using System;
using HeuristicLab.Algorithms.PushGP.Interpreter;
using HeuristicLab.Algorithms.PushGP.Stack;

namespace HeuristicLab.Algorithms.PushGP.Expressions.Templates
{
    public class DefineExpressionTemplate<T> : ExpressionTemplate
    {
        private readonly Func<IInterpreter, IStack<T>> sourceStackProvider;
        private readonly Func<T, Expression> creator;
        private readonly bool isCodeOp;
        public DefineExpressionTemplate(string symbol, Func<IInterpreter, IStack<T>> sourceStackProvider, Func<T, Expression> creator, bool isCodeOp = false) : base(symbol)
        {
            this.sourceStackProvider = sourceStackProvider;
            this.creator = creator;
            this.isCodeOp = isCodeOp;
        }

        public override bool IsCodeOp { get { return this.isCodeOp; } }

        public override void Eval(IInterpreter interpreter)
        {
            var sourceStack = this.sourceStackProvider(interpreter);

            // not enough arguments on stack
            if (interpreter.NameStack.Count == 0 ||
                sourceStack.Count == 0)
                return;

            var name = interpreter.NameStack.Pop();
            var expression = creator(sourceStack.Top);

            if (interpreter.CustomExpressions.ContainsKey(name))
            {
                interpreter.CustomExpressions[name] = expression;
            }
            else
            {
                interpreter.CustomExpressions.Add(name, expression);
            }
        }
    }
}