Make Bevy dependencies optional in azalea-protocol (#303)

* Make Bevy dependencies optional in azalea-protocol

* derive serde traits on Direction again

* update docs for types that may not have Component

1 files changed, 78 insertions, 0 deletions

diff --git a/azalea-core/src/entity_id.rs b/azalea-core/src/entity_id.rs
new file mode 100644
index 00000000..c66d3a2e
--- /dev/null
+++ b/azalea-core/src/entity_id.rs
@@ -0,0 +1,78 @@
+use std::{
+    fmt::{self, Display},
+    hash::{Hash, Hasher},
+    io::{self, Cursor},
+};
+
+use azalea_buf::{AzaleaRead, AzaleaReadVar, AzaleaWrite, AzaleaWriteVar, BufReadError};
+use derive_more::{Deref, DerefMut};
+
+// note: this is here instead of in azalea-entity because azalea-world depends
+// on it. and this isn't in azalea-world so azalea-protocol doesn't need to
+// depend on azalea-world.
+
+/// An entity ID used by Minecraft.
+///
+/// These IDs are picked by the server. Some server software (like Bungeecord)
+/// may pick entity IDs per-player, so you should avoid relying on them for
+/// identifying IDs (especially if you're using a shared world -- i.e. a swarm).
+///
+/// You might find [`Entity`] more useful, since that's an ID decided by us that
+/// is likely to be correct across shared worlds. You could also use the
+/// `EntityUuid` from `azalea_entity`, that one is unlikely to change even
+/// across server restarts.
+///
+/// This serializes as a i32. Usually it's a VarInt in the protocol, but not
+/// always. If you do need it to serialize as a VarInt, make sure to use use the
+/// `#[var]` attribute.
+///
+/// [`Entity`]: bevy_ecs::entity::Entity
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[cfg_attr(feature = "bevy_ecs", derive(bevy_ecs::component::Component))]
+#[derive(Clone, Copy, Debug, Default, Deref, DerefMut, Eq, PartialEq)]
+pub struct MinecraftEntityId(pub i32);
+
+impl Hash for MinecraftEntityId {
+    fn hash<H: Hasher>(&self, hasher: &mut H) {
+        hasher.write_i32(self.0);
+    }
+}
+impl nohash_hasher::IsEnabled for MinecraftEntityId {}
+
+// we can't have the default be #[var] because mojang doesn't use varints for
+// entities sometimes :(
+impl AzaleaRead for MinecraftEntityId {
+    fn azalea_read(buf: &mut Cursor<&[u8]>) -> Result<Self, BufReadError> {
+        i32::azalea_read(buf).map(MinecraftEntityId)
+    }
+}
+impl AzaleaWrite for MinecraftEntityId {
+    fn azalea_write(&self, buf: &mut impl io::Write) -> io::Result<()> {
+        i32::azalea_write(&self.0, buf)
+    }
+}
+impl AzaleaReadVar for MinecraftEntityId {
+    fn azalea_read_var(buf: &mut Cursor<&[u8]>) -> Result<Self, BufReadError> {
+        i32::azalea_read_var(buf).map(MinecraftEntityId)
+    }
+}
+impl AzaleaWriteVar for MinecraftEntityId {
+    fn azalea_write_var(&self, buf: &mut impl io::Write) -> io::Result<()> {
+        i32::azalea_write_var(&self.0, buf)
+    }
+}
+impl Display for MinecraftEntityId {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "eid({})", self.0)
+    }
+}
+impl From<i32> for MinecraftEntityId {
+    fn from(id: i32) -> Self {
+        Self(id)
+    }
+}
+impl From<u32> for MinecraftEntityId {
+    fn from(id: u32) -> Self {
+        Self(id as i32)
+    }
+}