add nbt

.gitignore

@@ -1 +1,3 @@
 /target
+configuration.toml
+features.toml

configuration.toml

@@ -1,14 +0,0 @@
-server_address = "127.0.0.1"
-server_port = 25565
-seed = ""
-max_plyers = 32
-view_distances = 10
-simulation_distance = 10
-resource_pack = ""
-resource_pack_sha1 = ""
-default_difficulty = "Normal"
-allow_nether = true
-hardcore = false
-online_mode = true
-spawn_protection = 16
-motd = "A Blazing fast Pumpkin Server!"

features.toml

@@ -1,2 +0,0 @@
-liquid_physics = true
-encryption = true

pumpkin/src/protocol/bytebuf/buffer.rs

@@ -1,4 +1,4 @@
-use crate::protocol::{nbt::NBT, VarInt, VarLong};
+use crate::protocol::{nbt::nbt::NBT, VarInt, VarLong};
 
 use super::{Endian, CONTINUE_BIT, SEGMENT_BITS};
 use byteorder::{BigEndian, ByteOrder, LittleEndian};
@@ -618,6 +618,29 @@ impl ByteBuffer {
         read_number!(self, read_f64, 8)
     }
 
+    pub fn read_list<T>(&mut self, val: impl Fn(&mut ByteBuffer) -> Result<T>) -> Result<Vec<T>> {
+        let len = self.read_var_int()?.try_into().unwrap();
+        let mut list = Vec::with_capacity(len);
+        for _ in 0..len {
+            list.push(val(self)?);
+        }
+        Ok(list)
+    }
+    /// Writes a list to the buffer.
+    pub fn write_list<T>(&mut self, list: &[T], write: impl Fn(&mut ByteBuffer, &T)) {
+        self.write_var_int(list.len().try_into().unwrap());
+        for v in list {
+            write(self, v);
+        }
+    }
+
+    pub fn read_varint_arr(&mut self) -> Result<Vec<i32>> {
+        self.read_list(|buf| buf.read_var_int())
+    }
+    pub fn write_varint_arr(&mut self, v: &[i32]) {
+        self.write_list(v, |p, &v| p.write_var_int(v))
+    }
+
     pub fn read_nbt(&mut self) -> Result<NBT> {
         match NBT::deserialize_buf(self) {
             Ok(v) => Ok(v),

pumpkin/src/protocol/client/config/mod.rs

@@ -1,26 +1,4 @@
-use crate::protocol::{nbt::NBT, ClientPacket, VarInt};
-
-pub struct CRegistryData {
-    registry_id: String,
-    entry_count: VarInt,
-    entries: NBT,
-}
-
-struct Entry {
-    entry_id: String,
-    has_data: bool,
-    data: NBT,
-}
-
-impl ClientPacket for CRegistryData {
-    const PACKET_ID: VarInt = 0x07;
-
-    fn write(&self, bytebuf: &mut crate::protocol::bytebuf::buffer::ByteBuffer) {
-        bytebuf.write_string(&self.registry_id);
-        bytebuf.write_var_int(self.entry_count);
-        //    bytebuf.write_array(self.entries);
-    }
-}
+use crate::protocol::{registry, ClientPacket, VarInt};
 
 pub struct CCookieRequest {
     // TODO
@@ -69,3 +47,69 @@ impl ClientPacket for CFinishConfig {
 
     fn write(&self, _bytebuf: &mut crate::protocol::bytebuf::buffer::ByteBuffer) {}
 }
+
+pub struct CKnownPacks {
+    count: VarInt,
+    known_packs: Vec<KnownPack>,
+}
+
+impl CKnownPacks {
+    pub fn new(count: VarInt, known_packs: Vec<KnownPack>) -> Self {
+        Self { count, known_packs }
+    }
+}
+
+pub struct KnownPack {
+    pub namespace: String,
+    pub id: String,
+    pub version: String,
+}
+
+impl ClientPacket for CKnownPacks {
+    const PACKET_ID: VarInt = 0x0E;
+
+    fn write(&self, bytebuf: &mut crate::protocol::bytebuf::buffer::ByteBuffer) {
+        bytebuf.write_var_int(self.count);
+        bytebuf.write_list::<KnownPack>(&self.known_packs, |p, v| {
+            p.write_string(&v.namespace);
+            p.write_string(&v.id);
+            p.write_string(&v.version);
+        });
+    }
+}
+
+pub struct CRegistryData {
+    registry_id: String,
+    entry_count: VarInt,
+    entries: Vec<Entry>,
+}
+
+impl CRegistryData {
+    pub fn new(registry_id: String, entry_count: VarInt, entries: Vec<Entry>) -> Self {
+        Self {
+            registry_id,
+            entry_count,
+            entries,
+        }
+    }
+}
+
+pub struct Entry {
+    pub entry_id: String,
+    pub has_data: bool,
+    // data provided by registry::write_codec
+}
+
+impl ClientPacket for CRegistryData {
+    const PACKET_ID: VarInt = 0x07;
+
+    fn write(&self, bytebuf: &mut crate::protocol::bytebuf::buffer::ByteBuffer) {
+        bytebuf.write_string(&self.registry_id);
+        bytebuf.write_var_int(self.entry_count);
+        bytebuf.write_list::<Entry>(&self.entries, |p, v| {
+            p.write_string(&v.entry_id);
+            p.write_bool(v.has_data);
+            registry::write_codec(p, -64, 320);
+        });
+    }
+}

pumpkin/src/protocol/client/play/mod.rs

@@ -1,4 +1,3 @@
-
 use crate::{
     entity::player::GameMode,
     protocol::{ClientPacket, VarInt},

pumpkin/src/protocol/nbt/deserialize.rs

@@ -1,29 +1,52 @@
-use std::{collections::HashMap, error::Error, fmt, string::FromUtf8Error};
+use flate2::read::{GzDecoder, ZlibDecoder};
+use std::{collections::HashMap, error::Error, fmt, io, io::Read, string::FromUtf8Error};
 
 use crate::protocol::bytebuf::buffer::ByteBuffer;
 
-use super::{Tag, NBT};
-
-#[derive(Debug)]
-pub enum ParseError {
-    InvalidType(u8),
-    InvalidString(FromUtf8Error),
-}
+use super::{nbt::ParseError, Tag, NBT};
 
 impl fmt::Display for ParseError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            Self::InvalidType(ty) => write!(f, "invalid tag type: {}", ty),
-            Self::InvalidString(e) => write!(f, "invalid string: {}", e),
+            Self::InvalidType(ty) => write!(f, "invalid tag type: {ty}"),
+            Self::InvalidString(e) => write!(f, "invalid string: {e}"),
+            Self::IO(e) => write!(f, "io error: {e}"),
         }
     }
 }
 
