From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jake Potrebic <jake.m.potrebic@gmail.com>
Date: Tue, 18 Jul 2023 17:49:38 -0700
Subject: [PATCH] Add Lifecycle Event system

This event system is separate from Bukkit's event system and is
meant for managing resources across reloads and from points in the
PluginBootstrap.

diff --git a/src/main/java/io/papermc/paper/plugin/bootstrap/PluginBootstrapContextImpl.java b/src/main/java/io/papermc/paper/plugin/bootstrap/PluginBootstrapContextImpl.java
index 30b50e6294c6eaade5e17cfaf34600d122e6251c..0bb7694188d5fb75bb756ce75d0060ea980027ee 100644
--- a/src/main/java/io/papermc/paper/plugin/bootstrap/PluginBootstrapContextImpl.java
+++ b/src/main/java/io/papermc/paper/plugin/bootstrap/PluginBootstrapContextImpl.java
@@ -1,6 +1,8 @@
 package io.papermc.paper.plugin.bootstrap;
 
 import io.papermc.paper.plugin.configuration.PluginMeta;
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventManager;
+import io.papermc.paper.plugin.lifecycle.event.PaperLifecycleEventManager;
 import io.papermc.paper.plugin.provider.PluginProvider;
 import java.nio.file.Path;
 import net.kyori.adventure.text.logger.slf4j.ComponentLogger;
@@ -12,6 +14,10 @@ public final class PluginBootstrapContextImpl implements BootstrapContext {
     private final Path dataFolder;
     private final ComponentLogger logger;
     private final Path pluginSource;
+    // Paper start - lifecycle events
+    private boolean allowsLifecycleRegistration = true;
+    private final PaperLifecycleEventManager<BootstrapContext> lifecycleEventManager = new PaperLifecycleEventManager<>(this, () -> this.allowsLifecycleRegistration); // Paper - lifecycle events
+    // Paper end - lifecycle events
 
     public PluginBootstrapContextImpl(PluginMeta config, Path dataFolder, ComponentLogger logger, Path pluginSource) {
         this.config = config;
@@ -45,4 +51,20 @@ public final class PluginBootstrapContextImpl implements BootstrapContext {
     public @NotNull Path getPluginSource() {
         return this.pluginSource;
     }
+
+    // Paper start - lifecycle event system
+    @Override
+    public @NotNull PluginMeta getPluginMeta() {
+        return this.config;
+    }
+
+    @Override
+    public LifecycleEventManager<BootstrapContext> getLifecycleManager() {
+        return this.lifecycleEventManager;
+    }
+
+    public void lockLifecycleEventRegistration() {
+        this.allowsLifecycleRegistration = false;
+    }
+    // Paper end
 }
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/LifecycleEventRunner.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/LifecycleEventRunner.java
new file mode 100644
index 0000000000000000000000000000000000000000..f84c9c80e701231e5c33ac3c5573f1093e80f38b
--- /dev/null
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/LifecycleEventRunner.java
@@ -0,0 +1,110 @@
+package io.papermc.paper.plugin.lifecycle.event;
+
+import com.google.common.base.Suppliers;
+import com.mojang.logging.LogUtils;
+import io.papermc.paper.plugin.bootstrap.BootstrapContext;
+import io.papermc.paper.plugin.lifecycle.event.registrar.PaperRegistrar;
+import io.papermc.paper.plugin.lifecycle.event.registrar.RegistrarEvent;
+import io.papermc.paper.plugin.lifecycle.event.registrar.RegistrarEventImpl;
+import io.papermc.paper.plugin.lifecycle.event.registrar.ReloadableRegistrarEvent;
+import io.papermc.paper.plugin.lifecycle.event.types.AbstractLifecycleEventType;
+import io.papermc.paper.plugin.lifecycle.event.types.LifecycleEventType;
+import io.papermc.paper.plugin.lifecycle.event.types.OwnerAwareLifecycleEvent;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+import java.util.function.Predicate;
+import java.util.function.Supplier;
+import org.bukkit.plugin.Plugin;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.checkerframework.framework.qual.DefaultQualifier;
+import org.slf4j.Logger;
+
+@DefaultQualifier(NonNull.class)
+public class LifecycleEventRunner {
+
+    private static final Logger LOGGER = LogUtils.getClassLogger();
+    private static final Supplier<Set<LifecycleEventType<?, ?, ?>>> BLOCKS_RELOADING = Suppliers.memoize(() -> Set.of( // lazy due to cyclic initialization
+    ));
+    public static final LifecycleEventRunner INSTANCE = new LifecycleEventRunner();
+
+    private final List<LifecycleEventType<?, ?, ?>> lifecycleEventTypes = new ArrayList<>();
+    private boolean blockPluginReloading = false;
+
+    public void checkRegisteredHandler(final LifecycleEventOwner owner, final LifecycleEventType<?, ?, ?> eventType) {
+        /*
+        Lifecycle event handlers for reloadable events that are registered from the BootstrapContext prevent
+        the server from reloading plugins. This is because reloading plugins requires disabling all the plugins,
+        running the reload logic (which would include places where these events should fire) and then re-enabling plugins.
