text-translate/src/llm.rs
flemming-it 027793bb02
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Signed-off-by: flemming-it <sf@flemming.it>
2026-08-20 22:30:30 +02:00

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Rust

//! Multi-API chat client: Ollama (default), OpenAI, Anthropic.
//!
//! The wire format is selected via the optional `api` input:
//!
//! - `ollama` (default) — Ollama `/api/chat`; unchanged v0.1.0
//! behavior including the best-effort model-digest probe.
//! - `openai` — OpenAI Chat Completions wire format
//! (`/v1/chat/completions`), the de-facto standard implemented
//! by vLLM and most self-hosted inference servers. Bearer auth.
//! - `anthropic` — Anthropic Messages API (`/v1/messages`),
//! `x-api-key` + `anthropic-version` headers, top-level
//! `system` field, mandatory `max_tokens`.
//!
//! No streaming, no tool calls — one prompt in, one completion out.
//!
//! All HTTP I/O lives behind a `LlmClient` trait so unit tests can
//! exercise request building, response parsing, and the digest
//! probe on the host without making real network calls.
use serde::Serialize;
/// Anthropic's Messages API requires `max_tokens`. This default is
/// large enough for document-processing completions while staying
/// well below every current model's output cap.
const ANTHROPIC_DEFAULT_MAX_TOKENS: u32 = 4096;
/// Pinned Messages API version header. Anthropic keeps old
/// versions working; bump deliberately, never implicitly.
const ANTHROPIC_VERSION: &str = "2023-06-01";
#[allow(dead_code)]
#[derive(Debug, thiserror::Error)]
pub enum LlmError {
#[error("missing required input '{0}'")]
MissingInput(&'static str),
#[error("unsupported api '{0}' (expected: ollama, openai, vllm, anthropic)")]
UnsupportedApi(String),
#[error("http error: {0}")]
Http(String),
#[error("non-success status: {0}")]
Status(u16),
#[error("response body could not be parsed as the expected schema: {0}")]
Decode(String),
}
/// Which wire format to speak. Selected by the `api` input.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Api {
Ollama,
Openai,
/// vLLM speaks the OpenAI wire format verbatim; it is a
/// separate variant ONLY so operators can write what they
/// mean (`api: vllm`) and get vLLM-specific error hints —
/// "openai" would read as the cloud company, not a
/// self-hosted server. Same rationale as the hub's
/// SystemLlmProvider vocabulary.
Vllm,
Anthropic,
}
impl Api {
/// Parse the `api` input. Empty string means the input was not
/// provided and falls back to Ollama (v0.1.0 behavior).
pub fn parse(raw: &str) -> Result<Self, LlmError> {
match raw.trim().to_ascii_lowercase().as_str() {
"" | "ollama" => Ok(Api::Ollama),
"openai" => Ok(Api::Openai),
"vllm" => Ok(Api::Vllm),
"anthropic" => Ok(Api::Anthropic),
other => Err(LlmError::UnsupportedApi(other.to_string())),
}
}
}
pub trait LlmClient {
/// POST `body` as JSON to `url` with the given extra headers.
/// `Content-Type: application/json` is implied. Header VALUES
/// may carry credentials — implementations must never log them.
fn post_json(
&self,
url: &str,
body: &str,
headers: &[(&'static str, String)],
) -> Result<String, LlmError>;
}
#[derive(Debug, Clone)]
pub struct ChatParams<'a> {
pub api: Api,
pub endpoint: &'a str,
pub model: &'a str,
pub api_key: &'a str,
pub system_prompt: &'a str,
pub prompt: &'a str,
}
/// Auth/protocol headers for the selected API. The api_key is only
/// ever placed into a header value here; it must not appear in any
/// error, output, or log line.
