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package org.jooby;

import com.typesafe.config.Config;

import org.jooby.funzy.Throwing;

import org.jooby.funzy.Try;

import javax.annotation.Nonnull;

import javax.annotation.PostConstruct;

import javax.annotation.PreDestroy;

import java.lang.annotation.Annotation;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.lang.reflect.Modifier;

import java.util.Optional;

/**

* <h2>life cycle</h2>

* <p>

* Listen for application start and stop events. Useful for starting/stopping services.

* </p>

*

* <h3>onStart/onStop events</h3>

* <p>

* Start/stop callbacks are accessible via application:

* </p>

* <pre>{@code

* {

* onStart(() -> {

* log.info("starting app");

* });

*

* onStop(() -> {

* log.info("stopping app");

* });

* }

* }</pre>

*

* <p>

* Or via module:

* </p>

*

* <pre>{@code

* public class MyModule implements Jooby.Module {

*

* public void configure(Env env, Config conf, Binder binder) {

* env.onStart(() -> {

* log.info("starting module");

* });

*

* env.onStop(() -> {

* log.info("stopping module");

* });

* }

* }

* }</pre>

*

* <h3>callbacks order</h3>

* <p>

* Callback order is preserved:

* </p>

*

* <pre>{@code

* {

* onStart(() -> {

* log.info("first");

* });

*

* onStart(() -> {

* log.info("second");

* });

*

* onStart(() -> {

* log.info("third");

* });

* }

* }</pre>

* <p>

* Order is useful for service dependencies, like ServiceB should be started after ServiceA.

* </p>

*

* <h3>service registry</h3>

* <p>

* You can also request for a service and start or stop it:

* </p>

*

* <pre>{@code

* {

* onStart(registry -> {

* MyService service = registry.require(MyService.class);

* service.start();

* });

*

* onStop(registry -> {

* MyService service = registry.require(MyService.class);

* service.stop();

* });

* }

* }</pre>

*

* <h3>PostConstruct/PreDestroy annotations</h3>

* <p>

* If you prefer the annotation way... you can too:

* </p>

*

* <pre>{@code

*

* &#64;Singleton

* public class MyService {

*

* &#64;PostConstruct

* public void start() {

* }

*

* &#64;PreDestroy

* public void stop() {

* }

* }

*

* App.java:

*

* {

* lifeCycle(MyService.class);

* }

*

* }</pre>

*

* <p>

* It works as expected just make sure <code>MyService</code> is a <strong>Singleton</strong>

* object.

* </p>

*

* @author edgar

* @since 1.0.0.CR3

*/

public interface LifeCycle {

/**

* Find a single method annotated with the given annotation in the provided type.

*

* @param rawType The type to look for a method.

* @param annotation Annotation to look for.

* @return A callback to the method. Or empty.

*/

static Optional<Throwing.Consumer<Object>> lifeCycleAnnotation(final Class<?> rawType,

final Class<? extends Annotation> annotation) {

for (Method method : rawType.getDeclaredMethods()) {

if (method.getAnnotation(annotation) != null) {

int mods = method.getModifiers();

if (Modifier.isStatic(mods)) {

throw new IllegalArgumentException(annotation.getSimpleName()

+ " method should not be static: " + method);

}

if (!Modifier.isPublic(mods)) {

throw new IllegalArgumentException(annotation.getSimpleName()

+ " method must be public: " + method);

}

if (method.getParameterCount() > 0) {

throw new IllegalArgumentException(annotation.getSimpleName()

+ " method should not accept arguments: " + method);

}

if (method.getReturnType() != void.class) {

throw new IllegalArgumentException(annotation.getSimpleName()

+ " method should not return anything: " + method);

}

return Optional.of(owner -> {

Try.run(() -> {

method.setAccessible(true);

method.invoke(owner);

}).unwrap(InvocationTargetException.class)

.throwException();

});

}

}

return Optional.empty();

}

;

/**

* Add to lifecycle the given service. Any method annotated with {@link PostConstruct} or

* {@link PreDestroy} will be executed at application startup or shutdown time.

