transcendental-lisp/src/eval/argument/ArgumentValidator.java

package eval.argument;

import java.text.MessageFormat;

import error.LispException;
import eval.LENGTH;
import sexpression.*;

public class ArgumentValidator {

    private Class<? extends SExpression> argumentType;
    private String functionName;
    private Integer maximumNumberOfArguments;
    private Integer minimumNumberOfArguments;

    public ArgumentValidator(String functionName) {
        this.argumentType = SExpression.class;
        this.functionName = functionName;
        this.minimumNumberOfArguments = null;
        this.maximumNumberOfArguments = null;
    }

    public void setArgumentType(Class<? extends SExpression> argumentType) {
        this.argumentType = argumentType;
    }

    public void setMaximumNumberOfArguments(int maximumNumberOfArguments) {
        this.maximumNumberOfArguments = maximumNumberOfArguments;
    }

    public void setMinimumNumberOfArguments(int minimumNumberOfArguments) {
        this.minimumNumberOfArguments = minimumNumberOfArguments;
    }

    public void setExactNumberOfArguments(int exactNumberOfArguments) {
        this.minimumNumberOfArguments = exactNumberOfArguments;
        this.maximumNumberOfArguments = exactNumberOfArguments;
    }

    public void validate(Cons argumentList) {
        if (containsTooFewArguments(argumentList))
            throw new TooFewArgumentsException(functionName, argumentList);
        else if (containsTooManyArguments(argumentList))
            throw new TooManyArgumentsException(functionName, argumentList);
        else if (!isExpectedArgumentType(argumentList.getCar()))
            throw new BadArgumentTypeException(functionName, argumentList.getCar());
    }

    private boolean containsTooFewArguments(Cons argumentList) {
        return (minimumNumberOfArguments != null) && (LENGTH.getLength(argumentList) < minimumNumberOfArguments);
    }

    private boolean containsTooManyArguments(Cons argumentList) {
        return (maximumNumberOfArguments != null) && (LENGTH.getLength(argumentList) > maximumNumberOfArguments);
    }

    private boolean isExpectedArgumentType(SExpression firstArgument) {
        return argumentType.isInstance(firstArgument);
    }

    public static class TooFewArgumentsException extends LispException {

        private static final long serialVersionUID = 1L;
        private String functionName;
        private Cons originalSExpression;

        public TooFewArgumentsException(String functionName, Cons argumentList) {
            this.functionName = functionName;
            this.originalSExpression = new Cons(new Symbol(this.functionName), argumentList);
        }

        @Override
        public String getMessage() {
            return MessageFormat.format("too few arguments given to {0}: {1}", functionName, originalSExpression);
        }
    }

    public static class TooManyArgumentsException extends LispException {

        private static final long serialVersionUID = 1L;
        private String functionName;
        private Cons originalSExpression;

        public TooManyArgumentsException(String functionName, Cons argumentList) {
            this.functionName = functionName;
            this.originalSExpression = new Cons(new Symbol(this.functionName), argumentList);
        }

        @Override
        public String getMessage() {
            return MessageFormat.format("too many arguments given to {0}: {1}", functionName, originalSExpression);
        }
    }

    public static class BadArgumentTypeException extends LispException {

        private static final long serialVersionUID = 1L;
        private String functionName;
        private String argument;

        public BadArgumentTypeException(String functionName, SExpression argument) {
            this.functionName = functionName;
            this.argument = argument.toString();
        }

        @Override
        public String getMessage() {
            return MessageFormat.format("{0}: {1} is not the expected type", functionName, argument);
        }
    }

}