FFI support for ain integration

* Parse args and run in a separate thread

* Native helper struct for static FFI invocation

* Wait until node starts when run as daemon

* Flags for success, daemon and displaying help

.gitignore

@@ -21,6 +21,11 @@ target/
 
 # These are backup files generated by rustfmt
 **/*.rs.bk
+# Rust package files
+pkg/
+# ain depends integration artifacts
+.stamp_*
+master-*
 
 ### Substrate
 .local

Makefile

@@ -0,0 +1,9 @@
+CARGO ?= cargo
+TARGET ?=
+
+build-native-pkg:
+	CRATE_CC_NO_DEFAULTS=1 $(CARGO) build --package meta-node --release $(if $(TARGET),--target $(TARGET),)
+	mkdir -p pkg/metachain/include pkg/metachain/lib
+	cp target/$(if $(TARGET),$(TARGET)/,)release/libmeta_node.a pkg/metachain/lib/libmetachain.a
+	cp target/libmc.hpp pkg/metachain/include/
+	cp target/libmc.cpp pkg/metachain/

meta/meta-node/Cargo.toml

@@ -4,12 +4,22 @@ version = "0.1.0"
 edition = "2021"
 build = "build.rs"
 
+[lib]
+crate-type = ["staticlib"]
+
+[[bin]]
+name = "meta-node"
+path = "src/main.rs"
+
 [dependencies]
 async-trait     = "0.1"
 clap            = { version = "3.1", features = ["derive"] }
+cxx             = "1.0"
 futures         = "0.3.21"
+lazy_static     = "1.4.0"
 log             = "0.4.17"
 serde_json      = "1.0"
+tokio           = { version = "1.22", features = ["sync"] }
 # Parity
 codec 			= { default-features = false, version = "3.1.5", features = ["derive"], package = "parity-scale-codec" }
 jsonrpsee       = { default-features = false, version = "0.14.0", features = ["server"] }
@@ -58,4 +68,5 @@ meta-runtime = { package = "meta-runtime", path = "../meta-runtime" }
 
 [build-dependencies]
 substrate-build-script-utils = { git = "https://github.com/paritytech/substrate.git", branch = "polkadot-v0.9.25" }
-
+cxx-gen = "0.7"
+proc-macro2 = "1.0"

meta/meta-node/build.rs

@@ -1,7 +1,39 @@
+use proc_macro2::TokenStream;
 use substrate_build_script_utils::{generate_cargo_keys, rerun_if_git_head_changed};
 
+use std::env;
+use std::fs::File;
+use std::io::{Read, Write};
+use std::path::PathBuf;
+
 fn main() {
 	generate_cargo_keys();
 
 	rerun_if_git_head_changed();
+
+	let mut root = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap());
+    let parent = root.clone();
+    root.pop();
+	root.pop();
+    let lib_path = &parent.join("src").join("lib.rs");
+	println!("cargo:rerun-if-changed={}", lib_path.display());
+    let target_dir = &root.join("target");
+
+    let mut content = String::new();
+    File::open(lib_path)
+        .unwrap()
+        .read_to_string(&mut content)
+        .unwrap();
+    let tt: TokenStream = content.parse().unwrap();
+    let codegen = cxx_gen::generate_header_and_cc(tt, &cxx_gen::Opt::default()).unwrap();
+
+    let cpp_stuff = String::from_utf8(codegen.implementation).unwrap();
+    File::create(target_dir.join("libmc.hpp"))
+        .unwrap()
+        .write_all(&codegen.header)
+        .unwrap();
+    File::create(target_dir.join("libmc.cpp"))
+        .unwrap()
+        .write_all(cpp_stuff.as_bytes())
+        .unwrap();
 }

meta/meta-node/src/command.rs

@@ -3,10 +3,12 @@ use crate::{
 	cli::{Cli, Subcommand},
 	service::{self, db_config_dir},
 };
-use clap::Parser;
 use fc_db::frontier_database_dir;
 use sc_cli::{ChainSpec, RuntimeVersion, SubstrateCli};
 use sc_service::{DatabaseSource, PartialComponents};
+use tokio::sync::mpsc;
+
+use std::thread::{self, JoinHandle};
 
 impl SubstrateCli for Cli {
 	fn impl_name() -> String {
@@ -48,11 +50,9 @@ impl SubstrateCli for Cli {
 	}
 }
 
