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//! mcp.* — MCP server client bridge (async).
//!
//! All functions use `create_async_function` so that Lua coroutines
//! yield while waiting for MCP server I/O.
//!
//! The manager is held under `RwLock`:
//! - `connect` / `disconnect` take the write lock (they mutate the
//! internal server map).
//! - `list_tools` / `call` take the read lock, so multiple RPCs — even
//! against the same server — can be in flight simultaneously. The
//! per-server multiplexing of concurrent requests is delegated to
//! rmcp's `RunningService`, which tracks pending requests by ID
//! internally over a channel-based peer.
use mlua::prelude::*;
use serde_json::Map;
use std::sync::Arc;
use crate::bridge::obs;
use crate::host::HostContext;
use super::{json_to_lua, lua_to_json};
pub fn register(lua: &Lua, ctx: &HostContext) -> LuaResult<()> {
let manager = &ctx.mcp_manager;
let mcp_tbl = lua.create_table()?;
let script_name: String = lua
.globals()
.get::<Option<String>>("_SCRIPT_NAME")?
.unwrap_or_else(|| "unknown".to_string());
let fallback_agent_id = ctx.mesh_agent.as_ref().map(|a| a.agent_id().to_string());
// mcp.connect(name, command, args)
{
let mgr = Arc::clone(manager);
mcp_tbl.set(
"connect",
lua.create_async_function(
move |_, (name, command, args): (String, String, Option<LuaTable>)| {
let mgr = Arc::clone(&mgr);
async move {
// Iterate by integer index (1..=len) so argv order is
// preserved regardless of table layout. `pairs` gives
// no ordering guarantee for integer-keyed tables.
let args: Vec<String> = match args {
Some(tbl) => {
let len = tbl.raw_len();
let mut v = Vec::with_capacity(len);
for i in 1..=len {
v.push(tbl.raw_get::<String>(i)?);
}
v
}
None => Vec::new(),
};
mgr.write()
.await
.connect(&name, &command, &args)
.await
.map_err(LuaError::external)
}
},
)?,
)?;
}
// mcp.list_tools(name)
{
let mgr = Arc::clone(manager);
mcp_tbl.set(
"list_tools",
lua.create_async_function(move |lua, name: String| {
let mgr = Arc::clone(&mgr);
async move {
let result = mgr.read().await.list_tools(&name).await;
let tbl = lua.create_table()?;
match result {
Ok(val) => {
tbl.set("ok", true)?;
tbl.set("tools", json_to_lua(&lua, val)?)?;
}
Err(e) => {
tbl.set("ok", false)?;
tbl.set("error", e.to_string())?;
}
}
Ok(tbl)
}
})?,
)?;
}
// mcp.call(name, tool_name, arguments)
//
// Return shape:
// { ok=true, content=[...], is_error=bool, structured_content=... } (RPC success)
// { ok=false, error="..." } (transport/protocol)
//
// `ok` is reserved for protocol / transport / timeout failures.
// `is_error` mirrors the server-reported `isError` from `CallToolResult`
// so tool-execution errors reach the LLM unchanged (MCP spec intent).
{
let mgr = Arc::clone(manager);
let fallback_agent_id = fallback_agent_id.clone();
let script_name = script_name.clone();
mcp_tbl.set(
"call",
lua.create_async_function(
move |lua, (name, tool_name, arguments): (String, String, Option<LuaValue>)| {
let mgr = Arc::clone(&mgr);
let fallback_agent_id = fallback_agent_id.clone();
let script_name = script_name.clone();
async move {
// None → Null (mcp_client treats Null as "no arguments").
let mut args_json = match arguments {
Some(v) => lua_to_json(&lua, v)?,
None => serde_json::Value::Null,
};
inject_obs_context(&mut args_json, fallback_agent_id.as_deref());
tracing::info!(
target: "lua",
script = %script_name,
"{}",
obs::obs_line(
"mcp",
"mcp_call",
&obs::obs_context(fallback_agent_id.as_deref()),
&[("server", name.as_str()), ("tool", tool_name.as_str())],
)
);
let result = mgr
.read()
.await
.call_tool(&name, &tool_name, args_json)
.await;
let tbl = lua.create_table()?;
match result {
Ok(val) => {
tracing::info!(
target: "lua",
script = %script_name,
"{}",
obs::obs_line(
"mcp",
"mcp_result",
&obs::obs_context(fallback_agent_id.as_deref()),
&[("server", name.as_str()), ("tool", tool_name.as_str()), ("ok", "true")],
)
);
tbl.set("ok", true)?;
let content = val
.get("content")
.cloned()
.unwrap_or(serde_json::Value::Array(vec![]));
tbl.set("content", json_to_lua(&lua, content)?)?;
let is_error = val
.get("isError")
.and_then(|v| v.as_bool())
.unwrap_or(false);
tbl.set("is_error", is_error)?;
if let Some(sc) = val.get("structuredContent").cloned() {
tbl.set("structured_content", json_to_lua(&lua, sc)?)?;
}
}
Err(e) => {
tracing::warn!(
target: "lua",
script = %script_name,
"{}",
obs::obs_line(
"mcp",
"mcp_result",
&obs::obs_context(fallback_agent_id.as_deref()),
&[("server", name.as_str()), ("tool", tool_name.as_str()), ("ok", "false")],
)
);
tbl.set("ok", false)?;
tbl.set("error", e.to_string())?;
}
}
Ok(tbl)
}
},
)?,
)?;
}
// mcp.disconnect(name)
{
let mgr = Arc::clone(manager);
mcp_tbl.set(
"disconnect",
lua.create_async_function(move |_, name: String| {
let mgr = Arc::clone(&mgr);
async move {
mgr.write()
.await
.disconnect(&name)
.await
.map_err(LuaError::external)
}
})?,
)?;
}
lua.globals().set("mcp", mcp_tbl)?;
Ok(())
}
fn inject_obs_context(args_json: &mut serde_json::Value, fallback_agent_id: Option<&str>) {
fn insert_obs(into: &mut Map<String, serde_json::Value>, fallback_agent_id: Option<&str>) {
if into.contains_key("__ab_obs") {
return;
}
let mut obs = Map::<String, serde_json::Value>::new();
if let Ok(v) = std::env::var("AGENT_BLOCK_TRACE_ID") {
if !v.is_empty() {
obs.insert("trace_id".to_string(), serde_json::Value::String(v));
}
}
if let Ok(v) = std::env::var("AGENT_BLOCK_RUN_ID") {
if !v.is_empty() {
obs.insert("run_id".to_string(), serde_json::Value::String(v));
}
}
let agent_id = std::env::var("AGENT_BLOCK_AGENT_ID")
.ok()
.filter(|s| !s.is_empty())
.or_else(|| fallback_agent_id.map(ToString::to_string));
if let Some(v) = agent_id {
obs.insert("agent_id".to_string(), serde_json::Value::String(v));
}
if let Ok(v) = std::env::var("AGENT_BLOCK_AGENT_NAME") {
if !v.is_empty() {
obs.insert("agent_name".to_string(), serde_json::Value::String(v));
}
}
if !obs.is_empty() {
into.insert("__ab_obs".to_string(), serde_json::Value::Object(obs));
}
}
match args_json {
serde_json::Value::Object(obj) => insert_obs(obj, fallback_agent_id),
serde_json::Value::Null => {
let mut obj = Map::<String, serde_json::Value>::new();
insert_obs(&mut obj, fallback_agent_id);
if !obj.is_empty() {
*args_json = serde_json::Value::Object(obj);
}
}
_ => {}
}
}