+         */
+        if (owner instanceof BootstrapContext && BLOCKS_RELOADING.get().contains(eventType)) {
+            this.blockPluginReloading = true;
+        }
+    }
+
+    public boolean blocksPluginReloading() {
+        return this.blockPluginReloading;
+    }
+
+    public <O extends LifecycleEventOwner, E extends LifecycleEvent, ET extends LifecycleEventType<O, E, ?>> ET addEventType(final ET eventType) {
+        this.lifecycleEventTypes.add(eventType);
+        return eventType;
+    }
+
+    public <O extends LifecycleEventOwner, E extends PaperLifecycleEvent> void callEvent(final LifecycleEventType<O, ? super E, ?> eventType, final E event) {
+        this.callEvent(eventType, event, $ -> true);
+    }
+
+    public <O extends LifecycleEventOwner, E extends PaperLifecycleEvent> void callEvent(final LifecycleEventType<O, ? super E, ?> eventType, final E event, final Predicate<? super O> ownerPredicate) {
+        final AbstractLifecycleEventType<O, ? super E, ?, ?> lifecycleEventType = (AbstractLifecycleEventType<O, ? super E, ?, ?>) eventType;
+        lifecycleEventType.forEachHandler(registeredHandler -> {
+            try {
+                if (event instanceof final OwnerAwareLifecycleEvent<?> ownerAwareEvent) {
+                    ownerAwareGenericHelper(ownerAwareEvent, registeredHandler.owner());
+                }
+                registeredHandler.lifecycleEventHandler().run(event);
+            } catch (final Throwable ex) {
+                LOGGER.error("Could not run '{}' lifecycle event handler from {}", lifecycleEventType.name(), registeredHandler.owner().getPluginMeta().getDisplayName(), ex);
+            } finally {
+                if (event instanceof final OwnerAwareLifecycleEvent<?> ownerAwareEvent) {
+                    ownerAwareEvent.setOwner(null);
+                }
+            }
+        }, handler -> ownerPredicate.test(handler.owner()));
+        event.invalidate();
+    }
+
+    private static <O extends LifecycleEventOwner> void ownerAwareGenericHelper(final OwnerAwareLifecycleEvent<O> event, final LifecycleEventOwner possibleOwner) {
+        final @Nullable O owner = event.castOwner(possibleOwner);
+        if (owner != null) {
+            event.setOwner(owner);
+        } else {
+            throw new IllegalStateException("Found invalid owner " + possibleOwner + " for event " + event);
+        }
+    }
+
+    public void unregisterAllEventHandlersFor(final Plugin plugin) {
+        for (final LifecycleEventType<?, ?, ?> lifecycleEventType : this.lifecycleEventTypes) {
+            this.removeEventHandlersOwnedBy(lifecycleEventType, plugin);
+        }
+    }
+
+    private <O extends LifecycleEventOwner> void removeEventHandlersOwnedBy(final LifecycleEventType<O, ?, ?> eventType, final Plugin possibleOwner) {
+        final AbstractLifecycleEventType<O, ?, ?, ?> lifecycleEventType = (AbstractLifecycleEventType<O, ?, ?, ?>) eventType;
+        lifecycleEventType.removeMatching(registeredHandler -> registeredHandler.owner().getPluginMeta().getName().equals(possibleOwner.getPluginMeta().getName()));
+    }
+
+    @SuppressWarnings("unchecked")
+    public <O extends LifecycleEventOwner, R extends PaperRegistrar<? super O>> void callStaticRegistrarEvent(final LifecycleEventType<O, ? extends RegistrarEvent<? super R>, ?> lifecycleEventType, final R registrar, final Class<? extends O> ownerClass) {
+        this.callEvent((LifecycleEventType<O, RegistrarEvent<? super R>, ?>) lifecycleEventType, new RegistrarEventImpl<>(registrar, ownerClass), ownerClass::isInstance);
+    }
+
+    @SuppressWarnings("unchecked")
+    public <O extends LifecycleEventOwner, R extends PaperRegistrar<? super O>> void callReloadableRegistrarEvent(final LifecycleEventType<O, ? extends ReloadableRegistrarEvent<? super R>, ?> lifecycleEventType, final R registrar, final Class<? extends O> ownerClass, final ReloadableRegistrarEvent.Cause cause) {
+        this.callEvent((LifecycleEventType<O, ReloadableRegistrarEvent<? super R>, ?>) lifecycleEventType, new RegistrarEventImpl.ReloadableImpl<>(registrar, ownerClass, cause), ownerClass::isInstance);
+    }
+
+    private LifecycleEventRunner() {
+    }
+}
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/PaperLifecycleEvent.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/PaperLifecycleEvent.java
new file mode 100644
index 0000000000000000000000000000000000000000..e941405269a773e8a77e26ffd1afd84f53fadff5
--- /dev/null
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/PaperLifecycleEvent.java
@@ -0,0 +1,10 @@
+package io.papermc.paper.plugin.lifecycle.event;
+
+public interface PaperLifecycleEvent extends LifecycleEvent {
+
+    // called after all handlers have been run. Can be
+    // used to invalid various contexts to plugins can't
+    // try to re-use them by storing them from the event
