zeph_bench/

channel.rs

// SPDX-FileCopyrightText: 2026 Andrei G <bug-ops>
// SPDX-License-Identifier: MIT OR Apache-2.0

//! Headless [`zeph_core::channel::Channel`] implementation for benchmark runs.
//!
//! [`BenchmarkChannel`] feeds a pre-loaded prompt queue into the agent loop and captures
//! each response without requiring a terminal, Telegram bot, or any other real I/O channel.
//!
//! Tool output events are captured via [`BenchmarkChannel::tool_outputs`] for Phase 2 scoring
//! (see [`ToolOutputEvent`] and #4237). They are not added to [`responses`][BenchmarkChannel::responses]
//! so that tool intermediaries do not corrupt response metrics.

use std::collections::VecDeque;
use std::time::Instant;

use zeph_core::channel::{ChannelError, ChannelMessage, ToolOutputEvent};

/// A single captured agent response corresponding to one benchmark prompt.
///
/// Produced by [`BenchmarkChannel`] after the agent calls [`send`][zeph_core::channel::Channel::send] or
/// [`flush_chunks`][zeph_core::channel::Channel::flush_chunks] for a given prompt.
///
/// # Examples
///
/// ```
/// use zeph_bench::channel::CapturedResponse;
/// use std::time::Duration;
///
/// let r = CapturedResponse {
///     prompt_index: 0,
///     text: "42".into(),
///     elapsed: Duration::from_millis(312),
///     input_tokens: 120,
///     output_tokens: 3,
///     context_window: 128_000,
/// };
/// assert_eq!(r.text, "42");
/// ```
#[derive(Debug, Clone)]
pub struct CapturedResponse {
    /// Zero-based index of the prompt this response corresponds to.
    pub prompt_index: usize,
    /// Full text of the agent response (or concatenated streaming chunks).
    pub text: String,
    /// Wall-clock time from the first streaming chunk to `flush_chunks`, or
    /// [`std::time::Duration::ZERO`] for non-streaming `send` calls.
    pub elapsed: std::time::Duration,
    /// Input token count reported by the LLM for this turn.
    pub input_tokens: u64,
    /// Output token count reported by the LLM for this turn.
    pub output_tokens: u64,
    /// Context window size reported by the LLM for this turn.
    pub context_window: u64,
}

/// Headless channel that feeds pre-loaded prompts and captures agent responses.
///
/// Used by the bench runner to drive the agent loop without a real terminal or
/// network connection. [`recv`][zeph_core::channel::Channel::recv] drains the prompt
/// queue; [`send`][zeph_core::channel::Channel::send] and
/// [`flush_chunks`][zeph_core::channel::Channel::flush_chunks] accumulate responses
/// into an internal list. Tool outputs are captured separately via [`tool_outputs()`][BenchmarkChannel::tool_outputs].
///
/// # Usage
///
/// ```no_run
/// use zeph_bench::BenchmarkChannel;
///
/// let prompts = vec!["What year did WWII end?".into()];
/// let channel = BenchmarkChannel::new(prompts);
/// assert_eq!(channel.total(), 1);
/// ```
///
/// After the agent loop completes, call [`into_responses`] to consume the channel
/// and retrieve all captured responses:
///
/// ```no_run
/// # use zeph_bench::BenchmarkChannel;
/// let channel = BenchmarkChannel::new(vec!["question".into()]);
/// // ... run agent loop ...
/// let responses = channel.into_responses();
/// ```
///
/// [`into_responses`]: BenchmarkChannel::into_responses
pub struct BenchmarkChannel {
    prompts: VecDeque<String>,
    responses: Vec<CapturedResponse>,
    tool_outputs: Vec<ToolOutputEvent>,
    current_index: usize,
    total: usize,
    // Streaming chunk accumulation
    chunk_buffer: String,
    chunk_start: Option<Instant>,
    // Token usage for the current prompt (updated by send_usage)
    pending_input_tokens: u64,
    pending_output_tokens: u64,
    pending_context_window: u64,
}

