//! Run summary metrics + the reproducible run manifest (C18 / C12): the
//! `(manifest, metrics)` pair a run produces "from day one". The metrics are a
//! **post-run pure reduction** over a run's recorded streams — a node cannot
//! reduce end-of-run (C8 caps a node at one record per `eval`, with no terminal
//! `eval`), so the World drains its recording sinks after [`Harness::run`](crate::Harness::run)
//! and folds them here. Output is canonical JSON (C14): the schema is tiny,
//! closed, and flat. `to_json` renders via serde (the report types derive it,
//! cycle 0029) — the same encoder the run registry uses, so a record's stdout
//! and on-disk shapes coincide.

use aura_core::{Scalar, ScalarKind, Timestamp};
use std::collections::HashMap;

/// Summary metrics reduced from a run's recorded streams — the `-> metrics`
/// half of C12's atomic sim unit. Pure function of the recorded streams.
#[derive(Clone, Debug, PartialEq, serde::Serialize, serde::Deserialize)]
pub struct RunMetrics {
    /// Final cumulative pip equity — the last value of the (cumulative)
    /// pip-equity curve. `0.0` if the curve is empty.
    pub total_pips: f64,
    /// Largest peak-to-trough drop on the cumulative pip curve:
    /// `max_t (running_peak(t) - equity(t))`, always `>= 0.0` (`0.0` if the
    /// curve is monotonic non-decreasing or empty).
    pub max_drawdown: f64,
    /// Count of adjacent recorded exposure samples whose sign differs (a zero
    /// exposure normalizes to sign `0`, so flat is distinct from long/short).
    /// A turnover proxy: it counts long<->short reversals *and* transitions
    /// into/out of flat — the plain sign-change count over the exposure series.
    pub exposure_sign_flips: u64,
}

/// The three position-event actions (C10). Direction IS the action; volume is
/// unsigned. Serde-encoded as its i64 mapping (`Buy=0, Sell=1, Close=2`) so the
/// persisted/columnar form stays C7-scalar and ledger-faithful (`action: i64`).
#[derive(Clone, Copy, Debug, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
#[serde(into = "i64", try_from = "i64")]
pub enum PositionAction {
    Buy,
    Sell,
    Close,
}

impl From<PositionAction> for i64 {
    fn from(a: PositionAction) -> i64 {
        match a {
            PositionAction::Buy => 0,
            PositionAction::Sell => 1,
            PositionAction::Close => 2,
        }
    }
}

impl TryFrom<i64> for PositionAction {
    type Error = String;
    fn try_from(v: i64) -> Result<Self, Self::Error> {
        match v {
            0 => Ok(PositionAction::Buy),
            1 => Ok(PositionAction::Sell),
            2 => Ok(PositionAction::Close),
            other => Err(format!("invalid PositionAction i64: {other}")),
        }
    }
}

/// One row of C10's derived position-event table — the broker-independent audit
/// view (the first difference of the exposure state). A post-run value type
/// (sibling of [`RunMetrics`]), NOT a per-`eval` node output (C8). Multiple events
/// may share one `event_ts` (a reversal: Close then open, close-before-open). No
/// `open_ts` — a position's open time is its opening event's `event_ts`.
#[derive(Clone, Copy, Debug, PartialEq, serde::Serialize, serde::Deserialize)]
pub struct PositionEvent {
    pub event_ts: Timestamp,
    pub action: PositionAction,
    /// Monotonic, assigned at open. A Close references an existing `position_id`.
    pub position_id: i64,
    pub instrument_id: i64,
    /// Lots, unsigned. A partial close carries its own (smaller) volume.
    pub volume: f64,
}

/// The reproducible run descriptor (C18). **Caller-supplied**: the engine
/// cannot introspect a git commit, an RNG seed, or a broker label — the World
/// that bootstraps and runs the harness fills these in.
#[derive(Clone, Debug, PartialEq, serde::Serialize, serde::Deserialize)]
pub struct RunManifest {
    /// Node/engine identity: the git commit of the frozen artifact (C18 —
    /// commit = identity; the frozen bot *is* a commit).
    pub commit: String,
    /// The bound tuning params as ordered `name -> value` pairs. Each value is a
    /// self-describing [`Scalar`], so the param's kind (an `i64` length vs an
    /// `f64` scale) survives into the record instead of collapsing to `f64`.
    pub params: Vec<(String, Scalar)>,
    /// The data-window: inclusive `(from, to)` epoch-ns bounds (C12).
    pub window: (Timestamp, Timestamp),
    /// The RNG seed (C12 seed-as-input). `0` for a seed-free synthetic run.
    pub seed: u64,
    /// The broker profile label, e.g. `"sim-optimal(pip_size=0.0001)"`.
    pub broker: String,
}

