can now save and cast spells from spellbooks!

src/main/java/at/petrak/hex/HexUtils.kt

@@ -1,6 +1,7 @@
 package at.petrak.hex
 
 import net.minecraft.nbt.LongArrayTag
+import net.minecraft.world.InteractionHand
 import net.minecraft.world.phys.Vec2
 import net.minecraft.world.phys.Vec3
 
@@ -10,7 +11,7 @@ object HexUtils {
         LongArrayTag(longArrayOf(this.x.toRawBits(), this.y.toRawBits(), this.z.toRawBits()))
 
     @JvmStatic
-    fun deserializeVec3FromNBT(tag: LongArray): Vec3 =
+    fun DeserializeVec3FromNBT(tag: LongArray): Vec3 =
         Vec3(
             Double.fromBits(tag[0]),
             Double.fromBits(tag[1]),
@@ -22,11 +23,15 @@ object HexUtils {
         LongArrayTag(longArrayOf(this.x.toDouble().toRawBits(), this.y.toDouble().toRawBits()))
 
     @JvmStatic
-    fun deserializeVec2FromNBT(tag: LongArray): Vec2 =
+    fun DeserializeVec2FromNBT(tag: LongArray): Vec2 =
         Vec2(
             Double.fromBits(tag[0]).toFloat(),
             Double.fromBits(tag[1]).toFloat(),
         )
 
+    @JvmStatic
+    fun OtherHand(hand: InteractionHand) =
+        if (hand == InteractionHand.MAIN_HAND) InteractionHand.OFF_HAND else InteractionHand.MAIN_HAND
+
     const val TAU = Math.PI * 2.0
 }

src/main/java/at/petrak/hex/client/ShiftScrollListener.java

@@ -17,7 +17,6 @@ import net.minecraftforge.fml.common.Mod;
 public class ShiftScrollListener {
     @SubscribeEvent
     public static void onScroll(InputEvent.MouseScrollEvent evt) {
-        HexMod.LOGGER.info("scrolling {}", evt.getScrollDelta());
         LocalPlayer player = Minecraft.getInstance().player;
         if (player.isCrouching()) {
             InteractionHand hand = null;

src/main/java/at/petrak/hex/client/gui/GuiSpellcasting.kt

@@ -1,7 +1,11 @@
 package at.petrak.hex.client.gui
 
 import at.petrak.hex.HexMod
+import at.petrak.hex.HexUtils
 import at.petrak.hex.HexUtils.TAU
+import at.petrak.hex.common.items.ItemSpellbook
+import at.petrak.hex.common.network.HexMessages
+import at.petrak.hex.common.network.MsgShiftScrollSyn
 import at.petrak.hex.hexmath.HexAngle
 import at.petrak.hex.hexmath.HexCoord
 import at.petrak.hex.hexmath.HexDir
@@ -101,7 +105,7 @@ class GuiSpellcasting(private val handOpenedWith: InteractionHand) : Screen(Text
                 this.drawState = PatternDrawState.BetweenPatterns
                 this.patterns.add(Pair(pat, start))
 
-                at.petrak.hex.common.network.HexMessages.getNetwork().sendToServer(
+                HexMessages.getNetwork().sendToServer(
                     at.petrak.hex.common.network.MsgNewSpellPatternSyn(
                         this.handOpenedWith,
                         pat
@@ -113,6 +117,16 @@ class GuiSpellcasting(private val handOpenedWith: InteractionHand) : Screen(Text
         return false
     }
 
+    override fun mouseScrolled(pMouseX: Double, pMouseY: Double, pDelta: Double): Boolean {
+        super.mouseScrolled(pMouseX, pMouseY, pDelta)
+
+        val otherHand = HexUtils.OtherHand(this.handOpenedWith)
+        if (Minecraft.getInstance().player!!.getItemInHand(otherHand).item is ItemSpellbook)
+            HexMessages.getNetwork().sendToServer(MsgShiftScrollSyn(otherHand, pDelta))
+
+        return true
+    }
+
     override fun onClose() {
         at.petrak.hex.common.network.HexMessages.getNetwork()
             .sendToServer(at.petrak.hex.common.network.MsgQuitSpellcasting())

