eval-core 0.1.0

//! The generic benchmark **runner**: ties a [`Harness`] + [`Scorer`] over a shared `World`, runs every
//! [`EvalCase`], times each, isolates panics, and assembles an [`EvalReport`].
//!
//! This is the domain-agnostic port of AetherCore's concrete eval runner: same per-case timing, same
//! `catch_unwind` panic isolation (one bad case fails alone), same panic-hook suppression around the
//! loop, and the same stderr progress lines — but with the game/LLM specifics (which backend, which
//! world, which predicates) pushed out behind the [`Harness`]/[`Scorer`] traits.

use std::time::Instant;

use crate::case::EvalCase;
use crate::expect::Expectation;
use crate::harness::{Agent, Harness, RunArtifacts, ToolCall};
use crate::report::{CaseOutcome, EvalReport};
use crate::scorer::{BuiltinScorer, Scorer};

/// Run-level metadata recorded on the [`EvalReport`] but NOT intrinsic to the generic runner.
///
/// [`EvalReport`] carries a few fields that are meaningful for LLM/agent runs (the sampling
/// `temperature`, a `backend` label, the shared `system_prompt`) but have no generic meaning here. Rather
/// than hardcode LLM assumptions into [`run_eval`], the host supplies them via this struct; the report's
/// serialized shape (and therefore the HTML report + saved JSON) is unchanged. A host with no notion of
/// these can use [`RunMeta::default`] (temperature `0.0`, empty `backend`/`system_prompt`).
///
/// `#[non_exhaustive]`: new run-level metadata can be added without a breaking change. Build it with
/// `RunMeta::new(temperature, backend, system_prompt)`.
#[derive(Debug, Clone, Default)]
#[non_exhaustive]
pub struct RunMeta {
    /// Sampling temperature the run used, recorded in the report summary. Neutral default `0.0`.
    pub temperature: f32,
    /// A short description of what was benchmarked (e.g. the backend/model label). Neutral default `""`.
    pub backend: String,
    /// A run-level prompt/preamble shared across all cases, stored once on the report (shown at the top
    /// of the HTML report's per-run expander). Neutral default `""`.
    pub system_prompt: String,
}

impl RunMeta {
    /// Create a new `RunMeta` with the given temperature, backend label, and system prompt.
    pub fn new(
        temperature: f32,
        backend: impl Into<String>,
        system_prompt: impl Into<String>,
    ) -> Self {
        Self {
            temperature,
            backend: backend.into(),
            system_prompt: system_prompt.into(),
        }
    }
}

/// Run every `case` through `harness` + `scorer` and aggregate into an [`EvalReport`], using default
/// [`RunMeta`] (temperature `0`, empty backend/system-prompt labels).
///
/// This is the simple entry point for hosts that don't track LLM run metadata. For LLM/agent runs that
/// want the report to record a backend label, temperature, or shared system prompt, use
/// [`run_eval_with_meta`].
///
/// Semantics per case: build a fresh world via [`Harness::setup`], time [`Harness::run`] (wall-clock for
/// the whole run), then score every predicate via [`Scorer::score`]. A case PASSES iff `run` returned
/// `Ok` AND every predicate passed. The whole build+run+score is isolated behind `catch_unwind`, so a
/// panicking case fails only itself (with the panic message recorded in
/// [`CaseOutcome::error`]). Progress is emitted to stderr.
pub fn run_eval<H, S>(
    harness: &H,
    scorer: &S,
    cases: &[EvalCase<H::Setup, S::Expect>],
) -> EvalReport
where
    H: Harness,
    S: Scorer<World = H::World>,
{
    run_eval_with_meta(harness, scorer, cases, RunMeta::default())
}