+impl From<FromUtf8Error> for ParseError {
+    fn from(e: FromUtf8Error) -> ParseError {
+        ParseError::InvalidString(e)
+    }
+}
+impl From<io::Error> for ParseError {
+    fn from(e: io::Error) -> ParseError {
+        ParseError::IO(e)
+    }
+}
 impl Error for ParseError {}
 
 impl NBT {
+    pub fn deserialize_file(buf: Vec<u8>) -> Result<Self, ParseError> {
+        if buf.len() >= 2 && buf[0] == 0x1f && buf[1] == 0x8b {
+            // This means its gzipped
+            let mut d: GzDecoder<&[u8]> = GzDecoder::new(buf.as_ref());
+            let mut buf = vec![];
+            d.read_to_end(&mut buf)?;
+            Self::deserialize(buf)
+        } else {
+            // It could be zlib compressed or not compressed
+            let mut d: ZlibDecoder<&[u8]> = ZlibDecoder::new(buf.as_ref());
+            let mut decompressed = vec![];
+            match d.read_to_end(&mut decompressed) {
+                Ok(_) => Self::deserialize(decompressed),
+                Err(_) => Self::deserialize(buf),
+            }
+        }
+    }
     /// Deserializes the given byte array as nbt data.
-    pub fn deserialize(buf: Vec<u8>) -> Result<Self, ParseError> {
+    pub fn deserialize(mut buf: Vec<u8>) -> Result<Self, ParseError> {
         Self::deserialize_buf(&mut ByteBuffer::from_vec(buf))
     }
     /// Deserializes the given buffer as nbt data. This will continue reading
@@ -32,10 +55,14 @@ impl NBT {
     /// buffer will be in an undefined state (it will still be safe, but there are
     /// no guarantees as too how far ahead the buffer will have been advanced).
     pub fn deserialize_buf(buf: &mut ByteBuffer) -> Result<Self, ParseError> {
-        let ty = buf.read_u8().unwrap();
-        let len = buf.read_u16().unwrap();
-        let name = String::from_utf8(buf.read_bytes(len as usize).unwrap()).unwrap();
-        Ok(NBT::new(&name, Tag::deserialize(ty, buf)?))
+        let ty = buf.read_u8()?;
+        if ty == 0 {
+            Ok(NBT::empty())
+        } else {
+            let len = buf.read_u16()?;
+            let name = String::from_utf8(buf.read_bytes(len as usize)?)?;
+            Ok(NBT::new(&name, Tag::deserialize(ty, buf)?))
+        }
     }
 }
 
@@ -43,26 +70,26 @@ impl Tag {
     fn deserialize(ty: u8, buf: &mut ByteBuffer) -> Result<Self, ParseError> {
         match ty {
             0 => Ok(Self::End),
-            1 => Ok(Self::Byte(buf.read_i8().unwrap())),
-            2 => Ok(Self::Short(buf.read_i16().unwrap())),
-            3 => Ok(Self::Int(buf.read_i32().unwrap())),
-            4 => Ok(Self::Long(buf.read_i64().unwrap())),
-            5 => Ok(Self::Float(buf.read_f32().unwrap())),
-            6 => Ok(Self::Double(buf.read_f64().unwrap())),
+            1 => Ok(Self::Byte(buf.read_i8()?)),
+            2 => Ok(Self::Short(buf.read_i16()?)),
+            3 => Ok(Self::Int(buf.read_i32()?)),
+            4 => Ok(Self::Long(buf.read_i64()?)),
+            5 => Ok(Self::Float(buf.read_f32()?)),
+            6 => Ok(Self::Double(buf.read_f64()?)),
             7 => {
-                let len = buf.read_i32().unwrap();
-                Ok(Self::ByteArr(buf.read_bytes(len as usize).unwrap()))
+                let len = buf.read_i32()?;
+                Ok(Self::ByteArr(buf.read_bytes(len as usize)?))
             }
             8 => {
-                let len = buf.read_u16().unwrap();
-                match String::from_utf8(buf.read_bytes(len as usize).unwrap()) {
+                let len = buf.read_u16()?;
+                match String::from_utf8(buf.read_bytes(len as usize)?) {
                     Ok(v) => Ok(Self::String(v)),
                     Err(e) => Err(ParseError::InvalidString(e)),
                 }
             }
             9 => {
-                let inner_ty = buf.read_u8().unwrap();
-                let len = buf.read_i32().unwrap();
+                let inner_ty = buf.read_u8()?;
+                let len = buf.read_i32()?;
                 let mut inner = Vec::with_capacity(len as usize);
                 for _ in 0..len {
                     inner.push(Tag::deserialize(inner_ty, buf)?);
@@ -72,30 +99,30 @@ impl Tag {
             10 => {
                 let mut inner = HashMap::new();
                 loop {
-                    let ty = buf.read_u8().unwrap();
+                    let ty = buf.read_u8()?;
                     if ty == Self::End.ty() {
                         break;
                     }
-                    let len = buf.read_u16().unwrap();
-                    let name = String::from_utf8(buf.read_bytes(len as usize).unwrap()).unwrap();
+                    let len = buf.read_u16()?;
+                    let name = String::from_utf8(buf.read_bytes(len as usize)?).unwrap();
                     let tag = Tag::deserialize(ty, buf)?;
                     inner.insert(name, tag);
                 }
-                Ok(Self::Compound(inner))
+                Ok(inner.into())
             }
             11 => {
-                let len = buf.read_i32().unwrap();
+                let len = buf.read_i32()?;
                 let mut inner = Vec::with_capacity(len as usize);
                 for _ in 0..len {
-                    inner.push(buf.read_i32().unwrap());
+                    inner.push(buf.read_i32()?);
                 }
                 Ok(Self::IntArray(inner))
             }
             12 => {
-                let len = buf.read_i32().unwrap();
+                let len = buf.read_i32()?;
                 let mut inner = Vec::with_capacity(len as usize);
                 for _ in 0..len {
-                    inner.push(buf.read_i64().unwrap());
+                    inner.push(buf.read_i64()?);
                 }
                 Ok(Self::LongArray(inner))
             }