src/main/java/at/petrak/hex/common/casting/CastException.kt

@@ -50,6 +50,13 @@ class CastException(val reason: Reason, vararg val data: Any) : Exception() {
          * `vec: Vec3`
          */
         TOO_FAR,
+
+        /**
+         * An operator needed a spellbook in the offhand.
+         *
+         * `no args`
+         */
+        REQUIRES_SPELLBOOK,
     }
 
     override val message: String
@@ -60,5 +67,6 @@ class CastException(val reason: Reason, vararg val data: Any) : Exception() {
             Reason.NOT_ENOUGH_ARGS -> "required at least ${this.data[0] as Int} args on the stack but only had ${this.data[1] as Int}"
             Reason.TOO_MANY_CLOSE_PARENS -> "too many close parentheses"
             Reason.TOO_FAR -> "tried to interact with something too far away at ${this.data[0] as Vec3}"
+            Reason.REQUIRES_SPELLBOOK -> "required a spellbook in the other hand"
         }
 }

src/main/java/at/petrak/hex/common/casting/CastingContext.kt

@@ -1,7 +1,11 @@
 package at.petrak.hex.common.casting
 
+import at.petrak.hex.HexUtils
+import at.petrak.hex.common.items.ItemSpellbook
 import net.minecraft.server.level.ServerLevel
 import net.minecraft.server.level.ServerPlayer
+import net.minecraft.world.InteractionHand
+import net.minecraft.world.item.ItemStack
 
 /**
  * Info about the moment the spell started being cast.
@@ -9,6 +13,17 @@ import net.minecraft.server.level.ServerPlayer
 @JvmRecord
 data class CastingContext(
     val caster: ServerPlayer,
+    val wandHand: InteractionHand,
 ) {
     val world: ServerLevel get() = caster.getLevel()
+
+    fun getSpellbook(): ItemStack {
+        val handItem =
+            caster.getItemInHand(HexUtils.OtherHand(wandHand))
+        return if (handItem.item is ItemSpellbook) {
+            handItem
+        } else {
+            throw CastException(CastException.Reason.REQUIRES_SPELLBOOK)
+        }
+    }
 }

src/main/java/at/petrak/hex/common/casting/CastingHarness.kt

@@ -6,6 +6,7 @@ import net.minecraft.nbt.CompoundTag
 import net.minecraft.nbt.ListTag
 import net.minecraft.nbt.Tag
 import net.minecraft.server.level.ServerPlayer
+import net.minecraft.world.InteractionHand
 
 /**
  * Keeps track of a player casting a spell on the server.
@@ -143,8 +144,8 @@ class CastingHarness private constructor(
         const val TAG_ESCAPE_NEXT = "escape_next"
 
         @JvmStatic
-        fun DeserializeFromNBT(nbt: Tag?, caster: ServerPlayer): CastingHarness {
+        fun DeserializeFromNBT(nbt: Tag?, caster: ServerPlayer, wandHand: InteractionHand): CastingHarness {
-            val ctx = CastingContext(caster)
+            val ctx = CastingContext(caster, wandHand)
             return try {
                 val nbt = nbt as CompoundTag
 

src/main/java/at/petrak/hex/common/casting/SpellDatum.kt

@@ -114,7 +114,7 @@ class SpellDatum<T : Any> private constructor(val payload: T) {
                     SpellDatum(if (entity == null || !entity.isAlive) SpellWidget.NULL else entity)
                 }
                 TAG_DOUBLE -> SpellDatum(nbt.getDouble(key))
-                TAG_VEC3 -> SpellDatum(HexUtils.deserializeVec3FromNBT(nbt.getLongArray(key)))
+                TAG_VEC3 -> SpellDatum(HexUtils.DeserializeVec3FromNBT(nbt.getLongArray(key)))
                 TAG_LIST -> {
                     val arr = nbt.getList(key, Tag.TAG_COMPOUND.toInt())
                     val out = ArrayList<SpellDatum<*>>(arr.size)

src/main/java/at/petrak/hex/common/casting/SpellOperator.kt

@@ -65,10 +65,12 @@ interface SpellOperator {
             // == Meta stuff ==
             "qqq" to SpellWidget.OPEN_PAREN,
             "eee" to SpellWidget.CLOSE_PAREN,
-            "aaaqw" to SpellWidget.ESCAPE,
+            "qqqaw" to SpellWidget.ESCAPE,
             // http://www.toroidalsnark.net/mkss3-pix/CalderheadJMM2014.pdf
             // eval being a space filling curve feels apt doesn't it
-            "deaqq" to OpEval
+            "deaqq" to OpEval,
+            "aqqqqq" to OpReadFromSpellbook,
+            "deeeee" to OpWriteToSpellbook,
         )
 