+    default void invalidate() {
+    }
+}
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/PaperLifecycleEventManager.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/PaperLifecycleEventManager.java
new file mode 100644
index 0000000000000000000000000000000000000000..f1be5b9a29435bae0afd2bd951bfe88d1669e7eb
--- /dev/null
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/PaperLifecycleEventManager.java
@@ -0,0 +1,26 @@
+package io.papermc.paper.plugin.lifecycle.event;
+
+import com.google.common.base.Preconditions;
+import io.papermc.paper.plugin.lifecycle.event.handler.configuration.AbstractLifecycleEventHandlerConfiguration;
+import io.papermc.paper.plugin.lifecycle.event.handler.configuration.LifecycleEventHandlerConfiguration;
+import java.util.function.BooleanSupplier;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public final class PaperLifecycleEventManager<O extends LifecycleEventOwner> implements LifecycleEventManager<O> {
+
+    private final O owner;
+    public final BooleanSupplier registrationCheck;
+
+    public PaperLifecycleEventManager(final O owner, final BooleanSupplier registrationCheck) {
+        this.owner = owner;
+        this.registrationCheck = registrationCheck;
+    }
+
+    @Override
+    public void registerEventHandler(final LifecycleEventHandlerConfiguration<? super O> handlerConfiguration) {
+        Preconditions.checkState(this.registrationCheck.getAsBoolean(), "Cannot register lifecycle event handlers");
+        ((AbstractLifecycleEventHandlerConfiguration<? super O, ?, ?>) handlerConfiguration).registerFrom(this.owner);
+    }
+}
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/handler/configuration/AbstractLifecycleEventHandlerConfiguration.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/handler/configuration/AbstractLifecycleEventHandlerConfiguration.java
new file mode 100644
index 0000000000000000000000000000000000000000..6a85a4f581612efff04c1a955493aa2e32476277
--- /dev/null
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/handler/configuration/AbstractLifecycleEventHandlerConfiguration.java
@@ -0,0 +1,26 @@
+package io.papermc.paper.plugin.lifecycle.event.handler.configuration;
+
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEvent;
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventOwner;
+import io.papermc.paper.plugin.lifecycle.event.handler.LifecycleEventHandler;
+import io.papermc.paper.plugin.lifecycle.event.types.AbstractLifecycleEventType;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public abstract class AbstractLifecycleEventHandlerConfiguration<O extends LifecycleEventOwner, E extends LifecycleEvent, CI extends AbstractLifecycleEventHandlerConfiguration<O, E, CI>> implements LifecycleEventHandlerConfiguration<O> {
+
+    private final LifecycleEventHandler<? super E> handler;
+    private final AbstractLifecycleEventType<O, E, ?, CI> type;
+
+    protected AbstractLifecycleEventHandlerConfiguration(final LifecycleEventHandler<? super E> handler, final AbstractLifecycleEventType<O, E, ?, CI> type) {
+        this.handler = handler;
+        this.type = type;
+    }
+
+    public abstract CI config();
+
+    public final void registerFrom(final O owner) {
+        this.type.tryRegister(owner, this.handler, this.config());
+    }
+}
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/handler/configuration/MonitorLifecycleEventHandlerConfigurationImpl.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/handler/configuration/MonitorLifecycleEventHandlerConfigurationImpl.java
new file mode 100644
index 0000000000000000000000000000000000000000..e0699fcd0a098abc5e1206e7c0fa80b96eca7884
--- /dev/null
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/handler/configuration/MonitorLifecycleEventHandlerConfigurationImpl.java
@@ -0,0 +1,33 @@
+package io.papermc.paper.plugin.lifecycle.event.handler.configuration;
+
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEvent;
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventOwner;
+import io.papermc.paper.plugin.lifecycle.event.handler.LifecycleEventHandler;
+import io.papermc.paper.plugin.lifecycle.event.types.AbstractLifecycleEventType;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public class MonitorLifecycleEventHandlerConfigurationImpl<O extends LifecycleEventOwner, E extends LifecycleEvent> extends AbstractLifecycleEventHandlerConfiguration<O, E, MonitorLifecycleEventHandlerConfigurationImpl<O, E>> implements MonitorLifecycleEventHandlerConfiguration<O> {
+
+    private boolean monitor = false;
+
+    public MonitorLifecycleEventHandlerConfigurationImpl(final LifecycleEventHandler<? super E> handler, final AbstractLifecycleEventType<O, E, ?, MonitorLifecycleEventHandlerConfigurationImpl<O, E>> eventType) {
+        super(handler, eventType);
+    }
+
+    @Override