/// A run's full structured result: the descriptor plus the metrics it
/// reproduces. The durable run record of C18 ("stores manifests + metrics,
/// re-derives full results on demand").
#[derive(Clone, Debug, PartialEq, serde::Serialize, serde::Deserialize)]
pub struct RunReport {
    pub manifest: RunManifest,
    pub metrics: RunMetrics,
}

impl RunReport {
    /// Render the canonical, machine-readable JSON (C14) via serde — the same
    /// encoder the run registry uses on disk, so a record's stdout shape and its
    /// `runs.jsonl` shape are byte-identical. `params` is an array of
    /// `[name, value]` pairs where `value` is a self-describing tagged scalar
    /// (serde's externally-tagged enum: `{"I64": 10}` for a length, `{"F64": 2.5}`
    /// for a scale). Consumers parse the tagged object, never a bare number.
    pub fn to_json(&self) -> String {
        serde_json::to_string(self).expect("a finite RunReport always serializes")
    }
}

/// Reduce a run's recorded pip-equity + exposure streams into summary metrics.
/// Pure — identical inputs yield identical metrics (C1/C12). Timestamps are
/// carried in the input to match exactly what a sink records; the reduction
/// itself is value-only (it does not read the timestamps).
pub fn summarize(
    equity: &[(Timestamp, f64)],
    exposure: &[(Timestamp, f64)],
) -> RunMetrics {
    // total pips: the last cumulative equity value (0.0 if empty).
    let total_pips = equity.last().map(|&(_, v)| v).unwrap_or(0.0);

    // max drawdown: the largest running-peak-minus-value, always >= 0.0.
    let mut peak = f64::NEG_INFINITY;
    let mut max_drawdown = 0.0_f64;
    for &(_, v) in equity {
        if v > peak {
            peak = v;
        }
        let dd = peak - v;
        if dd > max_drawdown {
            max_drawdown = dd;
        }
    }

    // exposure sign-flips: adjacent samples whose normalized sign differs.
    let mut exposure_sign_flips = 0u64;
    let mut prev: Option<f64> = None;
    for &(_, v) in exposure {
        let s = sign0(v);
        if let Some(p) = prev
            && s != p
        {
            exposure_sign_flips += 1;
        }
        prev = Some(s);
    }

    RunMetrics { total_pips, max_drawdown, exposure_sign_flips }
}

/// Three-way sign: `-1.0` / `0.0` / `+1.0`. Unlike `f64::signum` (which returns
/// `+1.0` for `+0.0`), a zero exposure maps to `0.0` so flat is distinct from
/// long/short in the sign-flip count.
fn sign0(v: f64) -> f64 {
    if v > 0.0 {
        1.0
    } else if v < 0.0 {
        -1.0
    } else {
        0.0
    }
}

/// Bridge a recording sink's recorded `(ts, row)` stream to [`summarize`]:
/// extract one `f64` field of each row into `(ts, f64)` samples. Panics if a
/// row has no such field or the field is not an `f64` scalar — a wiring bug (a
/// sink's declared kinds are fixed at bootstrap, so a correctly-wired
/// equity/exposure sink always yields `f64` at field 0), surfaced like the
/// engine's other "checked at wiring" contract violations rather than silently
/// dropped.
pub fn f64_field(rows: &[(Timestamp, Vec<Scalar>)], field: usize) -> Vec<(Timestamp, f64)> {
    rows.iter()
        .map(|(ts, row)| {
            let Some(&scalar) = row.get(field) else {
                panic!("f64_field: row has no field {field} (row width {})", row.len());
            };
            if scalar.kind() != ScalarKind::F64 {
                panic!("f64_field: field {field} is not an f64 scalar: {scalar:?}");
            }
            (*ts, scalar.as_f64())
        })
        .collect()
}

/// One spine row joined with each side stream's row recorded at the same
/// timestamp. `sides` is parallel to the `sides` argument of [`join_on_ts`]; an
/// entry is `None` where that side did not fire at this spine timestamp.
#[derive(Clone, Debug, PartialEq)]
pub struct JoinedRow {
    pub ts: Timestamp,
    pub spine: Vec<Scalar>,
    pub sides: Vec<Option<Vec<Scalar>>>,
}