impl BenchmarkChannel {
    /// Create a new channel pre-loaded with `prompts`.
    ///
    /// Prompts are fed to the agent one at a time in order via
    /// [`recv`][zeph_core::channel::Channel::recv]. The channel returns `Ok(None)` once
    /// all prompts have been drained.
    ///
    /// # Examples
    ///
    /// ```
    /// use zeph_bench::BenchmarkChannel;
    ///
    /// let ch = BenchmarkChannel::new(vec!["hello".into(), "world".into()]);
    /// assert_eq!(ch.total(), 2);
    /// ```
    #[must_use]
    pub fn new(prompts: Vec<String>) -> Self {
        let total = prompts.len();
        Self {
            prompts: VecDeque::from(prompts),
            responses: Vec::new(),
            tool_outputs: Vec::new(),
            current_index: 0,
            total,
            chunk_buffer: String::new(),
            chunk_start: None,
            pending_input_tokens: 0,
            pending_output_tokens: 0,
            pending_context_window: 0,
        }
    }

    /// Create a channel from a multi-turn scenario history.
    ///
    /// User turns are fed to the agent in order via [`recv`][zeph_core::channel::Channel::recv].
    /// Assistant turns are pre-seeded into [`responses`][BenchmarkChannel::responses] so that
    /// evaluators and Phase 2 scoring have access to the captured prior context.
    ///
    /// # Note
    ///
    /// If `turns` contains no [`crate::scenario::Role::User`] turns, [`total`][BenchmarkChannel::total] returns
    /// `0` and the channel cannot serve as a prompt source. The bench runner rejects this with
    /// [`BenchError::InvalidFormat`][crate::BenchError] — callers must ensure at least one user
    /// turn is present.
    ///
    /// # Examples
    ///
    /// ```
    /// use zeph_bench::BenchmarkChannel;
    /// use zeph_bench::scenario::{Role, Turn};
    ///
    /// let turns = vec![
    ///     Turn { role: Role::User, content: "Hello".into() },
    ///     Turn { role: Role::Assistant, content: "Hi there".into() },
    ///     Turn { role: Role::User, content: "What year?".into() },
    /// ];
    /// let ch = BenchmarkChannel::from_turns(turns);
    /// assert_eq!(ch.total(), 2); // two user turns
    /// assert_eq!(ch.responses().len(), 1); // one seeded assistant turn
    /// ```
    #[must_use]
    pub fn from_turns(turns: Vec<crate::scenario::Turn>) -> Self {
        use crate::scenario::Role;

        let mut prompts = VecDeque::new();
        let mut seeded_responses = Vec::new();
        let mut prompt_index: usize = 0;

        for turn in turns {
            match turn.role {
                Role::User => {
                    prompts.push_back(turn.content);
                    prompt_index += 1;
                }
                Role::Assistant => {
                    seeded_responses.push(CapturedResponse {
                        prompt_index: prompt_index.saturating_sub(1),
                        text: turn.content,
                        elapsed: std::time::Duration::ZERO,
                        input_tokens: 0,
                        output_tokens: 0,
                        context_window: 0,
                    });
                }
            }
        }

        let total = prompts.len();
        Self {
            prompts,
            responses: seeded_responses,
            tool_outputs: Vec::new(),
            current_index: 0,
            total,
            chunk_buffer: String::new(),
            chunk_start: None,
            pending_input_tokens: 0,
            pending_output_tokens: 0,
            pending_context_window: 0,
        }
    }

    /// Total number of prompts this channel was initialised with.
    ///
    /// # Examples
    ///
    /// ```
    /// use zeph_bench::BenchmarkChannel;
    ///
    /// let ch = BenchmarkChannel::new(vec!["a".into(), "b".into(), "c".into()]);
    /// assert_eq!(ch.total(), 3);
    /// ```
    #[must_use]
    pub fn total(&self) -> usize {
        self.total
    }

    /// Consume the channel and return all [`CapturedResponse`]s collected so far.
    ///
    /// Call this after the agent loop exits to retrieve every response in prompt order.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use zeph_bench::BenchmarkChannel;
    ///
    /// let ch = BenchmarkChannel::new(vec!["question".into()]);
    /// // ... run agent ...
    /// let responses = ch.into_responses();
    /// ```
    #[must_use]
    pub fn into_responses(self) -> Vec<CapturedResponse> {
        self.responses
    }

