added encode_nbt, added 'nbt' and 'nbt_merge' to modify entity API.

docs/scarpet/api/Auxiliary.md

@@ -130,6 +130,30 @@ Consult section about container operations in `Expression` to learn about possib
 Excapes all the special characters in the string or nbt tag and returns a string that can be stored in nbt directly 
 as a string value.
 
+### parse_nbt(tag)
+
+Converts NBT tag to a scarpet value, which you can navigate through much better.
+
+Converts:
+ - Compound tags into maps with string keys
+ - List tags into list values
+ - Numbers (Ints, Floats, Doubles, Longs) into a number
+ - Rest is converted to strings.
+ 
+### encode_nbt(expr, force?)
+
+Encodes value of the expression as an NBT tag. By default (or when `force` is false), it will only allow
+to encode values that are guaranteed to return the same value when applied the resulting tag to `parse_nbt()`.
+Supported types that can reliably convert back and forth to and from NBT values are:
+ - Maps with string keywords
+ - Lists of items of the same type (scarpet will take care of unifying value types if possible)
+ - Numbers (encoded as Ints -> Longs -> Doubles, as needed)
+ - Strings
+
+Other value types will only be converted to tags (including NBT tags) if `force` is true. They would require
+extra treatment when loading them back from NBT, but using `force` true will always produce output / never 
+produce an exception.
+
 ### `print(expr)`
 
 Displays the result of the expression to the chat. Overrides default `scarpet` behaviour of sending everyting to stderr.

docs/scarpet/api/Entities.md

@@ -532,6 +532,15 @@ Modifies directly player raw hunger components. Has no effect on non-players
 adds exhaustion value to the current player exhaustion level - that's the method you probably want to use
 to manipulate how much 'food' some action cost.
 
+### `modify(e, 'nbt_merge', partial_tag)`
+
+Merges a partial tag into the entity data and reloads the entity from its updated tag. Cannot be applied to players
+
+### `modify(e, 'nbt', tag)`
+
+Reloads the entity from a supplied tag. Better get a valid entity tag, what can go wrong. Wonder what would happen if
+transplant rabbit's brain into a villager. Cannot be applied to players.
+
 ## Entity Events
 
 There is a number of events that happen to entities that you can attach your own code to in the form of event handlers. 

src/main/java/carpet/script/CarpetExpression.java

@@ -2949,6 +2949,24 @@ public class CarpetExpression
             return (cc, tt) -> parsed;
         });
 
+        this.expr.addLazyFunction("encode_nbt", -1, (c, t, lv) -> {
+            int argSize = lv.size();
+            if (argSize==0 || argSize > 2) throw new InternalExpressionException("'encode_nbt' requires 1 or 2 parameters");
+            Value v = lv.get(0).evalValue(c);
+            boolean force = (argSize > 1) && lv.get(1).evalValue(c).getBoolean();
+            Tag tag;
+            try
+            {
+                tag = v.toTag(force);
+            }
+            catch (NBTSerializableValue.IncompatibleTypeException ignored)
+            {
+                throw new InternalExpressionException("cannot reliably encode to a tag the value of '"+ignored.val.getPrettyString()+"'");
+            }
+            Value tagValue = new NBTSerializableValue(tag);
+            return (cc, tt) -> tagValue;
+        });
+
         //"overridden" native call that prints to stderr
         this.expr.addLazyFunction("print", -1, (c, t, lv) ->
         {

src/main/java/carpet/script/value/BlockValue.java

@@ -12,7 +12,10 @@ import net.minecraft.block.Blocks;
 import net.minecraft.item.ItemPlacementContext;
 import net.minecraft.item.ItemStack;
 import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.StringTag;
+import net.minecraft.nbt.Tag;
 import net.minecraft.server.world.ServerWorld;
+import net.minecraft.state.property.Property;
 import net.minecraft.util.GlobalPos;
 import net.minecraft.util.Hand;
 import net.minecraft.util.hit.BlockHitResult;
@@ -24,8 +27,10 @@ import net.minecraft.world.World;
 import net.minecraft.world.chunk.WorldChunk;
 
