443 lines
16 KiB
Rust
443 lines
16 KiB
Rust
// Items used only in later phases or tests.
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#![allow(dead_code)]
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use futures::{SinkExt, Stream, StreamExt};
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use reqwest::Client;
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use serde::Deserialize;
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use crate::core::types::{ConversationMessage, StreamEvent};
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use super::ModelProvider;
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/// Errors that can occur when constructing or using a [`ClaudeProvider`].
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#[derive(Debug, thiserror::Error)]
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pub enum ClaudeProviderError {
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/// The `ANTHROPIC_API_KEY` environment variable is not set.
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#[error("ANTHROPIC_API_KEY environment variable not set")]
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MissingApiKey,
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/// An HTTP-level error from the reqwest client.
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#[error("HTTP request failed: {0}")]
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Http(#[from] reqwest::Error),
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}
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/// [`ModelProvider`] implementation that streams responses from the Anthropic Messages API.
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///
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/// Calls `POST /v1/messages` with `"stream": true` and parses the resulting
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/// [Server-Sent Events][sse] stream into [`StreamEvent`]s.
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///
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/// # Authentication
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///
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/// Reads the API key from the `ANTHROPIC_API_KEY` environment variable.
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/// See the [Anthropic authentication docs][auth] for how to obtain a key.
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///
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/// # API version
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///
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/// Sends the `anthropic-version: 2023-06-01` header on every request, which is
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/// the stable baseline version required by the API. See the
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/// [versioning docs][versioning] for details on how Anthropic handles API versions.
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///
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/// [sse]: https://html.spec.whatwg.org/multipage/server-sent-events.html
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/// [auth]: https://docs.anthropic.com/en/api/getting-started#authentication
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/// [versioning]: https://docs.anthropic.com/en/api/versioning
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pub struct ClaudeProvider {
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api_key: String,
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client: Client,
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model: String,
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}
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impl ClaudeProvider {
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/// Create a `ClaudeProvider` reading `ANTHROPIC_API_KEY` from the environment.
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/// The caller must supply the model ID (e.g. `"claude-opus-4-6"`).
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///
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/// See the [models overview][models] for available model IDs.
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///
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/// [models]: https://docs.anthropic.com/en/docs/about-claude/models/overview
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pub fn from_env(model: impl Into<String>) -> Result<Self, ClaudeProviderError> {
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let api_key =
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std::env::var("ANTHROPIC_API_KEY").map_err(|_| ClaudeProviderError::MissingApiKey)?;
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Ok(Self {
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api_key,
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client: Client::new(),
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model: model.into(),
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})
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}
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}
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impl ModelProvider for ClaudeProvider {
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fn stream<'a>(
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&'a self,
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messages: &'a [ConversationMessage],
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) -> impl Stream<Item = StreamEvent> + Send + 'a {
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let (mut tx, rx) = futures::channel::mpsc::channel(32);
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let client = self.client.clone();
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let api_key = self.api_key.clone();
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let model = self.model.clone();
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let messages = messages.to_vec();
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tokio::spawn(async move {
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run_stream(client, api_key, model, messages, &mut tx).await;
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});
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rx
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}
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}
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/// POST to `/v1/messages` with `stream: true`, then parse the SSE response into
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/// [`StreamEvent`]s and forward them to `tx`.
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///
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/// # Request shape
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///
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/// ```json
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/// {
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/// "model": "<model-id>",
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/// "max_tokens": 8192,
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/// "stream": true,
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/// "messages": [{ "role": "user"|"assistant", "content": "<text>" }, …]
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/// }
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/// ```
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///
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/// See the [Messages API reference][messages-api] for the full schema.
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///
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/// # SSE stream lifecycle
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///
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/// With streaming enabled the API sends a sequence of
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/// [Server-Sent Events][sse] separated by blank lines (`\n\n`). Each event
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/// has an `event:` line naming its type and a `data:` line containing a JSON
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/// object. The full event sequence for a successful turn is:
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///
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/// ```text
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/// event: message_start → InputTokens(n)
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/// event: content_block_start → (ignored — signals a new content block)
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/// event: ping → (ignored — keepalive)
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/// event: content_block_delta → TextDelta(chunk) (repeated)
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/// event: content_block_stop → (ignored — signals end of content block)
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/// event: message_delta → OutputTokens(n)
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/// event: message_stop → Done
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/// ```
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///
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/// We stop reading as soon as `Done` is emitted; any bytes arriving after
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/// `message_stop` are discarded.