/// Join recording-sink tap streams on their recorded timestamp (C8/C18: a post-run
/// reduction over recorded sink output; C3: NOT an in-graph join).
///
/// `spine` defines the row set — exactly one [`JoinedRow`] per spine entry, in
/// spine order. Each side stream is looked up by timestamp: `Some(row)` where it
/// fired at that timestamp, `None` where it did not. The helper does not interpret
/// a row's columns (it returns each whole); the caller maps `None` to whatever
/// default its column means.
///
/// Precondition (C1): each stream has at most one row per timestamp — a sink fires
/// at most once per cycle and cycles have unique timestamps. A duplicate timestamp
/// within one stream resolves last-write-wins. A side row whose timestamp is absent
/// from the spine is dropped (the spine defines the rows).
pub fn join_on_ts(
    spine: &[(Timestamp, Vec<Scalar>)],
    sides: &[&[(Timestamp, Vec<Scalar>)]],
) -> Vec<JoinedRow> {
    let side_maps: Vec<HashMap<i64, &Vec<Scalar>>> = sides
        .iter()
        .map(|s| s.iter().map(|(t, row)| (t.0, row)).collect())
        .collect();

    spine
        .iter()
        .map(|(ts, row)| JoinedRow {
            ts: *ts,
            spine: row.clone(),
            sides: side_maps.iter().map(|m| m.get(&ts.0).map(|r| (*r).clone())).collect(),
        })
        .collect()
}

/// One drained recorder tap in columnar (SoA) form: parallel arrays, one per
/// recorded column, plus the shared recorded-timestamp axis. Chart-ready (a column
/// is a series of numbers) and kind-tagged (C7) — values are coerced to f64 for
/// plotting; the base type survives in `kinds`. Pure: identical rows always encode
/// to the same value (C1).
#[derive(Clone, Debug, PartialEq, serde::Serialize, serde::Deserialize)]
pub struct ColumnarTrace {
    pub tap: String,
    pub kinds: Vec<String>,
    pub ts: Vec<i64>,
    pub columns: Vec<Vec<f64>>,
}

impl ColumnarTrace {
    /// Transpose a drained tap's `(ts, row)` pairs into columns. An empty `rows`
    /// yields empty `ts` and one empty column per kind. Each cell is coerced to f64:
    /// f64 as-is, i64 as f64, bool 1.0/0.0, timestamp epoch as f64. Panics if any
    /// row's width disagrees with `kinds.len()` — a wiring bug (a sink's column
    /// count is fixed at bootstrap), surfaced as a named panic like
    /// [`f64_field`] rather than a bare index-out-of-bounds (wider) or silent
    /// ragged columns (narrower).
    pub fn from_rows(tap: &str, kinds: &[ScalarKind], rows: &[(Timestamp, Vec<Scalar>)]) -> Self {
        let ts: Vec<i64> = rows.iter().map(|(t, _)| t.0).collect();
        let mut columns: Vec<Vec<f64>> = vec![Vec::with_capacity(rows.len()); kinds.len()];
        for (_, row) in rows {
            if row.len() != kinds.len() {
                panic!(
                    "from_rows: row width {} disagrees with kinds.len() {} (tap {tap:?})",
                    row.len(),
                    kinds.len(),
                );
            }
            for (c, scalar) in row.iter().enumerate() {
                columns[c].push(scalar_to_f64(*scalar));
            }
        }
        ColumnarTrace {
            tap: tap.to_string(),
            kinds: kinds.iter().map(kind_tag).collect(),
            ts,
            columns,
        }
    }

    /// Inverse for the serve/align path: rebuild `(ts, row)` pairs with each cell as
    /// `Scalar::f64(columns[c][r])` — uniformly f64 (the on-disk store is f64
    /// columns; the base type survives only in `kinds`). A true value round-trip for
    /// f64 taps; keeps the serve-side `as_f64` projection total.
    pub fn to_rows(&self) -> Vec<(Timestamp, Vec<Scalar>)> {
        self.ts
            .iter()
            .enumerate()
            .map(|(r, &t)| {
                let row = self.columns.iter().map(|col| Scalar::f64(col[r])).collect();
                (Timestamp(t), row)
            })
            .collect()
    }
}

/// The four-kind tag string for a column (the on-disk `kinds` form; `ScalarKind`
/// derives no serde, so tags are plain strings).
fn kind_tag(kind: &ScalarKind) -> String {
    match kind {
        ScalarKind::F64 => "F64",
        ScalarKind::I64 => "I64",
        ScalarKind::Bool => "Bool",
        ScalarKind::Timestamp => "Timestamp",
    }
    .to_string()
}

