fabric-carpet/src/main/java/carpet/CarpetExtension.java

package carpet;

import carpet.script.CarpetExpression;
import carpet.api.settings.SettingsManager;
import com.mojang.brigadier.CommandDispatcher;
import net.minecraft.commands.CommandBuildContext;
import net.minecraft.commands.CommandSourceStack;
import net.minecraft.server.MinecraftServer;
import net.minecraft.server.level.ServerPlayer;

import java.util.Collections;
import java.util.Map;

public interface CarpetExtension
{
    /**
     * When game started before world is loaded
     */
    default void onGameStarted() {}

    /**
     * Runs once per loaded world once the server / gamerules etc are fully loaded
     * but before worlds are loaded
     * Can be loaded multiple times in SinglePlayer
     * 
     * @param server The {@link MinecraftServer} instance that loaded
     */
    default void onServerLoaded(MinecraftServer server) {}

    /**
     * Runs once per loaded world once the World files are fully loaded
     * Can be loaded multiple times in SinglePlayer
     * 
     * @param server The current {@link MinecraftServer} instance
     * 
     */
    default void onServerLoadedWorlds(MinecraftServer server) {}

    /**
     * Runs once per game tick, as a first thing in the tick
     * 
     * @param server The current {@link MinecraftServer} instance
     * 
     */
    default void onTick(MinecraftServer server) {}

    /**
     * Register your own commands right after vanilla commands are added
     * If that matters for you
     *
     * Deprecated, Implement {@link CarpetExtension#registerCommands(CommandDispatcher, CommandBuildContext)}
     * 
     * @param dispatcher The current {@link CommandSource<ServerCommandSource>} dispatcher 
     *                   where you should register your commands
     * 
     */
    @Deprecated(forRemoval = true)
    default void registerCommands(CommandDispatcher<CommandSourceStack> dispatcher) {}

    /**
     * Register your own commands right after vanilla commands are added
     * If that matters for you
     *
     * @param dispatcher The current {@link CommandDispatcher<CommandSourceStack>} dispatcher
     *                   where you should register your commands
     * @param commandBuildContext The current {@link CommandBuildContext} context
     *      *                   which you can use for registries lookup
     */
    default void registerCommands(CommandDispatcher<CommandSourceStack> dispatcher, final CommandBuildContext commandBuildContext) {
        registerCommands(dispatcher);
    }

    /**
     * @deprecated Implement {@link #extensionSettingsManager()} instead
     */
    @Deprecated(forRemoval = true)
    default carpet.settings.SettingsManager customSettingsManager() {return null;}

    /**
     * Provide your own custom settings manager managed in the same way as base /carpet
     * command, but separated to its own command as defined in SettingsManager.
     * 
     * @return Your custom {@link SettingsManager} instance to be managed by Carpet
     * 
     */
    default SettingsManager extensionSettingsManager() {
        // Warn extensions overriding the other (deprecated) method, go ahead and override this if you want to provide a custom SettingsManager
        SettingsManager deprecatedManager = customSettingsManager();
        if (deprecatedManager != null) {
            // Extension is providing a manager via the old method (and also hasn't overriden this)
            CarpetServer.warnOutdatedManager(this);
        }
        return customSettingsManager();
    }

    /**
     * Event that gets called when a player logs in
     * 
     * @param player The {@link ServerPlayer} that logged in
     * 
     */
    default void onPlayerLoggedIn(ServerPlayer player) {}

    /**
     * Event that gets called when a player logs out
     * 
     * @param player The {@link ServerPlayer} that logged out
     * 
     */
    default void onPlayerLoggedOut(ServerPlayer player) {}

    /**
     * Event that gets called when the server closes.
     * Can be called multiple times in singleplayer
     * 
     * @param server The {@link MinecraftServer} that is closing
     * 
     */
    default void onServerClosed(MinecraftServer server) {}

    /**
     * Event that gets called when the server reloads (usually
     * when running the /reload command)
     * 
     * @param server The {@link MinecraftServer} that is reloading
     * 
     */
    default void onReload(MinecraftServer server) {}

    /**
     * @return A {@link String} usually being the extension's id
     * 
     */
    default String version() {return null;}

    /**
     * Called when registering custom loggers
     * 
     */
    default void registerLoggers() {}

    /**
     * Method for Carpet to get the translations for extension's
     * rules.
     * 
     * @param lang A {@link String} being the language id selected by the user
     * @return A {@link Map<String, String>} containing the string key with its 
     *         respective translation {@link String} or an empty map if not available
     * 
     */
    default Map<String, String> canHasTranslations(String lang) { return Collections.emptyMap();}

    /**
     * Handles each call that creates / parses the scarpet expression.
     * Extensions can add their own built-in functions here.
     *
     * Events such as generic events or entity events, can be added statically
     * by creating new events as
     *
     * CarpetEventServer.Event class: to handle `__on_foo()` type of call definitions
     *
     * or
     *
     * EntityEventsGroup.Event class: to handle `entity_event('foo', ...)` type of events
     *
     * @param expression Passed {@link CarpetExpression} to add built-in functions to
     */
    default void scarpetApi(CarpetExpression expression) {}

}