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use serde_json::Value;
use super::SSETransformer;
use crate::core::providers::unified_provider::ProviderError;
use crate::core::types::responses::{ChatChunk, ChatDelta, ChatStreamChoice, FinishReason, Usage};
/// Cohere SSE Transformer
///
/// Handles Cohere's streaming format with v1/v2 API version support.
#[derive(Debug, Clone)]
pub struct CohereTransformer {
model: String,
response_id: String,
/// true = v2, false = v1
use_v2: bool,
}
impl CohereTransformer {
pub fn new(model: impl Into<String>, use_v2: bool) -> Self {
Self {
model: model.into(),
response_id: format!("chatcmpl-{}", uuid::Uuid::new_v4()),
use_v2,
}
}
fn parse_cohere_finish_reason(reason: &str) -> FinishReason {
match reason.to_lowercase().as_str() {
"stop" | "complete" | "end_turn" => FinishReason::Stop,
"length" | "max_tokens" => FinishReason::Length,
"tool_calls" | "tool_use" => FinishReason::ToolCalls,
"content_filter" => FinishReason::ContentFilter,
_ => FinishReason::Stop,
}
}
}
impl SSETransformer for CohereTransformer {
fn provider_name(&self) -> &'static str {
"cohere"
}
fn transform_chunk(&self, data: &str) -> Result<Option<ChatChunk>, ProviderError> {
let json: Value = serde_json::from_str(data).map_err(|e| {
ProviderError::response_parsing("cohere", format!("Failed to parse Cohere SSE: {}", e))
})?;
let event_type = json
.get("type")
.or_else(|| json.get("event"))
.and_then(|v| v.as_str())
.unwrap_or("");
let created = chrono::Utc::now().timestamp();
if self.use_v2 {
match event_type {
"content-delta" => {
let text = json
.get("delta")
.and_then(|d| d.get("message"))
.and_then(|m| m.get("content"))
.and_then(|c| {
c.get("text")
.and_then(|t| t.as_str())
.or_else(|| c.as_str())
})
.unwrap_or("");
if text.is_empty() {
return Ok(None);
}
Ok(Some(ChatChunk {
id: self.response_id.clone(),
object: "chat.completion.chunk".to_string(),
created,
model: self.model.clone(),
choices: vec![ChatStreamChoice {
index: 0,
delta: ChatDelta {
role: None,
content: Some(text.to_string()),
thinking: None,
tool_calls: None,
function_call: None,
audio: None,
},
finish_reason: None,
logprobs: None,
}],
usage: None,
system_fingerprint: None,
}))
}
"message-end" => {
let data_field = json.get("data").or(json.get("delta"));
let finish_reason = data_field
.and_then(|d| d.get("delta"))
.and_then(|d| d.get("finish_reason"))
.and_then(|f| f.as_str())
.unwrap_or("stop");
let usage = data_field
.and_then(|d| d.get("delta"))
.and_then(|d| d.get("usage"))
.and_then(|u| u.get("tokens"))
.map(|tokens| {
let prompt = tokens
.get("input_tokens")
.and_then(|v| v.as_u64())
.unwrap_or(0) as u32;
let completion = tokens
.get("output_tokens")
.and_then(|v| v.as_u64())
.unwrap_or(0) as u32;
Usage {
prompt_tokens: prompt,
completion_tokens: completion,
total_tokens: prompt + completion,
prompt_tokens_details: None,
completion_tokens_details: None,
thinking_usage: None,
}
});
Ok(Some(ChatChunk {
id: self.response_id.clone(),
object: "chat.completion.chunk".to_string(),
created,
model: self.model.clone(),
choices: vec![ChatStreamChoice {
index: 0,
delta: ChatDelta {
role: None,
content: None,
thinking: None,
tool_calls: None,
function_call: None,
audio: None,
},
finish_reason: Some(Self::parse_cohere_finish_reason(finish_reason)),
logprobs: None,
}],
usage,
system_fingerprint: None,
}))
}
// message-start, content-start, content-end, tool-call-*, citation-* - skip
_ => Ok(None),
}
} else {
// v1 format
match event_type {
"text-generation" => {
let text = json.get("text").and_then(|t| t.as_str()).unwrap_or("");
Ok(Some(ChatChunk {
id: self.response_id.clone(),
object: "chat.completion.chunk".to_string(),
created,
model: self.model.clone(),
choices: vec![ChatStreamChoice {
index: 0,
delta: ChatDelta {
role: None,
content: Some(text.to_string()),
thinking: None,
tool_calls: None,
function_call: None,
audio: None,
},
finish_reason: None,
logprobs: None,
}],
usage: None,
system_fingerprint: None,
}))
}
"stream-end" => {
let finish_reason = json
.get("finish_reason")
.and_then(|f| f.as_str())
.unwrap_or("stop");
Ok(Some(ChatChunk {
id: self.response_id.clone(),
object: "chat.completion.chunk".to_string(),
created,
model: self.model.clone(),
choices: vec![ChatStreamChoice {
index: 0,
delta: ChatDelta {
role: None,
content: None,
thinking: None,
tool_calls: None,
function_call: None,
audio: None,
},
finish_reason: Some(Self::parse_cohere_finish_reason(finish_reason)),
logprobs: None,
}],
usage: None,
system_fingerprint: None,
}))
}
// stream-start, citation-generation, tool-calls-generation - skip
_ => Ok(None),
}
}
}
}