a lot of work to figure it out but in the end I don't need it because
                //a user will be moving attachments so they would no longer be existing on their old NOTYPE orphan location anyway
                // //DE-ORPHANIZE ACTION (clean up former orphans)                
                // //people can attach an orphan to another record so this cleans that up
                // //also, potentiallly
                // //iterate orphaned file attachments to NOTHING type, if found to be attached to any other object remove the orphaned object attachment record in db
                // //but keeping the physical file since it's attached to something else
                // var AllOrphansInDb = await ct.FileAttachment.Where(z => z.AttachToAType == SockType.NoType).ToListAsync();
                // foreach (FileAttachment OrphanInDb in AllOrphansInDb)
                // {
                //     if (await ct.FileAttachment.AnyAsync(z => z.StoredFileName==OrphanInDb.StoredFileName && z.AttachToAType != SockType.NoType))
                //     {
                //         //It is also attached to something else so remove it from the nothing type
                //         ct.FileAttachment.Remove(OrphanInDb);
                //         await ct.SaveChangesAsync();
                //     }
                // }

                // ORPHANED FILES CHECK
                var FilesOnDiskNotInDb = AllAttachmentFilesOnDisk.Except(AllDBFileFullPath);
                if (FilesOnDiskNotInDb.Count() > 0)
                    await JobsBiz.LogJobAsync(job.GId, $"Found {FilesOnDiskNotInDb.Count()} physical files not known to be existing Attachments, creating attachment records tied to 'NoType' so they show in UI");

                //     	FOREIGN FILES placed in folder directly outside of attachment system
                // user thinks they can just drop them in or accidentally copies them here
                // Or, user renames a folder for some reason?
                // 	This is a good reason not to delete them, because they can just un-rename them to fix it
                // SWEEPER JOB
                // 	I think it should delete them outright, but maybe that's a bad idea, not sure
                // 	ID them to see if they *should* be one of ours by the file name I guess since it's the only identifying characteristic
                // 		is it in the correct folder which is named based on it's hash?
                // 		Is it X characters long (they all are or not?)
                // 		Does it have an extension?  None of ours have an extension

                //Vet the file and see if it has the characteristics of an attachment before re-attaching it, if not, compile into a list then log it and notify

                //Attach any found into the NOTHING object type with id 0 so they will be represented in attachment list for being dealt with
                List<string> ForeignFilesNotLikelyAttachmentsFoundInAttachmentsFolder = new List<string>();
                foreach (string orphan in FilesOnDiskNotInDb)
                {
                    if (FileUtil.AppearsToBeAnOrphanedAttachment(orphan))
                    {
                        FileAttachment fa = new FileAttachment();
                        fa.AttachToObjectId = 0;
                        fa.AttachToAType = SockType.NoType;
                        fa.ContentType = "application/octet-stream";//most generic type, we don't know what it is
                        fa.DisplayFileName = "FOUND" + FileUtil.GetSafeDateFileName();
                        fa.LastModified = DateTime.UtcNow;
                        fa.Notes = "Found in attachments folder not linked to an object";
                        fa.StoredFileName = System.IO.Path.GetFileName(orphan);
                        await ct.FileAttachment.AddAsync(fa);
                        await ct.SaveChangesAsync();
                    }
                    else
                    {
                        log.LogDebug($"Foreign file found in attachments folder but doesn't appear to belong {orphan}");
                        ForeignFilesNotLikelyAttachmentsFoundInAttachmentsFolder.Add(orphan);
                    }
                }

                //ok, these files could be important and shouldn't be here so notify and log as much as possible
                var ffcount = ForeignFilesNotLikelyAttachmentsFoundInAttachmentsFolder.Count;
                if (ffcount > 0)
                {
                    string msg = string.Empty;
                    if (ffcount < 25)
                    {
                        //we can list them all
                        msg = $"{ffcount} files found in attachments folder that don't appear to belong there:";
                    }
                    else
                    {
                        msg = $"{ffcount} files found in attachments folder that don't appear to belong there, here are the first 25";
                    }

                    log.LogDebug(msg);
                    await JobsBiz.LogJobAsync(job.GId, msg);
                    await NotifyEventHelper.AddOpsProblemEvent($"Attachments issue:{msg}");
                    var outList = ForeignFilesNotLikelyAttachmentsFoundInAttachmentsFolder.Take(25).ToList();
                    foreach (string s in outList)
                    {
                        log.LogDebug(s);
                        await JobsBiz.LogJobAsync(job.GId, s);
                    }
                }

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



        //Other job handlers here...

        ////////////////////////////////////////////////////////////////////////////////////////////////
        //DUPLICATE ATTACHMENTS TO NEW OBJECT
        //    
        internal static async Task DuplicateAttachments(SockTypeId aSource, SockTypeId aDest, AyContext ct)
        {
            var sources = await ct.FileAttachment.AsNoTracking()
                .Where(z => z.AttachToAType == aSource.SockType && z.AttachToObjectId == aSource.ObjectId)
                .ToListAsync();
            if (sources.Count > 0)
            {
                foreach (var src in sources)
                {
                    ct.FileAttachment.Add(new FileAttachment { AttachToObjectId = aDest.ObjectId, AttachToAType = aDest.SockType, StoredFileName = src.StoredFileName, DisplayFileName = src.DisplayFileName, ContentType = src.ContentType, LastModified = src.LastModified, Notes = src.Notes, Exists = src.Exists, Size = src.Size });
                }
                await ct.SaveChangesAsync();
            }
        }

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

    }//eoc


}//eons