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.stream.Collectors;
 
@@ -180,6 +185,33 @@ public class BlockValue extends Value
 
     public ServerWorld getWorld() { return world;}
 
+    @Override
+    public Tag toTag(boolean force)
+    {
+        if (!force) throw new NBTSerializableValue.IncompatibleTypeException(this);
+        // follows falling block convertion
+        CompoundTag tag =  new CompoundTag();
+        CompoundTag state = new CompoundTag();
+        BlockState s = getBlockState();
+        state.put("Name", StringTag.of(Registry.BLOCK.getId(s.getBlock()).toString()));
+        Collection<Property<?>> properties = s.getProperties();
+        if (!properties.isEmpty())
+        {
+            CompoundTag props = new CompoundTag();
+            for (Property<?> p: properties)
+            {
+                props.put(p.getName(), StringTag.of(s.get(p).toString().toLowerCase(Locale.ROOT)));
+            }
+            state.put("Properties", props);
+        }
+        tag.put("BlockState", state);
+        CompoundTag dataTag = getData();
+        if (dataTag != null)
+        {
+            tag.put("TileEntityData", dataTag);
+        }
+        return tag;
+    }
 
     public enum SpecificDirection {
         UP("up",0.5, 0.0, 0.5, Direction.UP),

src/main/java/carpet/script/value/EntityValue.java

@@ -1,6 +1,5 @@
 package carpet.script.value;
 
-import carpet.CarpetSettings;
 import carpet.fakes.EntityInterface;
 import carpet.fakes.ItemEntityInterface;
 import carpet.fakes.LivingEntityInterface;
@@ -12,10 +11,10 @@ import carpet.script.CarpetContext;
 import carpet.script.EntityEventsGroup;
 import carpet.script.argument.Vector3Argument;
 import carpet.script.exception.InternalExpressionException;
-import carpet.utils.Messenger;
 import com.mojang.brigadier.StringReader;
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
-import net.minecraft.entity.player.HungerManager;
+import net.minecraft.nbt.StringTag;
+import net.minecraft.nbt.Tag;
 import net.minecraft.network.packet.s2c.play.EntityPassengersSetS2CPacket;
 import net.minecraft.network.packet.s2c.play.EntityPositionS2CPacket;
 import net.minecraft.network.packet.s2c.play.PlayerPositionLookS2CPacket;
@@ -61,6 +60,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.UUID;
 import java.util.function.BiConsumer;
 import java.util.function.BiFunction;
 import java.util.function.Predicate;
@@ -976,22 +976,37 @@ public class EntityValue extends Value
             if(e instanceof PlayerEntity) ((PlayerEntity) e).getHungerManager().setSaturationLevelClient((float)NumericValue.asNumber(v).getLong());
         });
 
-        // gamemode         [check]
-        // spectate         [check]
-        // "fire"           [check]
-        // "extinguish"     [set fire ticks to 0]
-        // "silent"         [check]
-        // "gravity"        [check]
-        // "invulnerable"   [check]
+        put("nbt", (e, v) -> {
+            if (!(e instanceof PlayerEntity))
+            {
+                UUID uUID = e.getUuid();
+                Value tagValue = NBTSerializableValue.fromValue(v);
+                if (tagValue instanceof NBTSerializableValue)
+                {
+                    e.fromTag(((NBTSerializableValue) tagValue).getCompoundTag());
+                    e.setUuid(uUID);
+                }
+            }
+        });
+        put("nbt_merge", (e, v) -> {
+            if (!(e instanceof PlayerEntity))
+            {
+                UUID uUID = e.getUuid();
+                Value tagValue = NBTSerializableValue.fromValue(v);
+                if (tagValue instanceof NBTSerializableValue)
+                {
+                    CompoundTag nbttagcompound = e.toTag((new CompoundTag()));
+                    nbttagcompound.copyFrom(((NBTSerializableValue) tagValue).getCompoundTag());
+                    e.fromTag(nbttagcompound);
+                    e.setUuid(uUID);
+                }
+            }
+        });
+
         // "dimension"      []
         // "item"           []
         // "count",         []
-        // "age",           [check]
         // "effect_"name    []
-        // "hold"           [inventory_set?]
-        // "hold_offhand"   [inventory_set?] 
-        // "jump"           [check]
-        // "nbt" <-big one, for now use run('data merge entity ...
     }};
 