+    public MonitorLifecycleEventHandlerConfigurationImpl<O, E> config() {
+        return this;
+    }
+
+    public boolean isMonitor() {
+        return this.monitor;
+    }
+
+    @Override
+    public MonitorLifecycleEventHandlerConfiguration<O> monitor() {
+        this.monitor = true;
+        return this;
+    }
+}
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/handler/configuration/PrioritizedLifecycleEventHandlerConfigurationImpl.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/handler/configuration/PrioritizedLifecycleEventHandlerConfigurationImpl.java
new file mode 100644
index 0000000000000000000000000000000000000000..c1d0070fc1594f7a7c29d7dc679da7b347a7140b
--- /dev/null
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/handler/configuration/PrioritizedLifecycleEventHandlerConfigurationImpl.java
@@ -0,0 +1,43 @@
+package io.papermc.paper.plugin.lifecycle.event.handler.configuration;
+
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEvent;
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventOwner;
+import io.papermc.paper.plugin.lifecycle.event.handler.LifecycleEventHandler;
+import io.papermc.paper.plugin.lifecycle.event.types.AbstractLifecycleEventType;
+import java.util.OptionalInt;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public class PrioritizedLifecycleEventHandlerConfigurationImpl<O extends LifecycleEventOwner, E extends LifecycleEvent> extends AbstractLifecycleEventHandlerConfiguration<O, E, PrioritizedLifecycleEventHandlerConfigurationImpl<O, E>> implements PrioritizedLifecycleEventHandlerConfiguration<O> {
+
+    private static final OptionalInt DEFAULT_PRIORITY = OptionalInt.of(0);
+    private static final OptionalInt MONITOR_PRIORITY = OptionalInt.empty();
+
+    private OptionalInt priority = DEFAULT_PRIORITY;
+
+    public PrioritizedLifecycleEventHandlerConfigurationImpl(final LifecycleEventHandler<? super E> handler, final AbstractLifecycleEventType<O, E, ?, PrioritizedLifecycleEventHandlerConfigurationImpl<O, E>> eventType) {
+        super(handler, eventType);
+    }
+
+    @Override
+    public PrioritizedLifecycleEventHandlerConfigurationImpl<O, E> config() {
+        return this;
+    }
+
+    public OptionalInt priority() {
+        return this.priority;
+    }
+
+    @Override
+    public PrioritizedLifecycleEventHandlerConfiguration<O> priority(final int priority) {
+        this.priority = OptionalInt.of(priority);
+        return this;
+    }
+
+    @Override
+    public PrioritizedLifecycleEventHandlerConfiguration<O> monitor() {
+        this.priority = MONITOR_PRIORITY;
+        return this;
+    }
+}
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/registrar/PaperRegistrar.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/registrar/PaperRegistrar.java
new file mode 100644
index 0000000000000000000000000000000000000000..b2586c881988fbabe07eef1b43eb1b55f2d3fa52
--- /dev/null
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/registrar/PaperRegistrar.java
@@ -0,0 +1,15 @@
+package io.papermc.paper.plugin.lifecycle.event.registrar;
+
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventOwner;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public interface PaperRegistrar<O extends LifecycleEventOwner> extends Registrar {
+
+    void setCurrentContext(@Nullable O owner);
+
+    default void invalidate() {
+    }
+}
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/registrar/RegistrarEventImpl.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/registrar/RegistrarEventImpl.java
new file mode 100644
index 0000000000000000000000000000000000000000..6d530c52aaf0dc2cdfe3bd56af557274a7f44256
--- /dev/null
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/registrar/RegistrarEventImpl.java
@@ -0,0 +1,70 @@
+package io.papermc.paper.plugin.lifecycle.event.registrar;
+
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventOwner;
+import io.papermc.paper.plugin.lifecycle.event.PaperLifecycleEvent;
+import io.papermc.paper.plugin.lifecycle.event.types.OwnerAwareLifecycleEvent;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public class RegistrarEventImpl<R extends PaperRegistrar<? super O>, O extends LifecycleEventOwner> implements PaperLifecycleEvent, OwnerAwareLifecycleEvent<O>, RegistrarEvent<R> {
+
+    private final R registrar;
+    private final Class<? extends O> ownerClass;
+
+    public RegistrarEventImpl(final R registrar, final Class<? extends O> ownerClass) {
+        this.registrar = registrar;
+        this.ownerClass = ownerClass;
+    }
+
+    @Override
+    public R registrar() {
+        return this.registrar;
+    }
+
+    @Override
+    public final void setOwner(final @Nullable O owner) {
+        this.registrar.setCurrentContext(owner);
+    }
+
+    @Override
+    public final @Nullable O castOwner(final LifecycleEventOwner owner) {