pumpkin/src/protocol/nbt/error.rs

@@ -0,0 +1,56 @@
+use super::Tag;
+use serde::{de, ser};
+use std::{fmt, fmt::Display, num::TryFromIntError};
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum Error {
+    Message(String),
+    Eof,
+
+    TryFromInt(TryFromIntError),
+    ListType(Tag, Tag),
+    MapKey(Tag),
+    CannotSerializeNone,
+    Enum,
+}
+
+pub type Result<T> = std::result::Result<T, Error>;
+
+impl ser::Error for Error {
+    fn custom<T: Display>(msg: T) -> Self {
+        Error::Message(msg.to_string())
+    }
+}
+
+impl de::Error for Error {
+    fn custom<T: Display>(msg: T) -> Self {
+        Error::Message(msg.to_string())
+    }
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Error::Message(msg) => write!(f, "{msg}"),
+            Error::Eof => write!(f, "unexpected end of input"),
+            Error::TryFromInt(e) => write!(f, "invalid integer: {e}"),
+            Error::ListType(expected, got) => {
+                write!(f, "expected type in list: {expected:?}, got: {got:?}")
+            }
+            Error::MapKey(got) => {
+                write!(f, "expected a string for map key, got: {got:?}")
+            }
+            Error::CannotSerializeNone => {
+                write!(
+          f,
+          "cannot serialize `None` or `()` (use `#[serde(skip_serializing_if = \"Option::is_none\")]`)"
+        )
+            }
+            Error::Enum => {
+                write!(f, "enums are not supported")
+            }
+        }
+    }
+}
+
+impl std::error::Error for Error {}

pumpkin/src/protocol/nbt/mod.rs

@@ -1,115 +1,445 @@
 use std::collections::HashMap;
 
+use error::Error;
+use error::Result;
+use nbt::Tag;
+use nbt::NBT;
+use serde::{ser, Serialize};
+
 mod deserialize;
+mod error;
+pub mod nbt;
 mod serialize;
 
-#[derive(Debug, Clone, PartialEq)]
-pub struct NBT {
+pub fn to_nbt<T>(name: &str, value: &T) -> anyhow::Result<NBT>
+where
+    T: Serialize,
+{
+    Ok(NBT::new(name, to_tag(value)?))
+}
+
+pub fn to_tag<T>(value: &T) -> anyhow::Result<Tag>
+where
+    T: Serialize,
+{
+    let mut serializer = Serializer { tag: Tag::End };
+    value.serialize(&mut serializer)?;
+    Ok(serializer.tag)
+}
+
+pub struct Serializer {
     tag: Tag,
-    name: String,
 }
 
-/// This is a single tag. It does not contain a name, but has the actual data
-/// for any of the nbt tags.
-#[derive(Debug, Clone, PartialEq)]
-pub enum Tag {
-    End,
-    Byte(i8),
-    Short(i16),
-    Int(i32),
-    Long(i64),
-    Float(f32),
-    Double(f64),
-    ByteArr(Vec<u8>),
-    String(String),
-    List(Vec<Tag>), // All elements must be the same type, and un-named.
-    Compound(HashMap<String, Tag>), // Types can be any kind, and are named. Order is not defined.
-    IntArray(Vec<i32>),
-    LongArray(Vec<i64>),
+pub struct SeqSerializer<'a> {
+    ser: &'a mut Serializer,
+    items: Vec<Tag>,
+}
+pub struct MapSerializer<'a> {
+    ser: &'a mut Serializer,
+    key: Option<String>,
+    items: HashMap<String, Tag>,
 }
 