     public void setEvent(CarpetContext cc, String eventName, FunctionValue fun, List<Value> args)
@@ -1001,4 +1016,14 @@ public class EntityValue extends Value
             throw new InternalExpressionException("Unknown entity event: " + eventName);
         ((EntityInterface)entity).getEventContainer().addEvent(event, cc, fun, args);
     }
+
+    @Override
+    public Tag toTag(boolean force)
+    {
+        if (!force) throw new NBTSerializableValue.IncompatibleTypeException(this);
+        CompoundTag tag = new CompoundTag();
+        tag.put("Data", getEntity().toTag( new CompoundTag()));
+        tag.put("Name", StringTag.of(Registry.ENTITY_TYPE.getId(entity.getType()).toString()));
+        return tag;
+    }
 }

src/main/java/carpet/script/value/FormattedTextValue.java

@@ -1,6 +1,9 @@
 package carpet.script.value;
 
+import net.minecraft.nbt.StringTag;
+import net.minecraft.nbt.Tag;
 import net.minecraft.text.BaseText;
+import net.minecraft.text.Text;
 
 public class FormattedTextValue extends StringValue
 {
@@ -37,4 +40,11 @@ public class FormattedTextValue extends StringValue
     {
         return text;
     }
+
+    @Override
+    public Tag toTag(boolean force)
+    {
+        if (!force) throw new NBTSerializableValue.IncompatibleTypeException(this);
+        return StringTag.of(Text.Serializer.toJson(text));
+    }
 }

src/main/java/carpet/script/value/FrameworkValue.java

@@ -1,5 +1,7 @@
 package carpet.script.value;
 
+import net.minecraft.nbt.Tag;
+
 public abstract class FrameworkValue extends Value
 {
     @Override
@@ -25,4 +27,10 @@ public abstract class FrameworkValue extends Value
     {
         throw new UnsupportedOperationException("Scarpet language component cannot be used as map key");
     }
+
+    @Override
+    public Tag toTag(boolean force)
+    {
+        throw new UnsupportedOperationException("Scarpet language component cannot be serialized to the tag");
+    }
 }

src/main/java/carpet/script/value/FunctionValue.java

@@ -13,6 +13,8 @@ import carpet.script.exception.ExpressionException;
 import carpet.script.exception.InternalExpressionException;
 import carpet.script.exception.ReturnStatement;
 import carpet.script.exception.ThrowStatement;
+import net.minecraft.nbt.StringTag;
+import net.minecraft.nbt.Tag;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -94,6 +96,8 @@ public class FunctionValue extends Value implements Fluff.ILazyFunction
         return name.hashCode()+(int)variant;
     }
 
+
+
     @Override
     public boolean equals(Object o)
     {
@@ -231,4 +235,11 @@ public class FunctionValue extends Value implements Fluff.ILazyFunction
     {
         return args;
     }
+
+    @Override
+    public Tag toTag(boolean force)
+    {
+        if (!force) throw new NBTSerializableValue.IncompatibleTypeException(this);
+        return StringTag.of(getString());
+    }
 }

src/main/java/carpet/script/value/GlobalValue.java

@@ -1,6 +1,7 @@
 package carpet.script.value;
 
 import carpet.script.exception.InternalExpressionException;
+import net.minecraft.nbt.Tag;
 
 public class GlobalValue extends Value
 {
@@ -28,4 +29,10 @@ public class GlobalValue extends Value
     {
         throw new UnsupportedOperationException("Global value cannot be used as a map key");
     }
+
+    @Override
+    public Tag toTag(boolean force)
+    {
+        throw new UnsupportedOperationException("Global value cannot be serialized to the tag");
+    }
 }

src/main/java/carpet/script/value/LazyListValue.java

@@ -1,6 +1,8 @@
 package carpet.script.value;
 