         /**

src/main/java/at/petrak/hex/common/casting/operators/OpReadFromSpellbook.kt

@@ -0,0 +1,17 @@
+package at.petrak.hex.common.casting.operators
+
+import at.petrak.hex.common.casting.CastingContext
+import at.petrak.hex.common.casting.SpellDatum
+import at.petrak.hex.common.casting.SpellWidget
+import at.petrak.hex.common.items.ItemSpellbook
+
+object OpReadFromSpellbook : SimpleOperator {
+    override val argc: Int
+        get() = 0
+
+    override fun execute(args: List<SpellDatum<*>>, ctx: CastingContext): List<SpellDatum<*>> {
+        val spellbook = ctx.getSpellbook()
+        val datum = ItemSpellbook.ReadDatum(spellbook.orCreateTag, ctx)
+        return listOf(datum ?: SpellDatum.make(SpellWidget.NULL))
+    }
+}

src/main/java/at/petrak/hex/common/casting/operators/OpWriteToSpellbook.kt

@@ -0,0 +1,17 @@
+package at.petrak.hex.common.casting.operators
+
+import at.petrak.hex.common.casting.CastingContext
+import at.petrak.hex.common.casting.SpellDatum
+import at.petrak.hex.common.casting.SpellOperator.Companion.spellListOf
+import at.petrak.hex.common.items.ItemSpellbook
+
+object OpWriteToSpellbook : SimpleOperator {
+    override val argc: Int
+        get() = 1
+
+    override fun execute(args: List<SpellDatum<*>>, ctx: CastingContext): List<SpellDatum<*>> {
+        val spellbook = ctx.getSpellbook()
+        ItemSpellbook.WriteDatum(spellbook.orCreateTag, args[0])
+        return spellListOf()
+    }
+}

src/main/java/at/petrak/hex/common/items/ItemSpellbook.java

@@ -1,9 +1,12 @@
 package at.petrak.hex.common.items;
 
+import at.petrak.hex.common.casting.CastingContext;
+import at.petrak.hex.common.casting.SpellDatum;
 import net.minecraft.nbt.CompoundTag;
 import net.minecraft.network.chat.Component;
 import net.minecraft.network.chat.TextComponent;
 import net.minecraft.network.chat.TranslatableComponent;
+import net.minecraft.world.entity.Entity;
 import net.minecraft.world.item.Item;
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.item.TooltipFlag;
@@ -15,7 +18,8 @@ import java.util.stream.Stream;
 
 public class ItemSpellbook extends Item {
     public static String TAG_SELECTED_PAGE = "page_idx";
-    // this is a CompoundTag of string numerical keys to SpellData
+    // this is a CompoundTag of string numerical keys to SpellData\
+    // it is 1-indexed, so that 0/0 can be the special case of "it is empty"
     public static String TAG_PAGES = "pages";
 
     public ItemSpellbook(Properties properties) {
@@ -40,6 +44,68 @@ public class ItemSpellbook extends Item {
         }
     }
 