-/// Parse and run command line arguments
-pub fn run() -> sc_cli::Result<()> {
-	let cli = Cli::parse();
-
-	match &cli.subcommand {
+/// Parse and run command line arguments in a separate thread and return handle
+pub fn run(cli: Cli) -> sc_cli::Result<Option<JoinHandle<sc_cli::Result<()>>>> {
+	let res = match &cli.subcommand {
 		Some(Subcommand::Key(cmd)) => cmd.run(&cli),
 		Some(Subcommand::BuildSpec(cmd)) => {
 			let runner = cli.create_runner(cmd)?;
@@ -151,10 +151,36 @@ pub fn run() -> sc_cli::Result<()> {
 			})
 		}
 		None => {
+			// Metachain should block until the network starts before handing over
+			// control to the native chain. One way to accomplish this is by moving
+			// everything over to a separate thread, wait for the result of node start,
+			// and let native chain take control after.
+			let (tx, mut rx) = mpsc::channel(1);
 			let runner = cli.create_runner(&cli.run.base)?;
-			runner.run_node_until_exit(|config| async move {
-				service::new_full(config, &cli).map_err(sc_cli::Error::Service)
-			})
+			let handle = thread::spawn(move || {
+				runner.run_node_until_exit(|config| async move {
+					match service::new_full(config, &cli) {
+						Ok((starter, manager)) => {
+							starter.start_network();
+							let _ = tx.send(None).await;
+							Ok(manager)
+						},
+						Err(e) => {
+							let _ = tx.send(Some(e.to_string())).await;
+							Err(sc_cli::Error::Service(e))
+						},
+					}
+				})
+			});
+
+			// Startup failure, if any
+			if let Some(Some(msg)) = rx.blocking_recv() {
+				return Err(msg.into());
+			}
+
+			return Ok(Some(handle));
 		}
-	}
+	};
+
+	res.map(|_| None)
 }

meta/meta-node/src/lib.rs

@@ -0,0 +1,87 @@
+mod chain_spec;
+mod native;
+#[macro_use]
+mod service;
+mod cli;
+mod command;
+mod rpc;
+
+use std::error::Error;
+
+use clap::{CommandFactory, ErrorKind, FromArgMatches};
+use cli::Cli;
+use cxx::{CxxString, CxxVector};
+
+// NOTE: Struct definitions for FFI should match those defined in libain-rs/protobuf
+
+#[cxx::bridge]
+mod ffi {
+    pub struct DmcTx {
+        pub from: String,
+        pub to: String,
+        pub amount: i64,
+    }
+
+    pub struct DmcBlock {
+        pub payload: Vec<u8>,
+    }
+
+    struct ExecResult {
+        is_help: bool,
+        success: bool,
+        daemon: bool,
+    }
+
+    extern "Rust" {
+        fn mint_block(dmc_txs: &CxxVector<DmcTx>) -> Result<DmcBlock>;
+        fn parse_args_and_run(args: &CxxVector<CxxString>) -> ExecResult;
+    }
+}
+
+#[inline]
+fn mint_block(dmc_txs: &CxxVector<ffi::DmcTx>) -> Result<ffi::DmcBlock, Box<dyn Error>> {
+	self::native::NATIVE_HELPER
+         .read().unwrap().as_ref().expect("uninitialized native helper")
+         .mint_block(dmc_txs.iter())
+}
+
+fn parse_args_and_run(args: &CxxVector<CxxString>) -> ffi::ExecResult {
+    let args: Vec<String> = args
+        .iter()
+        .map(|s| s.to_string_lossy().into_owned())
+        .collect();
+    let res = Cli::command().try_get_matches_from(args)
+        .and_then(|mut m| Cli::from_arg_matches_mut(&mut m));
+
+    let cli = match res {
+        Ok(c) => c,
+        Err(e) => {
+            let _ = e.print();
+            let is_help = match e.kind() {
+                ErrorKind::DisplayHelp | ErrorKind::DisplayVersion => true,
+                _ => false,
+            };
+            return ffi::ExecResult {
+                is_help,
+                success: is_help,
+                daemon: false,
+            }
+        },
+    };
+
+    let mut result = ffi::ExecResult {
+        is_help: false,
+        success: false,
+        daemon: cli.subcommand.is_none(),
+    };
+    match command::run(cli) {
+        Ok(_) => {
+            // Deciding to run the node, give control back to defid without joining handle
+            // FIXME: Figure out how to send SIGINT on defid exiting for cleanly shutting down
+            result.success = true;
+        },
+        Err(e) => eprintln!("{:?}", e),
+    }
+
+    result
+}