*

* The service must be a Singleton object.

*

* <pre>{@code

*

* &#64;Singleton

* public class MyService {

*

* &#64;PostConstruct

* public void start() {

* }

*

* &#64;PreDestroy

* public void stop() {

* }

* }

*

* App.java:

*

* {

* lifeCycle(MyService.class);

* }

*

* }</pre>

*

* You should ONLY call this method while the application is been initialized or while

* {@link Jooby.Module#configure(Env, Config, com.google.inject.Binder)} is been executed.

*

* The behavior of this method once application has been initialized is <code>undefined</code>.

*

* @param service Service type. Must be a singleton object.

* @return This instance.

*/

@Nonnull

default LifeCycle lifeCycle(final Class<?> service) {

lifeCycleAnnotation(service, PostConstruct.class)

.ifPresent(it -> onStart(app -> it.accept(app.require(service))));

lifeCycleAnnotation(service, PreDestroy.class)

.ifPresent(it -> onStop(app -> it.accept(app.require(service))));

return this;

}

/**

* Add a start lifecycle event, useful for initialize and/or start services at startup time.

*

* You should ONLY call this method while the application is been initialized or while

* {@link Jooby.Module#configure(Env, Config, com.google.inject.Binder)}.

*

* The behavior of this method once application has been initialized is <code>undefined</code>.

*

* @param task Task to run.

* @return This env.

*/

@Nonnull

LifeCycle onStart(Throwing.Consumer<Registry> task);

/**

* Add a started lifecycle event. Started callbacks are executed when the application is ready:

* modules and servers has been started.

*

* You should ONLY call this method while the application is been initialized or while

* {@link Jooby.Module#configure(Env, Config, com.google.inject.Binder)}.

*

* The behavior of this method once application has been initialized is <code>undefined</code>.

*

* @param task Task to run.

* @return This env.

*/

@Nonnull

LifeCycle onStarted(Throwing.Consumer<Registry> task);

/**

* Add a start lifecycle event, useful for initialize and/or start services at startup time.

*

* You should ONLY call this method while the application is been initialized or from

* {@link Jooby.Module#configure(Env, Config, com.google.inject.Binder)}.

*

* The behavior of this method once application has been initialized is <code>undefined</code>.

*

* @param task Task to run.

* @return This env.

*/

@Nonnull

default LifeCycle onStart(final Throwing.Runnable task) {

return onStart(app -> task.run());

}

/**

* Add a started lifecycle event. Started callbacks are executed when the application is ready:

* modules and servers has been started.

*

* You should ONLY call this method while the application is been initialized or while

* {@link Jooby.Module#configure(Env, Config, com.google.inject.Binder)}.

*

* The behavior of this method once application has been initialized is <code>undefined</code>.

*

* @param task Task to run.

* @return This env.

*/

@Nonnull

default LifeCycle onStarted(final Throwing.Runnable task) {

return onStarted(app -> task.run());

}

/**

* Add a stop lifecycle event, useful for cleanup and/or stop service at stop time.

*

* You should ONLY call this method while the application is been initialized or from

* {@link Jooby.Module#configure(Env, Config, com.google.inject.Binder)}.

*

* The behavior of this method once application has been initialized is <code>undefined</code>.

*

* @param task Task to run.

* @return This env.

*/

@Nonnull

default LifeCycle onStop(final Throwing.Runnable task) {

return onStop(app -> task.run());

}

/**

* Add a stop lifecycle event, useful for cleanup and/or stop service at stop time.

*

* You should ONLY call this method while the application is been initialized or from

* {@link Jooby.Module#configure(Env, Config, com.google.inject.Binder)}.

*

* The behaviour of this method once application has been initialized is <code>undefined</code>.

*

* @param task Task to run.

* @return This env.

*/

@Nonnull

LifeCycle onStop(Throwing.Consumer<Registry> task);

}