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//! Server-Sent Events (SSE) stream decoder for Anthropic Claude API
//!
//! Handles streaming responses from the Anthropic API, decoding SSE events
//! and accumulating partial content into a complete LLMResponse.
use crate::llm::provider::LLMError;
use crate::llm::provider::{LLMStreamEvent, Usage};
use crate::llm::providers::anthropic_types::{
AnthropicContentBlock, AnthropicStreamDelta, AnthropicStreamEvent,
};
use crate::llm::providers::error_handling::format_network_error;
use crate::llm::providers::shared;
use async_stream::try_stream;
use futures::StreamExt;
use serde_json::{Map, Value};
use std::collections::BTreeMap;
use super::response_parser::parse_finish_reason;
enum ReasoningBlockState {
Thinking {
thinking: String,
signature: Option<String>,
},
Redacted {
data: String,
},
}
pub fn create_stream(
response: reqwest::Response,
model: String,
request_id: Option<String>,
organization_id: Option<String>,
) -> crate::llm::provider::LLMStream {
let stream = try_stream! {
let mut body_stream = response.bytes_stream();
let mut buffer = String::new();
let mut aggregator = shared::StreamAggregator::new(model);
let mut reasoning_blocks = BTreeMap::new();
let mut finalized_reasoning_details = Vec::new();
while let Some(chunk_result) = body_stream.next().await {
let chunk = chunk_result.map_err(|err| {
format_network_error("Anthropic", &anyhow::Error::new(err))
})?;
buffer.push_str(&String::from_utf8_lossy(&chunk));
while let Some((split_idx, delimiter_len)) = shared::find_sse_boundary(&buffer) {
let event_text = buffer[..split_idx].to_string();
buffer.drain(..split_idx + delimiter_len);
if let Some(data_payload) = shared::extract_data_payload(&event_text) {
let trimmed_payload = data_payload.trim();
if trimmed_payload.is_empty() {
continue;
}
let event: AnthropicStreamEvent = serde_json::from_str(trimmed_payload).map_err(|err| {
LLMError::Provider {
message: format!("Failed to parse stream event: {}", err),
metadata: None,
}
})?;
match event {
AnthropicStreamEvent::MessageStart { message } => {
aggregator.set_usage(Usage {
prompt_tokens: message.usage.input_tokens,
completion_tokens: 0,
total_tokens: message.usage.input_tokens,
cached_prompt_tokens: message.usage.cache_read_input_tokens,
cache_creation_tokens: message.usage.cache_creation_input_tokens,
cache_read_tokens: message.usage.cache_read_input_tokens,
});
}
AnthropicStreamEvent::ContentBlockStart {
index,
content_block:
AnthropicContentBlock::Thinking {
thinking,
signature,
..
},
} => {
reasoning_blocks.insert(index, ReasoningBlockState::Thinking {
thinking,
signature,
});
}
AnthropicStreamEvent::ContentBlockStart {
content_block: AnthropicContentBlock::Compaction { content, .. },
..
