342 lines
12 KiB
Rust
342 lines
12 KiB
Rust
//! Streaming tool call handling for MCP interception.
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use std::collections::HashMap;
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use serde_json::Value;
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use tracing::warn;
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use super::{
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accumulator::StreamingResponseAccumulator,
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mcp::FunctionCallInProgress,
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streaming::{extract_output_index, get_event_type},
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};
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use crate::protocols::event_types::{
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is_function_call_type, FunctionCallEvent, OutputItemEvent, ResponseEvent,
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};
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// ============================================================================
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// Stream Action Enum
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// ============================================================================
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/// Action to take based on streaming event processing
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#[derive(Debug)]
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pub(crate) enum StreamAction {
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Forward, // Pass event to client
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Buffer, // Accumulate for tool execution
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ExecuteTools, // Function call complete, execute now
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}
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// ============================================================================
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// Output Index Mapper
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// ============================================================================
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/// Maps upstream output indices to sequential downstream indices
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#[derive(Debug, Default)]
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pub(crate) struct OutputIndexMapper {
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next_index: usize,
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// Map upstream output_index -> remapped output_index
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assigned: HashMap<usize, usize>,
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}
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impl OutputIndexMapper {
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pub fn with_start(next_index: usize) -> Self {
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Self {
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next_index,
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assigned: HashMap::new(),
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}
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}
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pub fn ensure_mapping(&mut self, upstream_index: usize) -> usize {
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*self.assigned.entry(upstream_index).or_insert_with(|| {
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let assigned = self.next_index;
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self.next_index += 1;
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assigned
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})
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}
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pub fn lookup(&self, upstream_index: usize) -> Option<usize> {
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self.assigned.get(&upstream_index).copied()
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}
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pub fn allocate_synthetic(&mut self) -> usize {
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let assigned = self.next_index;
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self.next_index += 1;
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assigned
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}
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pub fn next_index(&self) -> usize {
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self.next_index
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}
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}
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// ============================================================================
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// Streaming Tool Handler
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// ============================================================================
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/// Handles streaming responses with MCP tool call interception
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pub(super) struct StreamingToolHandler {
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/// Accumulator for response persistence
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pub accumulator: StreamingResponseAccumulator,
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/// Function calls being built from deltas
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pub pending_calls: Vec<FunctionCallInProgress>,
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/// Track if we're currently in a function call
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in_function_call: bool,
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/// Manage output_index remapping so they increment per item
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output_index_mapper: OutputIndexMapper,
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/// Original response id captured from the first response.created event
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pub original_response_id: Option<String>,
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}
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impl StreamingToolHandler {
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pub fn with_starting_index(start: usize) -> Self {
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Self {
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accumulator: StreamingResponseAccumulator::new(),
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pending_calls: Vec::new(),
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in_function_call: false,
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output_index_mapper: OutputIndexMapper::with_start(start),
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original_response_id: None,
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}
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}
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pub fn ensure_output_index(&mut self, upstream_index: usize) -> usize {
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self.output_index_mapper.ensure_mapping(upstream_index)
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}
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pub fn mapped_output_index(&self, upstream_index: usize) -> Option<usize> {
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self.output_index_mapper.lookup(upstream_index)
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}
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pub fn allocate_synthetic_output_index(&mut self) -> usize {
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self.output_index_mapper.allocate_synthetic()
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}
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pub fn next_output_index(&self) -> usize {
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self.output_index_mapper.next_index()
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}
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pub fn original_response_id(&self) -> Option<&str> {
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self.original_response_id
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.as_deref()
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.or_else(|| self.accumulator.original_response_id())
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}
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pub fn snapshot_final_response(&self) -> Option<Value> {
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self.accumulator.snapshot_final_response()
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}
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/// Process an SSE event and determine what action to take
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pub fn process_event(&mut self, event_name: Option<&str>, data: &str) -> StreamAction {
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// Always feed to accumulator for storage
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self.accumulator.ingest_block(&format!(
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"{}data: {}",
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event_name
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.map(|n| format!("event: {}\n", n))
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.unwrap_or_default(),
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data
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));
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let parsed: Value = match serde_json::from_str(data) {
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Ok(v) => v,
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Err(_) => return StreamAction::Forward,
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};
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match get_event_type(event_name, &parsed) {
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ResponseEvent::CREATED => {
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if self.original_response_id.is_none() {
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self.original_response_id = parsed
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.get("response")
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.and_then(|v| v.get("id"))
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.and_then(|v| v.as_str())
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.map(|s| s.to_string());
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}
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StreamAction::Forward
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}
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ResponseEvent::COMPLETED => StreamAction::Forward,
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OutputItemEvent::ADDED => self.handle_output_item_added(&parsed),
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FunctionCallEvent::ARGUMENTS_DELTA => self.handle_arguments_delta(&parsed),
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FunctionCallEvent::ARGUMENTS_DONE => self.handle_arguments_done(&parsed),
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OutputItemEvent::DELTA => self.process_output_delta(&parsed),
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OutputItemEvent::DONE => {
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if let Some(output_index) = extract_output_index(&parsed) {
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self.ensure_output_index(output_index);
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}
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if self.has_complete_calls() {
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StreamAction::ExecuteTools
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} else {
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StreamAction::Forward
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}
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}
