solo_api/

mcp_dispatch.rs

// SPDX-License-Identifier: Apache-2.0

//! v0.10.2 — transport-agnostic MCP JSON-RPC dispatcher.
//!
//! Until v0.10.1 the MCP server logic lived behind rmcp's stdio transport
//! ([`crate::mcp::serve_stdio`]); the only way an MCP client could reach
//! Solo's tools was by spawning `solo mcp-stdio` as a subprocess.
//! v0.10.2 adds an HTTP transport on `/mcp` so a single `solo daemon
//! --http-port` process can serve BOTH `/v1/graph/*` (REST, for solo-web)
//! and `/mcp` (JSON-RPC, for solo-jarvis) without the writer-lock dance.
//!
//! The dispatcher is the request -> response funnel that both transports
//! call into identically. It carries no transport-specific state — it
//! holds an [`Arc<SoloMcpServer>`](crate::mcp::SoloMcpServer) and routes
//! JSON-RPC method names to the existing direct-dispatch entry points
//! ([`SoloMcpServer::dispatch_list_tools`] +
//! [`SoloMcpServer::dispatch_tool`]). Today the stdio loop continues to
//! use rmcp's `ServerHandler` impl (which handles MCP framing for us);
//! the HTTP route uses this dispatcher directly to avoid hand-rolling
//! framing for one-shot request/response.
//!
//! ## Supported methods
//!
//! * `initialize` — returns the same `ServerInfo` shape rmcp emits over
//!   stdio. v0.10.2 returns the static info; the sampling-capability
//!   gating that lives in [`crate::mcp::SoloMcpServer::initialize`] is
//!   stdio-only because there's no `Peer<RoleServer>` over HTTP. HTTP
//!   clients that try to drive `mcp_sampling`-mode tenants will see
//!   sampling errors at tool-call time instead. Documented in the dev
//!   log for v0.10.2.
//! * `tools/list` — returns [`SoloMcpServer::dispatch_list_tools`].
//! * `tools/call` — returns [`SoloMcpServer::dispatch_tool`].
//! * `ping` — returns an empty object. Useful for HTTP-client liveness
//!   probes without paying the cost of `tools/list`.
//! * Anything else returns `MethodNotFound` per JSON-RPC 2.0.
//!
//! ## Notifications
//!
//! JSON-RPC notifications carry no `id` field; per spec the server MUST
//! NOT respond. `dispatch_notification` accepts these (e.g.
//! `notifications/initialized`) and returns `()`.
//!
//! ## Out of scope (deferred to v0.10.3+)
//!
//! - `Mcp-Session-Id` session affinity
//! - Resumable streams with `Last-Event-ID`
//! - Server-initiated requests over the GET SSE stream
//! - Per-tool streaming (progress events during long tool calls)

use std::sync::Arc;

use rmcp::model::{ErrorCode, ErrorData as McpError, Implementation};
use serde::{Deserialize, Serialize};
use solo_storage::{TenantHandle, TenantRegistry};

use crate::mcp::SoloMcpServer;

/// JSON-RPC 2.0 request envelope used by the HTTP transport.
///
/// `id` is `Option<Value>` per JSON-RPC 2.0: a missing `id` means the
/// message is a notification (no response expected). Requests with an
/// explicit `id: null` deserialise the same as a missing `id` (both
/// land as `None`) — we treat both as notifications per JSON-RPC 2.0
/// §4.1 ("`null` should not be used for the Id member of a Request
/// object"). Real MCP clients always send numeric or string ids.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct JsonRpcRequest {
    pub jsonrpc: String,
    #[serde(default)]
    pub id: Option<serde_json::Value>,
    pub method: String,
    #[serde(default)]
    pub params: Option<serde_json::Value>,
}

/// JSON-RPC 2.0 successful response envelope.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct JsonRpcSuccess {
    pub jsonrpc: String,
    pub id: serde_json::Value,
    pub result: serde_json::Value,
}

/// JSON-RPC 2.0 error response envelope. `id` is `Value::Null` when
/// the server could not read the request id (parse error / unreadable
/// envelope); otherwise it echoes the request id back so the client
/// can correlate.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct JsonRpcErrorResponse {
    pub jsonrpc: String,
    pub id: serde_json::Value,
    pub error: JsonRpcErrorBody,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct JsonRpcErrorBody {
    pub code: i32,
    pub message: String,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub data: Option<serde_json::Value>,
}

/// Either a success or error response, serialised as a single JSON-RPC
/// 2.0 message on the wire. `serde(untagged)` so both shapes share the
/// `{jsonrpc, id, ...}` prefix and are distinguished by the presence of
/// `result` vs. `error`.
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(untagged)]
pub enum JsonRpcResponse {
    Success(JsonRpcSuccess),
    Error(JsonRpcErrorResponse),
}

impl JsonRpcResponse {
    /// Build a success response with an explicit id.
    pub fn success(id: serde_json::Value, result: serde_json::Value) -> Self {
        Self::Success(JsonRpcSuccess {
            jsonrpc: "2.0".to_string(),
            id,
            result,
        })
    }

