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 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
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package fish.payara.microprofile.faulttolerance.policy;

import java.lang.reflect.Method;
import java.util.Objects;

import jakarta.interceptor.InvocationContext;

import org.eclipse.microprofile.faulttolerance.ExecutionContext;
import org.eclipse.microprofile.faulttolerance.Fallback;
import org.eclipse.microprofile.faulttolerance.FallbackHandler;
import org.eclipse.microprofile.faulttolerance.exceptions.FaultToleranceDefinitionException;

import fish.payara.microprofile.faulttolerance.FaultToleranceConfig;
import javassist.Modifier;

/**
 * The resolved "cached" information of a {@link Fallback} annotation an a specific method.
 *
 * @author Jan Bernitt
 */
public final class FallbackPolicy extends Policy {

    public final Class> value;
    public final String fallbackMethod;
    public final Method method;
    private final Class[] applyOn;
    private final Class[] skipOn;

    @SuppressWarnings("unchecked")
    public FallbackPolicy(Method annotated, Class> value, String fallbackMethod) {
        this(annotated, value, fallbackMethod, new Class[] { Throwable.class }, new Class[0]);
    }

    public FallbackPolicy(Method annotated, Class> value, String fallbackMethod,
            Class[] applyOn, Class[] skipOn) {
        checkUnambiguous(annotated, value, fallbackMethod);
        this.value = value;
        this.fallbackMethod = fallbackMethod;
        if (fallbackMethod != null && !fallbackMethod.isEmpty()) {
            method = MethodLookupUtils.findMethodWithMatchingNameAndArguments(fallbackMethod, annotated);
            if (method == null) {
                throw new FaultToleranceDefinitionException(describe(annotated, Fallback.class, "fallbackMethod")
                        + "value referring to a method that is not defined or has a incompatible method signature.");
            }
            checkReturnsSameAs(annotated, Fallback.class, "fallbackMethod", method);
            checkAccessible(annotated, method);
        } else {
            method = null;
        }
        if (isHandlerPresent()) {
            checkReturnsSameAs(annotated, Fallback.class, "value", value, "handle", ExecutionContext.class);
        }
        this.applyOn = applyOn;
        this.skipOn = skipOn;
    }

    public static FallbackPolicy create(InvocationContext context, FaultToleranceConfig config) {
        if (config.isAnnotationPresent(Fallback.class) && config.isEnabled(Fallback.class)) {
            Fallback annotation = config.getAnnotation(Fallback.class);
            return new FallbackPolicy(context.getMethod(),
                    config.value(annotation),
                    config.fallbackMethod(annotation),
                    config.applyOn(annotation),
                    config.skipOn(annotation));
        }
        return null;
    }

    private static void checkUnambiguous(Method annotated, Class> value, String fallbackMethod) {
        if (fallbackMethod != null && !fallbackMethod.isEmpty() && value != null && value != Fallback.DEFAULT.class) {
            throw new FaultToleranceDefinitionException(
                    describe(annotated, Fallback.class, "") + "defined both a fallback handler and a fallback method.");
        }
    }

    private static void checkAccessible(Method annotated, Method fallback) {
        boolean samePackage = Objects.equals(
            fallback.getDeclaringClass().getPackage(),
            annotated.getDeclaringClass().getPackage()
        );
        boolean sameClass = fallback.getDeclaringClass().equals(annotated.getDeclaringClass());
        if (Modifier.isPackage(fallback.getModifiers()) && !samePackage
                || Modifier.isPrivate(fallback.getModifiers()) && !sameClass) {
            throw new FaultToleranceDefinitionException(describe(annotated, Fallback.class, "fallbackMethod")
                    + "value referring to a method that is not accessible.");
        }
    }

    public boolean isHandlerPresent() {
        return value != null && value != Fallback.DEFAULT.class;
    }

    /**
     * Helper method that checks whether or not the given exception is should trigger applying the fallback or not.
     * 
     * Relevant section from {@link Fallback} javadocs:
     * 
     * When a method returns and the Fallback policy is present, the following rules are applied:
     * 
     * If the method returns normally (doesn't throw), the result is simply returned.
     * 
Otherwise, if the thrown object is assignable to any value in the {@link #skipOn()} parameter, the thrown object will be rethrown.
     * 
Otherwise, if the thrown object is assignable to any value in the {@link #applyOn()} parameter, 
     * the Fallback policy, detailed above, will be applied.
     * 
Otherwise the thrown object will be rethrown.
     * 
     * 
     * 
     * @param ex The exception to check
     * @return true, when fallback should be applied, false to rethrow the exception
     */
    public boolean isFallbackApplied(Throwable ex) {
        return !Policy.isCaught(ex, skipOn) && Policy.isCaught(ex, applyOn);
    }
}