transcendental-lisp/src/function/ArgumentValidator.java

package function;

import java.text.MessageFormat;

import error.LispException;
import function.builtin.LENGTH;
import sexpression.*;

public class ArgumentValidator {

    private Class<? extends SExpression> firstArgumentType;
    private Class<? extends SExpression> trailingArgumentType;
    private String functionName;
    private Integer maximumNumberOfArguments;
    private Integer minimumNumberOfArguments;
    private boolean isNilAcceptable;

    public ArgumentValidator(String functionName) {
        this.firstArgumentType = SExpression.class;
        this.trailingArgumentType = SExpression.class;
        this.functionName = functionName;
        this.minimumNumberOfArguments = null;
        this.maximumNumberOfArguments = null;
        this.isNilAcceptable = true;
    }

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

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

    public void setEveryArgumentExpectedType(Class<? extends SExpression> argumentType) {
        this.firstArgumentType = argumentType;
        this.trailingArgumentType = 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 doNotAcceptNil() {
        this.isNilAcceptable = false;
    }

    public void validate(Cons argumentList) {
        validateListNotDotted(argumentList);
        validateListLength(argumentList);
        validateArgumentTypes(argumentList);
    }

    private void validateListNotDotted(Cons argumentList) {
        SExpression next = argumentList.getCdr();

        for (Cons current = argumentList; next.consp(); next = current.getCdr())
            current = (Cons) next;

        if (!next.nullp())
            throw new DottedArgumentListException(functionName, argumentList);
    }

    private void validateListLength(Cons argumentList) {
        if (containsTooFewArguments(argumentList))
            throw new TooFewArgumentsException(functionName, argumentList);
        else if (containsTooManyArguments(argumentList))
            throw new TooManyArgumentsException(functionName, argumentList);
    }

    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 void validateArgumentTypes(Cons argumentList) {
        validateFirstArgument(argumentList);
        validateTrailingArguments(argumentList);
    }

    private void validateFirstArgument(Cons argumentList) {
        if (!isFirstArgumentValid(argumentList))
            throw new BadArgumentTypeException(functionName, argumentList.getCar(), firstArgumentType);
    }

    private boolean isFirstArgumentValid(Cons argumentList) {
        return argumentList.nullp() || isExpectedFirstArgumentType(argumentList.getCar());
    }

    private boolean isExpectedFirstArgumentType(SExpression firstArgument) {
        return firstArgumentType.isInstance(firstArgument) && !isDisallowedNil(firstArgument);
    }

    private boolean isDisallowedNil(SExpression argument) {
        return !isNilAcceptable && argument.nullp();
    }

    private void validateTrailingArguments(Cons argumentList) {
        for (Cons cons = (Cons) argumentList.getCdr(); !cons.nullp(); cons = (Cons) cons.getCdr())
            if (!isExpectedTrailingArgumentType(cons.getCar()))
                throw new BadArgumentTypeException(functionName, cons.getCar(), trailingArgumentType);
    }

    private boolean isExpectedTrailingArgumentType(SExpression trailingArgument) {
        return trailingArgumentType.isInstance(trailingArgument) && !isDisallowedNil(trailingArgument);
    }

    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 DottedArgumentListException extends LispException {

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

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

        @Override
        public String getMessage() {
            return MessageFormat.format("dotted argument list given to {0}: {1}", functionName, originalSExpression);
        }
    }

    public static class BadArgumentTypeException extends LispException {

        private static final long serialVersionUID = 1L;
        private String functionName;
        private String argument;
        private Class<? extends SExpression> expected;

        public BadArgumentTypeException(String functionName, SExpression argument,
                                        Class<? extends SExpression> expected) {
            this.functionName = functionName;
            this.argument = argument.toString();
            this.expected = expected;
        }

        @Override
        public String getMessage() {
            DisplayName displayName = expected.getAnnotation(DisplayName.class);
            String expectedType = (displayName == null) ? "unknown" : displayName.value();

            return MessageFormat.format("{0}: {1} is not the expected type of ''{2}''", functionName, argument,
                                        expectedType);
        }
    }

}