inabox/InABox.Mobile/InABox.Mobile.Shared/DataModels/Lists/ListModel.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using InABox.Core;
using System.Diagnostics.CodeAnalysis;

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

        protected ListModel(IModelHost host, Func<Filter<TEntity>> filter, [NotNull] String filename) : base(host, filter, filename)
        {
            Reset();
        }
        
        protected override void Initialize()
        {
            _allitems = null;
            _items.Clear();
        }

        public virtual SortOrder<TEntity> Sort => LookupFactory.DefineSort<TEntity>();
        
        private IList<TItem> _allitems;

        private CoreTable _table = new CoreTable();
        
        private readonly CoreObservableCollection<TItem> _items = new CoreObservableCollection<TItem>();
        
        public IList<TItem> Items => _items;

        IEnumerable IListModel.Items => this.Items;
        
        public Func<TItem, bool> SearchPredicate { get; set; }

        public void Search(Func<TItem, bool> predicate)
        {
            SearchPredicate = predicate;
            Search();
        }

        public void Search()
        {
            _items.ReplaceRange(
                SearchPredicate != null
                    ? new List<TItem>(_allitems.Where(SearchPredicate))
                    : new List<TItem>(_allitems)
            );
        }

        protected virtual Expression<Func<TEntity, object>> ImageColumn => null;
        
        public override void BeforeLoad(MultiQuery query)
        {
            
        }        
        
        public override void AfterLoad(MultiQuery query)
        {
      
        }
        
        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(); 
        }
        
        public override void Load(Action loaded = null)
        {
            MultiQuery query = new MultiQuery();
            
            query.Add(
                Filter(),
                GetColumns<TItem,TEntity>(),
                Sort
            );
            
            if (ImageColumn != null)
            {
                query.Add<Document>(
                    new Filter<Document>(x => x.ID).InQuery(Filter(), ImageColumn),
                    new Columns<Document>(x => x.ID)
                        .Add(x => x.Data)
                );
            }
            
            BeforeLoad(query);

            // If we have a valid transport, always try and get new data from the server
            if (Host.IsConnected())
            {
                if (loaded != null)
                    query.Query((q) =>
                    {
                        if (Type == ModelType.Persistent)
                            SaveToStorage(q);
                        DoAfterLoad(q, loaded);
                    });
                else
                {
                    query.Query();
                    if (Type == ModelType.Persistent)
                        SaveToStorage(query);
                    DoAfterLoad(query);
                }
            }
            else
            {
                if (Type == ModelType.Transient)
                {
                    InitializeTables(query);
                }
                else if (Type == ModelType.Normal)
                {
                    // Only load 
                    if (_allitems == 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 (_allitems == null)
                        LoadFromStorage(query);
                }

                DoAfterLoad(query, loaded);
            }
        }
        
        private void DoAfterLoad(MultiQuery query, Action loaded = null)
        {
            _table = query.Get<TEntity>();
            _allitems = new List<TItem>(query.Get<TEntity>().Rows.Select(row => CreateItem<TItem>(row)));
                    
            if (ImageColumn != null)
            {
                Images.Clear();
                query.Get<Document>().IntoDictionary<Document, Guid, byte[]>(Images, x => x.ID,
                    r => r.Get<Document, byte[]>(x => x.Data));
            }
            Search(null);
            AfterLoad(query);
            Loaded = true;
            loaded?.Invoke();   
            NotifyChanged();
        }

        protected T CreateItem<T>(CoreRow row) 
            where T : Shell<TParent,TEntity>, new()
        {
            var result = new T() { Row = row, Parent = (TParent)this };
            result.PropertyChanged += (sender, args) => DoPropertyChanged(result, args);
            return result;
        }

        public TItem CreateItem()
        {
            CoreRow row = _table.NewRow();
            var result = CreateItem<TItem>(row);
            return result;
        }
        
        public void CommitItem(TItem item)
        {
            _table.Rows.Add(item.Row);
            _allitems.Add(item);
            NotifyChanged();
        }
        
        public TItem AddItem()
        {
            var result = CreateItem();
            CommitItem(result);
            return result;
        }
        
        public void DeleteItem(TItem item)
        {
            _table.Rows.Remove(item.Row);
            _allitems.Remove(item);
            NotifyChanged();
        }

        object IListModel.CreateItem() => this.CreateItem();
        
        void IListModel.CommitItem(object item)
        {
            if (item is TItem titem)
                CommitItem(titem);
        }
        
        object IListModel.AddItem() => this.AddItem();
        
        void IListModel.DeleteItem(object item)
        {
            if (item is TItem titem)
                DeleteItem(titem);
        }

        IEnumerator<TItem> IEnumerable<TItem>.GetEnumerator()
        {
            return Items.GetEnumerator();
        }

        public IEnumerator GetEnumerator()
        {
            return Items.GetEnumerator();
        }

    }
    

    
}