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///
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/// See the [streaming reference][streaming] for the authoritative description
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/// of each event type and its JSON payload.
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///
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/// [messages-api]: https://docs.anthropic.com/en/api/messages
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/// [streaming]: https://docs.anthropic.com/en/api/messages-streaming
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/// [sse]: https://html.spec.whatwg.org/multipage/server-sent-events.html
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async fn run_stream(
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client: Client,
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api_key: String,
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model: String,
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messages: Vec<ConversationMessage>,
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tx: &mut futures::channel::mpsc::Sender<StreamEvent>,
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) {
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let body = serde_json::json!({
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"model": model,
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"max_tokens": 8192,
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"stream": true,
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"messages": messages,
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});
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let response = match client
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.post("https://api.anthropic.com/v1/messages")
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.header("x-api-key", &api_key)
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.header("anthropic-version", "2023-06-01")
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.header("content-type", "application/json")
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.json(&body)
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.send()
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.await
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{
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Ok(r) => r,
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Err(e) => {
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let _ = tx.send(StreamEvent::Error(e.to_string())).await;
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return;
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}
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};
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if !response.status().is_success() {
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let status = response.status();
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let body_text = response.text().await.unwrap_or_default();
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let _ = tx
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.send(StreamEvent::Error(format!("HTTP {status}: {body_text}")))
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.await;
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return;
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}
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let mut stream = response.bytes_stream();
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let mut buffer: Vec<u8> = Vec::new();
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while let Some(chunk) = stream.next().await {
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match chunk {
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Err(e) => {
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let _ = tx.send(StreamEvent::Error(e.to_string())).await;
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return;
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}
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Ok(bytes) => {
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buffer.extend_from_slice(&bytes);
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// Drain complete SSE events (delimited by blank lines).
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loop {
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match find_double_newline(&buffer) {
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None => break,
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Some(pos) => {
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let event_bytes: Vec<u8> = buffer.drain(..pos + 2).collect();
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let event_str = String::from_utf8_lossy(&event_bytes);
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if let Some(event) = parse_sse_event(&event_str) {
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let is_done = matches!(event, StreamEvent::Done);
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let _ = tx.send(event).await;
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if is_done {
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return;
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}
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}
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}
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}
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}
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}
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}
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}
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let _ = tx.send(StreamEvent::Done).await;
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}
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/// Return the byte offset of the first `\n\n` in `buf`, or `None`.
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///
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/// SSE uses a blank line (two consecutive newlines) as the event boundary.
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/// See [§9.2.6 of the SSE spec][sse-dispatch].
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///
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/// [sse-dispatch]: https://html.spec.whatwg.org/multipage/server-sent-events.html#event-stream-interpretation
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fn find_double_newline(buf: &[u8]) -> Option<usize> {
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buf.windows(2).position(|w| w == b"\n\n")
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}
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// ── SSE JSON types ────────────────────────────────────────────────────────────
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//
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// These structs mirror the subset of the Anthropic SSE payload we actually
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// consume. Unknown fields are silently ignored by serde. Full schemas are
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// documented in the [streaming reference][streaming].
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//
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// [streaming]: https://docs.anthropic.com/en/api/messages-streaming
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/// Top-level SSE data object. The `type` field selects which other fields
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/// are present; we use `Option` for all of them so a single struct covers
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/// every event type without needing an enum.
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#[derive(Deserialize, Debug)]
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struct SseEvent {
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#[serde(rename = "type")]
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event_type: String,
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/// Present on `content_block_delta` events.
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delta: Option<SseDelta>,
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/// Present on `message_start` events; carries initial token usage.
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message: Option<SseMessageStart>,
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/// Present on `message_delta` events; carries final output token count.
