create macro to not duplicate as much code and improve the PackageId parsing with it

mc-rust-server-macros/Cargo.lock

@@ -0,0 +1,47 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "mc-rust-server-macros"
+version = "0.1.0"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.89"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f139b0662de085916d1fb67d2b4169d1addddda1919e696f3252b740b629986e"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.37"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b5b9d34b8991d19d98081b46eacdd8eb58c6f2b201139f7c5f643cc155a633af"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "syn"
+version = "2.0.87"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "25aa4ce346d03a6dcd68dd8b4010bcb74e54e62c90c573f394c46eae99aba32d"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e91b56cd4cadaeb79bbf1a5645f6b4f8dc5bde8834ad5894a8db35fda9efa1fe"

mc-rust-server-macros/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "mc-rust-server-macros"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+name = "mc_rust_server_macros"
+path = "src/lib.rs"
+proc-macro = true
+
+[dependencies]
+quote = "*"
+syn = { version = "*", features = ["extra-traits"] }
+proc-macro2 = "*"

mc-rust-server-macros/src/lib.rs

@@ -0,0 +1,9 @@
+extern crate proc_macro;
+
+use syn::{parse_macro_input, DeriveInput};
+
+#[proc_macro_derive(McProtocol, attributes(protocol_read, protocol_write))]
+pub fn proc_macro_protocol(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    mc_protocol::proc_macro_protocol(parse_macro_input!(input as DeriveInput)).into()
+}
+mod mc_protocol;

mc-rust-server-macros/src/mc_protocol.rs

@@ -0,0 +1,78 @@
+use proc_macro2::{Ident, TokenStream};
+use quote::quote;
+use syn::parse::Parse;
+use syn::{Data, DeriveInput, Lit, Token};
+
+pub fn proc_macro_protocol(input: DeriveInput) -> TokenStream {
+    match input.data {
+        Data::Enum(e) => {
+            let variants = e.variants.into_iter();
+            let mut variant_data = vec![];
+            for v in variants {
+                let attr = v.attrs.into_iter().find_map(|a| {
+                    if a.path().is_ident("protocol_read") {
+                        Some(a.parse_args::<ProtocolAttribute>().ok()?)
+                    } else {
+                        None
+                    }
+                });
+                if let Some(attr) = attr {
+                    variant_data.push(ProtocolVariant {
+                        attr,
+                        ident: v.ident,
+                    })
+                }
+            }
+
+            let variant_match = variant_data.into_iter().map(|v| {
+                let state = v.attr.state;
+                let id = v.attr.packet_id;
+                let name = v.ident;
+                quote! {(#state, #id)=>Self::#name (read_protocol_data(stream).await?)}
+            });
+            let variants_match = quote! {#(#variant_match),*};
+
+            let enum_name = input.ident;
+            quote! {
+                #[automatically_derived]
+                impl #enum_name {
+                    pub async fn read_protocol_data<T:AsyncRead + AsyncWrite + Unpin>(
+                        protocol_id: VarInt,
+                        connection_state: ConnectionState,
+                        stream: &mut RWStreamWithLimit<'_, T>,
+                    )-> Result<IncomingPackageContent, String> {
+                        Ok(match (connection_state, protocol_id.to_rs()){
+                            #variants_match,
+                            (other_state, other_id) => {
+                                return Err(format!("Unrecognized protocol+state combination: {:?}/{}", other_state, other_id));
+                            }
+                        })
+                    }
+                }
+            }
+        }
+        _ => {
+            panic!("This macro is only supported for Enums")
+        }
+    }
+}
+
+#[derive(Debug)]
+struct ProtocolVariant {
+    attr: ProtocolAttribute,
+    ident: Ident,
+}
+#[derive(Debug)]
+struct ProtocolAttribute {
+    state: syn::ExprPath,
+    packet_id: Lit,
+}
+impl Parse for ProtocolAttribute {
+    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
+        let state = input.parse()?;
+        input.parse::<Token![,]>()?;
+        let packet_id = input.parse()?;
+
+        Ok(ProtocolAttribute { state, packet_id })
+    }
+}