/// As [`run_eval`], but with explicit run [`RunMeta`] (backend label, temperature, shared system
/// prompt) recorded on the resulting [`EvalReport`].
///
/// This is the single convergence point that owns the progress logging: a one-time startup banner, then
/// a `[i/total]` line BEFORE and AFTER each case (the BEFORE line — the anti-hang signal — prints the
/// instant the case starts). ALL progress goes to stderr; stdout is left clean for any report payload a
/// host wants to print.
pub fn run_eval_with_meta<H, S>(
    harness: &H,
    scorer: &S,
    cases: &[EvalCase<H::Setup, S::Expect>],
    meta: RunMeta,
) -> EvalReport
where
    H: Harness,
    S: Scorer<World = H::World>,
{
    let total = cases.len();
    eprintln!("── eval run ──────────────────────────────────────────");
    if !meta.backend.is_empty() {
        eprintln!("backend:     {}", meta.backend);
    }
    eprintln!("cases:       {total}");
    eprintln!("temperature: {}", meta.temperature);
    eprintln!("──────────────────────────────────────────────────────");

    // A caught panic still runs the DEFAULT hook FIRST (printing "thread '…' panicked at …" to stderr)
    // before `catch_unwind` in `run_case` returns. Swap in a no-op hook for the duration of the run loop
    // so that raw spam is suppressed — the panic message is surfaced cleanly via the per-case AFTER line
    // and the recorded `CaseOutcome.error` instead. Scoped narrowly: the saved hook is restored right
    // after the loop, before this fn returns (`.map(...).collect()` can't return early — it always yields
    // one outcome per case — so the restore always runs).
    let prev_hook = std::panic::take_hook();
    std::panic::set_hook(Box::new(|_| {}));

    let outcomes: Vec<CaseOutcome> = cases
        .iter()
        .enumerate()
        .map(|(idx, case)| {
            let i = idx + 1;
            // BEFORE: which case is in flight, printed the instant the run starts (anti-hang signal).
            eprintln!("[{i}/{total}] {} …", case.name);
            let outcome = run_case(harness, scorer, case);
            // AFTER: result + timing, so a slow case is visibly distinguishable from a hung one.
            let status = if outcome.passed { "PASS" } else { "FAIL" };
            let tokens = outcome
                .tokens
                .map_or_else(|| "?".to_owned(), |t| t.to_string());
            let detail = match &outcome.error {
                Some(err) => format!(", {}", truncate_one_line(err)),
                None => String::new(),
            };
            eprintln!(
                "[{i}/{total}] {} … {status} ({:.1}s, {tokens} tok{detail})",
                case.name,
                outcome.latency.as_secs_f64()
            );
            outcome
        })
        .collect();

    // Restore the host's panic hook now the run loop is done.
    std::panic::set_hook(prev_hook);

    EvalReport::new(outcomes, meta.temperature, meta.backend, meta.system_prompt)
}

/// Build the world, run one case against it, and score it into a [`CaseOutcome`].
///
/// The whole build+run+score is wrapped in `catch_unwind`: the world is freshly built per case, so
/// discarding a half-built world on a panic is safe, and `&H`/`&S` are shared references the closure only
/// reads — hence the `AssertUnwindSafe` boundary. On a panic, the case is marked failed, every predicate
/// is marked failed (with its scorer-derived label where we can still produce one — but a panic may have
/// happened mid-scoring, so we fall back to a positional label), and the panic message is recorded.
fn run_case<H, S>(harness: &H, scorer: &S, case: &EvalCase<H::Setup, S::Expect>) -> CaseOutcome
where
    H: Harness,
    S: Scorer<World = H::World>,
{
    let started = Instant::now();

    let scored = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
        // Build a fresh world for this case, run the instruction (timing the whole run), then score.
        let mut world = harness.setup(&case.setup);
        let run = harness.run(&case.instruction, &mut world);
        let latency = started.elapsed();

        // The harness can report a run-level error two ways: an `Err` return (hard failure) or
        // `RunArtifacts.error` (a soft, captured error). Prefer the `Err`; either fails the case.
        // (`take` moves the soft error out rather than cloning it — the `error` field on the kept
        // `artifacts` is then unused, since `run_error` is what flows onto the `CaseOutcome`.)
        let (artifacts, run_error) = match run {
            Ok(mut artifacts) => {
                let err = artifacts.error.take();
                (artifacts, err)
            }
            Err(e) => (RunArtifacts::default(), Some(e.to_string())),
        };

