Class to simplify eval commands for kotlin discord bots using kord. Currently uses slash commands, it would be easy to just use regular commands. To use, just initialize, and invoke with a string containing code to be executed.

EvalContext.kt

import dev.kord.common.annotation.KordPreview
import dev.kord.core.Kord
import dev.kord.core.behavior.interaction.EphemeralInteractionResponseBehavior
import dev.kord.core.behavior.interaction.followUp
import dev.kord.core.entity.Guild
import dev.kord.core.entity.channel.Channel
import java.io.ByteArrayOutputStream
import java.io.PrintStream
import javax.script.ScriptEngineManager
import javax.script.ScriptException

@Suppress("unused") @KordPreview class EvalContext(
	val client: Kord,
	val channel: Channel,
	val guild: Guild,
	private val ack: EphemeralInteractionResponseBehavior
) {

	private companion object {

		/** This must contain the FULLY QUALIFIED NAME of this class!! */
		const val CLASS_NAME = "EvalContext"

		private val man = object : ScriptEngineManager(Thread.currentThread().contextClassLoader) {
			operator fun invoke() = getEngineByExtension("kts")!!
		}
	}

	private val buf = StringBuilder()

	private var ret: Any? = Unit
	private var error = true

	internal suspend operator fun invoke(code: String) = try {
		@Suppress("UNCHECKED_CAST")
		ret = (man().eval("run<suspend $CLASS_NAME.()->Any?>{{$code}}")
			as suspend EvalContext.() -> Any?)(this)
		error = false
	} catch (e: ScriptException) {
		out("```" + buildString {
			var a = true
			var b = false
			for (line in ByteArrayOutputStream().also { e.printStackTrace(PrintStream(it)) }.toString(Charsets.UTF_8)
				.lines()) {
				if (a) {
					val s = line.split(':', limit = 2)[1].trimStart()
					appendLine(s)
					if (s.startsWith("Error: incomplete code")) break
					a = false
					continue
				}
				if (b && line.isBlank()) break
				if (line.trimStart().startsWith('^')) b = true
				appendLine(line)

			}
		}.also(System.err::print) + "```")
	} catch (e: Throwable) {
		out("```" + buildString {
			append("Exception in thread \"${Thread.currentThread().name}\" ")
			for (line in ByteArrayOutputStream().also { e.printStackTrace(PrintStream(it)) }.toString(Charsets.UTF_8)
				.lines()) {
				if (line.startsWith("\tat Line_1\$1\$1.invokeSuspend(Line_1.kts:")) {
					appendLine("\tat <eval>(<eval>:${line.split(':', limit = 2)[1].dropLast(1)})")
					break
				}
				appendLine(line)
			}
		}.also(System.err::print) + "```")
	} finally {
		try {
			var out = buf.toString()
			if (!error) {
				val hr = ret != Unit
				val b = out.isBlank()
				if (b && !hr) out = "\u200B" else {
					if (!b) out = "```\n$out\n```"
					if (hr) out += "```Return value: ${ret.toString()}```"
				}
			}

			ack.followUp(out)
		} catch (e: Exception) { e.printStackTrace() }
	}

	fun out(message: Any?) { buf.append(message) }

	fun out(message: Int) { buf.append(message) }

	fun out(message: Long) { buf.append(message) }

	fun out(message: Byte) { buf.append(message) }

	fun out(message: Short) { buf.append(message) }

	fun out(message: Char) { buf.append(message) }

	fun out(message: Boolean) { buf.append(message) }

	fun out(message: Float) { buf.append(message) }

	fun out(message: Double) { buf.append(message) }

	fun out(message: CharArray) { buf.append(message) }

	fun outln(message: Any?) { buf.appendLine(message) }

	fun outln(message: Int) { buf.appendLine(message) }

	fun outln(message: Long) { buf.appendLine(message) }

	fun outln(message: Byte) { buf.appendLine(message) }

	fun outln(message: Short) { buf.appendLine(message) }

	fun outln(message: Char) { buf.appendLine(message) }

	fun outln(message: Boolean) { buf.appendLine(message) }

	fun outln(message: Float) { buf.appendLine(message) }

	fun outln(message: Double) { buf.appendLine(message) }

	fun outln(message: CharArray) { buf.appendLine(message) }

	fun outln() { buf.appendLine() }

}