inabox/InABox.Mobile/InABox.Mobile.Shared/DataModels/Details/DetailModel.cs

using System;
using System.IO;
using System.Linq;
using System.Linq.Expressions;
using System.Threading;
using InABox.Clients;
using InABox.Core;
using System.Diagnostics.CodeAnalysis;

namespace InABox.Mobile
{
    public abstract class DetailModel<TParent, TItem, TEntity> : Model<TParent,TItem,TEntity>, IDetailModel<TParent, TItem, TEntity>
        where TParent : DetailModel<TParent, TItem, TEntity>, IModel
        where TEntity : Entity, IRemotable, IPersistent, new() 
        where TItem : Shell<TParent, TEntity>, new()
    {
        protected DetailModel(IModelHost host, Func<Filter<TEntity>> filter, bool transient = false) : base(host, filter, transient)
        {
        }

        protected DetailModel(IModelHost host, Func<Filter<TEntity>> filter, [NotNull] String filename) : base(host, filter, filename)
        {
        }
        
        protected override void Initialize()
        {
            Filter = null;
            Item = null;
        }
        
        private TItem _item;

        public TItem Item
        {
            get => _item;
            set => SetProperty(ref _item, value);
        }
        
        protected virtual Expression<Func<TEntity, object>> ImageColumn { get; }

        private void DoBeforeLoad(MultiQuery query)
        {
            if (ImageColumn != null)
                query.Add<Document>(
                    new Filter<Document>(x => x.ID).InQuery<TEntity>(Filter(),ImageColumn),
                    new Columns<Document>(x=>x.ID).Add(x=>x.Data)
                );
            BeforeLoad(query);
        }
        
        public override void BeforeLoad(MultiQuery query)
        {
            
        }

        private void DoAfterLoad(MultiQuery query, Action loaded = null)
        {
            if (ImageColumn != null)
            {
                Images.Clear();
                query.Get<Document>().IntoDictionary<Document, Guid, byte[]>(Images, x => x.ID,
                    r => r.Get<Document, byte[]>(x => x.Data));
            }
            AfterLoad(query);
            Loaded = true;
            loaded?.Invoke();
            NotifyChanged();
        }
        
        public override void AfterLoad(MultiQuery query)
        {

        }

        private TItem CreateItemFromEntity(TEntity entity)
        {
            CoreTable table = new CoreTable();
            table.LoadColumns(GetColumns<TItem,TEntity>());
            CoreRow row = table.NewRow();
            if (entity != null)
                table.LoadRow(row, entity);
            var item = new TItem() { Row = row, Parent = this as TParent };
            item.PropertyChanged += DoPropertyChanged;
            return item;
        }
        
        private TItem CreateItemFromRow(CoreRow row)
        {
            var item = (row != null)
                ? new TItem() { Row = row, Parent = this as TParent }
                : CreateItemFromEntity(null);
            item.PropertyChanged += DoPropertyChanged;
            return item;
        }

        public void Load(TEntity entity, Action loaded = null)
        {

            Filter = () => new Filter<TEntity>(x => x.ID).IsEqualTo(entity.ID);
            MultiQuery query = new MultiQuery();
            
            DoBeforeLoad(query);

            Item = CreateItemFromEntity(entity);

            if (loaded != null)
                query.Query((q) => DoAfterLoad(q, loaded));
            else
            {
                query.Query();
                DoAfterLoad(query);
            }
        }
        
        public override void Load(Action loaded = null)
        {
            
            MultiQuery query = new MultiQuery();
            
            query.Add(
                Filter(),
                GetColumns<TItem,TEntity>()
            );
            
            DoBeforeLoad(query);
            
            if (Host.IsConnected())
            {
                if (loaded != null)
                    query.Query((q) =>
                    {
                        if (Type == ModelType.Persistent)
                            SaveToStorage(query);
                        Item = CreateItemFromRow(q.Get<TEntity>().Rows.FirstOrDefault());
                        DoAfterLoad(q, loaded);
                    });
                else
                {
                    query.Query();
                    if (Type == ModelType.Persistent)
                        SaveToStorage(query);
                    Item = CreateItemFromRow(query.Get<TEntity>().Rows.FirstOrDefault());
                    DoAfterLoad(query);
                }
            }
            else
            {
                if (Type == ModelType.Transient)
                {
                    InitializeTables(query);
                }
                else if (Type == ModelType.Normal)
                {
                    // Only load 
                    if (_item == null)
                        InitializeTables(query);
                }
                else if (Type == ModelType.Persistent)
                {
                    // Treat it as normal, unless its the first time through
                    // in which case try to load it from storage, if the 
                    //  data has been previously cached
                    if (_item == null)
                        LoadFromStorage(query);
                }
                Item = CreateItemFromRow(query.Get<TEntity>().Rows.FirstOrDefault());
                DoAfterLoad(query, loaded);
            }

        }
        
        protected virtual void BeforeSave(TItem item)
        {
            
        }
        
        protected virtual void AfterSave(TItem item)
        {
            
        }
        
        public void Save(String auditmessage)
        {
            BeforeSave(Item);
            new Client<TEntity>().Save(Item.Entity,auditmessage);
            AfterSave(Item);
        }
        
        public override IModel Refresh(bool force)
        {
            if (!Loaded || force)
                Load();
            return this;
        }
        
        public override void Refresh(bool force, Action loaded)
        {
            if (!Loaded || force)
                Load(loaded);
            else
                loaded?.Invoke(); 
        }

    }
}