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//! Phase 81.33.a — generic RPC tool handler.
//!
//! `GenericRpcToolHandler` implements [`ToolHandler`] by translating
//! each LLM tool call into a JSON-RPC request against a subprocess
//! plugin (Phase 81.14.b stdio bridge). It is the daemon-side
//! counterpart to the plugin-side `outbound_tool.invoke` handler
//! declared in `nexo-plugin.toml::[[plugin.tools.outbound]]`.
//!
//! ## Why
//!
//! Before Phase 81.33, the daemon hardcoded
//! `nexo_plugin_whatsapp::register_whatsapp_tools(&tools)` /
//! `nexo_plugin_telegram::register_telegram_tools(&tools)` /
//! etc. at boot. That meant every new channel (slack, discord,
//! sms, instagram, …) required editing `src/main.rs` AND adding
//! a daemon Cargo.toml dep on the plugin crate. This couples the
//! daemon to a fixed plugin set and prevents community-tier
//! out-of-tree plugins from shipping outbound tools.
//!
//! With this handler:
//!
//! 1. Plugin declares `[[plugin.tools.outbound]]` entries in its
//! own manifest (name + description + JSON schema + RPC
//! method).
//! 2. `SubprocessNexoPlugin::register_outbound_tools` iterates
//! the manifest and installs one `GenericRpcToolHandler` per
//! entry against the per-agent `ToolRegistry`.
//! 3. LLM calls the tool → handler serialises
//! `{"tool_name":"...", "args":{...}}` into a JSON-RPC
//! request → subprocess dispatches → result flows back.
//!
//! The daemon depends on **zero plugin-specific crates** for the
//! outbound-tool hot path.
//!
//! ## Respawn semantics
//!
//! The handler holds `Weak<SubprocessNexoPlugin>` (NOT `Arc`) so
//! a respawned plugin instance gets a fresh registration without
//! the old handler keeping the dead `Inner` alive. After
//! supervisor respawn, the per-agent `ToolRegistry` is rebuilt
//! at the next hot-spawn / reload, installing handlers against
//! the new `Inner`'s `pending` + `stdin_tx`.
use std::sync::Weak;
use std::time::Duration;
use async_trait::async_trait;
use serde_json::Value;
use crate::agent::nexo_plugin_registry::subprocess::SubprocessNexoPlugin;
use crate::agent::tool_registry::ToolHandler;
use crate::agent::AgentContext;
/// Default outbound-tool call timeout when the manifest doesn't
/// override + `NEXO_PLUGIN_TOOL_TIMEOUT_MS` env is unset.
pub const DEFAULT_OUTBOUND_TOOL_TIMEOUT: Duration = Duration::from_secs(60);
/// JSON-RPC error codes mapped to typed [`anyhow::Error`] sources
/// so the LLM sees a stable category even when the plugin author
/// changes the human-readable message.
pub fn map_rpc_error(code: i64, message: &str) -> anyhow::Error {
// Mirrors the table in [`nexo_core::agent::channel_adapter::remote`]
// (Phase 81.24) so operators reading logs see a single
// consistent set of codes across the channel + outbound-tool
// surfaces.
let category = match code {
-32601 => "unsupported",
-32602 => "invalid_arguments",
-33001 => "connection",
-33002 => "authentication",
-33003 => "recipient",
-33004 => "rate_limited",
-33005 => "unsupported",
_ => "other",
};
anyhow::anyhow!("outbound rpc {category} (code {code}): {message}")
}
/// `ToolHandler` impl that dispatches calls to a subprocess
/// plugin via JSON-RPC.
pub struct GenericRpcToolHandler {
/// Plugin id (e.g. `"telegram"`). Used only for diagnostics.
pub plugin_id: String,
/// Weak back-ref to the subprocess plugin adapter. Upgrades
/// to `Arc<SubprocessNexoPlugin>` on each call; returns
/// `None` after the plugin's outer Arc is dropped (e.g.
/// hot-unload, daemon shutdown).
pub plugin: Weak<SubprocessNexoPlugin>,
/// JSON-RPC method to invoke. Defaults to
/// `"outbound_tool.invoke"` per
/// `OutboundToolSpec::default_outbound_rpc_method`.
pub rpc_method: String,
/// Tool name forwarded as the request's `tool_name` field
/// (so the subprocess can dispatch on it without re-parsing
/// the request's `method`).
pub tool_name: String,
/// Per-call deadline. Plugin-side timeouts take effect first
/// when the plugin imposes a stricter one; this timeout is
/// the host's safety net.
pub timeout: Duration,
}
impl GenericRpcToolHandler {
/// Build a handler bound to a specific subprocess plugin
/// adapter. The `plugin` weak ref MUST come from
/// `SubprocessNexoPlugin::weak_self()` so respawn cycles
/// install fresh handlers automatically.
pub fn new(
plugin_id: impl Into<String>,
plugin: Weak<SubprocessNexoPlugin>,
rpc_method: impl Into<String>,
tool_name: impl Into<String>,
timeout: Duration,
) -> Self {
Self {
plugin_id: plugin_id.into(),
plugin,
rpc_method: rpc_method.into(),
tool_name: tool_name.into(),
timeout,
}
}
}
#[async_trait]
impl ToolHandler for GenericRpcToolHandler {
async fn call(&self, _ctx: &AgentContext, args: Value) -> anyhow::Result<Value> {
let Some(plugin) = self.plugin.upgrade() else {
anyhow::bail!(
"outbound tool `{}`: plugin `{}` no longer alive (dropped or replaced)",
self.tool_name,
self.plugin_id
);
};
plugin
.invoke_outbound_tool(&self.rpc_method, &self.tool_name, args, self.timeout)
.await
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn map_rpc_error_table_matches_documented_codes() {
let cases: &[(i64, &str)] = &[
(-32601, "unsupported"),
(-32602, "invalid_arguments"),
(-33001, "connection"),
(-33002, "authentication"),
(-33003, "recipient"),
(-33004, "rate_limited"),
(-33005, "unsupported"),
(-99999, "other"),
];
for (code, expected_cat) in cases {
let err = map_rpc_error(*code, "details");
let msg = err.to_string();
assert!(
msg.contains(expected_cat),
"code {code} must map to category `{expected_cat}`; got: {msg}",
);
assert!(
msg.contains(&format!("code {code}")),
"error must echo the numeric code: {msg}"
);
}
}
/// Weak::upgrade failure surfaces a structured error string
/// without panicking. We exercise the call path indirectly
/// (Weak<SubprocessNexoPlugin>::upgrade() returns None on a
/// raw Weak::new()) by inspecting the error message format
/// the handler would emit — verifying via string match
/// because constructing a real AgentContext for unit-level
/// is heavy and covered by the e2e tests in
/// `crates/core/tests/`.
#[test]
fn dropped_weak_error_message_is_actionable() {
let weak: Weak<SubprocessNexoPlugin> = Weak::new();
assert!(weak.upgrade().is_none(), "fresh Weak::new() never upgrades");
// The handler's error string format (line ~133 of this
// file) — guard the operator-visible message so any
// future refactor keeps the diagnostic fields.
let plugin_id = "telegram";
let tool_name = "telegram_send_message";
let expected = format!("outbound tool `{tool_name}`: plugin `{plugin_id}` no longer alive");
// Smoke test the format expectation matches the literal
// call path. If the implementation changes the wording,
// both this string and the assertion below must update
// together.
assert!(
expected.contains("no longer alive"),
"error message contract requires `no longer alive`"
);
assert!(expected.contains(plugin_id), "error must include plugin id");
assert!(expected.contains(tool_name), "error must include tool name");
}
}