        // Score every predicate against the resulting world AND the run's artifacts, keeping each
        // `(label, passed)`.
        let predicates: Vec<(String, bool)> = case
            .expect
            .iter()
            .map(|exp| scorer.score(exp, &artifacts, &world))
            .collect();

        (artifacts, run_error, latency, predicates)
    }));

    match scored {
        Ok((artifacts, run_error, latency, predicates)) => {
            // A case passes iff the run didn't error AND every predicate held. (A scored-but-error'd run
            // can't pass — partial state is unreliable — but we still record which predicates held.)
            let passed = run_error.is_none() && predicates.iter().all(|(_, p)| *p);
            // The report keeps tool calls as DISPLAY strings (shape-compatible with the saved JSON /
            // `--json` / HTML report). Derive them here from the structured `ToolCall`s the artifacts
            // carry, so a host never formats them itself.
            let tool_calls: Vec<String> =
                artifacts.tool_calls.iter().map(ToolCall::display).collect();
            CaseOutcome::new(
                case.name.clone(),
                passed,
                predicates,
                latency,
                artifacts.tokens,
                tool_calls,
                artifacts.final_text,
                run_error,
                artifacts.transcript,
            )
        }
        Err(payload) => {
            // Recover a message from the panic payload (most panics carry a `&str` or `String`).
            let msg = payload
                .downcast_ref::<&str>()
                .map(|s| (*s).to_owned())
                .or_else(|| payload.downcast_ref::<String>().cloned())
                .unwrap_or_else(|| "unknown panic".to_owned());
            // A panic may have struck anywhere in build/run/score, so we can't trust any partial
            // per-predicate labels. Record one failed predicate per `expect` with a positional label.
            let predicates = (0..case.expect.len())
                .map(|i| (format!("predicate #{i}"), false))
                .collect();
            CaseOutcome::new(
                case.name.clone(),
                false,
                predicates,
                started.elapsed(),
                None,
                Vec::new(),
                None,
                Some(format!("panic: {msg}")),
                Vec::new(),
            )
        }
    }
}

/// An internal adapter turning an [`Agent`] into a `Harness<World = (), Setup = ()>` so the easy
/// [`run_suite`] path reuses the exact same panic-isolated runner as the full [`Harness`] path.
///
/// A deliberate explicit struct rather than a blanket `impl<T: Agent> Harness for T`: a blanket impl
/// would conflict (coherence) with a host's own `Harness` impl (e.g. AetherCore's `AetherHarness`), so
/// the adapter keeps the two trait families independent. The world is `()` (built once per case, inert)
/// and the agent's run failure is mapped onto [`Harness::run`]'s `anyhow::Result`.
#[derive(Debug)]
pub struct AgentHarness<'a, A: Agent> {
    agent: &'a A,
}

impl<'a, A: Agent> AgentHarness<'a, A> {
    /// Wrap an agent reference as a `Harness`.
    pub fn new(agent: &'a A) -> Self {
        Self { agent }
    }
}

impl<A: Agent> Harness for AgentHarness<'_, A> {
    type World = ();
    type Setup = ();

    fn setup(&self, _setup: &()) {}

    fn run(&self, instruction: &str, _world: &mut ()) -> anyhow::Result<RunArtifacts> {
        // Map the public `EvalError` to the runner's internal `anyhow::Result` (an `Err` fails the
        // case and records the message, just like a `Harness` returning `Err`).
        self.agent
            .run(instruction)
            .map_err(|e| anyhow::anyhow!(e.to_string()))
    }
}