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usage: Option<SseUsage>,
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}
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/// The `delta` object inside a `content_block_delta` event.
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///
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/// `type` is `"text_delta"` for plain text chunks; other delta types
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/// (e.g. `"input_json_delta"` for tool-use blocks) are not yet handled.
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#[derive(Deserialize, Debug)]
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struct SseDelta {
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#[serde(rename = "type")]
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delta_type: Option<String>,
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/// The text chunk; present when `delta_type == "text_delta"`.
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text: Option<String>,
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}
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/// The `message` object inside a `message_start` event.
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#[derive(Deserialize, Debug)]
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struct SseMessageStart {
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usage: Option<SseUsage>,
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}
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/// Token counts reported at the start and end of a turn.
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///
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/// `input_tokens` is set in the `message_start` event;
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/// `output_tokens` is set in the `message_delta` event.
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/// Both fields are `Option` so the same struct works for both events.
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#[derive(Deserialize, Debug)]
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struct SseUsage {
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input_tokens: Option<u32>,
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output_tokens: Option<u32>,
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}
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/// Parse a single SSE event string into a [`StreamEvent`], returning `None` for
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/// event types we don't care about (`ping`, `content_block_start`,
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/// `content_block_stop`).
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///
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/// # SSE format
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///
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/// Each event is a block of `field: value` lines. We only read the `data:`
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/// field; the `event:` line is redundant with the `type` key inside the JSON
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/// payload so we ignore it. See the [SSE spec][sse-fields] for the full field
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/// grammar.
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///
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/// # Mapping to [`StreamEvent`]
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///
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/// | API event type | JSON path | Emits |
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/// |----------------------|------------------------------------|------------------------------|
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/// | `message_start` | `.message.usage.input_tokens` | `InputTokens(n)` |
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/// | `content_block_delta`| `.delta.type == "text_delta"` | `TextDelta(chunk)` |
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/// | `message_delta` | `.usage.output_tokens` | `OutputTokens(n)` |
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/// | `message_stop` | — | `Done` |
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/// | everything else | — | `None` (caller skips) |
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///
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/// [sse-fields]: https://html.spec.whatwg.org/multipage/server-sent-events.html#parsing-an-event-stream
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fn parse_sse_event(event_str: &str) -> Option<StreamEvent> {
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// SSE events may have multiple fields; we only need `data:`.
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let data = event_str
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.lines()
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.find_map(|line| line.strip_prefix("data: "))?;
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let event: SseEvent = serde_json::from_str(data).ok()?;
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match event.event_type.as_str() {
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"message_start" => event
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.message
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.and_then(|m| m.usage)
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.and_then(|u| u.input_tokens)
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.map(StreamEvent::InputTokens),
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"content_block_delta" => {
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let delta = event.delta?;
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if delta.delta_type.as_deref() == Some("text_delta") {
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delta.text.map(StreamEvent::TextDelta)
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} else {
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None
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}
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}
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// usage lives at the top level of message_delta, not inside delta.
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"message_delta" => event
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.usage
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.and_then(|u| u.output_tokens)
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.map(StreamEvent::OutputTokens),
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"message_stop" => Some(StreamEvent::Done),
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// error, ping, content_block_start, content_block_stop — ignored or
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// handled by the caller.
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_ => None,
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}
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}
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// ── Tests ─────────────────────────────────────────────────────────────────────
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#[cfg(test)]
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mod tests {
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use super::*;
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use crate::core::types::Role;
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/// A minimal but complete Anthropic SSE fixture.