 import carpet.script.exception.InternalExpressionException;
+import net.minecraft.nbt.StringTag;
+import net.minecraft.nbt.Tag;
 
 import java.util.ArrayList;
 import java.util.Iterator;
@@ -152,4 +154,11 @@ public abstract class LazyListValue extends AbstractListValue implements Iterato
     {
         return ("i"+getString()).hashCode();
     }
+
+    @Override
+    public Tag toTag(boolean force)
+    {
+        if (!force) throw new NBTSerializableValue.IncompatibleTypeException(this);
+        return StringTag.of(getString());
+    }
 }

src/main/java/carpet/script/value/ListValue.java

@@ -3,13 +3,23 @@ package carpet.script.value;
 import carpet.script.LazyValue;
 import carpet.script.exception.InternalExpressionException;
 import net.minecraft.item.ItemStack;
+import net.minecraft.nbt.AbstractNumberTag;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.DoubleTag;
+import net.minecraft.nbt.IntTag;
+import net.minecraft.nbt.ListTag;
+import net.minecraft.nbt.LongTag;
+import net.minecraft.nbt.StringTag;
+import net.minecraft.nbt.Tag;
 import net.minecraft.util.registry.Registry;
 
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.EnumSet;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Set;
 import java.util.stream.Collectors;
 import java.util.stream.StreamSupport;
 
@@ -454,4 +464,65 @@ public class ListValue extends AbstractListValue implements ContainerValueInterf
     {
         return items.hashCode();
     }
+
+    private enum TagTypeCompat
+    {
+        INT,
+        LONG,
+        DBL,
+        LIST,
+        MAP,
+        STRING;
+        private static TagTypeCompat getType(Tag tag)
+        {
+            if (tag instanceof IntTag) return INT;
+            if (tag instanceof LongTag) return LONG;
+            if (tag instanceof DoubleTag) return DBL;
+            if (tag instanceof ListTag) return LIST;
+            if (tag instanceof CompoundTag) return MAP;
+            return STRING;
+        }
+    }
+
+
+    @Override
+    public Tag toTag(boolean force)
+    {
+        int argSize = items.size();
+        if (argSize == 0) return new ListTag();
+        ListTag tag = new ListTag();
+        if (argSize ==1)
+        {
+            tag.add(items.get(0).toTag(force));
+            return tag;
+        }
+        // figuring out the types
+        List<Tag> tags= new ArrayList<>();
+        items.forEach(v -> tags.add(v.toTag(force)));
+        Set<TagTypeCompat> cases = EnumSet.noneOf(TagTypeCompat.class);
+        tags.forEach(t -> cases.add(TagTypeCompat.getType(t)));
+        if (cases.size()==1) // well, one type of items
+        {
+            tag.addAll(tags);
+            return tag;
+        }
+        if (cases.contains(TagTypeCompat.LIST)
+                || cases.contains(TagTypeCompat.MAP)
+                || cases.contains(TagTypeCompat.STRING)) // incompatible types
+        {
+            if (!force) throw new NBTSerializableValue.IncompatibleTypeException(this);
+            tags.forEach(t -> tag.add(StringTag.of(t.asString())));
+            return tag;
+        }
+        // only numbers / mixed types
+        if (cases.contains(TagTypeCompat.DBL))
+        {
+            tags.forEach(t -> tag.add(DoubleTag.of(((AbstractNumberTag)t).getDouble())));
+        }
+        else
+        {
+            tags.forEach(t -> tag.add(LongTag.of(((AbstractNumberTag)t).getLong())));
+        }
+        return tag;
+    }
 }

src/main/java/carpet/script/value/MapValue.java

@@ -1,6 +1,8 @@
 package carpet.script.value;
 
 import carpet.script.exception.InternalExpressionException;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.Tag;
 