-impl NBT {
-    /// Creates a new nbt tag. The tag value can be anything.
-    ///
-    /// # Panics
-    /// This will panic if the tag is a list, and the values within that list
-    /// contain multiple types. This is a limitation with the nbt data format:
-    /// lists can only contain one type of data.
-    pub fn new(name: &str, tag: Tag) -> Self {
-        if let Tag::List(inner) = &tag {
-            if let Some(v) = inner.get(0) {
-                let ty = v.ty();
-                for v in inner {
-                    if v.ty() != ty {
-                        panic!("the given list contains multiple types: {:?}", inner);
-                    }
-                }
+impl<'a> ser::Serializer for &'a mut Serializer {
+    // The output type produced by this `Serializer` during successful
+    // serialization. Most serializers that produce text or binary output should
+    // set `Ok = ()` and serialize into an `io::Write` or buffer contained
+    // within the `Serializer` instance, as happens here. Serializers that build
+    // in-memory data structures may be simplified by using `Ok` to propagate
+    // the data structure around.
+    type Ok = ();
+    type Error = Error;
+
+    // Associated types for keeping track of additional state while serializing
+    // compound data structures like sequences and maps. In this case no
+    // additional state is required beyond what is already stored in the
+    // Serializer struct.
+    type SerializeSeq = SeqSerializer<'a>;
+    type SerializeTuple = SeqSerializer<'a>;
+    type SerializeTupleStruct = SeqSerializer<'a>;
+    type SerializeTupleVariant = SeqSerializer<'a>;
+    type SerializeMap = MapSerializer<'a>;
+    type SerializeStruct = MapSerializer<'a>;
+    type SerializeStructVariant = MapSerializer<'a>;
+
+    // Here we go with the simple methods. The following 12 methods receive one
+    // of the primitive types of the data model and map it to JSON by appending
+    // into the output string.
+    fn serialize_bool(self, v: bool) -> Result<()> {
+        self.tag = Tag::Byte(v as i8);
+        Ok(())
+    }
+
+    // JSON does not distinguish between different sizes of integers, so all
+    // signed integers will be serialized the same and all unsigned integers
+    // will be serialized the same. Other formats, especially compact binary
+    // formats, may need independent logic for the different sizes.
+    fn serialize_i8(self, v: i8) -> Result<()> {
+        self.tag = Tag::Byte(v);
+        Ok(())
+    }
+    fn serialize_i16(self, v: i16) -> Result<()> {
+        self.tag = Tag::Short(v);
+        Ok(())
+    }
+    fn serialize_i32(self, v: i32) -> Result<()> {
+        self.tag = Tag::Int(v);
+        Ok(())
+    }
+    fn serialize_i64(self, v: i64) -> Result<()> {
+        self.tag = Tag::Long(v);
+        Ok(())
+    }
+
+    fn serialize_u8(self, v: u8) -> Result<()> {
+        self.serialize_i8(v as i8)
+    }
+    fn serialize_u16(self, v: u16) -> Result<()> {
+        self.serialize_i16(v as i16)
+    }
+    fn serialize_u32(self, v: u32) -> Result<()> {
+        self.serialize_i32(v as i32)
+    }
+    fn serialize_u64(self, v: u64) -> Result<()> {
+        self.serialize_i64(v as i64)
+    }
+
+    fn serialize_f32(self, v: f32) -> Result<()> {
+        self.tag = Tag::Float(v);
+        Ok(())
+    }
+    fn serialize_f64(self, v: f64) -> Result<()> {
+        self.tag = Tag::Double(v);
+        Ok(())
+    }
+
+    fn serialize_char(self, v: char) -> Result<()> {
+        self.serialize_str(&v.to_string())
+    }
+    fn serialize_str(self, v: &str) -> Result<()> {
+        self.tag = Tag::String(v.into());
+        Ok(())
+    }
+
+    fn serialize_bytes(self, v: &[u8]) -> Result<()> {
+        self.tag = Tag::ByteArr(v.into());
+        Ok(())
+    }
+
+    // There isn't really a `None` in NBT. There is `Tag::End`, which could be
+    // searched and removed if this was in a struct or map, which would essentially
+    // skip this value if it's `None`. However, I don't care enough, so I'm just
+    // going to produce an error.
+    fn serialize_none(self) -> Result<()> {
+        Err(Error::CannotSerializeNone)
+    }
+    fn serialize_some<T>(self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        value.serialize(self)
+    }
+
+    fn serialize_unit(self) -> Result<()> {
+        Err(Error::CannotSerializeNone)
+    }
+
+    // Unit struct means a named value containing no data. Again, since there is
+    // no data, map this to JSON as `null`. There is no need to serialize the
+    // name in most formats.
+    fn serialize_unit_struct(self, _name: &'static str) -> Result<()> {
+        self.serialize_unit()
+    }
+
+    // As is done here, serializers are encouraged to treat newtype structs as
+    // insignificant wrappers around the data they contain.
+    fn serialize_newtype_struct<T>(self, _name: &'static str, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        value.serialize(self)
+    }
+
+    // Now we get to the serialization of compound types.
+    //
+    // The start of the sequence, each value, and the end are three separate
+    // method calls. This one is responsible only for serializing the start,
+    // which in JSON is `[`.
+    //
+    // The length of the sequence may or may not be known ahead of time. This
+    // doesn't make a difference in JSON because the length is not represented
+    // explicitly in the serialized form. Some serializers may only be able to
+    // support sequences for which the length is known up front.
+    fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq> {
+        Ok(SeqSerializer {
+            ser: self,
+            items: vec![],
+        })
+    }
+
+    // Tuples look just like sequences in JSON. Some formats may be able to
+    // represent tuples more efficiently by omitting the length, since tuple
+    // means that the corresponding `Deserialize implementation will know the
+    // length without needing to look at the serialized data.
+    fn serialize_tuple(self, len: usize) -> Result<Self::SerializeTuple> {
+        self.serialize_seq(Some(len))
+    }
+
+    // Tuple structs look just like sequences in JSON.
+    fn serialize_tuple_struct(
+        self,
+        _name: &'static str,
+        len: usize,
+    ) -> Result<Self::SerializeTupleStruct> {
+        self.serialize_seq(Some(len))
+    }
+
+    // Maps are represented in JSON as `{ K: V, K: V, ... }`.
+    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap> {
+        Ok(MapSerializer {
+            ser: self,
+            key: None,
+            items: HashMap::new(),
+        })
+    }
+
+    // Structs look just like maps in JSON. In particular, JSON requires that we
+    // serialize the field names of the struct. Other formats may be able to
+    // omit the field names when serializing structs because the corresponding
+    // Deserialize implementation is required to know what the keys are without
+    // looking at the serialized data.
+    fn serialize_struct(self, _name: &'static str, len: usize) -> Result<Self::SerializeStruct> {
+        self.serialize_map(Some(len))
+    }
+
+    // We don't support enums (they don't really make sense)
+    fn serialize_unit_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+    ) -> Result<()> {
+        Err(Error::Enum)
+    }
+    fn serialize_newtype_variant<T>(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+        _value: &T,
+    ) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        Err(Error::Enum)
+    }
+    fn serialize_tuple_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+        _len: usize,
+    ) -> Result<Self::SerializeTupleVariant> {
+        Err(Error::Enum)
+    }
+    fn serialize_struct_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+        _len: usize,
+    ) -> Result<Self::SerializeStructVariant> {
+        Err(Error::Enum)
+    }
+}
+
+// The following 7 impls deal with the serialization of compound types like
+// sequences and maps. Serialization of such types is begun by a Serializer
+// method and followed by zero or more calls to serialize individual elements of
+// the compound type and one call to end the compound type.
+//
+// This impl is SerializeSeq so these methods are called after `serialize_seq`
+// is called on the Serializer.
+impl<'a> ser::SerializeSeq for SeqSerializer<'a> {
+    type Ok = ();
+    type Error = Error;
+
+    // Serialize a single element of the sequence.
+    fn serialize_element<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        value.serialize(&mut *self.ser)?;
+        let tag = std::mem::replace(&mut self.ser.tag, Tag::End);
+        if let Some(first) = self.items.first() {
+            let expected_ty = first.ty();
+            let actual_ty = tag.ty();
+            if expected_ty != actual_ty {
+                return Err(Error::ListType(first.clone(), tag));
             }
         }
-        NBT {
-            tag,
-            name: name.into(),
-        }
+        self.items.push(tag);
+        Ok(())
     }
 
-    /// Creates an empty nbt tag.
-    pub fn empty(name: &str) -> Self {
-        NBT {
-            tag: Tag::End,
-            name: name.into(),
-        }
-    }
-
-    /// Appends the given element to the list. This will panic if self is not a
-    /// list, or if tag does not match the type of the existing elements.
-    pub fn list_add(&mut self, tag: Tag) {
-        if let Tag::List(inner) = &mut self.tag {
-            if let Some(v) = inner.get(0) {
-                if tag.ty() != v.ty() {
-                    panic!(
-                        "cannot add different types to list. current: {:?}, new: {:?}",
-                        inner, tag
-                    );
-                } else {
-                    inner.push(tag);
-                }
-            } else {
-                // No elements yet, so we add this no matter what type it is.
-                inner.push(tag);
-            }
-        } else {
-            panic!("called list_add on non-list type: {:?}", self);
-        }
-    }
-
-    /// Appends the given element to the compound. This will panic if self is not
-    /// a compound tag.
-    pub fn compound_add(&mut self, name: String, value: Tag) {
-        if let Tag::Compound(inner) = &mut self.tag {
-            inner.insert(name, value);
-        } else {
-            panic!("called compound_add on non-compound type: {:?}", self);
-        }
-    }
-
-    /// If this is a compound tag, this returns the inner data of the tag.
-    /// Otherwise, this panics.
-    pub fn compound(&self) -> &HashMap<String, Tag> {
-        if let Tag::Compound(inner) = &self.tag {
-            &inner
-        } else {
-            panic!("called compound on non-compound type: {:?}", self);
-        }
+    fn end(self) -> Result<()> {
+        self.ser.tag = Tag::List(self.items);
+        Ok(())
     }
 }
 