    /// Borrow the captured responses without consuming the channel.
    ///
    /// # Examples
    ///
    /// ```
    /// use zeph_bench::BenchmarkChannel;
    ///
    /// let ch = BenchmarkChannel::new(vec![]);
    /// assert!(ch.responses().is_empty());
    /// ```
    #[must_use]
    pub fn responses(&self) -> &[CapturedResponse] {
        &self.responses
    }

    /// Borrow the tool output events captured during the agent run.
    ///
    /// Events are appended by [`send_tool_output`][zeph_core::channel::Channel::send_tool_output]
    /// and are available for Phase 2 evaluation (#4234) after the agent loop exits.
    ///
    /// # Examples
    ///
    /// ```
    /// use zeph_bench::BenchmarkChannel;
    ///
    /// let ch = BenchmarkChannel::new(vec![]);
    /// assert!(ch.tool_outputs().is_empty());
    /// ```
    #[must_use]
    pub fn tool_outputs(&self) -> &[zeph_core::channel::ToolOutputEvent] {
        &self.tool_outputs
    }

    fn flush_chunk_buffer(&mut self) {
        if self.chunk_buffer.is_empty() {
            return;
        }
        let elapsed = self
            .chunk_start
            .map_or(std::time::Duration::ZERO, |s| s.elapsed());
        self.responses.push(CapturedResponse {
            prompt_index: self.current_index.saturating_sub(1),
            text: std::mem::take(&mut self.chunk_buffer),
            elapsed,
            input_tokens: self.pending_input_tokens,
            output_tokens: self.pending_output_tokens,
            context_window: self.pending_context_window,
        });
        self.chunk_start = None;
        self.pending_input_tokens = 0;
        self.pending_output_tokens = 0;
        self.pending_context_window = 0;
    }
}

impl zeph_core::channel::Channel for BenchmarkChannel {
    async fn recv(&mut self) -> Result<Option<ChannelMessage>, ChannelError> {
        match self.prompts.pop_front() {
            Some(text) => {
                self.current_index += 1;
                Ok(Some(ChannelMessage {
                    text,
                    attachments: vec![],
                    is_guest_context: false,
                    is_from_bot: false,
                }))
            }
            None => Ok(None),
        }
    }

    fn supports_exit(&self) -> bool {
        false
    }

    async fn send(&mut self, text: &str) -> Result<(), ChannelError> {
        self.responses.push(CapturedResponse {
            prompt_index: self.current_index.saturating_sub(1),
            text: text.to_owned(),
            elapsed: std::time::Duration::ZERO,
            input_tokens: self.pending_input_tokens,
            output_tokens: self.pending_output_tokens,
            context_window: self.pending_context_window,
        });
        self.pending_input_tokens = 0;
        self.pending_output_tokens = 0;
        self.pending_context_window = 0;
        Ok(())
    }

    async fn send_chunk(&mut self, chunk: &str) -> Result<(), ChannelError> {
        if self.chunk_start.is_none() {
            self.chunk_start = Some(Instant::now());
        }
        self.chunk_buffer.push_str(chunk);
        Ok(())
    }

    async fn flush_chunks(&mut self) -> Result<(), ChannelError> {
        self.flush_chunk_buffer();
        Ok(())
    }

    async fn send_usage(
        &mut self,
        input_tokens: u64,
        output_tokens: u64,
        context_window: u64,
        _cache_read_tokens: u64,
        _cache_write_tokens: u64,
        _cost_cents: f64,
    ) -> Result<(), ChannelError> {
        self.pending_input_tokens = input_tokens;
        self.pending_output_tokens = output_tokens;
        self.pending_context_window = context_window;
        Ok(())
    }

    async fn send_tool_output(&mut self, event: ToolOutputEvent) -> Result<(), ChannelError> {
        self.tool_outputs.push(event);
        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use std::assert_matches;
    use zeph_core::channel::{
        Channel, ElicitationField, ElicitationFieldType, ElicitationRequest, ElicitationResponse,
        ToolOutputEvent,
    };

    use super::*;

    #[tokio::test]
    async fn recv_drains_queue_and_returns_none_when_empty() {
        let mut ch = BenchmarkChannel::new(vec!["hello".into(), "world".into()]);
        let msg1 = ch.recv().await.unwrap().unwrap();
        assert_eq!(msg1.text, "hello");
        let msg2 = ch.recv().await.unwrap().unwrap();
        assert_eq!(msg2.text, "world");
        let msg3 = ch.recv().await.unwrap();
        assert!(msg3.is_none());
    }

