use crate::error::AppError;
use crate::gcp::vertex::client::VertexClient;
use crate::gcp::vertex::config::ResolvedAuth;
use crate::llm::{ContentPart, GenerateRequest, GenerateResponse, Role, StreamChunk, Usage};
use futures::Stream;
use serde::{Deserialize, Serialize};
use std::pin::Pin;
#[derive(Serialize)]
#[serde(rename_all = "camelCase")]
struct Request {
contents: Vec<Content>,
#[serde(skip_serializing_if = "Option::is_none")]
tools: Option<Vec<Tool>>,
#[serde(skip_serializing_if = "Option::is_none")]
system_instruction: Option<Content>,
#[serde(skip_serializing_if = "Option::is_none")]
generation_config: Option<GenConfig>,
}
#[derive(Serialize, Deserialize)]
struct Content {
role: String,
parts: Vec<Part>,
}
#[derive(Serialize, Deserialize)]
#[serde(untagged)]
enum Part {
Text {
text: String,
},
FunctionCall {
#[serde(rename = "functionCall")]
function_call: FnCall,
},
FunctionResponse {
#[serde(rename = "functionResponse")]
function_response: FnResponse,
},
}
#[derive(Serialize, Deserialize)]
struct FnCall {
name: String,
args: serde_json::Value,
}
#[derive(Serialize, Deserialize)]
struct FnResponse {
name: String,
response: serde_json::Value,
}
#[derive(Serialize)]
#[serde(rename_all = "camelCase")]
struct Tool {
function_declarations: Vec<FunctionDecl>,
}
#[derive(Serialize)]
struct FunctionDecl {
name: String,
description: String,
parameters: crate::llm::ParameterSchema,
}
#[derive(Serialize)]
#[serde(rename_all = "camelCase")]
struct GenConfig {
#[serde(skip_serializing_if = "Option::is_none")]
max_output_tokens: Option<u32>,
#[serde(skip_serializing_if = "Option::is_none")]
temperature: Option<f32>,
#[serde(skip_serializing_if = "Option::is_none")]
top_p: Option<f32>,
#[serde(skip_serializing_if = "Option::is_none")]
top_k: Option<u32>,
}
#[derive(Deserialize)]
#[serde(rename_all = "camelCase")]
struct Response {
candidates: Option<Vec<Candidate>>,
usage_metadata: Option<UsageMeta>,
}
#[derive(Deserialize)]
#[serde(rename_all = "camelCase")]
struct Candidate {
content: Option<Content>,
finish_reason: Option<String>,
}
#[derive(Deserialize)]
#[serde(rename_all = "camelCase")]
struct UsageMeta {
prompt_token_count: Option<u32>,
candidates_token_count: Option<u32>,
total_token_count: Option<u32>,
}
impl From<UsageMeta> for Usage {
fn from(u: UsageMeta) -> Self {
Usage {
input_tokens: u.prompt_token_count,
output_tokens: u.candidates_token_count,
total_tokens: u.total_token_count,
}
}
}
pub(crate) async fn generate(
client: &VertexClient,
request: &GenerateRequest,
) -> Result<GenerateResponse, AppError> {
let url = endpoint(&client.auth, &request.model, false);
let wire = to_wire(request);
let mut req = client.http.post(&url).json(&wire);
if let Some(auth) = client.auth_header().await? {
req = req.header("Authorization", auth);
}
let resp = client.send(req).await?;
let wire: Response = resp
.json()
.await
.map_err(|e| AppError::dependency_failed("vertex-ai", format!("Parse failed: {e}")))?;
Ok(from_wire(wire))
}
pub(crate) async fn stream_generate(
client: &VertexClient,
request: &GenerateRequest,
) -> Result<Pin<Box<dyn Stream<Item = Result<StreamChunk, AppError>> + Send>>, AppError> {
let base = endpoint(&client.auth, &request.model, true);
let sep = if base.contains('?') { '&' } else { '?' };
let url = format!("{base}{sep}alt=sse");
let wire = to_wire(request);
let mut req = client.http.post(&url).json(&wire);
if let Some(auth) = client.auth_header().await? {
req = req.header("Authorization", auth);
}
let resp = client.send(req).await?;
Ok(parse_sse(resp))
}
fn endpoint(auth: &ResolvedAuth, model: &str, stream: bool) -> String {
let method = if stream {
"streamGenerateContent"
} else {
"generateContent"
};
match auth {
ResolvedAuth::ApiKey { api_key } => format!(
"https://generativelanguage.googleapis.com/v1beta/models/{model}:{method}?key={api_key}"
),
ResolvedAuth::ServiceAccount {
project_id, region, ..
} => {
let host = if region == "global" {
"aiplatform.googleapis.com".to_string()
} else {
format!("{region}-aiplatform.googleapis.com")
};
format!(
"https://{host}/v1/projects/{project_id}/locations/{region}/publishers/google/models/{model}:{method}"
)
}
}
}
fn to_wire(req: &GenerateRequest) -> Request {
let contents = req
.messages
.iter()
.map(|m| Content {
role: match m.role {
Role::User => "user".into(),
Role::Assistant => "model".into(),
},
parts: m
.content
.iter()
.map(|p| match p {
ContentPart::Text(text) => Part::Text { text: text.clone() },
ContentPart::ToolCall {
name, arguments, ..
