package function.builtin.special

import function.ArgumentValidator
import function.FunctionNames
import function.LispSpecialFunction
import function.builtin.Eval.Companion.eval
import sexpression.Cons
import sexpression.SExpression

@FunctionNames("OR")
class Or(name: String) : LispSpecialFunction() {

    private val argumentValidator = ArgumentValidator(name)

    override fun call(argumentList: Cons): SExpression {
        argumentValidator.validate(argumentList)

        return callTailRecursive(argumentList)
    }

    private tailrec fun callTailRecursive(argumentList: Cons): SExpression {
        val currentValue = eval(argumentList.first)
        val remainingValues = argumentList.rest as Cons

        return if (remainingValues.isNull || !currentValue.isNull)
            currentValue
        else
            callTailRecursive(remainingValues)
    }
}