Developing Extensions

Extensions provide an easy way to add your own functionality to Ledger

Note

The docs shown here have Kotlin code, but you can write your extension in Java should you wish

Set up project

1. Set up your mod environment as usual
2. Publish Ledger to mavenLocal
3. Add the following to your build.gradle:

modImplementation(include("com.github.quiltservertools:ledger:LATEST_LEDGER_VERSION"))

Creating your extension

object Extension : DatabaseExtension {
    override fun getDatabase(server: MinecraftServer): Database {
        TODO("Tutorial")
    }

    override fun getIdentifier(): Identifier {
        TODO("Tutorial")
    }
    override fun getConfigSpecs(): List<ConfigSpec> {
        return ArrayList()
    }
}

We now need to fill out the methods.

getDatabase: Returns an Exposed Database object. This is how you add new database types to Ledger

getIdentifier: Should return a new Identifier(YOUR_MODID, DATABASE_TYPE) object.

Register extension

In the entrypoint of your mod, add the relevant call to ExtensionManager#registerExtension

object MyMod : ModInitializer {
    override fun onInitialize() {
        ExtensionManager.registerExtension(Extension)
    }
}

It's as simple as that

Command extension

Create a command class:

object MyLedgerSubCommand : BuildableCommand {
    override fun build(): LiteralCommandNode<ServerCommandSource> {
        return CommandManager.literal("subcommand")
            .executes { ctx.source.sendFeedback(LiteralText("Subcommand run"), false) }
    }
}

Now you create your extension class and register it like shown above

object Extension : CommandExtension {
    fun registerSubcommands(): List<BuildableCommand> {
        val list = mutableListOf<BuildableCommand>()
        list.add(MyLedgerSubCommand)
        return list
    }
    override fun getConfigSpecs(): List<ConfigSpec> {
        return ArrayList()
    }
}

Config specs

Ledger uses the Konf library for configuration. You can add your own config specs to Ledger's file if your extension needs it

Create a config spec:

object ExtensionSpec : ConfigSpec() {
    val myProperty by optional(true)
    val myRequiredProperty by required<Boolean>()
}

Add the relevant line to your config file:

# Config file above

[extension]
myProperty = false
myRequiredProperty = true

You should make all properties optional unless your extension cannot function without a value. This is because existing config files will not have these values automatically added.

Register your spec:

override fun getConfigSpecs(): List<ConfigSpec> {
        return listOf(ExtensionSpec)
    }