+    @Override
+    public void inventoryTick(ItemStack stack, Level pLevel, Entity pEntity, int pSlotId, boolean pIsSelected) {
+        var tag = stack.getOrCreateTag();
+        if (ArePagesEmpty(tag)) {
+            tag.putInt(TAG_SELECTED_PAGE, 0);
+        } else if (!tag.contains(TAG_SELECTED_PAGE)) {
+            tag.putInt(TAG_SELECTED_PAGE, 1);
+        } else {
+            var pageIdx = tag.getInt(TAG_SELECTED_PAGE);
+            if (pageIdx == 0) {
+                tag.putInt(TAG_SELECTED_PAGE, 1);
+            }
+        }
+    }
+
+    public static boolean ArePagesEmpty(CompoundTag tag) {
+        return !tag.contains(ItemSpellbook.TAG_PAGES) ||
+                tag.getCompound(ItemSpellbook.TAG_PAGES).isEmpty();
+    }
+
+    public static void WriteDatum(CompoundTag tag, SpellDatum<?> datum) {
+        int idx;
+        if (tag.contains(TAG_SELECTED_PAGE)) {
+            idx = tag.getInt(TAG_SELECTED_PAGE);
+            // But we want to write to page *1* to start if this is our first page
+            if (idx == 0 && ArePagesEmpty(tag)) {
+                idx = 1;
+            }
+        } else {
+            idx = 1;
+        }
+        var key = String.valueOf(idx);
+        if (tag.contains(TAG_PAGES)) {
+            tag.getCompound(TAG_PAGES).put(key, datum.serializeToNBT());
+        } else {
+            var pagesTag = new CompoundTag();
+            pagesTag.put(key, datum.serializeToNBT());
+            tag.put(TAG_PAGES, pagesTag);
+        }
+    }
+
+    @Nullable
+    public static SpellDatum<?> ReadDatum(CompoundTag tag, CastingContext ctx) {
+        int idx;
+        if (tag.contains(TAG_SELECTED_PAGE)) {
+            idx = tag.getInt(TAG_SELECTED_PAGE);
+        } else {
+            idx = 0;
+        }
+        var key = String.valueOf(idx);
+        if (tag.contains(TAG_PAGES)) {
+            var pagesTag = tag.getCompound(TAG_PAGES);
+            if (pagesTag.contains(key)) {
+                return SpellDatum.DeserializeFromNBT(pagesTag.getCompound(key), ctx);
+            } else {
+                return null;
+            }
+        } else {
+            return null;
+        }
+    }
+
     public static int HighestPage(CompoundTag tag) {
         var highestKey = tag.getAllKeys().stream().flatMap(s -> {
             try {
@@ -53,12 +119,14 @@ public class ItemSpellbook extends Item {
 
     public static void RotatePageIdx(CompoundTag tag, boolean increase) {
         int newIdx;
-        if (tag.contains(ItemSpellbook.TAG_SELECTED_PAGE)) {
+        if (ArePagesEmpty(tag)) {
-            var delta = increase ? 1 : -1;
-            newIdx = Math.max(0, tag.getInt(ItemSpellbook.TAG_SELECTED_PAGE) + delta);
-        } else {
             newIdx = 0;
+        } else if (tag.contains(TAG_SELECTED_PAGE)) {
+            var delta = increase ? 1 : -1;
+            newIdx = Math.max(1, tag.getInt(TAG_SELECTED_PAGE) + delta);
+        } else {
+            newIdx = 1;
         }
-        tag.putInt(ItemSpellbook.TAG_SELECTED_PAGE, newIdx);
+        tag.putInt(TAG_SELECTED_PAGE, newIdx);
     }
 }

src/main/java/at/petrak/hex/common/network/MsgNewSpellPatternSyn.java

@@ -42,11 +42,11 @@ public record MsgNewSpellPatternSyn(InteractionHand handUsed, HexPattern pattern
                 var held = sender.getItemInHand(this.handUsed);
                 if (held.getItem() instanceof ItemWand) {
                     var tag = held.getOrCreateTag();
-                    var harness = CastingHarness.DeserializeFromNBT(tag, sender);
+                    var harness = CastingHarness.DeserializeFromNBT(tag, sender, this.handUsed);
 
                     var res = harness.update(this.pattern);
                     if (res instanceof CastResult.Success success) {
-                        success.getSpell().cast(new CastingContext(sender));
+                        success.getSpell().cast(new CastingContext(sender, this.handUsed));
                     } else if (res instanceof CastResult.Error error) {
                         sender.sendMessage(new TextComponent(error.getExn().getMessage()), Util.NIL_UUID);
                     }

src/main/java/at/petrak/hex/common/network/MsgShiftScrollSyn.java

@@ -12,7 +12,8 @@ import net.minecraftforge.network.NetworkEvent;
 import java.util.function.Supplier;
 
 /**
- * Sent client->server when the client shift+scrolls with a shift-scrollable item.
+ * Sent client->server when the client shift+scrolls with a shift-scrollable item
+ * or scrolls in the spellcasting UI.
  */
 public record MsgShiftScrollSyn(InteractionHand hand, double scrollDelta) {
     public static MsgShiftScrollSyn deserialize(ByteBuf buffer) {