Create ChainableRunnables.kt

src/main/kotlin/net/axay/kspigot/runnables/ChainableRunnables.kt

@@ -0,0 +1,52 @@
+@file:Suppress("MemberVisibilityCanBePrivate")
+
+package net.axay.kspigot.runnables
+
+import org.bukkit.Bukkit
+import org.bukkit.plugin.Plugin
+
+/*
+ * Chainable bukkit runnable.
+ */
+
+class ChainedRunnablePart<T, R>(
+        val plugin: Plugin,
+        val runnable: (T?) -> R,
+        val sync: Boolean,
+        var previous: ChainedRunnablePart<*, T>? = null,
+        var next: ChainedRunnablePart<R, *>? = null
+) {
+
+    fun execute() {
+        previous?.execute() ?: kotlin.run { start(null) }
+    }
+
+    private fun start(data: T?) {
+        val realRunnable = Runnable {
+            val result = runnable.invoke(data)
+            next?.start(result)
+        }
+        if (sync)
+            Bukkit.getScheduler().runTask(plugin, realRunnable)
+        else
+            Bukkit.getScheduler().runTaskAsynchronously(plugin, realRunnable)
+    }
+
+}
+
+// FIRST
+fun <R> Plugin.firstDo(sync: Boolean, runnable: (Unit?) -> R)
+        = ChainedRunnablePart<Unit, R>(this, runnable, sync)
+fun <R> Plugin.firstSync(runnable: (Unit?) -> R) = firstDo(true, runnable)
+fun <R> Plugin.firstAsync(runnable: (Unit?) -> R) = firstDo(false, runnable)
+
+// THEN
+fun <T, R, U> ChainedRunnablePart<T, R>.thenDo(sync: Boolean, runnable: (R?) -> U): ChainedRunnablePart<R, U> {
+    ChainedRunnablePart<R, U>(plugin, runnable, sync).apply {
+        previous = this@thenDo
+        this@thenDo.next = this
+        return this
+    }
+}
+fun <T, R, U> ChainedRunnablePart<T, R>.thenSync(runnable: (R?) -> U) = thenDo(true, runnable)
+fun <T, R, U> ChainedRunnablePart<T, R>.thenAsync(runnable: (R?) -> U) = thenDo(false, runnable)