io-harness 0.7.0

//! The provider layer — provider-agnostic by design.
//!
//! No vendor type appears in these public types. A [`Provider`] takes a
//! [`CompletionRequest`] and returns a [`CompletionResponse`]; OpenRouter,
//! Anthropic, and OpenAI are implementation details behind the trait.

pub mod anthropic;
pub mod openai;
pub(crate) mod openai_wire;
pub mod openrouter;

pub use anthropic::Anthropic;
pub use openai::OpenAi;
pub use openrouter::OpenRouter;

use futures_util::StreamExt;

use crate::error::{Error, Result};

/// Read an SSE byte stream line by line, handing each `data:` payload (the text
/// after `data:`) to `ingest`. `ingest` returns `true` to stop early on a
/// provider's terminal event. Shared by every provider so the transport lives
/// in one place; each provider supplies its own JSON accumulation.
pub(crate) async fn read_sse<F>(resp: reqwest::Response, mut ingest: F) -> Result<()>
where
    F: FnMut(&str) -> bool,
{
    let mut stream = resp.bytes_stream();
    let mut buf = String::new();
    while let Some(chunk) = stream.next().await {
        let chunk = chunk.map_err(|e| Error::Provider(e.to_string()))?;
        buf.push_str(&String::from_utf8_lossy(&chunk));
        while let Some(nl) = buf.find('\n') {
            let line = buf[..nl].trim_end_matches('\r').to_string();
            buf.drain(..=nl);
            let Some(data) = line.strip_prefix("data:") else {
                continue;
            };
            let data = data.trim();
            if data.is_empty() {
                continue;
            }
            if ingest(data) {
                return Ok(());
            }
        }
    }
    Ok(())
}

/// A tool the model may call, described in a vendor-neutral shape.
#[derive(Debug, Clone)]
pub struct ToolSpec {
    /// Tool name the model calls.
    pub name: String,
    /// What the tool does, for the model.
    pub description: String,
    /// JSON Schema of the arguments object.
    pub parameters: serde_json::Value,
}

/// A request for one model completion.
#[derive(Debug, Clone)]
pub struct CompletionRequest {
    /// System instructions.
    pub system: String,
    /// The user turn.
    pub user: String,
    /// Tools the model may call.
    pub tools: Vec<ToolSpec>,
}

/// A tool call the model decided to make.
#[derive(Debug, Clone)]
pub struct ToolCall {
    /// Tool name.
    pub name: String,
    /// Parsed arguments object.
    pub arguments: serde_json::Value,
}

/// Token usage for one completion, in a vendor-neutral shape. Used to enforce
/// the cost budget and to record spend in the trace.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub struct Usage {
    /// Tokens in the prompt.
    pub prompt_tokens: u64,
    /// Tokens the model generated.
    pub completion_tokens: u64,
    /// Total tokens billed for this completion.
    pub total_tokens: u64,
}

/// One model completion.
///
/// Construct with `..Default::default()` for forward compatibility — fields are
/// added in minor releases (e.g. `usage` in 0.2.0).
#[derive(Debug, Clone, Default)]
pub struct CompletionResponse {
    /// Any free text the model returned.
    pub text: Option<String>,
    /// Tool calls the model requested, in order.
    pub tool_calls: Vec<ToolCall>,
    /// Token usage, when the provider reports it. `None` if unknown.
    pub usage: Option<Usage>,
}

/// Anything that can turn a [`CompletionRequest`] into a [`CompletionResponse`].
///
/// Implemented by [`OpenRouter`], [`Anthropic`], and [`OpenAi`]; tests supply
/// their own to run the loop offline. Selecting a provider is just constructing
/// a different implementer and handing it to [`crate::run`] — no vendor type
/// appears in the task contract.
pub trait Provider {
    /// Perform one completion.
    fn complete(
        &self,
        request: CompletionRequest,
    ) -> impl std::future::Future<Output = Result<CompletionResponse>> + Send;

    /// A short label recorded in the run's trace so an audit shows which
    /// provider ran. Defaults to `"provider"` so existing implementers keep
    /// compiling; the built-in providers override it.
    fn name(&self) -> &str {
        "provider"
    }
}