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -226,4 +228,16 @@ public class MapValue extends AbstractListValue implements ContainerValueInterfa
     {
         return map.hashCode();
     }
+
+    @Override
+    public Tag toTag(boolean force)
+    {
+        CompoundTag tag = new CompoundTag() ;
+        map.forEach( (k, v) ->
+        {
+            if (!force && !(k instanceof StringValue)) throw new NBTSerializableValue.IncompatibleTypeException(k);
+            tag.put(k.getString(), v.toTag(force));
+        });
+        return tag;
+    }
 }

src/main/java/carpet/script/value/NBTSerializableValue.java

@@ -638,4 +638,23 @@ public class NBTSerializableValue extends Value implements ContainerValueInterfa
     {
         return "nbt";
     }
+
+
+    @Override
+    public Tag toTag(boolean force)
+    {
+        if (!force) throw new NBTSerializableValue.IncompatibleTypeException(this);
+        ensureOwnership();
+        return getTag();
+    }
+
+    public static class IncompatibleTypeException extends RuntimeException
+    {
+        private IncompatibleTypeException() {}
+        public Value val;
+        public IncompatibleTypeException(Value val)
+        {
+            this.val = val;
+        }
+    };
 }

src/main/java/carpet/script/value/NullValue.java

@@ -1,5 +1,8 @@
 package carpet.script.value;
 
+import net.minecraft.nbt.StringTag;
+import net.minecraft.nbt.Tag;
+
 public class NullValue extends NumericValue // TODO check nonsingleton code
 {
     @Override
@@ -50,4 +53,11 @@ public class NullValue extends NumericValue // TODO check nonsingleton code
     {
         return 0;
     }
+
+    @Override
+    public Tag toTag(boolean force)
+    {
+        if (!force) throw new NBTSerializableValue.IncompatibleTypeException(this);
+        return StringTag.of("null");
+    }
 }

src/main/java/carpet/script/value/NumericValue.java

@@ -1,6 +1,10 @@
 package carpet.script.value;
 
 import carpet.script.exception.InternalExpressionException;
+import net.minecraft.nbt.DoubleTag;
+import net.minecraft.nbt.IntTag;
+import net.minecraft.nbt.LongTag;
+import net.minecraft.nbt.Tag;
 import org.apache.commons.lang3.StringUtils;
 
 import java.math.BigDecimal;
@@ -204,4 +208,20 @@ public class NumericValue extends Value
     {
         return (int)getLong();
     }
+
+    @Override
+    public Tag toTag(boolean force)
+    {
+        long longValue = getLong();
+        if (value == (double)longValue)
+        {
+            if (abs(value) < Integer.MAX_VALUE-2)
+                return IntTag.of((int)longValue);
+            return LongTag.of(getLong());
+        }
+        else
+        {
+            return DoubleTag.of(value);
+        }
+    }
 }

src/main/java/carpet/script/value/StringValue.java

@@ -1,5 +1,8 @@
 package carpet.script.value;
 
+import net.minecraft.nbt.StringTag;
+import net.minecraft.nbt.Tag;
+
 public class StringValue extends Value
 {
     private String str;
@@ -30,4 +33,10 @@ public class StringValue extends Value
     {
         return "string";
     }
+
+    @Override
+    public Tag toTag(boolean force)
+    {
+        return StringTag.of(str);
+    }
 }

src/main/java/carpet/script/value/ThreadValue.java

@@ -6,6 +6,7 @@ import carpet.script.LazyValue;
 import carpet.script.Tokenizer;
 import carpet.script.exception.ExpressionException;
 import carpet.script.exception.InternalExpressionException;
+import net.minecraft.nbt.Tag;
 
 import java.util.HashMap;
 import java.util.List;
@@ -144,4 +145,10 @@ public class ThreadValue extends Value
         locks.clear();
     }
 
+    @Override
+    public Tag toTag(boolean force)
+    {
+        if (!force) throw new NBTSerializableValue.IncompatibleTypeException(this);
+        return getValue().toTag(true);
+    }
 }

src/main/java/carpet/script/value/Value.java

@@ -1,6 +1,7 @@
 package carpet.script.value;
 
 import carpet.script.exception.InternalExpressionException;
+import net.minecraft.nbt.Tag;
 
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -203,4 +204,6 @@ public abstract class Value implements Comparable<Value>, Cloneable
             throw new InternalExpressionException("Cannot make a copy of value: "+this);
         }
     }
+
+    public abstract Tag toTag(boolean force);
 }