+        return this.ownerClass.isInstance(owner) ? this.ownerClass.cast(owner) : null;
+    }
+
+    @Override
+    public void invalidate() {
+        this.registrar.invalidate();
+    }
+
+    @Override
+    public String toString() {
+        return "RegistrarEventImpl{" +
+            "registrar=" + this.registrar +
+            ", ownerClass=" + this.ownerClass +
+            '}';
+    }
+
+    public static class ReloadableImpl<R extends PaperRegistrar<? super O>, O extends LifecycleEventOwner> extends RegistrarEventImpl<R, O> implements ReloadableRegistrarEvent<R> {
+
+        private final ReloadableRegistrarEvent.Cause cause;
+
+        public ReloadableImpl(final R registrar, final Class<? extends O> ownerClass, final Cause cause) {
+            super(registrar, ownerClass);
+            this.cause = cause;
+        }
+
+        @Override
+        public Cause cause() {
+            return this.cause;
+        }
+
+        @Override
+        public String toString() {
+            return "ReloadableImpl{" +
+                "cause=" + this.cause +
+                "} " + super.toString();
+        }
+    }
+}
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/AbstractLifecycleEventType.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/AbstractLifecycleEventType.java
new file mode 100644
index 0000000000000000000000000000000000000000..a65fb37f4a729e2fe9fb81af822db626ec7e6d7b
--- /dev/null
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/AbstractLifecycleEventType.java
@@ -0,0 +1,50 @@
+package io.papermc.paper.plugin.lifecycle.event.types;
+
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEvent;
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventOwner;
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventRunner;
+import io.papermc.paper.plugin.lifecycle.event.handler.LifecycleEventHandler;
+import io.papermc.paper.plugin.lifecycle.event.handler.configuration.AbstractLifecycleEventHandlerConfiguration;
+import io.papermc.paper.plugin.lifecycle.event.handler.configuration.LifecycleEventHandlerConfiguration;
+import java.util.function.Consumer;
+import java.util.function.Predicate;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public abstract class AbstractLifecycleEventType<O extends LifecycleEventOwner, E extends LifecycleEvent, C extends LifecycleEventHandlerConfiguration<O>, CI extends AbstractLifecycleEventHandlerConfiguration<O, E, CI>> implements LifecycleEventType<O, E, C> {
+
+    private final String name;
+    private final Class<? extends O> ownerType;
+
+    protected AbstractLifecycleEventType(final String name, final Class<? extends O> ownerType) {
+        this.name = name;
+        this.ownerType = ownerType;
+    }
+
+    @Override
+    public String name() {
+        return this.name;
+    }
+
+    private void verifyOwner(final O owner) {
+        if (!this.ownerType.isInstance(owner)) {
+            throw new IllegalArgumentException("You cannot register the lifecycle event '" + this.name + "' on " + owner);
+        }
+    }
+
+    public abstract void forEachHandler(Consumer<? super RegisteredHandler<O, E>> consumer, Predicate<? super RegisteredHandler<O, E>> predicate);
+
+    public abstract void removeMatching(Predicate<? super RegisteredHandler<O, E>> predicate);
+
+    protected abstract void register(O owner, LifecycleEventHandler<? super E> handler, CI config);
+
+    public final void tryRegister(final O owner, final LifecycleEventHandler<? super E> handler, final CI config) {
+        this.verifyOwner(owner);
+        LifecycleEventRunner.INSTANCE.checkRegisteredHandler(owner, this);
+        this.register(owner, handler, config);
+    }
+
+    public record RegisteredHandler<O, E extends LifecycleEvent>(O owner, LifecycleEventHandler<? super E> lifecycleEventHandler) {
+    }
+}
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/LifecycleEventTypeProviderImpl.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/LifecycleEventTypeProviderImpl.java
new file mode 100644
index 0000000000000000000000000000000000000000..0886edad92b40276f268bd745b31bac359fd28af
--- /dev/null
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/LifecycleEventTypeProviderImpl.java
@@ -0,0 +1,25 @@
+package io.papermc.paper.plugin.lifecycle.event.types;
+
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEvent;
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventOwner;
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventRunner;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public final class LifecycleEventTypeProviderImpl implements LifecycleEventTypeProvider {
+
+    public static LifecycleEventTypeProviderImpl instance() {
+        return (LifecycleEventTypeProviderImpl) LifecycleEventTypeProvider.PROVIDER;
+    }
+
+    @Override
+    public <O extends LifecycleEventOwner, E extends LifecycleEvent> LifecycleEventType.Monitorable<O, E> monitor(final String name, final Class<? extends O> ownerType) {
