using System.DirectoryServices;

namespace KumiScript.Interpreter
{
    public class LispProcedure : Procedure
    {
        readonly List<Symbol> _parameters;
        readonly Expression _body;
        readonly Environment _closureEnv;
        public LispProcedure(List<Symbol> parameters, Expression body, Environment closureEnv)
        {
            _parameters = parameters;
            _body = body;
            _closureEnv = closureEnv;
        }

        public override Expression ApplyWithArgs(ListExpression args, Environment env)
        {
            List<Expression> evaluatedArgs = args.EvalMembers(env);
            if (_parameters.Count != evaluatedArgs.Count)
                throw new InterpreterInvalidApplicationException();
            
            Environment inner = MapArgs(evaluatedArgs, _closureEnv);
            return _body.Eval(inner);
        }

        private Environment MapArgs(List<Expression> args, Environment env)
        {
            Environment inner = new Environment(env);
            for (int i = 0; i < _parameters.Count; i++)
                inner.AddSymbol(_parameters[i], args[i]);

            return inner;
        }
        
        public override bool IsPrimitive()
        {
            return false;
        }

        public override string ToString()
        {
            return string.Concat("λ(", string.Join(' ', _parameters), ")");
        }
    }
}