JSON-RPC stdio server

It speaks JSON-RPC serialized into JSON Lines over stdio.

deltachat-rpc-server/Cargo.toml

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+[package]
+name = "deltachat-rpc-server"
+version = "1.98.0"
+description = "DeltaChat JSON-RPC server"
+authors = ["Delta Chat Developers (ML) <delta@codespeak.net>"]
+edition = "2021"
+readme = "README.md"
+license = "MPL-2.0"
+
+keywords = ["deltachat", "chat", "openpgp", "email", "encryption"]
+categories = ["cryptography", "std", "email"]
+
+[[bin]]
+name = "deltachat-rpc-server"
+
+[dependencies]
+deltachat-jsonrpc = { path = "../deltachat-jsonrpc" }
+
+anyhow = "1"
+env_logger = { version = "0.9.1" }
+futures-lite = "1.12.0"
+log = "0.4"
+serde_json = "1.0.85"
+serde = { version = "1.0", features = ["derive"] }
+tokio = { version = "1.21.2", features = ["io-std"] }
+yerpc = { version = "0.3.1", features = ["anyhow_expose"] }

deltachat-rpc-server/src/bin/deltachat-rpc-server/main.rs

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+///! Delta Chat core RPC server.
+///!
+///! It speaks JSON Lines over stdio.
+use std::path::PathBuf;
+
+use anyhow::Result;
+use deltachat_jsonrpc::api::events::event_to_json_rpc_notification;
+use deltachat_jsonrpc::api::{Accounts, CommandApi};
+use futures_lite::stream::StreamExt;
+use tokio::io::{self, AsyncBufReadExt, BufReader};
+use tokio::task::JoinHandle;
+use yerpc::{RpcClient, RpcSession};
+
+#[tokio::main(flavor = "multi_thread")]
+async fn main() -> Result<()> {
+    env_logger::Builder::from_env(env_logger::Env::default().default_filter_or("info")).init();
+
+    let path = std::env::var("DC_ACCOUNTS_PATH").unwrap_or_else(|_| "accounts".to_string());
+    log::info!("Starting with accounts directory `{}`.", path);
+    let accounts = Accounts::new(PathBuf::from(&path)).await?;
+    let events = accounts.get_event_emitter();
+
+    log::info!("Creating JSON-RPC API.");
+    let state = CommandApi::new(accounts);
+
+    let (client, mut out_receiver) = RpcClient::new();
+    let session = RpcSession::new(client.clone(), state);
+
+    // Events task converts core events to JSON-RPC notifications.
+    let events_task: JoinHandle<Result<()>> = tokio::spawn(async move {
+        while let Some(event) = events.recv().await {
+            let event = event_to_json_rpc_notification(event);
+            client.send_notification("event", Some(event)).await?;
+        }
+        Ok(())
+    });
+
+    // Send task prints JSON responses to stdout.
+    let send_task: JoinHandle<anyhow::Result<()>> = tokio::spawn(async move {
+        while let Some(message) = out_receiver.next().await {
+            let message = serde_json::to_string(&message)?;
+            log::trace!("RPC send {}", message);
+            println!("{}", message);
+        }
+        Ok(())
+    });
+
+    // Receiver task reads JSON requests from stdin.
+    let recv_task: JoinHandle<anyhow::Result<()>> = tokio::spawn(async move {
+        let stdin = io::stdin();
+        let mut lines = BufReader::new(stdin).lines();
+        while let Some(message) = lines.next_line().await? {
+            log::trace!("RPC recv {}", message);
+            session.handle_incoming(&message).await;
+        }
+        log::info!("EOF reached on stdin");
+        Ok(())
+    });
+
+    // Wait for the end of stdin.
+    recv_task.await??;
+
+    // Shutdown the server.
+    send_task.abort();
+    events_task.abort();
+
+    Ok(())
+}