pub fn build_headers(p: &ChatParams) -> Vec<(&'static str, String)> {
let mut headers = Vec::with_capacity(2);
match p.api {
Api::Ollama | Api::Openai | Api::Vllm => {
if !p.api_key.is_empty() {
headers.push(("Authorization", format!("Bearer {}", p.api_key)));
}
}
Api::Anthropic => {
if !p.api_key.is_empty() {
headers.push(("x-api-key", p.api_key.to_string()));
}
headers.push(("anthropic-version", ANTHROPIC_VERSION.to_string()));
}
}
headers
}
#[derive(Serialize)]
struct ChatMessage<'a> {
role: &'a str,
content: &'a str,
}
#[derive(Serialize)]
struct OllamaRequest<'a> {
model: &'a str,
messages: Vec<ChatMessage<'a>>,
stream: bool,
}
#[derive(Serialize)]
struct OpenAiRequest<'a> {
model: &'a str,
messages: Vec<ChatMessage<'a>>,
stream: bool,
}
#[derive(Serialize)]
struct AnthropicRequest<'a> {
model: &'a str,
max_tokens: u32,
#[serde(skip_serializing_if = "Option::is_none")]
system: Option<&'a str>,
messages: Vec<ChatMessage<'a>>,
}
/// System-then-user message list shared by the Ollama and OpenAI
/// wire formats. The system message is omitted when empty so a
/// deployment can use the model's built-in system prompt.
fn build_messages<'a>(p: &ChatParams<'a>) -> Vec<ChatMessage<'a>> {
let mut messages = Vec::with_capacity(2);
if !p.system_prompt.is_empty() {
messages.push(ChatMessage {
role: "system",
content: p.system_prompt,
});
}
messages.push(ChatMessage {
role: "user",
content: p.prompt,
});
messages
}
/// Build the request body for an Ollama `/api/chat` invocation.
pub fn build_ollama_body(p: &ChatParams) -> String {
let req = OllamaRequest {
model: p.model,
messages: build_messages(p),
stream: false,
};
serde_json::to_string(&req).unwrap_or_else(|_| String::from("{}"))
}
/// Build the request body for an OpenAI-compatible
/// `/v1/chat/completions` invocation (OpenAI, vLLM, most
/// self-hosted inference servers).
pub fn build_openai_body(p: &ChatParams) -> String {
let req = OpenAiRequest {
model: p.model,
messages: build_messages(p),
stream: false,
};
serde_json::to_string(&req).unwrap_or_else(|_| String::from("{}"))
}
/// Build the request body for an Anthropic `/v1/messages`
/// invocation. `system` is a top-level field (not a message);
/// `max_tokens` is mandatory in the Messages API.
pub fn build_anthropic_body(p: &ChatParams) -> String {
let req = AnthropicRequest {
model: p.model,
max_tokens: ANTHROPIC_DEFAULT_MAX_TOKENS,
system: if p.system_prompt.is_empty() {
None
} else {
Some(p.system_prompt)
},
messages: vec![ChatMessage {
role: "user",
content: p.prompt,
}],
};
serde_json::to_string(&req).unwrap_or_else(|_| String::from("{}"))
}
/// Extract the assistant's message text from an Ollama
/// /api/chat response.
pub fn extract_ollama_content(body: &str) -> Result<String, LlmError> {
let v: serde_json::Value =
serde_json::from_str(body).map_err(|e| LlmError::Decode(e.to_string()))?;
v.get("message")
.and_then(|m| m.get("content"))
.and_then(|c| c.as_str())
.map(|s| s.to_string())
.ok_or_else(|| LlmError::Decode("missing message.content".into()))
}
/// Extract the assistant text from an OpenAI Chat Completions
/// response: `choices[0].message.content`.
pub fn extract_openai_content(body: &str) -> Result<String, LlmError> {
let v: serde_json::Value =
serde_json::from_str(body).map_err(|e| LlmError::Decode(e.to_string()))?;
v.get("choices")
.and_then(|c| c.get(0))
.and_then(|c| c.get("message"))
.and_then(|m| m.get("content"))
.and_then(|c| c.as_str())
.map(|s| s.to_string())
.ok_or_else(|| LlmError::Decode("missing choices[0].message.content".into()))
}
/// Extract the assistant text from an Anthropic Messages
/// response: `content[0].text`.