+        return LifecycleEventRunner.INSTANCE.addEventType(new MonitorableLifecycleEventType<>(name, ownerType));
+    }
+
+    @Override
+    public <O extends LifecycleEventOwner, E extends LifecycleEvent> LifecycleEventType.Prioritizable<O, E> prioritized(final String name, final Class<? extends O> ownerType) {
+        return LifecycleEventRunner.INSTANCE.addEventType(new PrioritizableLifecycleEventType<>(name, ownerType));
+    }
+}
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/MonitorableLifecycleEventType.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/MonitorableLifecycleEventType.java
new file mode 100644
index 0000000000000000000000000000000000000000..6d92c1d3adf220154dfe7cba3a3f8158356c3e3c
--- /dev/null
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/MonitorableLifecycleEventType.java
@@ -0,0 +1,54 @@
+package io.papermc.paper.plugin.lifecycle.event.types;
+
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEvent;
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventOwner;
+import io.papermc.paper.plugin.lifecycle.event.handler.LifecycleEventHandler;
+import io.papermc.paper.plugin.lifecycle.event.handler.configuration.MonitorLifecycleEventHandlerConfiguration;
+import io.papermc.paper.plugin.lifecycle.event.handler.configuration.MonitorLifecycleEventHandlerConfigurationImpl;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Consumer;
+import java.util.function.Predicate;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public class MonitorableLifecycleEventType<O extends LifecycleEventOwner, E extends LifecycleEvent> extends AbstractLifecycleEventType<O, E, MonitorLifecycleEventHandlerConfiguration<O>, MonitorLifecycleEventHandlerConfigurationImpl<O, E>> implements LifecycleEventType.Monitorable<O, E> {
+
+    final List<RegisteredHandler<O, E>> handlers = new ArrayList<>();
+    int nonMonitorIdx = 0;
+
+    public MonitorableLifecycleEventType(final String name, final Class<? extends O> ownerType) {
+        super(name, ownerType);
+    }
+
+    @Override
+    public MonitorLifecycleEventHandlerConfigurationImpl<O, E> newHandler(final LifecycleEventHandler<? super E> handler) {
+        return new MonitorLifecycleEventHandlerConfigurationImpl<>(handler, this);
+    }
+
+    @Override
+    protected void register(final O owner, final LifecycleEventHandler<? super E> handler, final MonitorLifecycleEventHandlerConfigurationImpl<O, E> config) {
+        final RegisteredHandler<O, E> registeredHandler = new RegisteredHandler<>(owner, handler);
+        if (!config.isMonitor()) {
+            this.handlers.add(this.nonMonitorIdx, registeredHandler);
+            this.nonMonitorIdx++;
+        } else {
+            this.handlers.add(registeredHandler);
+        }
+    }
+
+    @Override
+    public void forEachHandler(final Consumer<? super RegisteredHandler<O, E>> consumer, final Predicate<? super RegisteredHandler<O, E>> predicate) {
+        for (final RegisteredHandler<O, E> handler : this.handlers) {
+            if (predicate.test(handler)) {
+                consumer.accept(handler);
+            }
+        }
+    }
+
+    @Override
+    public void removeMatching(final Predicate<? super RegisteredHandler<O, E>> predicate) {
+        this.handlers.removeIf(predicate);
+    }
+}
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/OwnerAwareLifecycleEvent.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/OwnerAwareLifecycleEvent.java
new file mode 100644
index 0000000000000000000000000000000000000000..3e7e7474f301c0725fa2bcd6e19e476fc35f2d5a
--- /dev/null
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/OwnerAwareLifecycleEvent.java
@@ -0,0 +1,15 @@
+package io.papermc.paper.plugin.lifecycle.event.types;
+
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEvent;
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventOwner;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public interface OwnerAwareLifecycleEvent<O extends LifecycleEventOwner> extends LifecycleEvent {
+
+    void setOwner(@Nullable O owner);
+
+    @Nullable O castOwner(LifecycleEventOwner owner);
+}
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/PrioritizableLifecycleEventType.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/PrioritizableLifecycleEventType.java
new file mode 100644
index 0000000000000000000000000000000000000000..6629f7fabf66ce761024268043cc30076ba8a3f1
--- /dev/null
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/PrioritizableLifecycleEventType.java
@@ -0,0 +1,64 @@
+package io.papermc.paper.plugin.lifecycle.event.types;
+
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEvent;
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventOwner;
+import io.papermc.paper.plugin.lifecycle.event.handler.LifecycleEventHandler;