    /// Build an error response with an explicit id. Pass
    /// `serde_json::Value::Null` for `id` when the server could not read
    /// the request id (parse error / unreadable envelope).
    pub fn error(id: serde_json::Value, code: i32, message: impl Into<String>) -> Self {
        Self::Error(JsonRpcErrorResponse {
            jsonrpc: "2.0".to_string(),
            id,
            error: JsonRpcErrorBody {
                code,
                message: message.into(),
                data: None,
            },
        })
    }

    /// Convenience constructor: map an rmcp [`McpError`] to a JSON-RPC
    /// error response.
    pub fn from_mcp_error(id: serde_json::Value, err: McpError) -> Self {
        Self::error(id, err.code.0, err.message.to_string())
    }
}

/// Transport-agnostic MCP dispatcher used by the v0.10.2 HTTP `/mcp`
/// route. Holds the per-tenant [`SoloMcpServer`] needed to answer
/// `tools/list` and `tools/call`.
///
/// The dispatcher itself is stateless beyond the held server — callers
/// build a fresh dispatcher per request (cheap; the server is
/// `Arc`-cloneable) and discard it after dispatch returns.
#[derive(Clone)]
pub struct McpDispatcher {
    server: SoloMcpServer,
}

impl McpDispatcher {
    /// Build a dispatcher for one tenant. The caller is expected to
    /// resolve the tenant (via `X-Solo-Tenant` header for HTTP, or via
    /// `--tenant` flag for stdio) and pass an `Arc<TenantHandle>` here.
    ///
    /// `audit_principal` is the subject that authored every tool call
    /// dispatched through this server — typically `"bearer"` for
    /// bearer-authenticated HTTP requests, the `SOLO_MCP_PRINCIPAL_TOKEN`
    /// env-var value for stdio, or `None` for unauthenticated loopback.
    pub fn new(
        registry: Arc<TenantRegistry>,
        tenant: Arc<TenantHandle>,
        user_aliases: Vec<String>,
        audit_principal: Option<String>,
    ) -> Self {
        let server = SoloMcpServer::new_for_tenant_with_principal(
            registry,
            tenant,
            user_aliases,
            audit_principal,
        );
        Self { server }
    }

    /// Wrap an already-built [`SoloMcpServer`]. Used by tests that want
    /// to pin the underlying server's principal exactly; production
    /// callers should prefer [`Self::new`].
    pub fn from_server(server: SoloMcpServer) -> Self {
        Self { server }
    }

    /// Dispatch one JSON-RPC request and return the wire response.
    ///
    /// Returns `None` when the input is a notification (no `id` field) —
    /// per JSON-RPC 2.0 the server MUST NOT respond to notifications.
    /// The HTTP transport translates `None` into a 204 No Content or
    /// empty 200, depending on the client; the stdio path doesn't use
    /// this method (rmcp handles framing for stdio).
    pub async fn dispatch(&self, request: JsonRpcRequest) -> Option<JsonRpcResponse> {
        // Notifications: no `id`, no reply per JSON-RPC 2.0 §4.1.
        let Some(id) = request.id.clone() else {
            // We still want to log unexpected notification methods so
            // operators can diagnose silent client bugs.
            tracing::debug!(
                method = %request.method,
                "mcp-http: notification received (no id; no reply)"
            );
            return None;
        };

        let params = request.params.unwrap_or(serde_json::Value::Null);

        let response = match request.method.as_str() {
            "initialize" => self.handle_initialize(id.clone(), params),
            "tools/list" => self.handle_tools_list(id.clone()),
            "tools/call" => self.handle_tools_call(id.clone(), params).await,
            "ping" => JsonRpcResponse::success(id.clone(), serde_json::json!({})),
            other => JsonRpcResponse::error(
                id.clone(),
                ErrorCode::METHOD_NOT_FOUND.0,
                format!("unknown method `{other}`"),
            ),
        };
        Some(response)
    }

