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

namespace HeuristicLab.Algorithms.PushGP.Expressions.Templates
{
    public class PushResultExpressionTemplate<T, R> : ExpressionTemplate
    {
        private readonly Func<IInterpreter, IStack<T>> sourceStackProvider;
        private readonly Func<IInterpreter, IStack<R>> targetStackProvider;
        private readonly Func<T[], R> templateFunc;
        private readonly bool isCodeOp;
        public PushResultExpressionTemplate(string symbol, Func<IInterpreter, IStack<T>> sourceStackProvider, Func<IInterpreter, IStack<R>> targetSourceProvider, Func<T[], R> templateFunc, bool isCodeOp = false) : base(symbol)
        {
            this.sourceStackProvider = sourceStackProvider;
            this.targetStackProvider = targetSourceProvider;
            this.templateFunc = templateFunc;

            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 (sourceStack.Count < 2)
                return;

            var targetStack = this.targetStackProvider(interpreter);

            var values = sourceStack.Pop(2);
            var result = this.templateFunc(values);

            targetStack.Push(result);
        }
    }
}