inabox/InABox.Mobile/InABox.Mobile.Shared/DataModels/Model.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.CompilerServices;
using InABox.Clients;
using InABox.Core;
using InABox.Mobile;
using Xamarin.Forms;

namespace InABox.Mobile
{
    
    public abstract class Model<TParent, TItem, TEntity> : BindableObject, IModel
        where TParent : Model<TParent, TItem, TEntity>, IModel
        where TEntity : Entity, IRemotable, IPersistent, new() 
        where TItem : Shell<TParent, TEntity>, new()
    {
        
        public Model(IModelHost host, Func<Filter<TEntity>> filter, bool transient = false)
        {
            Reset();
            new TItem();
            Host = host;
            Filter = filter;
            Type = transient ? ModelType.Transient : ModelType.Normal;
        }

        public Model(IModelHost host, Func<Filter<TEntity>> filter, [NotNull] String filename)
        {
            Reset();
            new TItem();
            Host = host;
            Type = ModelType.Persistent;
            Filter = filter;
            FileName = filename;
        }
        
        #region INotifyPropertyChanged
        
        public event PropertyChangedEventHandler PropertyChanged;

        protected void DoPropertyChanged(object sender, PropertyChangedEventArgs args)
        {
            PropertyChanged?.Invoke(sender, args);
        }
        
        protected bool SetProperty<T>(ref T field, T value, [CallerMemberName] string propertyName = null)
        {
            if (EqualityComparer<T>.Default.Equals(field, value)) return false;
            field = value;
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
            return true;
        }
        
        #endregion
        
        public bool Loaded { get; protected set; }
        
        public abstract void BeforeLoad(MultiQuery query);
        public abstract void AfterLoad(MultiQuery query);
        public abstract void Load(Action loaded = null);
        public abstract IModel Refresh(bool force);
        public abstract void Refresh(bool force, Action loaded);

        public event ModelChangedEvent Changed;
        protected void NotifyChanged() => Changed?.Invoke(this, new ModelChangedEventArgs());

        protected abstract void Initialize();
        
        public void Reset()
        {
            Loaded = false;
            Images.Clear();
            Initialize();
        }
        
        protected Func<Filter<TEntity>> Filter { get; set; }
        
        // // Use "new" to replace this with your actual columns 
        // public Columns<TEntity> Columns
        // {
        //     get
        //     {
        //         var prop = typeof(TItem).GetProperty("Columns",
        //             BindingFlags.Public | BindingFlags.Static | BindingFlags.FlattenHierarchy);
        //         var cols = prop?.GetValue(null) as IShellColumns<TEntity>;
        //         return cols?.Columns;
        //     }
        // }
        
        protected Columns<TOtherEntity> GetColumns<TOtherItem, TOtherEntity>()
            where TOtherItem : Shell<TParent, TOtherEntity>, new()
            where TOtherEntity : Entity, IRemotable, IPersistent, new()
        {
            return new TOtherItem().Columns.Columns;
        }

        //public IColumns GetColumns() => Columns;
        
        public Dictionary<Guid, byte[]> Images { get; private set; } = new Dictionary<Guid, byte[]>();

        public ImageSource GetImage(Guid id)
        {
            ImageSource result = null;
            if (Images.TryGetValue(id, out byte[] data))
                result = ImageSource.FromStream(() => new MemoryStream(data));
            return result;
            
        }
        
        public bool HasImages() => Images.Any();

        public IModelHost Host { get; private set; }
        
        public ModelType Type { get; private set; }
        
        public String FileName { get; private set; }
        
        protected void InitializeTables(MultiQuery query)
        {
            var defs = query.Definitions();
            foreach (var def in defs)
            {
                var table = InitializeTable(def.Value);
                query.Set(def.Key, table);
            }
        }

        protected CoreTable InitializeTable(IQueryDef def)
        {
            var table = new CoreTable();
            if (def.Columns != null)
                table.LoadColumns(def.Columns);
            else
                table.LoadColumns(def.Type);
            return table;
        }

        protected class QueryStorage : ISerializeBinary
        {
            private Dictionary<String, CoreTable> _data = new Dictionary<string, CoreTable>();

            public CoreTable Get([NotNull] String key) => _data[key];
            
            public void Set([NotNull] String key, CoreTable table) => _data[key] = table;

            public bool Contains([NotNull] String key) => _data.ContainsKey(key);
            
            public void SerializeBinary(CoreBinaryWriter writer)
            {
               writer.Write(_data.Count);
               foreach (var key in _data.Keys)
               {
                   writer.Write(key);
                   _data[key].SerializeBinary(writer);
               }
            }

            public void DeserializeBinary(CoreBinaryReader reader)
            {
                int count = reader.ReadInt32();
                for (int i = 0; i < count; i++)
                {
                    String key = reader.ReadString();
                    CoreTable table = new CoreTable();
                    table.DeserializeBinary(reader);
                    _data[key] = table;
                }
            }
        }
        
        protected void LoadFromStorage(MultiQuery query)
        {
            QueryStorage storage = new QueryStorage();
            var file = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), FileName);
            if (File.Exists(file))
            {
                using (var stream = new FileStream(file, FileMode.Open))
                    storage = Serialization.ReadBinary<QueryStorage>(stream, BinarySerializationSettings.Latest);
                var defs = query.Definitions();
                foreach (var key in defs.Keys)
                {
                    var table = storage.Contains(key.ToString())
                        ? storage.Get(key.ToString())
                        : InitializeTable(defs[key]);
                    query.Set(key, table);
                }
            }
            else
                InitializeTables(query);
        }
        
        protected void SaveToStorage(MultiQuery query)
        {
            QueryStorage storage = new QueryStorage();
            var results = query.Results();
            foreach (var key in results.Keys)
                storage.Set(key.ToString(),results[key]);
            var data = storage.WriteBinary(BinarySerializationSettings.Latest);
            try
            {
                var file = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), FileName);
                File.WriteAllBytes(file,data);
            }
            catch (Exception e)
            {
                MobileLogging.Log(e);
            }

        }

    }
}