package function.builtin.special;

import java.text.MessageFormat;

import environment.Environment;
import function.*;
import function.builtin.cons.LIST;
import sexpression.*;
import table.FunctionTable;

public class DEFUN extends LispFunction {

    private ArgumentValidator argumentValidator;
    private ArgumentValidator lambdaListIsListValidator;
    private ArgumentValidator lambdaListValidator;
    private Environment environment;

    public DEFUN() {
        this.argumentValidator = new ArgumentValidator("DEFUN");
        this.argumentValidator.setMinimumNumberOfArguments(2);
        this.argumentValidator.setFirstArgumentExpectedType(Symbol.class);

        this.lambdaListIsListValidator = new ArgumentValidator("DEFUN|lambda-list|");
        this.lambdaListIsListValidator.setEveryArgumentExpectedType(Cons.class);

        this.lambdaListValidator = new ArgumentValidator("DEFUN|parameter|");
        this.lambdaListValidator.setEveryArgumentExpectedType(Symbol.class);

        this.environment = Environment.getInstance();
    }

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

        Cons remainingArguments = (Cons) argumentList.getCdr();
        SExpression functionName = argumentList.getCar();
        SExpression secondArgument = remainingArguments.getCar();
        lambdaListIsListValidator.validate(LIST.makeList(secondArgument));

        Cons lambdaList = (Cons) secondArgument;
        lambdaListValidator.validate(lambdaList);

        Cons functionBody = (Cons) remainingArguments.getCdr();
        UserDefinedFunction function = new UserDefinedFunction(functionName.toString(), lambdaList, functionBody);

        if (FunctionTable.isAlreadyDefined(functionName.toString()))
            printWarning(functionName);

        FunctionTable.defineFunction(functionName.toString(), function);

        return functionName;
    }

    private void printWarning(SExpression functionName) {
        String message = MessageFormat.format("WARNING: redefining function {0}", functionName.toString());
        environment.getOutput().println(message);
    }

    public boolean evaluateArguments() {
        return false;
    }

}