} => Part::FunctionCall {
function_call: FnCall {
name: name.clone(),
args: arguments.clone(),
},
},
ContentPart::ToolResult { name, content, .. } => Part::FunctionResponse {
function_response: FnResponse {
name: name.clone(),
response: content.clone(),
},
},
})
.collect(),
})
.collect();
let system_instruction = req.system.as_ref().map(|s| Content {
role: "user".into(),
parts: vec![Part::Text { text: s.clone() }],
});
let generation_config = if req.max_tokens.is_some()
|| req.temperature.is_some()
|| req.top_p.is_some()
|| req.top_k.is_some()
{
Some(GenConfig {
max_output_tokens: req.max_tokens,
temperature: req.temperature,
top_p: req.top_p,
top_k: req.top_k,
})
} else {
None
};
let tools = if req.tools.is_empty() {
None
} else {
Some(vec![Tool {
function_declarations: req
.tools
.iter()
.map(|t| FunctionDecl {
name: t.name.clone(),
description: t.description.clone(),
parameters: t.parameters.clone(),
})
.collect(),
}])
};
Request {
contents,
system_instruction,
generation_config,
tools,
}
}
fn from_wire(resp: Response) -> GenerateResponse {
let mut content = Vec::new();
let mut stop_reason = None;
if let Some(candidates) = &resp.candidates
&& let Some(candidate) = candidates.first()
{
stop_reason = candidate.finish_reason.clone();
if let Some(c) = &candidate.content {
for part in &c.parts {
match part {
Part::Text { text } => {
content.push(ContentPart::Text(text.clone()));
}
Part::FunctionCall { function_call } => {
content.push(ContentPart::ToolCall {
id: nanoid::nanoid!(),
name: function_call.name.clone(),
arguments: function_call.args.clone(),
});
}
Part::FunctionResponse { .. } => {}
}
}
}
}
GenerateResponse {
content,
stop_reason,
usage: resp.usage_metadata.map(Usage::from),
}
}
fn parse_sse(
resp: reqwest::Response,
) -> Pin<Box<dyn Stream<Item = Result<StreamChunk, AppError>> + Send>> {
let stream = async_stream::stream! {
let mut byte_stream = futures::StreamExt::fuse(resp.bytes_stream());
let mut buffer: Vec<u8> = Vec::new();
let mut latest_usage: Option<Usage> = None;
let mut done_sent = false;
while let Some(chunk) = futures::StreamExt::next(&mut byte_stream).await {
let bytes = chunk.map_err(|e| {
AppError::dependency_failed("vertex-ai", format!("Stream read error: {e}"))
})?;
buffer.extend_from_slice(&bytes);
while let Some((pos, sep_len)) = find_frame_boundary(&buffer) {
let frame = buffer.drain(..pos + sep_len).collect::<Vec<u8>>();
let Ok(event) = std::str::from_utf8(&frame[..frame.len() - sep_len]) else {
tracing::debug!("Gemini SSE frame was not valid UTF-8");
continue;
};
let Some(data) = event.strip_prefix("data: ") else {
continue;
};
if data.trim() == "[DONE]" {
if !done_sent {
yield Ok(StreamChunk::Done {
finish_reason: "STOP".into(),
usage: latest_usage.take(),
});
done_sent = true;
}
continue;
}
match serde_json::from_str::<Response>(data) {
Ok(response) => {
if let Some(meta) = response.usage_metadata {
latest_usage = Some(meta.into());
}
let Some(candidates) = response.candidates else { continue };
for candidate in candidates {
if let Some(content) = candidate.content {
for part in content.parts {
match part {
Part::Text { text } => {
yield Ok(StreamChunk::Text(text));
}
Part::FunctionCall { function_call } => {
yield Ok(StreamChunk::ToolCall {
id: nanoid::nanoid!(),
name: function_call.name,
arguments: function_call.args,
});
}
Part::FunctionResponse { .. } => {}
}
}
}
if !done_sent
&& let Some(reason) = candidate.finish_reason
&& (reason == "STOP" || reason == "MAX_TOKENS")
{
yield Ok(StreamChunk::Done {
finish_reason: reason,
usage: latest_usage.take(),
});
done_sent = true;
}
}
}
Err(e) => {
tracing::warn!("Failed to parse Gemini SSE chunk: {e}, data: {data}");
}
}
}
}
};
Box::pin(stream)
}
fn find_frame_boundary(buf: &[u8]) -> Option<(usize, usize)> {
let crlf = buf.windows(4).position(|w| w == b"\r\n\r\n");
let lf = buf.windows(2).position(|w| w == b"\n\n");
match (crlf, lf) {
(Some(c), Some(l)) => {
if c <= l {
Some((c, 4))
} else {
Some((l, 2))
}
}
(Some(c), None) => Some((c, 4)),
(None, Some(l)) => Some((l, 2)),
(None, None) => None,
}
}