+import io.papermc.paper.plugin.lifecycle.event.handler.configuration.PrioritizedLifecycleEventHandlerConfiguration;
+import io.papermc.paper.plugin.lifecycle.event.handler.configuration.PrioritizedLifecycleEventHandlerConfigurationImpl;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.List;
+import java.util.OptionalInt;
+import java.util.function.Consumer;
+import java.util.function.Predicate;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public class PrioritizableLifecycleEventType<O extends LifecycleEventOwner, E extends LifecycleEvent> extends AbstractLifecycleEventType<O, E, PrioritizedLifecycleEventHandlerConfiguration<O>, PrioritizedLifecycleEventHandlerConfigurationImpl<O, E>> implements LifecycleEventType.Prioritizable<O, E> {
+
+    private static final Comparator<PrioritizedHandler<?, ?>> COMPARATOR = Comparator.comparing(PrioritizedHandler::priority, (o1, o2) -> {
+        if (o1.equals(o2)) {
+            return 0;
+        } else if (o1.isEmpty()) {
+            return 1;
+        } else if (o2.isEmpty()) {
+            return -1;
+        } else {
+            return Integer.compare(o1.getAsInt(), o2.getAsInt());
+        }
+    });
+
+    private final List<PrioritizedHandler<O, E>> handlers = new ArrayList<>();
+
+    public PrioritizableLifecycleEventType(final String name, final Class<? extends O> ownerType) {
+        super(name, ownerType);
+    }
+
+    @Override
+    public PrioritizedLifecycleEventHandlerConfiguration<O> newHandler(final LifecycleEventHandler<? super E> handler) {
+        return new PrioritizedLifecycleEventHandlerConfigurationImpl<>(handler, this);
+    }
+
+    @Override
+    protected void register(final O owner, final LifecycleEventHandler<? super E> handler, final PrioritizedLifecycleEventHandlerConfigurationImpl<O, E> config) {
+        this.handlers.add(new PrioritizedHandler<>(new RegisteredHandler<>(owner, handler), config.priority()));
+        this.handlers.sort(COMPARATOR);
+    }
+
+    @Override
+    public void forEachHandler(final Consumer<? super RegisteredHandler<O, E>> consumer, final Predicate<? super RegisteredHandler<O, E>> predicate) {
+        for (final PrioritizedHandler<O, E> handler : this.handlers) {
+            if (predicate.test(handler.handler())) {
+                consumer.accept(handler.handler());
+            }
+        }
+    }
+
+    @Override
+    public void removeMatching(final Predicate<? super RegisteredHandler<O, E>> predicate) {
+        this.handlers.removeIf(prioritizedHandler -> predicate.test(prioritizedHandler.handler()));
+    }
+
+    private record PrioritizedHandler<O extends LifecycleEventOwner, E extends LifecycleEvent>(RegisteredHandler<O, E> handler, OptionalInt priority) {}
+}
diff --git a/src/main/java/io/papermc/paper/plugin/manager/PaperPluginInstanceManager.java b/src/main/java/io/papermc/paper/plugin/manager/PaperPluginInstanceManager.java
index 834b85f24df023642f8abf7213fe578ac8c17a3e..3e82ea07ca4194844c5528446e2c4a46ff4acee5 100644
--- a/src/main/java/io/papermc/paper/plugin/manager/PaperPluginInstanceManager.java
+++ b/src/main/java/io/papermc/paper/plugin/manager/PaperPluginInstanceManager.java
@@ -293,6 +293,15 @@ class PaperPluginInstanceManager {
                 + pluginName + " (Is it up to date?)", ex, plugin); // Paper
         }
 
+        // Paper start - lifecycle event system
+        try {
+            io.papermc.paper.plugin.lifecycle.event.LifecycleEventRunner.INSTANCE.unregisterAllEventHandlersFor(plugin);
+        } catch (Throwable ex) {
+            this.handlePluginException("Error occurred (in the plugin loader) while unregistering lifecycle event handlers for "
+                + pluginName + " (Is it up to date?)", ex, plugin);
+        }
+        // Paper end
+
         try {
             this.server.getMessenger().unregisterIncomingPluginChannel(plugin);
             this.server.getMessenger().unregisterOutgoingPluginChannel(plugin);
diff --git a/src/main/java/io/papermc/paper/plugin/storage/BootstrapProviderStorage.java b/src/main/java/io/papermc/paper/plugin/storage/BootstrapProviderStorage.java
index 2e96308696e131f3f013469a395e5ddda2c5d529..65a66e484c1c39c5f41d97db52f31c67b4479d20 100644
--- a/src/main/java/io/papermc/paper/plugin/storage/BootstrapProviderStorage.java
+++ b/src/main/java/io/papermc/paper/plugin/storage/BootstrapProviderStorage.java
@@ -32,8 +32,9 @@ public class BootstrapProviderStorage extends SimpleProviderStorage<PluginBootst
             @Override
             public boolean load(PluginProvider<PluginBootstrap> provider, PluginBootstrap provided) {
                 try {
-                    BootstrapContext context = PluginBootstrapContextImpl.create(provider, PluginInitializerManager.instance().pluginDirectoryPath());
