GuardedInvocationComponent.java

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/*
   Copyright 2009-2013 Attila Szegedi

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are
   met:
   * Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.
   * Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in the
     documentation and/or other materials provided with the distribution.
   * Neither the name of the copyright holder nor the names of
     contributors may be used to endorse or promote products derived from
     this software without specific prior written permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
   IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
   PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
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*/

package jdk.dynalink.beans;

import java.lang.invoke.MethodHandle;
import jdk.dynalink.linker.GuardedInvocation;

/**
 * Represents one component for a GuardedInvocation of a potentially multi-namespace operation of an
 * {@link AbstractJavaLinker}. In addition to holding a guarded invocation, it holds semantic information about its
 * guard. All guards produced in the AbstractJavaLinker are either "Class.isInstance()" or "getClass() == clazz"
 * expressions. This allows choosing the most restrictive guard as the guard for the composition of two components.
 */
class GuardedInvocationComponent {
    enum ValidationType {
        NONE, // No guard; the operation can be linked unconditionally (quite rare); least strict.
        INSTANCE_OF, // "validatorClass.isInstance(obj)" guard
        EXACT_CLASS, // "obj.getClass() == validatorClass" guard; most strict.
        IS_ARRAY, // "obj.getClass().isArray()"
    }

    private final GuardedInvocation guardedInvocation;
    private final Validator validator;

    GuardedInvocationComponent(final MethodHandle invocation) {
        this(invocation, null, ValidationType.NONE);
    }

    GuardedInvocationComponent(final MethodHandle invocation, final MethodHandle guard, final ValidationType validationType) {
        this(invocation, guard, null, validationType);
    }

    GuardedInvocationComponent(final MethodHandle invocation, final MethodHandle guard, final Class<?> validatorClass,
            final ValidationType validationType) {
        this(invocation, guard, new Validator(validatorClass, validationType));
    }

    GuardedInvocationComponent(final GuardedInvocation guardedInvocation, final Class<?> validatorClass,
            final ValidationType validationType) {
        this(guardedInvocation, new Validator(validatorClass, validationType));
    }

    GuardedInvocationComponent replaceInvocation(final MethodHandle newInvocation) {
        return replaceInvocation(newInvocation, guardedInvocation.getGuard());
    }

    GuardedInvocationComponent replaceInvocation(final MethodHandle newInvocation, final MethodHandle newGuard) {
        return new GuardedInvocationComponent(guardedInvocation.replaceMethods(newInvocation,
                newGuard), validator);
    }

    private GuardedInvocationComponent(final MethodHandle invocation, final MethodHandle guard, final Validator validator) {
        this(new GuardedInvocation(invocation, guard), validator);
    }

    private GuardedInvocationComponent(final GuardedInvocation guardedInvocation, final Validator validator) {
        this.guardedInvocation = guardedInvocation;
        this.validator = validator;
    }

    GuardedInvocation getGuardedInvocation() {
        return guardedInvocation;
    }

    Class<?> getValidatorClass() {
        return validator.validatorClass;
    }

    ValidationType getValidationType() {
        return validator.validationType;
    }

    GuardedInvocationComponent compose(final MethodHandle compositeInvocation, final MethodHandle otherGuard,
            final Class<?> otherValidatorClass, final ValidationType otherValidationType) {
        final Validator compositeValidator = validator.compose(new Validator(otherValidatorClass, otherValidationType));
        final MethodHandle compositeGuard = compositeValidator == validator ? guardedInvocation.getGuard() : otherGuard;
        return new GuardedInvocationComponent(compositeInvocation, compositeGuard, compositeValidator);
    }

    private static class Validator {
        /*private*/ final Class<?> validatorClass;
        /*private*/ final ValidationType validationType;

        Validator(final Class<?> validatorClass, final ValidationType validationType) {
            this.validatorClass = validatorClass;
            this.validationType = validationType;
        }

        Validator compose(final Validator other) {
            if(other.validationType == ValidationType.NONE) {
                return this;
            }
            switch(validationType) {
                case NONE:
                    return other;
                case INSTANCE_OF:
                    switch(other.validationType) {
                        case INSTANCE_OF:
                            if(isAssignableFrom(other)) {
                                return other;
                            } else if(other.isAssignableFrom(this)) {
                                return this;
                            }
                            break;
                        case EXACT_CLASS:
                            if(isAssignableFrom(other)) {
                                return other;
                            }
                            break;
                        case IS_ARRAY:
                            if(validatorClass.isArray()) {
                                return this;
                            }
                            break;
                        default:
                            throw new AssertionError();
                    }
                    break;
                case EXACT_CLASS:
                    switch(other.validationType) {
                        case INSTANCE_OF:
                            if(other.isAssignableFrom(this)) {
                                return this;
                            }
                            break;
                        case EXACT_CLASS:
                            if(validatorClass == other.validatorClass) {
                                return this;
                            }
                            break;
                        case IS_ARRAY:
                            if(validatorClass.isArray()) {
                                return this;
                            }
                            break;
                        default:
                            throw new AssertionError();
                    }
                    break;
                case IS_ARRAY:
                    switch(other.validationType) {
                        case INSTANCE_OF:
                        case EXACT_CLASS:
                            if(other.validatorClass.isArray()) {
                                return other;
                            }
                            break;
                        case IS_ARRAY:
                            return this;
                        default:
                            throw new AssertionError();
                    }
                    break;
                default:
                    throw new AssertionError();
            }
            throw new AssertionError("Incompatible composition " + this + " vs " + other);
        }

        private boolean isAssignableFrom(final Validator other) {
            return validatorClass.isAssignableFrom(other.validatorClass);
        }

        @Override
        public String toString() {
            return "Validator[" + validationType + (validatorClass == null ? "" : (" " + validatorClass.getName())) + "]";
        }
    }
}