RecordEnumerator.cs

using System;
using System.Collections;
using System.Threading.Tasks;
using Waher.Events;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Model;
 
namespace Waher.Script.Persistence.SQL.Enumerators
{
    public class RecordEnumerator : IResultSetEnumerator
    {
        private readonly IResultSetEnumerator e;
        private readonly ScriptNode[] columns;
        private readonly Variables variables;
        private readonly int count;
        private IElement[] record;
        private ObjectProperties properties = null;
 
        public RecordEnumerator(IResultSetEnumerator ItemEnumerator, ScriptNode[] Columns, Variables Variables)
        {
            this.e = ItemEnumerator;
            this.columns = Columns;
            this.variables = Variables;
            this.count = this.columns?.Length ?? 0;
        }
 
        public object Current => this.e.Current;
 
        public IElement[] CurrentRecord => this.record;
 
        public virtual bool MoveNext()
        {
            return this.MoveNextAsync().Result;
        }
 
        public virtual async Task<bool> MoveNextAsync()
        {
            if (!await this.e.MoveNextAsync())
                return false;
 
            int i;
            object Item = this.e.Current;
            IElement Element = Item as IElement;
 
            if (this.properties is null)
                this.properties = new ObjectProperties(Element?.AssociatedObjectValue ?? Item, this.variables);
            else
                this.properties.Object = Element?.AssociatedObjectValue ?? Item;
 
            if (this.columns is null)
                this.record = new IElement[1] { Element ?? Expression.Encapsulate(Item) };
            else
            {
                this.record = new IElement[this.count];
 
                for (i = 0; i < this.count; i++)
                {
                    try
                    {
                        this.record[i] = await this.columns[i].EvaluateAsync(this.properties);
                    }
                    catch (Exception ex)
                    {
                        ex = Log.UnnestException(ex);
                        this.record[i] = Expression.Encapsulate(ex);
                    }
                }
            }
 
            return true;
        }
 
        public virtual void Reset()
        {
            this.e.Reset();
        }
 
    }
}