inabox/InABox.Core/DigitalForms/DigitalFormDocumentFactory.cs

using System;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using InABox.Clients;

namespace InABox.Core
{

    public interface IDigitalFormDocumentHandler
    {
        Task<byte[]?> LoadDocumentAsync(Guid id);
        byte[]? LoadDocument(Guid id);
        Guid SaveDocument(byte[] data);
        void Run();
        void Stop();
    }

    public abstract class DigitalFormDocumentHandler : IDigitalFormDocumentHandler
    {

        private static String FileName(Guid id) => $"{id}.formdocument";
        
        protected abstract String CachePath { get; }
        
        protected abstract bool IsConnected { get; }
        
        private static Action<bool>? _status;

        public byte[]? LoadDocument(Guid id)
        {
            var fullpath = Path.Combine(CachePath, FileName(id));
            if (File.Exists(fullpath))
                return File.ReadAllBytes(fullpath);

            var result = new Client<Document>().Query(
                Filter<Document>.Where(x => x.FileName).IsEqualTo(FileName(id)),
                null,
                null
            ).Rows.FirstOrDefault()?.Get<Document,byte[]>(c=>c.Data);
            return result;
        }
        
        public async Task<byte[]?> LoadDocumentAsync(Guid id)
        {
            var fullpath = Path.Combine(CachePath, FileName(id));
            if (File.Exists(fullpath))
                return File.ReadAllBytes(fullpath);
            else
            {
                var data = await Client.QueryAsync(
                    Filter<Document>.Where(x => x.FileName).IsEqualTo(FileName(id)),
                    Columns.None<Document>().Add(x => x.Data),
                    null,
                    CoreRange.All);
                return data.Rows.FirstOrDefault()?.Get<Document, byte[]>(x => x.Data);
            }
        }

        public Guid SaveDocument(byte[] data)
        {
            Guid result = Guid.NewGuid();
            var filename = Path.Combine(CachePath, FileName(result));
            File.WriteAllBytes(filename,data);
            return result;
        }

        private CancellationTokenSource? _cancel;

        public void Stop()
        {
            if (_cancel != null)
            {
                _cancel.Cancel();
                _cancel = null;
            }
        }
        
        protected DigitalFormDocumentHandler(Action<bool> status)
        {
            _status = status;
        }
        
        public void Run()
        {
            Stop();
            _cancel = new CancellationTokenSource();
            Task.Run(
                () =>
                {
                    bool? previouslyActive = null;
                    while (_cancel?.IsCancellationRequested != true)
                    {
                        try
                        {
                            var file = Directory.EnumerateFiles(CachePath, "*.formdocument")
                                .FirstOrDefault();

                            var isActive = !String.IsNullOrWhiteSpace(file);
                            if (isActive != previouslyActive)
                            {
                                previouslyActive = isActive;
                                _status?.Invoke(isActive);
                            }

                            if (!String.IsNullOrWhiteSpace(file) && File.Exists(file) && IsConnected)
                            {
                                var data = File.ReadAllBytes(file);
                                var document = new Document()
                                {
                                    FileName = Path.GetFileName(file),
                                    Data = data,
                                    CRC = CoreUtils.CalculateCRC(data),
                                    TimeStamp = DateTime.Now,
                                    Created = DateTime.Now,
                                    CreatedBy = ClientFactory.UserID
                                };
                                new Client<Document>().Save(document, "Uploaded from Mobile Device");
                                File.Delete(file);
                            }
                        }
                        catch(Exception e)
                        {
                            CoreUtils.LogException("", e);
                        }

                        Thread.Sleep(1000);
                    }
                },
                _cancel.Token
            );
        }
    }

    public static class DigitalFormDocumentFactory
    {

        private static IDigitalFormDocumentHandler? _handler;
        

        public static void Init<THandler>(THandler handler) where THandler : IDigitalFormDocumentHandler
        {
            _handler = handler;
        }

        public static IDigitalFormDocumentHandler Handler => _handler ?? throw new Exception("Digital form document handler uninitialised.");

        public static void Run() => _handler?.Run();
        public static void Stop() => _handler?.Stop();

        public static void LoadDocument(Guid id, Action<byte[]> callback) =>
            LoadDocumentAsync(id).ContinueWith(task => callback(task.Result), TaskScheduler.FromCurrentSynchronizationContext());
        public static Task<byte[]> LoadDocumentAsync(Guid id) => Handler.LoadDocumentAsync(id).ContinueWith(task => task.Result ?? Array.Empty<byte>());
        public static byte[] LoadDocument(Guid id) => Handler.LoadDocument(id) ?? Array.Empty<byte>();
        public static Guid SaveDocument(byte[] data) => Handler.SaveDocument(data);
        
    }
}