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_ => StreamAction::Forward,
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}
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}
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fn handle_output_item_added(&mut self, parsed: &Value) -> StreamAction {
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if let Some(output_index) = extract_output_index(parsed) {
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self.ensure_output_index(output_index);
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}
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// Check if this is a function_call item being added
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let Some(item) = parsed.get("item") else {
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return StreamAction::Forward;
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};
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let Some(item_type) = item.get("type").and_then(|v| v.as_str()) else {
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return StreamAction::Forward;
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};
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if !is_function_call_type(item_type) {
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return StreamAction::Forward;
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}
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let Some(output_index) = extract_output_index(parsed) else {
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warn!(
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"Missing output_index in function_call added event, \
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forwarding without processing for tool execution"
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);
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return StreamAction::Forward;
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};
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let assigned_index = self.ensure_output_index(output_index);
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let call_id = item.get("call_id").and_then(|v| v.as_str()).unwrap_or("");
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let name = item.get("name").and_then(|v| v.as_str()).unwrap_or("");
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let call = self.get_or_create_call(output_index, item);
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call.call_id = call_id.to_string();
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call.name = name.to_string();
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call.assigned_output_index = Some(assigned_index);
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self.in_function_call = true;
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StreamAction::Forward
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}
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fn handle_arguments_delta(&mut self, parsed: &Value) -> StreamAction {
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let Some(output_index) = extract_output_index(parsed) else {
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return StreamAction::Forward;
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};
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let assigned_index = self.ensure_output_index(output_index);
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if let Some(delta) = parsed.get("delta").and_then(|v| v.as_str()) {
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if let Some(call) = self.find_call_mut(output_index) {
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call.arguments_buffer.push_str(delta);
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if let Some(obfuscation) = parsed.get("obfuscation").and_then(|v| v.as_str()) {
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call.last_obfuscation = Some(obfuscation.to_string());
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}
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if call.assigned_output_index.is_none() {
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call.assigned_output_index = Some(assigned_index);
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}
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}
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}
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StreamAction::Forward
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}
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fn handle_arguments_done(&mut self, parsed: &Value) -> StreamAction {
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if let Some(output_index) = extract_output_index(parsed) {
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let assigned_index = self.ensure_output_index(output_index);
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if let Some(call) = self.find_call_mut(output_index) {
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if call.assigned_output_index.is_none() {
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call.assigned_output_index = Some(assigned_index);
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}
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}
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}
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if self.has_complete_calls() {
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StreamAction::ExecuteTools
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} else {
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StreamAction::Forward
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}
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}
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fn find_call_mut(&mut self, output_index: usize) -> Option<&mut FunctionCallInProgress> {
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self.pending_calls
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.iter_mut()
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.find(|c| c.output_index == output_index)
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}
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/// Process output delta events to detect and accumulate function calls
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fn process_output_delta(&mut self, event: &Value) -> StreamAction {
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let output_index = extract_output_index(event).unwrap_or(0);
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let assigned_index = self.ensure_output_index(output_index);
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let delta = match event.get("delta") {
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Some(d) => d,
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None => return StreamAction::Forward,
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};
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// Check if this is a function call delta
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let item_type = delta.get("type").and_then(|v| v.as_str());
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if item_type.is_some_and(is_function_call_type) {
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self.in_function_call = true;
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// Get or create function call for this output index
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let call = self.get_or_create_call(output_index, delta);
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call.assigned_output_index = Some(assigned_index);
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// Accumulate call_id if present
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if let Some(call_id) = delta.get("call_id").and_then(|v| v.as_str()) {
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call.call_id = call_id.to_string();
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}
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// Accumulate name if present
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if let Some(name) = delta.get("name").and_then(|v| v.as_str()) {
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call.name.push_str(name);
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}
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// Accumulate arguments if present
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if let Some(args) = delta.get("arguments").and_then(|v| v.as_str()) {
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call.arguments_buffer.push_str(args);
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}
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if let Some(obfuscation) = delta.get("obfuscation").and_then(|v| v.as_str()) {
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call.last_obfuscation = Some(obfuscation.to_string());
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}
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// Buffer this event, don't forward to client
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return StreamAction::Buffer;
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}
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// Forward non-function-call events
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StreamAction::Forward
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}
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fn get_or_create_call(
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&mut self,
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output_index: usize,
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delta: &Value,
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) -> &mut FunctionCallInProgress {
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// Find existing call for this output index
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if let Some(pos) = self
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.pending_calls
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.iter()
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.position(|c| c.output_index == output_index)
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{
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return &mut self.pending_calls[pos];
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}
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// Create new call
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let call_id = delta
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.get("call_id")
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.and_then(|v| v.as_str())
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.unwrap_or("")
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.to_string();
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let mut call = FunctionCallInProgress::new(call_id, output_index);
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if let Some(obfuscation) = delta.get("obfuscation").and_then(|v| v.as_str()) {
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call.last_obfuscation = Some(obfuscation.to_string());
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}
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self.pending_calls.push(call);
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self.pending_calls
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.last_mut()
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.expect("Just pushed to pending_calls, must have at least one element")
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}
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fn has_complete_calls(&self) -> bool {
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!self.pending_calls.is_empty() && self.pending_calls.iter().all(|c| c.is_complete())
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}
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pub fn take_pending_calls(&mut self) -> Vec<FunctionCallInProgress> {
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std::mem::take(&mut self.pending_calls)
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}
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}
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