-impl Tag {
-    /// A simpler way to construct compound tags inline.
-    pub fn compound(value: &[(&str, Tag)]) -> Self {
-        let mut inner = HashMap::new();
-        for (name, tag) in value {
-            inner.insert(name.to_string(), tag.clone());
-        }
-        Self::Compound(inner)
+// Same thing but for tuples.
+impl<'a> ser::SerializeTuple for SeqSerializer<'a> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_element<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        <Self as ser::SerializeSeq>::serialize_element(self, value)
+    }
+
+    fn end(self) -> Result<()> {
+        <Self as ser::SerializeSeq>::end(self)
+    }
+}
+
+// Same thing but for tuple structs.
+impl<'a> ser::SerializeTupleStruct for SeqSerializer<'a> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        <Self as ser::SerializeSeq>::serialize_element(self, value)
+    }
+
+    fn end(self) -> Result<()> {
+        <Self as ser::SerializeSeq>::end(self)
+    }
+}
+
+// Tuple variants are a little different. Refer back to the
+// `serialize_tuple_variant` method above:
+//
+//    self.output += "{";
+//    variant.serialize(&mut *self)?;
+//    self.output += ":[";
+//
+// So the `end` method in this impl is responsible for closing both the `]` and
+// the `}`.
+impl<'a> ser::SerializeTupleVariant for SeqSerializer<'a> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        <Self as ser::SerializeSeq>::serialize_element(self, value)
+    }
+
+    fn end(self) -> Result<()> {
+        <Self as ser::SerializeSeq>::end(self)
+    }
+}
+
+// Some `Serialize` types are not able to hold a key and value in memory at the
+// same time so `SerializeMap` implementations are required to support
+// `serialize_key` and `serialize_value` individually.
+//
+// There is a third optional method on the `SerializeMap` trait. The
+// `serialize_entry` method allows serializers to optimize for the case where
+// key and value are both available simultaneously. In JSON it doesn't make a
+// difference so the default behavior for `serialize_entry` is fine.
+impl<'a> ser::SerializeMap for MapSerializer<'a> {
+    type Ok = ();
+    type Error = Error;
+
+    // The Serde data model allows map keys to be any serializable type. JSON
+    // only allows string keys so the implementation below will produce invalid
+    // JSON if the key serializes as something other than a string.
+    //
+    // A real JSON serializer would need to validate that map keys are strings.
+    // This can be done by using a different Serializer to serialize the key
+    // (instead of `&mut **self`) and having that other serializer only
+    // implement `serialize_str` and return an error on any other data type.
+    fn serialize_key<T>(&mut self, key: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        key.serialize(&mut *self.ser)?;
+        let tag = std::mem::replace(&mut self.ser.tag, Tag::End);
+        self.key = match tag {
+            Tag::String(key) => Some(key),
+            other => return Err(Error::MapKey(other)),
+        };
+        Ok(())
+    }
+
+    // It doesn't make a difference whether the colon is printed at the end of
+    // `serialize_key` or at the beginning of `serialize_value`. In this case
+    // the code is a bit simpler having it here.
+    fn serialize_value<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        value.serialize(&mut *self.ser)?;
+        let tag = std::mem::replace(&mut self.ser.tag, Tag::End);
+        self.items.insert(self.key.take().unwrap(), tag);
+        Ok(())
+    }
+
+    fn end(self) -> Result<()> {
+        self.ser.tag = self.items.into();
+        Ok(())
+    }
+}
+
+// Structs are like maps in which the keys are constrained to be compile-time
+// constant strings.
+impl<'a> ser::SerializeStruct for MapSerializer<'a> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        value.serialize(&mut *self.ser)?;
+        let tag = std::mem::replace(&mut self.ser.tag, Tag::End);
+        self.items.insert(key.into(), tag);
+        Ok(())
+    }
+
+    fn end(self) -> Result<()> {
+        self.ser.tag = self.items.into();
+        Ok(())
+    }
+}
+
+// Similar to `SerializeTupleVariant`, here the `end` method is responsible for
+// closing both of the curly braces opened by `serialize_struct_variant`.
+impl<'a> ser::SerializeStructVariant for MapSerializer<'a> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        value.serialize(&mut *self.ser)?;
+        let tag = std::mem::replace(&mut self.ser.tag, Tag::End);
+        self.items.insert(key.into(), tag);
+        Ok(())
+    }
+
+    fn end(self) -> Result<()> {
+        self.ser.tag = self.items.into();
+        Ok(())
     }
 }