    #[tokio::test]
    async fn send_accumulates_response() {
        let mut ch = BenchmarkChannel::new(vec!["prompt".into()]);
        let _ = ch.recv().await.unwrap();
        ch.send("response text").await.unwrap();
        assert_eq!(ch.responses().len(), 1);
        assert_eq!(ch.responses()[0].text, "response text");
    }

    #[tokio::test]
    async fn confirm_returns_true() {
        let mut ch = BenchmarkChannel::new(vec![]);
        let result = ch.confirm("delete?").await.unwrap();
        assert!(result);
    }

    #[tokio::test]
    async fn elicit_returns_declined() {
        let mut ch = BenchmarkChannel::new(vec![]);
        let req = ElicitationRequest {
            server_name: "test-server".into(),
            message: "provide input".into(),
            fields: vec![ElicitationField {
                name: "field".into(),
                description: None,
                field_type: ElicitationFieldType::String,
                required: true,
            }],
        };
        let result = ch.elicit(req).await.unwrap();
        assert_matches!(result, ElicitationResponse::Declined);
    }

    #[tokio::test]
    async fn send_chunk_and_flush_captures_response() {
        let mut ch = BenchmarkChannel::new(vec!["p".into()]);
        let _ = ch.recv().await.unwrap();
        ch.send_chunk("part1").await.unwrap();
        ch.send_chunk(" part2").await.unwrap();
        ch.flush_chunks().await.unwrap();
        assert_eq!(ch.responses().len(), 1);
        assert_eq!(ch.responses()[0].text, "part1 part2");
    }

    #[tokio::test]
    async fn supports_exit_returns_false() {
        let ch = BenchmarkChannel::new(vec![]);
        assert!(!ch.supports_exit());
    }

    #[tokio::test]
    async fn send_usage_captured_on_send() {
        let mut ch = BenchmarkChannel::new(vec!["p".into()]);
        let _ = ch.recv().await.unwrap();
        ch.send_usage(10, 20, 128_000, 0, 0, 0.0).await.unwrap();
        ch.send("answer").await.unwrap();
        let r = &ch.responses()[0];
        assert_eq!(r.input_tokens, 10);
        assert_eq!(r.output_tokens, 20);
        assert_eq!(r.context_window, 128_000);
    }

    #[tokio::test]
    async fn send_tool_output_captured_separately_from_responses() {
        let mut ch = BenchmarkChannel::new(vec!["p".into()]);
        let _ = ch.recv().await.unwrap();
        ch.send_tool_output(ToolOutputEvent {
            tool_name: "bash".into(),
            display: "some tool output".into(),
            diff: None,
            filter_stats: None,
            kept_lines: None,
            locations: None,
            tool_call_id: "tc-1".into(),
            terminal_id: None,
            is_error: false,
            parent_tool_use_id: None,
            raw_response: None,
            started_at: None,
        })
        .await
        .unwrap();
        // Tool output must not pollute benchmark responses.
        assert_eq!(ch.responses().len(), 0);
        // Tool output must be accessible for Phase 2 scoring.
        assert_eq!(ch.tool_outputs().len(), 1);
        assert_eq!(ch.tool_outputs()[0].tool_name, "bash");
    }

    #[test]
    fn from_turns_splits_user_and_assistant() {
        use crate::scenario::{Role, Turn};

        let turns = vec![
            Turn {
                role: Role::User,
                content: "Q1".into(),
            },
            Turn {
                role: Role::Assistant,
                content: "A1".into(),
            },
            Turn {
                role: Role::User,
                content: "Q2".into(),
            },
        ];
        let ch = BenchmarkChannel::from_turns(turns);
        assert_eq!(ch.total(), 2);
        assert_eq!(ch.responses().len(), 1);
        assert_eq!(ch.responses()[0].text, "A1");
    }

    #[test]
    fn from_turns_user_only() {
        use crate::scenario::{Role, Turn};

        let turns = vec![Turn {
            role: Role::User,
            content: "Q".into(),
        }];
        let ch = BenchmarkChannel::from_turns(turns);
        assert_eq!(ch.total(), 1);
        assert!(ch.responses().is_empty());
    }
}