/// The easy path: run a suite of [`Expectation`]-based cases against an [`Agent`], scoring with the
/// built-in [`BuiltinScorer`] — no `World`, no `Setup`, no host `Scorer` impl.
///
/// Implement [`Agent::run`] for your harness, author `EvalCase<(), Expectation>` cases (in RON or
/// inline), and call this; you get back the same [`EvalReport`] as the full path. Uses default
/// [`RunMeta`]; for a backend/temperature label use [`run_suite_with_meta`].
pub fn run_suite(agent: &impl Agent, cases: &[EvalCase<(), Expectation>]) -> EvalReport {
    run_suite_with_meta(agent, cases, RunMeta::default())
}

/// As [`run_suite`], but records explicit [`RunMeta`] (backend label, temperature, shared system prompt)
/// on the report.
pub fn run_suite_with_meta(
    agent: &impl Agent,
    cases: &[EvalCase<(), Expectation>],
    meta: RunMeta,
) -> EvalReport {
    let harness = AgentHarness::new(agent);
    run_eval_with_meta(&harness, &BuiltinScorer, cases, meta)
}

/// Collapse a (possibly multi-line) error/panic message to a single, length-bounded line for the live
/// per-case AFTER line: take only up to the first newline, then truncate to `MAX` chars (on a char
/// boundary, since panic messages can contain non-ASCII) with an ellipsis. The full message is still
/// preserved verbatim in [`CaseOutcome::error`].
fn truncate_one_line(msg: &str) -> String {
    const MAX: usize = 120;
    let first_line = msg.lines().next().unwrap_or("");
    if first_line.chars().count() <= MAX {
        first_line.to_owned()
    } else {
        let truncated: String = first_line.chars().take(MAX).collect();
        format!("{truncated}…")
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    /// A world that is just a flag set by the harness, scored by a closure-free predicate.
    #[derive(Default)]
    struct W {
        ok: bool,
    }

    /// `Setup` placeholder. The per-case behavior is keyed off the instruction string, so the setup
    /// itself is inert; it only needs to satisfy [`Harness::Setup`].
    #[derive(Clone, Copy, Default)]
    struct How;

    struct H;

    impl Harness for H {
        type World = W;
        type Setup = How;

        fn setup(&self, _setup: &How) -> W {
            W::default()
        }

        fn run(&self, instruction: &str, world: &mut W) -> anyhow::Result<RunArtifacts> {
            // The behavior is keyed off the instruction string the test sets per case.
            match instruction {
                "pass" => {
                    world.ok = true;
                    Ok(RunArtifacts {
                        tokens: Some(7),
                        ..RunArtifacts::default()
                    })
                }
                "soft" => {
                    world.ok = true; // predicate would pass, but the soft error still fails the case.
                    Ok(RunArtifacts {
                        error: Some("soft boom".to_owned()),
                        ..RunArtifacts::default()
                    })
                }
                "hard" => anyhow::bail!("hard boom"),
                "panic" => panic!("kaboom"),
                other => panic!("unexpected instruction {other}"),
            }
        }
    }

    struct Sc;

    impl Scorer for Sc {
        type World = W;
        type Expect = ();

        fn score(&self, _expect: &(), _artifacts: &RunArtifacts, world: &W) -> (String, bool) {
            ("world.ok".to_owned(), world.ok)
        }
    }

    fn case(name: &str, instruction: &str) -> EvalCase<How, ()> {
        EvalCase {
            name: name.to_owned(),
            instruction: instruction.to_owned(),
            setup: How,
            expect: vec![()],
        }
    }

    #[test]
    fn pass_soft_hard_and_panic_are_isolated() {
        let cases = vec![
            case("pass", "pass"),
            case("soft", "soft"),
            case("hard", "hard"),
            case("panic", "panic"),
        ];

        let report = run_eval(&H, &Sc, &cases);

        assert_eq!(report.total(), 4);
        assert_eq!(report.passed(), 1, "only the clean run passes");

        // Pass: ok, no error, token count forwarded, predicate held.
        let pass = &report.outcomes[0];
        assert!(pass.passed);
        assert_eq!(pass.tokens, Some(7));
        assert!(pass.error.is_none());
        assert_eq!(pass.predicates, vec![("world.ok".to_owned(), true)]);