+                    PluginBootstrapContextImpl context = PluginBootstrapContextImpl.create(provider, PluginInitializerManager.instance().pluginDirectoryPath()); // Paper - lifecycle events
                     provided.bootstrap(context);
+                    context.lockLifecycleEventRegistration(); // Paper - lifecycle events
                     return true;
                 } catch (Throwable e) {
                     LOGGER.error("Failed to run bootstrapper for %s. This plugin will not be loaded.".formatted(provider.getSource()), e);
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
index b1cfc6f5a2511e9bb145442dfb765951a1ee0fca..b9ad8446d702f729673d75dd6978b9db820f380b 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
@@ -1017,6 +1017,11 @@ public final class CraftServer implements Server {
 
     @Override
     public void reload() {
+        // Paper start - lifecycle events
+        if (io.papermc.paper.plugin.lifecycle.event.LifecycleEventRunner.INSTANCE.blocksPluginReloading()) {
+            throw new IllegalStateException("A lifecycle event handler has been registered which makes reloading plugins not possible");
+        }
+        // Paper end - lifecycle events
         org.spigotmc.WatchdogThread.hasStarted = false; // Paper - Disable watchdog early timeout on reload
         this.reloadCount++;
         this.configuration = YamlConfiguration.loadConfiguration(this.getConfigFile());
diff --git a/src/main/java/org/bukkit/craftbukkit/scheduler/MinecraftInternalPlugin.java b/src/main/java/org/bukkit/craftbukkit/scheduler/MinecraftInternalPlugin.java
index d96399e9bf1a58db5a4a22e58abb99e7660e0694..66bdac50130f523f9dc4379b103b7a469f9ca36b 100644
--- a/src/main/java/org/bukkit/craftbukkit/scheduler/MinecraftInternalPlugin.java
+++ b/src/main/java/org/bukkit/craftbukkit/scheduler/MinecraftInternalPlugin.java
@@ -143,4 +143,11 @@ public class MinecraftInternalPlugin extends PluginBase {
     public List<String> onTabComplete(CommandSender sender, Command command, String alias, String[] args) {
         throw new UnsupportedOperationException("Not supported.");
     }
+
+    // Paper start - lifecycle events
+    @Override
+    public @NotNull io.papermc.paper.plugin.lifecycle.event.LifecycleEventManager<org.bukkit.plugin.Plugin> getLifecycleManager() {
+        throw new UnsupportedOperationException("Not supported.");
+    }
+    // Paper end - lifecycle events
 }
diff --git a/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java b/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
index cf29c541b74ab37592997c31adb7b240d92b2bea..12289984948b0cc34df39767945222616844aebb 100644
--- a/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
+++ b/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
@@ -653,6 +653,13 @@ public final class CraftMagicNumbers implements UnsafeValues {
     }
     // Paper end - spawn egg color visibility
 
+    // Paper start - lifecycle event API
+    @Override
+    public io.papermc.paper.plugin.lifecycle.event.LifecycleEventManager<org.bukkit.plugin.Plugin> createPluginLifecycleEventManager(final org.bukkit.plugin.java.JavaPlugin plugin, final java.util.function.BooleanSupplier registrationCheck) {
+        return new io.papermc.paper.plugin.lifecycle.event.PaperLifecycleEventManager<>(plugin, registrationCheck);
+    }
+    // Paper end - lifecycle event API
+
     /**
      * This helper class represents the different NBT Tags.
      * <p>
diff --git a/src/main/resources/META-INF/services/io.papermc.paper.plugin.lifecycle.event.types.LifecycleEventTypeProvider b/src/main/resources/META-INF/services/io.papermc.paper.plugin.lifecycle.event.types.LifecycleEventTypeProvider
new file mode 100644
index 0000000000000000000000000000000000000000..808b1192b60348ad05f0bfbdeda6f94df4876743
--- /dev/null
+++ b/src/main/resources/META-INF/services/io.papermc.paper.plugin.lifecycle.event.types.LifecycleEventTypeProvider
@@ -0,0 +1 @@
+io.papermc.paper.plugin.lifecycle.event.types.LifecycleEventTypeProviderImpl
diff --git a/src/test/java/io/papermc/paper/plugin/PaperTestPlugin.java b/src/test/java/io/papermc/paper/plugin/PaperTestPlugin.java
index 1d14f530ef888102e47eeeaf0d1a6076e51871c4..90cf0c702ca2ff9de64d9718ecba5f2d128953a6 100644
--- a/src/test/java/io/papermc/paper/plugin/PaperTestPlugin.java
+++ b/src/test/java/io/papermc/paper/plugin/PaperTestPlugin.java
@@ -143,4 +143,11 @@ public class PaperTestPlugin extends PluginBase {
     public List<String> onTabComplete(CommandSender sender, Command command, String alias, String[] args) {
         throw new UnsupportedOperationException("Not supported.");
     }
+
+    // Paper start - lifecycle events
+    @Override
+    public io.papermc.paper.plugin.lifecycle.event.LifecycleEventManager<org.bukkit.plugin.Plugin> getLifecycleManager() {
+        throw new UnsupportedOperationException("Not supported.");
+    }
+    // Paper end - lifecycle events
 }