pub fn extract_anthropic_content(body: &str) -> Result<String, LlmError> {
let v: serde_json::Value =
serde_json::from_str(body).map_err(|e| LlmError::Decode(e.to_string()))?;
v.get("content")
.and_then(|c| c.get(0))
.and_then(|c| c.get("text"))
.and_then(|t| t.as_str())
.map(|s| s.to_string())
.ok_or_else(|| LlmError::Decode("missing content[0].text".into()))
}
#[derive(Debug, Clone)]
pub struct ChatWithIdentity {
pub response: String,
pub model_digest: Option<String>,
}
/// Run one chat call in the selected wire format AND, for Ollama,
/// probe the model digest. The probe is best-effort — non-Ollama
/// APIs expose no digest endpoint, so `model_digest = None` there
/// (documented empty, never invented); transient probe failures on
/// Ollama also yield `None` rather than failing the whole call.
pub fn chat_with_identity<C: LlmClient>(
client: &C,
p: &ChatParams,
) -> Result<ChatWithIdentity, LlmError> {
if p.endpoint.is_empty() {
return Err(LlmError::MissingInput("endpoint"));
}
if p.model.is_empty() {
return Err(LlmError::MissingInput("model"));
}
if p.prompt.is_empty() {
return Err(LlmError::MissingInput("prompt"));
}
let body = match p.api {
Api::Ollama => build_ollama_body(p),
Api::Openai | Api::Vllm => build_openai_body(p),
Api::Anthropic => build_anthropic_body(p),
};
let headers = build_headers(p);
let response_body = client.post_json(p.endpoint, &body, &headers)?;
let response = match p.api {
Api::Ollama => extract_ollama_content(&response_body)?,
Api::Openai | Api::Vllm => extract_openai_content(&response_body)?,
Api::Anthropic => extract_anthropic_content(&response_body)?,
};
let model_digest = match p.api {
Api::Ollama => probe_model_digest(client, p),
Api::Openai | Api::Vllm | Api::Anthropic => None,
};
Ok(ChatWithIdentity {
response,
model_digest,
})
}
fn probe_model_digest<C: LlmClient>(client: &C, p: &ChatParams) -> Option<String> {
let show_url = derive_show_url(p.endpoint)?;
let body = serde_json::to_string(&serde_json::json!({ "name": p.model })).ok()?;
let headers = build_headers(p);
let response = client.post_json(&show_url, &body, &headers).ok()?;
extract_show_digest(&response)
}
pub fn derive_show_url(chat_endpoint: &str) -> Option<String> {
if chat_endpoint.ends_with("/api/chat") {
let head_len = chat_endpoint.len() - "/api/chat".len();
let mut url = String::with_capacity(head_len + "/api/show".len());
url.push_str(&chat_endpoint[..head_len]);
url.push_str("/api/show");
Some(url)
} else {
None
}
}
pub fn extract_show_digest(body: &str) -> Option<String> {
let v: serde_json::Value = serde_json::from_str(body).ok()?;
let candidates = [
v.get("digest"),
v.get("details").and_then(|d| d.get("digest")),
v.get("model_info").and_then(|d| d.get("digest")),
];
for cand in candidates {
if let Some(s) = cand.and_then(|v| v.as_str()) {
if !s.is_empty() {
return Some(s.to_string());
}
}
}
None
}
#[cfg(test)]
mod tests {
#![allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
use super::*;
use std::cell::RefCell;
/// (url, body, headers) of one recorded call.
type RecordedCall = (String, String, Vec<(String, String)>);
struct MockClient {
responses: RefCell<Vec<Result<String, LlmError>>>,
/// Every call, in call order.