pumpkin/src/protocol/nbt/nbt.rs

@@ -0,0 +1,283 @@
+use std::{collections::HashMap, fmt, io, ops::Index, string::FromUtf8Error};
+
+#[derive(Debug)]
+pub enum ParseError {
+    InvalidType(u8),
+    InvalidString(FromUtf8Error),
+    IO(io::Error),
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct WrongTag(Tag);
+
+impl fmt::Display for WrongTag {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "wrong tag: {:?}", self.0)
+    }
+}
+
+impl std::error::Error for WrongTag {}
+
+/// This is an nbt tag. It has a name, and any amount of data. This can be used
+/// to store item data, entity data, level data, and more.
+#[derive(Debug, Clone, PartialEq)]
+pub struct NBT {
+    pub tag: Tag,
+    pub name: String,
+}
+
+impl Default for NBT {
+    fn default() -> Self {
+        NBT::new("", Tag::new_compound(&[]))
+    }
+}
+
+/// This is a single tag. It does not contain a name, but has the actual data
+/// for any of the nbt tags.
+#[derive(Debug, Clone, PartialEq)]
+pub enum Tag {
+    End,
+    Byte(i8),
+    Short(i16),
+    Int(i32),
+    Long(i64),
+    Float(f32),
+    Double(f64),
+    ByteArr(Vec<u8>),
+    String(String),
+    List(Vec<Tag>),     // All elements must be the same type, and un-named.
+    Compound(Compound), // Types can be any kind, and are named. Order is not defined.
+    IntArray(Vec<i32>),
+    LongArray(Vec<i64>),
+}
+
+/// An NBT Compound tag. This is essentially a map, with some extra helper
+/// functions.
+#[derive(Debug, Clone, PartialEq)]
+pub struct Compound {
+    pub inner: HashMap<String, Tag>,
+}
+
+impl Compound {
+    pub fn new() -> Self {
+        Compound {
+            inner: HashMap::new(),
+        }
+    }
+    pub fn insert(&mut self, key: impl Into<String>, value: impl Into<Tag>) {
+        self.inner.insert(key.into(), value.into());
+    }
+    pub fn get_or_create_compound(&mut self, key: impl Into<String>) -> &mut Compound {
+        self.inner
+            .entry(key.into())
+            .or_insert_with(|| Tag::Compound(Compound::new()))
+            .compound_mut()
+            .unwrap()
+    }
+
+    pub fn contains_key(&self, key: impl AsRef<str>) -> bool {
+        self.inner.contains_key(key.as_ref())
+    }
+
+    pub fn iter(&self) -> std::collections::hash_map::Iter<String, Tag> {
+        self.inner.iter()
+    }
+    pub fn iter_mut(&mut self) -> std::collections::hash_map::IterMut<String, Tag> {
+        self.inner.iter_mut()
+    }
+}
+impl IntoIterator for Compound {
+    type Item = (String, Tag);
+    type IntoIter = std::collections::hash_map::IntoIter<String, Tag>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.inner.into_iter()
+    }
+}
+impl<'a> IntoIterator for &'a Compound {
+    type Item = (&'a String, &'a Tag);
+    type IntoIter = std::collections::hash_map::Iter<'a, String, Tag>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.inner.iter()
+    }
+}
+impl<'a> IntoIterator for &'a mut Compound {
+    type Item = (&'a String, &'a mut Tag);
+    type IntoIter = std::collections::hash_map::IterMut<'a, String, Tag>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.inner.iter_mut()
+    }
+}
+impl From<HashMap<String, Tag>> for Compound {
+    fn from(v: HashMap<String, Tag>) -> Self {
+        Compound { inner: v }
+    }
+}
+
+impl Index<&str> for Compound {
+    type Output = Tag;
+    fn index(&self, index: &str) -> &Tag {
+        &self.inner[index]
+    }
+}
+
+impl From<bool> for Tag {
+    fn from(v: bool) -> Self {
+        Tag::Byte(v as i8)
+    }
+}
+impl From<&str> for Tag {
+    fn from(s: &str) -> Self {
+        Tag::String(s.into())
+    }
+}
+impl From<String> for Tag {
+    fn from(s: String) -> Self {
+        Tag::String(s)
+    }
+}
+impl From<HashMap<String, Tag>> for Tag {
+    fn from(v: HashMap<String, Tag>) -> Self {
+        Tag::Compound(Compound::from(v))
+    }
+}
+
+impl<T> From<Vec<T>> for Tag
+where
+    Tag: From<T>,
+{
+    fn from(list: Vec<T>) -> Self {
+        Tag::List(list.into_iter().map(|it| it.into()).collect())
+    }
+}
+
+impl NBT {
+    /// Creates a new nbt tag. The tag value can be anything.
+    ///
+    /// # Panics
+    /// This will panic if the tag is a list, and the values within that list
+    /// contain multiple types. This is a limitation with the nbt data format:
+    /// lists can only contain one type of data.
+    pub fn new(name: &str, tag: Tag) -> Self {
+        if let Tag::List(inner) = &tag {
+            if let Some(v) = inner.get(0) {
+                let ty = v.ty();
+                for v in inner {
+                    if v.ty() != ty {
+                        panic!("the given list contains multiple types: {inner:?}");
+                    }
+                }
+            }
+        }
+        NBT {
+            tag,
+            name: name.into(),
+        }
+    }
+
+    /// Creates an empty nbt tag.
+    pub const fn empty() -> Self {
+        NBT {
+            tag: Tag::End,
+            name: String::new(),
+        }
+    }
+
+    /// Appends the given element to the list. This will panic if self is not a
+    /// list, or if tag does not match the type of the existing elements.
+    pub fn list_add(&mut self, tag: Tag) {
+        if let Tag::List(inner) = &mut self.tag {
+            if let Some(v) = inner.get(0) {
+                if tag.ty() != v.ty() {
+                    panic!("cannot add different types to list. current: {inner:?}, new: {tag:?}");
+                } else {
+                    inner.push(tag);
+                }
+            } else {
+                // No elements yet, so we add this no matter what type it is.
+                inner.push(tag);
+            }
+        } else {
+            panic!("called list_add on non-list type: {self:?}");
+        }
+    }
+
+    /// Appends the given element to the compound. This will panic if self is not
+    /// a compound tag.
+    pub fn compound_add(&mut self, name: String, value: Tag) {
+        if let Tag::Compound(inner) = &mut self.tag {
+            inner.insert(name, value);
+        } else {
+            panic!("called compound_add on non-compound type: {self:?}");
+        }
+    }
+
+    /// If this is a compound tag, this returns the inner data of the tag.
+    /// Otherwise, this panics.
+    pub fn compound(&self) -> Option<&Compound> {
+        if let Tag::Compound(inner) = &self.tag {
+            Some(inner)
+        } else {
+            None
+        }
+    }
+    /// If this is a compound tag, this returns the inner data of the tag.
+    /// Otherwise, this panics.
+    pub fn compound_mut(&mut self) -> Option<&mut Compound> {
+        if let Tag::Compound(inner) = &mut self.tag {
+            Some(inner)
+        } else {
+            None
+        }
+    }
+
+    pub fn tag(&self) -> &Tag {
+        &self.tag
+    }
+    pub fn into_tag(self) -> Tag {
+        self.tag
+    }
+}
+
+macro_rules! getter {
+  ( $(: $conv:tt)? $name:ident -> $variant:ident ( $ty:ty ) ) => {
+    pub fn $name(&self) -> Result<$ty, WrongTag> {
+      match self {
+        Self::$variant(v) => Ok($($conv)? v),
+        _ => Err(WrongTag(self.clone())),
+      }
+    }
+  };
+}
+
+impl Tag {
+    /// A simpler way to construct compound tags inline.
+    pub fn new_compound(value: &[(&str, Tag)]) -> Self {
+        let mut inner = HashMap::new();
+        for (name, tag) in value {
+            inner.insert(name.to_string(), tag.clone());
+        }
+        inner.into()
+    }
+
+    getter!(:*byte -> Byte(i8));
+    getter!(:*short -> Short(i16));
+    getter!(:*int -> Int(i32));
+    getter!(:*long -> Long(i64));
+    getter!(:*float -> Float(f32));
+    getter!(:*double -> Double(f64));
+    getter!(string -> String(&str));
+    getter!(byte_arr -> ByteArr(&[u8]));
+    getter!(list -> List(&Vec<Tag>));
+    getter!(compound -> Compound(&Compound));
+    getter!(long_arr -> LongArray(&Vec<i64>));
+
+    pub fn compound_mut(&mut self) -> Result<&mut Compound, WrongTag> {
+        match self {
+            Self::Compound(v) => Ok(v),
+            _ => Err(WrongTag(self.clone())),
+        }
+    }
+}