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const SSE_FIXTURE: &str = concat!(
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"event: message_start\n",
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"data: {\"type\":\"message_start\",\"message\":{\"id\":\"msg_123\",\"type\":\"message\",",
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"\"role\":\"assistant\",\"content\":[],\"model\":\"claude-opus-4-6\",",
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"\"stop_reason\":null,\"stop_sequence\":null,",
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"\"usage\":{\"input_tokens\":10,\"cache_creation_input_tokens\":0,",
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"\"cache_read_input_tokens\":0,\"output_tokens\":1}}}\n",
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"\n",
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"event: content_block_start\n",
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"data: {\"type\":\"content_block_start\",\"index\":0,",
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"\"content_block\":{\"type\":\"text\",\"text\":\"\"}}\n",
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"\n",
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"event: ping\n",
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"data: {\"type\":\"ping\"}\n",
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"\n",
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"event: content_block_delta\n",
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"data: {\"type\":\"content_block_delta\",\"index\":0,",
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"\"delta\":{\"type\":\"text_delta\",\"text\":\"Hello\"}}\n",
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"\n",
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"event: content_block_delta\n",
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"data: {\"type\":\"content_block_delta\",\"index\":0,",
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"\"delta\":{\"type\":\"text_delta\",\"text\":\", world!\"}}\n",
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"\n",
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"event: content_block_stop\n",
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"data: {\"type\":\"content_block_stop\",\"index\":0}\n",
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"\n",
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"event: message_delta\n",
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"data: {\"type\":\"message_delta\",\"delta\":{\"stop_reason\":\"end_turn\",",
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"\"stop_sequence\":null},\"usage\":{\"output_tokens\":5}}\n",
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"\n",
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"event: message_stop\n",
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"data: {\"type\":\"message_stop\"}\n",
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"\n",
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);
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#[test]
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fn test_parse_sse_events_from_fixture() {
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let events: Vec<StreamEvent> = SSE_FIXTURE
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.split("\n\n")
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.filter(|s| !s.trim().is_empty())
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.filter_map(parse_sse_event)
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.collect();
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// content_block_start, ping, content_block_stop → None (filtered out)
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assert_eq!(events.len(), 5);
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assert!(matches!(events[0], StreamEvent::InputTokens(10)));
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assert!(matches!(&events[1], StreamEvent::TextDelta(s) if s == "Hello"));
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assert!(matches!(&events[2], StreamEvent::TextDelta(s) if s == ", world!"));
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assert!(matches!(events[3], StreamEvent::OutputTokens(5)));
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assert!(matches!(events[4], StreamEvent::Done));
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}
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#[test]
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fn test_parse_message_stop_yields_done() {
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let event_str = "event: message_stop\ndata: {\"type\":\"message_stop\"}\n";
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assert!(matches!(
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parse_sse_event(event_str),
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Some(StreamEvent::Done)
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));
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}
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#[test]
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fn test_parse_ping_yields_none() {
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let event_str = "event: ping\ndata: {\"type\":\"ping\"}\n";
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assert!(parse_sse_event(event_str).is_none());
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}
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#[test]
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fn test_parse_content_block_start_yields_none() {
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let event_str = concat!(
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"event: content_block_start\n",
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"data: {\"type\":\"content_block_start\",\"index\":0,",
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"\"content_block\":{\"type\":\"text\",\"text\":\"\"}}\n",
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);
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assert!(parse_sse_event(event_str).is_none());
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}
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#[test]
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fn test_messages_serialize_to_anthropic_format() {
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let messages = vec![
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ConversationMessage {
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role: Role::User,
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content: "Hello".to_string(),
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},
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ConversationMessage {
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role: Role::Assistant,
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content: "Hi there!".to_string(),
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},
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];
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let json = serde_json::json!({
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"model": "claude-opus-4-6",
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"max_tokens": 8192,
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"stream": true,
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"messages": messages,
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});
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assert_eq!(json["messages"][0]["role"], "user");
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assert_eq!(json["messages"][0]["content"], "Hello");
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assert_eq!(json["messages"][1]["role"], "assistant");
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assert_eq!(json["messages"][1]["content"], "Hi there!");
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assert_eq!(json["stream"], true);
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assert!(json["max_tokens"].as_u64().unwrap() > 0);
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}
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#[test]
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fn test_find_double_newline() {
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assert_eq!(find_double_newline(b"abc\n\ndef"), Some(3));
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assert_eq!(find_double_newline(b"abc\ndef"), None);
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assert_eq!(find_double_newline(b"\n\n"), Some(0));
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assert_eq!(find_double_newline(b""), None);
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}
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}
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