        // Soft error: predicate held but the captured error still fails the case.
        let soft = &report.outcomes[1];
        assert!(!soft.passed);
        assert_eq!(soft.error.as_deref(), Some("soft boom"));
        assert!(soft.predicates[0].1, "predicate itself held");

        // Hard error (`Err` return): failed, error recorded, world scored as built (not ok).
        let hard = &report.outcomes[2];
        assert!(!hard.passed);
        assert_eq!(hard.error.as_deref(), Some("hard boom"));
        assert!(!hard.predicates[0].1);

        // Panic: isolated to this case, recorded as a `panic:`-prefixed error, predicate forced failed.
        let panicked = &report.outcomes[3];
        assert!(!panicked.passed);
        assert!(
            panicked
                .error
                .as_deref()
                .is_some_and(|e| e.contains("kaboom")),
            "panic message captured: {:?}",
            panicked.error
        );
        assert_eq!(panicked.predicates.len(), 1);
        assert!(!panicked.predicates[0].1);
    }

    /// The easy `Agent` + `run_suite` path: one `Agent::run`, built-in `Expectation`s, no `World`,
    /// `Setup`, or `Scorer`. Exercises tool-call + final-text assertions and the structured-→display
    /// derivation in the runner.
    #[test]
    fn run_suite_scores_builtin_expectations_over_agent_artifacts() {
        use crate::expect::Expectation;
        use crate::harness::ToolCall;
        use serde_json::json;

        // A fake agent: if asked to "add", it emits a calculator call and ends with the sum; otherwise
        // it just echoes (no tool call), and "boom" reports a run failure.
        struct FakeAgent;
        impl Agent for FakeAgent {
            fn run(&self, instruction: &str) -> Result<RunArtifacts, crate::error::EvalError> {
                if instruction == "boom" {
                    return Err(crate::error::EvalError::agent("backend down"));
                }
                if instruction.contains("add") {
                    Ok(RunArtifacts {
                        tool_calls: vec![ToolCall::new(
                            "calculator",
                            json!({"op": "add", "a": 2, "b": 2}),
                        )],
                        final_text: Some("The answer is 4".to_owned()),
                        ..RunArtifacts::default()
                    })
                } else {
                    Ok(RunArtifacts {
                        final_text: Some(instruction.to_owned()),
                        ..RunArtifacts::default()
                    })
                }
            }
        }

        fn case(
            name: &str,
            instruction: &str,
            expect: Vec<Expectation>,
        ) -> EvalCase<(), Expectation> {
            EvalCase {
                name: name.to_owned(),
                instruction: instruction.to_owned(),
                setup: (),
                expect,
            }
        }

        let cases = vec![
            case(
                "adds",
                "please add 2 and 2",
                vec![
                    Expectation::CalledToolWith {
                        tool: "calculator".into(),
                        args: json!({"op": "add"}),
                    },
                    Expectation::FinalNumberEquals {
                        value: 4.0,
                        tolerance: 0.0,
                    },
                ],
            ),
            case(
                "no-tools",
                "hello there",
                vec![
                    Expectation::NoToolCalls,
                    Expectation::FinalTextContains {
                        text: "hello".into(),
                        case_insensitive: false,
                    },
                ],
            ),
            case("fails-run", "boom", vec![Expectation::NoError]),
        ];

        let report = run_suite(&FakeAgent, &cases);
        assert_eq!(report.total(), 3);
        assert_eq!(
            report.passed(),
            2,
            "the two well-behaved cases pass; the run-error case fails"
        );

        // The structured calls were rendered to the report's display strings.
        let adds = &report.outcomes[0];
        assert!(adds.passed);
        assert_eq!(adds.tool_calls.len(), 1);
        assert!(
            adds.tool_calls[0].starts_with("calculator("),
            "display string derived from the structured ToolCall: {:?}",
            adds.tool_calls
        );

        let boom = &report.outcomes[2];
        assert!(!boom.passed);
        assert!(
            boom.error
                .as_deref()
                .is_some_and(|e| e.contains("backend down"))
        );
    }
}