rig/providers/openai/completion/

streaming.rs

use crate::completion::{CompletionError, CompletionRequest, GetTokenUsage};
use crate::json_utils;
use crate::json_utils::merge;
use crate::providers::openai::completion::{CompletionModel, Usage};
use crate::streaming;
use crate::streaming::RawStreamingChoice;
use async_stream::stream;
use futures::StreamExt;
use reqwest::RequestBuilder;
use reqwest_eventsource::Event;
use reqwest_eventsource::RequestBuilderExt;
use serde::{Deserialize, Serialize};
use serde_json::json;
use std::collections::HashMap;
use tracing::debug;

// ================================================================
// OpenAI Completion Streaming API
// ================================================================
#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct StreamingFunction {
    #[serde(default)]
    pub name: Option<String>,
    #[serde(default)]
    pub arguments: String,
}

#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct StreamingToolCall {
    pub index: usize,
    pub id: Option<String>,
    pub function: StreamingFunction,
}

#[derive(Deserialize, Debug)]
struct StreamingDelta {
    #[serde(default)]
    content: Option<String>,
    #[serde(default, deserialize_with = "json_utils::null_or_vec")]
    tool_calls: Vec<StreamingToolCall>,
}

#[derive(Deserialize, Debug)]
struct StreamingChoice {
    delta: StreamingDelta,
}

#[derive(Deserialize, Debug)]
struct StreamingCompletionChunk {
    choices: Vec<StreamingChoice>,
    usage: Option<Usage>,
}

#[derive(Clone, Serialize, Deserialize)]
pub struct StreamingCompletionResponse {
    pub usage: Usage,
}

impl GetTokenUsage for StreamingCompletionResponse {
    fn token_usage(&self) -> Option<crate::completion::Usage> {
        let mut usage = crate::completion::Usage::new();
        usage.input_tokens = self.usage.prompt_tokens as u64;
        usage.output_tokens = self.usage.total_tokens as u64 - self.usage.prompt_tokens as u64;
        usage.total_tokens = self.usage.total_tokens as u64;
        Some(usage)
    }
}

impl CompletionModel {
    pub(crate) async fn stream(
        &self,
        completion_request: CompletionRequest,
    ) -> Result<streaming::StreamingCompletionResponse<StreamingCompletionResponse>, CompletionError>
    {
        let mut request = self.create_completion_request(completion_request)?;
        request = merge(
            request,
            json!({"stream": true, "stream_options": {"include_usage": true}}),
        );

        let builder = self.client.post("/chat/completions").json(&request);
        send_compatible_streaming_request(builder).await
    }
}

pub async fn send_compatible_streaming_request(
    request_builder: RequestBuilder,
) -> Result<streaming::StreamingCompletionResponse<StreamingCompletionResponse>, CompletionError> {
    // Build the request with proper headers for SSE
    let mut event_source = request_builder
        .eventsource()
        .expect("Cloning request must always succeed");

    let stream = Box::pin(stream! {
        let mut final_usage = Usage::new();

        // Track in-progress tool calls
        let mut tool_calls: HashMap<usize, (String, String, String)> = HashMap::new();

        while let Some(event_result) = event_source.next().await {
            match event_result {
                Ok(Event::Open) => {
                    tracing::trace!("SSE connection opened");
                    continue;
                }
                Ok(Event::Message(message)) => {
                    if message.data.trim().is_empty() || message.data == "[DONE]" {
                        continue;
                    }

                    let data = serde_json::from_str::<StreamingCompletionChunk>(&message.data);
                    let Ok(data) = data else {
                        let err = data.unwrap_err();
                        debug!("Couldn't serialize data as StreamingCompletionChunk: {:?}", err);
                        continue;
                    };

                    if let Some(choice) = data.choices.first() {
                        let delta = &choice.delta;

                        // Tool calls
                        if !delta.tool_calls.is_empty() {
                            for tool_call in &delta.tool_calls {
                                let function = tool_call.function.clone();

                                // Start of tool call
                                if function.name.is_some() && function.arguments.is_empty() {
                                    let id = tool_call.id.clone().unwrap_or_default();
                                    tool_calls.insert(
                                        tool_call.index,
                                        (id, function.name.clone().unwrap(), "".to_string()),
                                    );
                                }
                                // tool call partial (ie, a continuation of a previously received tool call)
                                // name: None or Empty String
                                // arguments: Some(String)
                                else if function.name.clone().is_none_or(|s| s.is_empty())
                                    && !function.arguments.is_empty()
                                {
                                    if let Some((id, name, arguments)) =
                                        tool_calls.get(&tool_call.index)
                                    {
                                        let new_arguments = &tool_call.function.arguments;
                                        let arguments = format!("{arguments}{new_arguments}");
                                        tool_calls.insert(
                                            tool_call.index,
                                            (id.clone(), name.clone(), arguments),
                                        );
                                    } else {
                                        debug!("Partial tool call received but tool call was never started.");
                                    }
                                }
                                // Complete tool call
                                else {
                                    let id = tool_call.id.clone().unwrap_or_default();
                                    let name = function.name.expect("tool call should have a name");
                                    let arguments = function.arguments;
                                    let Ok(arguments) = serde_json::from_str(&arguments) else {
                                        debug!("Couldn't serialize '{arguments}' as JSON");
                                        continue;
                                    };

                                    yield Ok(streaming::RawStreamingChoice::ToolCall {
                                        id,
                                        name,
                                        arguments,
                                        call_id: None,
                                    });
                                }
                            }
                        }

                        // Message content
                        if let Some(content) = &choice.delta.content {
                            yield Ok(streaming::RawStreamingChoice::Message(content.clone()))
                        }
                    }

                    // Usage updates
                    if let Some(usage) = data.usage {
                        final_usage = usage.clone();
                    }
                }
                Err(reqwest_eventsource::Error::StreamEnded) => {
                    break;
                }
                Err(error) => {
                    tracing::error!(?error, "SSE error");
                    yield Err(CompletionError::ResponseError(error.to_string()));
                    break;
                }
            }
        }

        // Ensure event source is closed when stream ends
        event_source.close();

        // Flush any tool calls that weren’t fully yielded
        for (_, (id, name, arguments)) in tool_calls {
            let Ok(arguments) = serde_json::from_str(&arguments) else {
                continue;
            };

            yield Ok(RawStreamingChoice::ToolCall {
                id,
                name,
                arguments,
                call_id: None,
            });
        }

        yield Ok(RawStreamingChoice::FinalResponse(StreamingCompletionResponse {
            usage: final_usage.clone()
        }));
    });

    Ok(streaming::StreamingCompletionResponse::stream(stream))
}