Add price checker

src/main/kotlin/moe/nea/firmament/util/async/input.kt

@@ -0,0 +1,45 @@
+package moe.nea.firmament.util.async
+
+import kotlinx.coroutines.suspendCancellableCoroutine
+import kotlin.coroutines.resume
+import moe.nea.firmament.events.HandledScreenKeyPressedEvent
+import moe.nea.firmament.keybindings.IKeyBinding
+
+private object InputHandler {
+    data class KeyInputContinuation(val keybind: IKeyBinding, val onContinue: () -> Unit)
+
+    private val activeContinuations = mutableListOf<KeyInputContinuation>()
+
+    fun registerContinuation(keyInputContinuation: KeyInputContinuation): () -> Unit {
+        synchronized(InputHandler) {
+            activeContinuations.add(keyInputContinuation)
+        }
+        return {
+            synchronized(this) {
+                activeContinuations.remove(keyInputContinuation)
+            }
+        }
+    }
+
+    init {
+        HandledScreenKeyPressedEvent.subscribe { event ->
+            synchronized(InputHandler) {
+                val toRemove = activeContinuations.filter {
+                    event.matches(it.keybind)
+                }
+                toRemove.forEach { it.onContinue() }
+                activeContinuations.removeAll(toRemove)
+            }
+        }
+    }
+}
+
+suspend fun waitForInput(keybind: IKeyBinding): Unit = suspendCancellableCoroutine { cont ->
+    val unregister =
+        InputHandler.registerContinuation(InputHandler.KeyInputContinuation(keybind) { cont.resume(Unit) })
+    cont.invokeOnCancellation {
+        unregister()
+    }
+}
+
+