pumpkin/src/protocol/nbt/serialize.rs

@@ -3,12 +3,18 @@ use crate::protocol::bytebuf::buffer::ByteBuffer;
 use super::{Tag, NBT};
 
 impl NBT {
-    pub fn serialize(&self) -> Vec<u8> {
-        let mut out = ByteBuffer::new();
+    pub fn serialize_buf(&self, out: &mut ByteBuffer) {
         out.write_u8(self.tag.ty());
+        if matches!(self.tag, Tag::End) {
+            return;
+        }
         out.write_u16(self.name.len() as u16);
         out.write_bytes(self.name.as_bytes());
-        out.write_bytes(&self.tag.serialize());
+        self.tag.serialize(out);
+    }
+    pub fn serialize(&self) -> Vec<u8> {
+        let mut out = ByteBuffer::new();
+        self.serialize_buf(&mut out);
         out.into_vec()
     }
 }
@@ -33,8 +39,8 @@ impl Tag {
         }
     }
 
-    fn serialize(&self) -> Vec<u8> {
-        let mut out = ByteBuffer::new();
+    /// Serializes the data of the tag. Does not add type byte.
+    fn serialize(&self, out: &mut ByteBuffer) {
         match self {
             Self::End => (),
             Self::Byte(v) => out.write_i8(*v),
@@ -55,11 +61,11 @@ impl Tag {
                 out.write_u8(v.get(0).unwrap_or(&Self::End).ty());
                 out.write_i32(v.len() as i32);
                 for tag in v {
-                    out.write_bytes(&tag.serialize());
+                    tag.serialize(out);
                 }
             }
             Self::Compound(v) => {
-                for (name, tag) in v {
+                for (name, tag) in &v.inner {
                     // Each element in the HashMap is essentially a NBT, but we store it in a
                     // separated form, so we have a manual implementation of serialize() here.
                     out.write_u8(tag.ty());
@@ -69,7 +75,7 @@ impl Tag {
                     }
                     out.write_u16(name.len() as u16);
                     out.write_bytes(name.as_bytes());
-                    out.write_bytes(&tag.serialize());
+                    tag.serialize(out);
                 }
                 out.write_u8(Self::End.ty());
             }
@@ -86,6 +92,5 @@ impl Tag {
                 }
             }
         }
-        out.into_vec()
     }
 }

pumpkin/src/protocol/registry/biomes.rs

@@ -0,0 +1,73 @@
+use super::CodecItem;
+use serde::Serialize;
+
+#[derive(Debug, Clone, Serialize)]
+pub struct Biome {
+    category: String,
+    depth: f32,
+    downfall: f32,
+    effects: BiomeEffects,
+    precipitation: String,
+    scale: f32,
+    temperature: f32,
+    has_precipitation: bool,
+}
+#[derive(Debug, Clone, Serialize)]
+struct BiomeEffects {
+    sky_color: i32,
+    fog_color: i32,
+    water_fog_color: i32,
+    water_color: i32,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    foliage_color: Option<i32>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    grass_color: Option<i32>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    mood_sound: Option<MoodSound>, // 1.18.2+
+}
+#[derive(Debug, Clone, Serialize)]
+struct MoodSound {
+    block_search_extent: i32,
+    offset: f64,
+    sound: String,
+    tick_delay: i32,
+}
+
+pub(super) fn all() -> Vec<CodecItem<Biome>> {
+    let biome = Biome {
+        precipitation: "rain".into(),
+        depth: 1.0,
+        temperature: 1.0,
+        scale: 1.0,
+        downfall: 1.0,
+        category: "none".into(),
+        has_precipitation: true,
+        effects: BiomeEffects {
+            sky_color: 0x78a7ff,
+            fog_color: 0xc0d8ff,
+            water_fog_color: 0x050533,
+            water_color: 0x3f76e4,
+            foliage_color: None,
+            grass_color: None,
+            mood_sound: Some(MoodSound {
+                block_search_extent: 8,
+                offset: 2.0,
+                sound: "minecraft:ambient.cave".into(),
+                tick_delay: 6000,
+            }),
+            // sky_color:       0xff00ff,
+            // water_color:     0xff00ff,
+            // fog_color:       0xff00ff,
+            // water_fog_color: 0xff00ff,
+            // grass_color:     0xff00ff,
+            // foliage_color:   0x00ffe5,
+            // grass_color:     0xff5900,
+        },
+    };
+
+    vec![CodecItem {
+        name: "minecraft:plains".into(),
+        id: 0,
+        element: biome,
+    }]
+}

pumpkin/src/protocol/registry/chat_type.rs

@@ -0,0 +1,30 @@
+use super::CodecItem;
+use serde::Serialize;
+
+#[derive(Debug, Clone, Serialize)]
+pub struct ChatType {
+    chat: ChatParams,
+    narration: ChatParams,
+}
+#[derive(Debug, Clone, Serialize)]
+struct ChatParams {
+    parameters: Vec<String>,
+    translation_key: String,
+}
+
+pub(super) fn all() -> Vec<CodecItem<ChatType>> {
+    vec![CodecItem {
+        name: "minecraft:chat".into(),
+        id: 0,
+        element: ChatType {
+            chat: ChatParams {
+                parameters: vec!["sender".into(), "content".into()],
+                translation_key: "chat.type.text".into(),
+            },
+            narration: ChatParams {
+                parameters: vec!["sender".into(), "content".into()],
+                translation_key: "chat.type.text.narrate".into(),
+            },
+        },
+    }]
+}

