feat: fall flying prevention & allow manual equip

* User can manually drag the elytra into their chestplate slot even when
  it is locked, although this would display a log
* Locking the elytra now prevents fall flying if the user has it
  equipped at the time of lock

src/main/java/xyz/devcomp/elytralock/events/ClientTickEndHandler.java

@@ -8,8 +8,11 @@ import net.minecraft.item.Items;
 import xyz.devcomp.elytralock.ElytraLock;
 
 public class ClientTickEndHandler implements EndTick {
+    private static boolean hasWarned = false;
+
     public void onEndTick(MinecraftClient client) {
-        if (client.isWindowFocused() && ElytraLock.isLocked() && client.player != null) {
+        if (ElytraLock.isLocked()) {
+            if (!hasWarned && client.isWindowFocused() && client.player != null) {
                 PlayerInventory inventory = client.player.getInventory();
     
                 // 0 -> boots 
@@ -17,18 +20,13 @@ public class ClientTickEndHandler implements EndTick {
                 // 2 -> chestplate
                 // 3 -> helmet
                 ItemStack chestArmor = inventory.armor.get(2);
-
                 if (chestArmor.isOf(Items.ELYTRA)) {
                     ElytraLock.LOGGER.info("Detected player wearing elytra even though it's locked");
-                ItemStack elytra = chestArmor.copyAndEmpty();
+                    hasWarned = true;
-                int inventorySlot = inventory.getSwappableHotbarSlot();
+                }
-                
+            }
-                boolean ok = inventory.insertStack(inventorySlot, elytra);
+        } else {
-
+            hasWarned = false;
-                if (!ok) {
-                    ElytraLock.LOGGER.warn("Failed to remove equipped elytra, which is locked");
-                }
-            }
         }
     }
 }

src/main/java/xyz/devcomp/elytralock/mixin/PlayerEntityMixin.java

@@ -0,0 +1,25 @@
+package xyz.devcomp.elytralock.mixin;
+
+import xyz.devcomp.elytralock.ElytraLock;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+import net.minecraft.entity.player.PlayerEntity;
+
+// TODO: In the future, make fall flying prevention and elytra lock separate
+// Fall flying prevention should be subset of elytra locking which should be 
+// individually toggleable
+
+@Mixin(PlayerEntity.class)
+public class PlayerEntityMixin {
+    @Inject(method = "checkFallFlying()Z", at = @At("HEAD"), cancellable = true)
+    private void preventFallFlying(CallbackInfoReturnable<Boolean> info) {
+        if (ElytraLock.isLocked()) {
+            ElytraLock.LOGGER.info("Elytra is locked, so preventing fall flying");
+            info.setReturnValue(false);
+        }
+    }
+}

src/main/resources/elytra-lock.mixins.json

@@ -3,7 +3,8 @@
 	"package": "xyz.devcomp.elytralock.mixin",
 	"compatibilityLevel": "JAVA_17",
 	"mixins": [
-		"ClientPlayerInteractionManagerMixin"
+		"ClientPlayerInteractionManagerMixin",
+		"PlayerEntityMixin"
 	],
 	"injectors": {
 		"defaultRequire": 1