Mid.cs

using System;
using System.Collections.Generic;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Abstraction.Sets;
using Waher.Script.Exceptions;
using Waher.Script.Model;
using Waher.Script.Objects;
 
namespace Waher.Script.Functions.Vectors
{
    public class Mid : FunctionMultiVariate
    {
        public Mid(ScriptNode X, ScriptNode Pos, ScriptNode Len, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { X, Pos, Len }, new ArgumentType[] { ArgumentType.Normal, ArgumentType.Scalar, ArgumentType.Scalar },
                  Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(Mid);
 
        public override string[] DefaultArgumentNames
        {
            get { return new string[] { "x", "Pos", "Len" }; }
        }
 
        public override IElement Evaluate(IElement[] Arguments, Variables Variables)
        {
            double Pos = Expression.ToDouble(Arguments[1].AssociatedObjectValue);
            if (Pos < 0 || Pos > int.MaxValue || Pos != Math.Truncate(Pos))
                throw new ScriptRuntimeException("Expected nonnegative integer in second argument.", this);
 
            int i = (int)Pos;
 
            double Len = Expression.ToDouble(Arguments[2].AssociatedObjectValue);
            if (Len < 0 || Len > int.MaxValue || Len != Math.Truncate(Len))
                throw new ScriptRuntimeException("Expected nonnegative integer in third argument.", this);
 
            int c = (int)Len;
 
            if (Arguments[0].AssociatedObjectValue is string s)
            {
                int l = s.Length;
 
                if (i > l)
                    return StringValue.Empty;
                else if (i + c >= l)
                    return new StringValue(s.Substring(i));
                else
                    return new StringValue(s.Substring(i, c));
            }
            else
            {
                ICollection<IElement> ChildElements;
 
                if (Arguments[0] is IVector Vector)
                {
                    int l = Vector.Dimension;
 
                    if (i > l)
                        i = l;
 
                    if (i + c > l)
                        c = l - i;
 
                    if (i == 0 && c == l)
                        return Vector;
 
                    ChildElements = Vector.VectorElements;
                }
                else if (Arguments[0] is ISet Set)
                {
                    int? Size = Set.Size;
 
                    if (Size.HasValue)
                    {
                        int l = Size.Value;
 
                        if (i > l)
                            i = l;
 
                        if (i + c > l)
                            c = l - i;
 
                        if (i == 0 && c == l)
                            return Set;
                    }
 
                    ChildElements = Set.ChildElements;
                }
                else
                    throw new ScriptRuntimeException("First argument expected to be a string, vector or a set.", this);
 
                IElement[] Result = new IElement[c];
 
                if (ChildElements is IElement[] V)
                    Array.Copy(V, i, Result, 0, c);
                else if (c > 0)
                {
                    int j = 0;
 
                    foreach (IElement Element in ChildElements)
                    {
                        if (i-- <= 0)
                        {
                            Result[j++] = Element;
                            if (j == c)
                                break;
                        }
                    }
                }
 
                return Arguments[0].Encapsulate(Result, this);
            }
        }
 
    }
}