pumpkin/src/protocol/registry/damage_type.rs

@@ -0,0 +1,58 @@
+use super::CodecItem;
+use serde::Serialize;
+
+#[derive(Debug, Clone, Serialize)]
+pub struct DamageType {
+    exhaustion: f32,
+    message_id: String,
+    scaling: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    effects: Option<String>,
+}
+
+const NAMES: &[&str] = &[
+    "in_fire",
+    "lightning_bolt",
+    "on_fire",
+    "lava",
+    "hot_floor",
+    "in_wall",
+    "cramming",
+    "drown",
+    "starve",
+    "cactus",
+    "fall",
+    "fly_into_wall",
+    "out_of_world",
+    "generic",
+    "magic",
+    "wither",
+    "dragon_breath",
+    "dry_out",
+    "sweet_berry_bush",
+    "freeze",
+    "stalagmite",
+    // 1.20+
+    "outside_border",
+    "generic_kill",
+];
+
+pub(super) fn all() -> Vec<CodecItem<DamageType>> {
+    let mut items: Vec<_> = NAMES
+        .iter()
+        .map(|name| CodecItem {
+            name: (*name).into(),
+            id: 0,
+            element: DamageType {
+                exhaustion: 0.1,
+                message_id: "inFire".into(),
+                scaling: "when_caused_by_living_non_player".into(),
+                effects: None,
+            },
+        })
+        .collect();
+
+    items[1].element.effects = Some("burning".into());
+
+    items
+}

pumpkin/src/protocol/registry/dimensions.rs

@@ -0,0 +1,49 @@
+use serde::Serialize;
+
+#[derive(Debug, Clone, Serialize)]
+pub struct Dimension {
+    ambient_light: f32,
+    bed_works: bool,
+    coordinate_scale: f32,
+    effects: String,
+    has_ceiling: bool,
+    has_raids: bool,
+    has_skylight: bool,
+    height: i32, // 1.17+
+    infiniburn: String,
+    logical_height: i32,
+    min_y: i32, // 1.17+
+    natural: bool,
+    piglin_safe: bool,
+    fixed_time: i64,
+    respawn_anchor_works: bool,
+    ultrawarm: bool,
+
+    // 1.19+
+    monster_spawn_light_level: i32,
+    monster_spawn_block_light_limit: i32,
+}
+
+pub fn overworld(world_min_y: i32, world_height: u32) -> Dimension {
+    Dimension {
+        piglin_safe: false,
+        natural: true,
+        ambient_light: 0.0,
+        fixed_time: 6000,
+        infiniburn: "#minecraft:infiniburn_overworld".into(),
+        respawn_anchor_works: false,
+        has_skylight: true,
+        bed_works: true,
+        effects: "minecraft:overworld".into(),
+        has_raids: false,
+        logical_height: 128,
+        coordinate_scale: 1.0,
+        ultrawarm: false,
+        has_ceiling: false,
+        min_y: world_min_y,
+        height: (world_height as i32 + 15) / 16 * 16,
+
+        monster_spawn_light_level: 7,
+        monster_spawn_block_light_limit: 7,
+    }
+}

pumpkin/src/protocol/registry/mod.rs

@@ -1 +1,75 @@
+use serde::Serialize;
 
+use super::{bytebuf::buffer::ByteBuffer, nbt};
+
+mod biomes;
+mod chat_type;
+mod damage_type;
+mod dimensions;
+
+#[derive(Debug, Clone, Serialize)]
+struct LoginInfo {
+    #[serde(rename = "minecraft:dimension_type")]
+    dimensions: Codec<dimensions::Dimension>,
+    #[serde(rename = "minecraft:worldgen/biome")]
+    biomes: Codec<biomes::Biome>,
+    #[serde(rename = "minecraft:chat_type")]
+    chat: Codec<chat_type::ChatType>,
+    #[serde(rename = "minecraft:damage_type")]
+    damage: Codec<damage_type::DamageType>,
+}
+
+#[derive(Debug, Clone, Serialize)]
+struct Codec<T> {
+    #[serde(rename = "type")]
+    ty: String,
+    value: Vec<CodecItem<T>>,
+}
+#[derive(Debug, Clone, Serialize)]
+struct CodecItem<T> {
+    name: String,
+    id: i32,
+    element: T,
+}
+
+pub fn write_single_dimension<T>(out: &mut ByteBuffer, world_min_y: i32, world_height: u32)
+where
+    std::io::Cursor<T>: std::io::Write,
+{
+    let dimension = dimensions::overworld(world_min_y, world_height);
+    out.write_bytes(&nbt::to_nbt("", &dimension).unwrap().serialize());
+}
+
+pub fn write_codec(out: &mut ByteBuffer, world_min_y: i32, world_height: u32) {
+    let dimension = dimensions::overworld(world_min_y, world_height);
+
+    let info = LoginInfo {
+        dimensions: Codec {
+            ty: "minecraft:dimension_type".into(),
+            value: vec![CodecItem {
+                name: "minecraft:overworld".into(),
+                id: 0,
+                element: dimension,
+            }],
+        },
+        biomes: Codec {
+            ty: "minecraft:worldgen/biome".into(),
+            value: biomes::all(),
+        },
+        chat: Codec {
+            ty: "minecraft:chat_type".into(),
+            value: chat_type::all(),
+        },
+        damage: Codec {
+            ty: "minecraft:damage_type".into(),
+            value: damage_type::all(),
+        },
+    };
+
+    // Dimension codec
+    out.write_bytes(&nbt::to_nbt("", &info).unwrap().serialize());
+    // Current dimension type (key in dimension codec)
+    out.write_string("minecraft:overworld");
+    // Current world
+    out.write_string("minecraft:overworld");
+}

pumpkin/src/server.rs

@@ -15,7 +15,13 @@ use crate::{
         player::{GameMode, Player},
         Entity, EntityId,
     },
-    protocol::{client::play::CLogin, Players, Sample, StatusResponse, VarInt, Version},
+    protocol::{
+        client::{
+            config::{CKnownPacks, CRegistryData, Entry, KnownPack},
+            play::CLogin,
+        },
+        Players, Sample, StatusResponse, VarInt, Version,
+    },
     world::World,
 };
 
@@ -88,6 +94,23 @@ impl Server {
                 entity_id: self.new_entity_id(),
             },
         };
+        // known data packs
+        client.send_packet(CKnownPacks::new(
+            1,
+            vec![KnownPack {
+                namespace: "minecraft".to_string(),
+                id: "core".to_string(),
+                version: "1.21".to_string(),
+            }],
+        ));
+        client.send_packet(CRegistryData::new(
+            "0".into(),
+            1,
+            vec![Entry {
+                entry_id: "minecraft:dimension_type".into(),
+                has_data: true,
+            }],
+        ));
 
         client.send_packet(CLogin::new(
             player.entity_id(),