package function.builtin.special;

import static function.builtin.cons.LIST.makeList;

import function.*;
import sexpression.*;

public class LAMBDA extends LispSpecialFunction {

    public static boolean isLambdaExpression(SExpression sexpr) {
        if (sexpr.isCons()) {
            SExpression first = ((Cons) sexpr).getFirst();

            return "LAMBDA".equals(first.toString());
        }

        return false;
    }

    public static UserDefinedFunction createFunction(Cons lambdaExpression) {
        SExpression rest = lambdaExpression.getRest();

        ArgumentValidator lambdaValidator = new ArgumentValidator("LAMBDA|create|");
        lambdaValidator.setEveryArgumentExpectedType(Cons.class);
        lambdaValidator.validate(makeList(rest));

        LambdaExpression lambda = new LAMBDA().call((Cons) rest);

        return lambda.getFunction();
    }

    private ArgumentValidator argumentValidator;
    private ArgumentValidator lambdaListValidator;

    public LAMBDA() {
        this.argumentValidator = new ArgumentValidator("LAMBDA");
        this.argumentValidator.setFirstArgumentExpectedType(Cons.class);
        this.argumentValidator.setMinimumNumberOfArguments(1);

        this.lambdaListValidator = new ArgumentValidator("LAMBDA|lambda-list|");
        this.lambdaListValidator.setEveryArgumentExpectedType(Symbol.class);
    }

    public LambdaExpression call(Cons argumentList) {
        argumentValidator.validate(argumentList);

        SExpression first = argumentList.getFirst();
        Cons lambdaList = (Cons) first;
        Cons body = (Cons) argumentList.getRest();

        lambdaListValidator.validate(lambdaList);

        UserDefinedFunction function = new UserDefinedFunction(":LAMBDA", lambdaList, body);

        return new LambdaExpression(makeOriginalLambdaExpression(argumentList), function);
    }

    private Cons makeOriginalLambdaExpression(Cons argumentList) {
        return new Cons(new Symbol("LAMBDA"), argumentList);
    }

}