calls: RefCell<Vec<RecordedCall>>,
}
impl MockClient {
fn new(responses: Vec<Result<String, LlmError>>) -> Self {
Self {
responses: RefCell::new(responses),
calls: RefCell::new(Vec::new()),
}
}
}
impl LlmClient for MockClient {
fn post_json(
&self,
url: &str,
body: &str,
headers: &[(&'static str, String)],
) -> Result<String, LlmError> {
self.calls.borrow_mut().push((
url.to_string(),
body.to_string(),
headers
.iter()
.map(|(k, v)| (k.to_string(), v.clone()))
.collect(),
));
self.responses
.borrow_mut()
.pop()
.unwrap_or(Err(LlmError::Http("no more mock responses".into())))
}
}
fn params<'a>(api: Api) -> ChatParams<'a> {
ChatParams {
api,
endpoint: "http://x/api/chat",
model: "qwen",
api_key: "",
system_prompt: "",
prompt: "hello",
}
}
// ---------------- api input parsing ----------------
#[test]
fn api_parse_defaults_to_ollama() {
assert_eq!(Api::parse("").unwrap(), Api::Ollama);
assert_eq!(Api::parse("ollama").unwrap(), Api::Ollama);
assert_eq!(Api::parse(" OpenAI ").unwrap(), Api::Openai);
assert_eq!(Api::parse("anthropic").unwrap(), Api::Anthropic);
}
#[test]
fn api_parse_rejects_unknown() {
assert!(matches!(
Api::parse("gemini"),
Err(LlmError::UnsupportedApi(_))
));
}
// ---------------- Ollama wire format (regression) ----------------
#[test]
fn ollama_body_includes_system_when_provided() {
let p = ChatParams {
system_prompt: "be helpful",
..params(Api::Ollama)
};
let body = build_ollama_body(&p);
let v: serde_json::Value = serde_json::from_str(&body).unwrap();
let messages = v["messages"].as_array().unwrap();
assert_eq!(messages.len(), 2);
assert_eq!(messages[0]["role"], "system");
assert_eq!(messages[0]["content"], "be helpful");
assert_eq!(messages[1]["role"], "user");
assert_eq!(messages[1]["content"], "hello");
assert_eq!(v["stream"], false);
}
#[test]
fn ollama_body_omits_system_when_empty() {
let body = build_ollama_body(&params(Api::Ollama));
let v: serde_json::Value = serde_json::from_str(&body).unwrap();
let messages = v["messages"].as_array().unwrap();
assert_eq!(messages.len(), 1);
assert_eq!(messages[0]["role"], "user");
}
#[test]
fn extract_content_pulls_message_content() {
let body = r#"{"message":{"role":"assistant","content":"hi there"},"done":true}"#;
assert_eq!(extract_ollama_content(body).unwrap(), "hi there");
}
#[test]
fn extract_content_errors_on_missing_field() {
let body = r#"{"done":true}"#;
assert!(matches!(
extract_ollama_content(body),
Err(LlmError::Decode(_))
));
}
#[test]
fn ollama_bearer_header_only_with_key() {
assert!(build_headers(&params(Api::Ollama)).is_empty());
let p = ChatParams {
api_key: "sk-test",
..params(Api::Ollama)
};
assert_eq!(
build_headers(&p),
vec![("Authorization", "Bearer sk-test".to_string())]
);
}
// ---------------- OpenAI wire format ----------------
#[test]
fn openai_body_matches_chat_completions_format() {
let p = ChatParams {
api: Api::Openai,
endpoint: "http://vllm:8000/v1/chat/completions",
model: "meta-llama/Llama-3.1-8B-Instruct",
api_key: "sk-x",
system_prompt: "be terse",
prompt: "hello",
};
let body = build_openai_body(&p);
let v: serde_json::Value = serde_json::from_str(&body).unwrap();
assert_eq!(v["model"], "meta-llama/Llama-3.1-8B-Instruct");
assert_eq!(v["stream"], false);
let messages = v["messages"].as_array().unwrap();
assert_eq!(messages.len(), 2);
assert_eq!(messages[0]["role"], "system");
assert_eq!(messages[0]["content"], "be terse");
assert_eq!(messages[1]["role"], "user");
assert_eq!(messages[1]["content"], "hello");
// No Anthropic-only fields leak into the OpenAI body.
assert!(v.get("max_tokens").is_none());
assert!(v.get("system").is_none());
}
#[test]
fn openai_response_parses_fixture() {
// Shape as returned by OpenAI / vLLM /v1/chat/completions.