} => {
aggregator.compaction = Some(content);
}
AnthropicStreamEvent::ContentBlockStart {
index,
content_block: AnthropicContentBlock::ToolUse(tool_use),
} => {
if aggregator.tool_builders.len() <= index {
aggregator.tool_builders.resize_with(index + 1, shared::ToolCallBuilder::default);
}
let mut delta = Map::new();
delta.insert("id".to_string(), Value::String(tool_use.id));
let mut func = Map::new();
func.insert("name".to_string(), Value::String(tool_use.name));
delta.insert("function".to_string(), Value::Object(func));
aggregator.tool_builders[index].apply_delta(&Value::Object(delta));
}
AnthropicStreamEvent::ContentBlockDelta { index, delta } => {
match delta {
AnthropicStreamDelta::TextDelta { text } => {
for event in aggregator.handle_content(&text) {
yield event;
}
}
AnthropicStreamDelta::ThinkingDelta { thinking } => {
match reasoning_blocks.entry(index) {
std::collections::btree_map::Entry::Occupied(mut entry) => {
if let ReasoningBlockState::Thinking { thinking: accumulated, .. } = entry.get_mut() {
accumulated.push_str(&thinking);
}
}
std::collections::btree_map::Entry::Vacant(entry) => {
entry.insert(ReasoningBlockState::Thinking {
thinking: thinking.clone(),
signature: None,
});
}
}
if let Some(delta) = aggregator.handle_reasoning(&thinking) {
yield LLMStreamEvent::Reasoning { delta };
}
}
AnthropicStreamDelta::SignatureDelta { signature } => {
match reasoning_blocks.entry(index) {
std::collections::btree_map::Entry::Occupied(mut entry) => {
if let ReasoningBlockState::Thinking { signature: current, .. } = entry.get_mut() {
*current = Some(signature.clone());
}
}
std::collections::btree_map::Entry::Vacant(entry) => {
entry.insert(ReasoningBlockState::Thinking {
thinking: String::new(),
signature: Some(signature.clone()),
});
}
}
yield LLMStreamEvent::ReasoningSignature { signature };
}
AnthropicStreamDelta::CompactionDelta { content } => {
aggregator.compaction = Some(content);
}
AnthropicStreamDelta::InputJsonDelta { partial_json } => {
if aggregator.tool_builders.len() <= index {
aggregator.tool_builders.resize_with(index + 1, shared::ToolCallBuilder::default);
}
let mut delta_map = Map::new();
let mut func = Map::new();
func.insert("arguments".to_string(), Value::String(partial_json));
delta_map.insert("function".to_string(), Value::Object(func));
aggregator.tool_builders[index].apply_delta(&Value::Object(delta_map));
}
}
}
AnthropicStreamEvent::ContentBlockStop { index } => {
if let Some(reasoning_block) = reasoning_blocks.remove(&index) {
let detail = match reasoning_block {
ReasoningBlockState::Thinking { thinking, signature } => {
let mut detail = serde_json::json!({
"type": "thinking",
"thinking": thinking,
});
if let Some(signature) = signature
&& let Some(obj) = detail.as_object_mut()
{
obj.insert(
"signature".to_string(),
Value::String(signature),
);
}
detail.to_string()
}
ReasoningBlockState::Redacted { data } => serde_json::json!({
"type": "redacted_thinking",
"data": data,
})
.to_string(),
};
finalized_reasoning_details.push(detail);
}
}
AnthropicStreamEvent::MessageDelta { delta, usage } => {
if let Some(u) = usage
&& let Some(mut current_usage) = aggregator.usage
{
current_usage.completion_tokens = u.output_tokens;
current_usage.total_tokens = u.input_tokens + u.output_tokens;
aggregator.usage = Some(current_usage);
}
if let Some(reason) = delta.stop_reason {
aggregator.set_finish_reason(parse_finish_reason(&reason));
}
}
AnthropicStreamEvent::Error { error } => {
Err(LLMError::Provider {
message: error.message,
metadata: None,
})?
}
_ => {}
}
}
}
}
for (_, reasoning_block) in reasoning_blocks {
let detail = match reasoning_block {
ReasoningBlockState::Thinking { thinking, signature } => {
let mut detail = serde_json::json!({
"type": "thinking",
"thinking": thinking,
});
if let Some(signature) = signature
&& let Some(obj) = detail.as_object_mut()
{
obj.insert("signature".to_string(), Value::String(signature));
}
detail.to_string()
}
ReasoningBlockState::Redacted { data } => serde_json::json!({
"type": "redacted_thinking",
"data": data,
})
.to_string(),
};
finalized_reasoning_details.push(detail);
}
let mut response = aggregator.finalize();
if !finalized_reasoning_details.is_empty() {
response.reasoning_details = Some(finalized_reasoning_details);
}
response.request_id = request_id.clone();
response.organization_id = organization_id.clone();
yield LLMStreamEvent::Completed { response: Box::new(response) };
};
Box::pin(stream)
}