Add price checker

src/main/kotlin/moe/nea/firmament/keybindings/IKeyBinding.kt

@@ -0,0 +1,27 @@
+package moe.nea.firmament.keybindings
+
+import net.minecraft.client.option.KeyBinding
+
+interface IKeyBinding {
+    fun matches(keyCode: Int, scanCode: Int, modifiers: Int): Boolean
+
+    fun withModifiers(wantedModifiers: Int): IKeyBinding {
+        val old = this
+        return object : IKeyBinding {
+            override fun matches(keyCode: Int, scanCode: Int, modifiers: Int): Boolean {
+                return old.matches(keyCode, scanCode, modifiers) && (modifiers and wantedModifiers) == wantedModifiers
+            }
+        }
+    }
+
+    companion object {
+        fun minecraft(keyBinding: KeyBinding) = object : IKeyBinding {
+            override fun matches(keyCode: Int, scanCode: Int, modifiers: Int) =
+                keyBinding.matchesKey(keyCode, scanCode)
+        }
+
+        fun ofKeyCode(wantedKeyCode: Int) = object : IKeyBinding {
+            override fun matches(keyCode: Int, scanCode: Int, modifiers: Int): Boolean = keyCode == wantedKeyCode
+        }
+    }
+}