let body = r#"{
"id": "chatcmpl-123",
"object": "chat.completion",
"created": 1719000000,
"model": "meta-llama/Llama-3.1-8B-Instruct",
"choices": [{
"index": 0,
"message": {"role": "assistant", "content": "Hi from vLLM"},
"finish_reason": "stop"
}],
"usage": {"prompt_tokens": 9, "completion_tokens": 4, "total_tokens": 13}
}"#;
assert_eq!(extract_openai_content(body).unwrap(), "Hi from vLLM");
}
#[test]
fn openai_response_errors_on_missing_choices() {
assert!(matches!(
extract_openai_content(r#"{"object":"chat.completion","choices":[]}"#),
Err(LlmError::Decode(_))
));
assert!(matches!(
extract_openai_content(r#"{"error":{"message":"invalid key"}}"#),
Err(LlmError::Decode(_))
));
}
#[test]
fn openai_uses_bearer_auth() {
let p = ChatParams {
api_key: "sk-test",
..params(Api::Openai)
};
assert_eq!(
build_headers(&p),
vec![("Authorization", "Bearer sk-test".to_string())]
);
}
#[test]
fn openai_chat_returns_content_and_no_digest() {
let canned = r#"{"choices":[{"message":{"role":"assistant","content":"ok"}}]}"#;
let client = MockClient::new(vec![Ok(canned.to_string())]);
let p = ChatParams {
api: Api::Openai,
endpoint: "http://vllm:8000/v1/chat/completions",
model: "m",
api_key: "sk",
system_prompt: "",
prompt: "hi",
};
let result = chat_with_identity(&client, &p).unwrap();
assert_eq!(result.response, "ok");
// No digest API on OpenAI-compatible endpoints — documented
// empty, and exactly one HTTP call (no probe).
assert_eq!(result.model_digest, None);
assert_eq!(client.calls.borrow().len(), 1);
}
// ---------------- Anthropic wire format ----------------
#[test]
fn anthropic_body_matches_messages_format() {
let p = ChatParams {
api: Api::Anthropic,
endpoint: "https://api.anthropic.com/v1/messages",
model: "claude-fable-5",
api_key: "sk-ant",
system_prompt: "be terse",
prompt: "hello",
};
let body = build_anthropic_body(&p);
let v: serde_json::Value = serde_json::from_str(&body).unwrap();
assert_eq!(v["model"], "claude-fable-5");
// max_tokens is mandatory in the Messages API.
assert_eq!(v["max_tokens"], 4096);
// system is a top-level field, never a message.
assert_eq!(v["system"], "be terse");
let messages = v["messages"].as_array().unwrap();
assert_eq!(messages.len(), 1);
assert_eq!(messages[0]["role"], "user");
assert_eq!(messages[0]["content"], "hello");
// No OpenAI/Ollama-only fields leak in.
assert!(v.get("stream").is_none());
}
#[test]
fn anthropic_body_omits_system_when_empty() {
let body = build_anthropic_body(&params(Api::Anthropic));
let v: serde_json::Value = serde_json::from_str(&body).unwrap();
assert!(v.get("system").is_none());
assert_eq!(v["max_tokens"], 4096);
}
#[test]
fn anthropic_response_parses_fixture() {
// Shape as returned by the Anthropic Messages API.
let body = r#"{
"id": "msg_01XFDUDYJgAACzvnptvVoYEL",
"type": "message",
"role": "assistant",
"model": "claude-fable-5",
"content": [{"type": "text", "text": "Hi from Claude"}],
"stop_reason": "end_turn",
"usage": {"input_tokens": 10, "output_tokens": 5}
}"#;
assert_eq!(extract_anthropic_content(body).unwrap(), "Hi from Claude");
}
#[test]
fn anthropic_response_errors_on_missing_content() {
assert!(matches!(
extract_anthropic_content(r#"{"type":"message","content":[]}"#),
Err(LlmError::Decode(_))
));
assert!(matches!(
extract_anthropic_content(r#"{"type":"error","error":{"message":"x"}}"#),
Err(LlmError::Decode(_))
));
}
#[test]
fn anthropic_uses_x_api_key_and_version_headers() {
let p = ChatParams {
api_key: "sk-ant-test",
..params(Api::Anthropic)
};
let headers = build_headers(&p);
assert_eq!(
headers,
vec![
("x-api-key", "sk-ant-test".to_string()),
("anthropic-version", "2023-06-01".to_string()),
]
);
// Never Bearer auth on the Anthropic path.