    /// `initialize` — return a minimal `ServerInfo` matching the stdio
    /// transport's shape. v0.10.2 returns the static info; the
    /// sampling-capability gating that lives in the rmcp `ServerHandler`
    /// path is intentionally not replicated here — HTTP has no `Peer`
    /// to call back into. Tenants configured with `[llm] mode =
    /// "mcp_sampling"` will see sampling failures at consolidate-time
    /// instead of at `initialize` (documented in v0.10.2 dev log).
    fn handle_initialize(
        &self,
        id: serde_json::Value,
        _params: serde_json::Value,
    ) -> JsonRpcResponse {
        // Mirror the shape rmcp emits for stdio `initialize`. The
        // `protocolVersion` echoes the MCP version Solo speaks today;
        // `capabilities.tools = {}` is the bare-minimum capability set
        // (we expose tools, nothing else); `serverInfo` is pinned to
        // `{"name": "solo", "version": <crate version>}` per the
        // `server_info_identity_is_solo_not_rmcp_or_solo_api` invariant.
        let server_info = Implementation::new(
            "solo".to_string(),
            env!("CARGO_PKG_VERSION").to_string(),
        );
        let result = serde_json::json!({
            "protocolVersion": "2024-11-05",
            "capabilities": {
                "tools": {},
            },
            "serverInfo": server_info,
        });
        JsonRpcResponse::success(id, result)
    }

    /// `tools/list` — wraps [`SoloMcpServer::dispatch_list_tools`].
    fn handle_tools_list(&self, id: serde_json::Value) -> JsonRpcResponse {
        let tools = self.server.dispatch_list_tools();
        let result = serde_json::json!({ "tools": tools });
        JsonRpcResponse::success(id, result)
    }

    /// `tools/call` — wraps [`SoloMcpServer::dispatch_tool`]. JSON-RPC
    /// `params` carries `{"name": "...", "arguments": {...}}`.
    async fn handle_tools_call(
        &self,
        id: serde_json::Value,
        params: serde_json::Value,
    ) -> JsonRpcResponse {
        let name = match params.get("name").and_then(|v| v.as_str()) {
            Some(n) => n.to_string(),
            None => {
                return JsonRpcResponse::error(
                    id,
                    ErrorCode::INVALID_PARAMS.0,
                    "tools/call: missing `name` field",
                );
            }
        };
        // `arguments` is optional; treat absent / null as empty object so
        // tools with all-optional args (e.g. `memory_themes`) can be
        // called with `{}` from the wire.
        let arguments = params
            .get("arguments")
            .cloned()
            .unwrap_or(serde_json::Value::Object(serde_json::Map::new()));
        match self.server.dispatch_tool(&name, arguments).await {
            Ok(call_result) => {
                // Serialise the rmcp `CallToolResult` directly — it
                // already round-trips through serde and matches the
                // MCP wire shape the stdio transport emits.
                let result = match serde_json::to_value(&call_result) {
                    Ok(v) => v,
                    Err(e) => {
                        return JsonRpcResponse::error(
                            id,
                            ErrorCode::INTERNAL_ERROR.0,
                            format!("serialize tool result: {e}"),
                        );
                    }
                };
                JsonRpcResponse::success(id, result)
            }
            Err(e) => JsonRpcResponse::from_mcp_error(id, e),
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn jsonrpc_success_serialises_with_jsonrpc_field() {
        let resp =
            JsonRpcResponse::success(serde_json::json!(1), serde_json::json!({"ok": true}));
        let s = serde_json::to_string(&resp).unwrap();
        assert!(s.contains(r#""jsonrpc":"2.0""#));
        assert!(s.contains(r#""id":1"#));
        assert!(s.contains(r#""result":{"ok":true}"#));
        assert!(!s.contains(r#""error":"#));
    }

    #[test]
    fn jsonrpc_error_serialises_with_error_field() {
        let resp = JsonRpcResponse::error(
            serde_json::json!(7),
            ErrorCode::METHOD_NOT_FOUND.0,
            "unknown method `foo`",
        );
        let s = serde_json::to_string(&resp).unwrap();
        assert!(s.contains(r#""jsonrpc":"2.0""#));
        assert!(s.contains(r#""id":7"#));
        assert!(s.contains(r#""error":{"#));
        assert!(s.contains(r#""code":-32601"#));
        assert!(!s.contains(r#""result":"#));
    }

    #[test]
    fn jsonrpc_notification_has_no_id() {
        let raw = r#"{"jsonrpc":"2.0","method":"notifications/initialized","params":{}}"#;
        let req: JsonRpcRequest = serde_json::from_str(raw).unwrap();
        assert_eq!(req.method, "notifications/initialized");
        assert!(req.id.is_none());
    }

    #[test]
    fn jsonrpc_request_with_null_id_parses_as_notification() {
        // Per JSON-RPC 2.0 §4.1 `null` is discouraged for request ids;
        // serde's `#[serde(default)]` deserialises an explicit null the
        // same as a missing field, so both land as a notification
        // (no reply). Real MCP clients always send numeric/string ids.
        let raw = r#"{"jsonrpc":"2.0","id":null,"method":"ping"}"#;
        let req: JsonRpcRequest = serde_json::from_str(raw).unwrap();
        assert!(req.id.is_none());
    }
}