assert!(headers.iter().all(|(k, _)| *k != "Authorization"));
}
#[test]
fn anthropic_chat_returns_content_and_no_digest() {
let canned = r#"{"content":[{"type":"text","text":"ok"}]}"#;
let client = MockClient::new(vec![Ok(canned.to_string())]);
let p = ChatParams {
api: Api::Anthropic,
endpoint: "https://api.anthropic.com/v1/messages",
model: "claude-fable-5",
api_key: "sk-ant",
system_prompt: "",
prompt: "hi",
};
let result = chat_with_identity(&client, &p).unwrap();
assert_eq!(result.response, "ok");
assert_eq!(result.model_digest, None);
assert_eq!(client.calls.borrow().len(), 1);
}
// ---------------- digest probe (Ollama only) ----------------
#[test]
fn derive_show_url_swaps_chat_suffix() {
assert_eq!(
derive_show_url("http://localhost:11434/api/chat").as_deref(),
Some("http://localhost:11434/api/show")
);
}
#[test]
fn derive_show_url_returns_none_for_non_ollama() {
assert!(derive_show_url("https://api.openai.com/v1/chat/completions").is_none());
}
#[test]
fn extract_show_digest_finds_top_level() {
let body = r#"{"digest":"sha256:abc"}"#;
assert_eq!(extract_show_digest(body).as_deref(), Some("sha256:abc"));
}
#[test]
fn extract_show_digest_falls_back_to_nested() {
let body = r#"{"details":{"digest":"sha256:nested"}}"#;
assert_eq!(extract_show_digest(body).as_deref(), Some("sha256:nested"));
}
#[test]
fn chat_with_identity_records_digest_when_show_responds() {
let canned_chat = r#"{"message":{"content":"the response"},"done":true}"#.to_string();
let canned_show = r#"{"digest":"sha256:deadbeef"}"#.to_string();
let client = MockClient::new(vec![Ok(canned_show), Ok(canned_chat)]);
let p = ChatParams {
endpoint: "http://localhost:11434/api/chat",
..params(Api::Ollama)
};
let result = chat_with_identity(&client, &p).unwrap();
assert_eq!(result.response, "the response");
assert_eq!(result.model_digest.as_deref(), Some("sha256:deadbeef"));
}
#[test]
fn chat_with_identity_swallows_show_failure() {
let canned_chat = r#"{"message":{"content":"ok"}}"#.to_string();
let client = MockClient::new(vec![Err(LlmError::Status(500)), Ok(canned_chat)]);
let p = ChatParams {
endpoint: "http://localhost:11434/api/chat",
..params(Api::Ollama)
};
let result = chat_with_identity(&client, &p).unwrap();
assert_eq!(result.response, "ok");
assert_eq!(result.model_digest, None);
}
#[test]
fn chat_with_identity_skips_probe_for_non_ollama_url() {
let canned_chat = r#"{"message":{"content":"ok"}}"#.to_string();
let client = MockClient::new(vec![Ok(canned_chat)]);
let p = ChatParams {
endpoint: "https://example.com/proxy/chat",
..params(Api::Ollama)
};
let result = chat_with_identity(&client, &p).unwrap();
assert_eq!(result.response, "ok");
assert_eq!(result.model_digest, None);
}
// ---------------- input guards ----------------
#[test]
fn empty_prompt_is_rejected() {
let client = MockClient::new(vec![]);
let p = ChatParams {
prompt: "",
..params(Api::Ollama)
};
assert!(matches!(
chat_with_identity(&client, &p),
Err(LlmError::MissingInput("prompt"))
));
}
/// Guard: `api: vllm` exists ONLY for operator clarity — the
/// request it emits (URL, body, headers) must stay identical to
/// `api: openai`. If the two ever diverge, that is a new wire
/// dialect and needs its own deliberate design, not drift.
#[test]
fn vllm_is_the_openai_wire_verbatim() {
assert_eq!(Api::parse("vllm").unwrap(), Api::Vllm);
let openai_reply = r#"{"choices":[{"message":{"role":"assistant","content":"x"}}]}"#;
let recorded: Vec<RecordedCall> = [Api::Vllm, Api::Openai]
.into_iter()
.map(|api| {
let client = MockClient::new(vec![Ok(openai_reply.to_string())]);
chat_with_identity(&client, &params(api)).unwrap();
client.calls.into_inner().pop().unwrap()
})
.collect();
assert_eq!(recorded[0], recorded[1], "vllm request drifted from openai");
}
}