/// Coerce a recorded scalar to the f64 a chart plots: f64 as-is, i64 as f64,
/// bool 1.0/0.0, timestamp epoch as f64.
fn scalar_to_f64(s: Scalar) -> f64 {
    match s.kind() {
        ScalarKind::F64 => s.as_f64(),
        ScalarKind::I64 => s.as_i64() as f64,
        ScalarKind::Bool => {
            if s.as_bool() {
                1.0
            } else {
                0.0
            }
        }
        ScalarKind::Timestamp => s.as_ts().0 as f64,
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{Edge, FlatGraph, Harness, SourceSpec, Target, VecSource};
    use aura_core::{Firing, NodeSchema, PortSpec, ScalarKind};
    use aura_std::{Exposure, Recorder, SimBroker, Sma, Sub};
    use std::sync::mpsc;

    #[test]
    fn position_action_round_trips_through_i64() {
        for a in [PositionAction::Buy, PositionAction::Sell, PositionAction::Close] {
            let n: i64 = a.into();
            assert_eq!(PositionAction::try_from(n), Ok(a));
        }
        assert_eq!(i64::from(PositionAction::Buy), 0);
        assert_eq!(i64::from(PositionAction::Sell), 1);
        assert_eq!(i64::from(PositionAction::Close), 2);
    }

    #[test]
    fn position_action_rejects_out_of_range_i64() {
        assert!(PositionAction::try_from(3).is_err());
        assert!(PositionAction::try_from(-1).is_err());
    }

    #[test]
    fn position_event_serde_round_trips_with_bare_int_action() {
        let ev = PositionEvent {
            event_ts: Timestamp(42),
            action: PositionAction::Sell,
            position_id: 7,
            instrument_id: 3,
            volume: 0.5,
        };
        let json = serde_json::to_string(&ev).expect("serialize");
        // action encodes as a bare integer (C7 scalar shape), not a tagged enum
        assert!(json.contains("\"action\":1"), "action not bare-int encoded: {json}");
        let back: PositionEvent = serde_json::from_str(&json).expect("deserialize");
        assert_eq!(back, ev);
    }

    #[test]
    fn position_events_may_share_one_event_ts_on_reversal() {
        // a stop-and-reverse: Close then open at the SAME event_ts (close-before-open).
        let ts = Timestamp(100);
        let close = PositionEvent {
            event_ts: ts, action: PositionAction::Close,
            position_id: 1, instrument_id: 3, volume: 0.5,
        };
        let open = PositionEvent {
            event_ts: ts, action: PositionAction::Sell,
            position_id: 2, instrument_id: 3, volume: 0.5,
        };
        let table = [close, open];
        assert_eq!(table[0].event_ts, table[1].event_ts);
        assert_eq!(table[0].action, PositionAction::Close);
        assert_eq!(table[1].action, PositionAction::Sell);
    }

    /// The declared signature of a `Recorder` over one f64 column (the sink shape
    /// the two-sink harness uses).
    fn f64_recorder_sig() -> NodeSchema {
        NodeSchema {
            inputs: vec![PortSpec { kind: ScalarKind::F64, firing: Firing::Any, name: "in".into() }],
            output: vec![],
            params: vec![],
        }
    }

    /// Build an f64 source stream from (timestamp, value) points (mirrors the
    /// harness.rs test helper; the e2e test needs its own copy — the harness
    /// test module's is private to that module).
    fn f64_stream(points: &[(i64, f64)]) -> Vec<(Timestamp, Scalar)> {
        points.iter().map(|&(t, v)| (Timestamp(t), Scalar::f64(v))).collect()
    }

    /// Bootstrap the cycle-0007 signal-quality harness with TWO sinks: one on
    /// the SimBroker equity output (node 4 -> node 5) and one on the Exposure
    /// output (node 3 -> node 6). Returns the harness plus the two receivers.
    #[allow(clippy::type_complexity)]
    fn build_two_sink_harness() -> (
        Harness,
        mpsc::Receiver<(Timestamp, Vec<Scalar>)>,
        mpsc::Receiver<(Timestamp, Vec<Scalar>)>,
    ) {
        let (tx_eq, rx_eq) = mpsc::channel();
        let (tx_ex, rx_ex) = mpsc::channel();
        let h = Harness::bootstrap(FlatGraph {
            nodes: vec![
                Box::new(Sma::new(2)),                                       // 0
                Box::new(Sma::new(4)),                                       // 1
                Box::new(Sub::new()),                                        // 2
                Box::new(Exposure::new(0.5)),                                // 3
                Box::new(SimBroker::new(0.0001)),                            // 4
                Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx_eq)), // 5 equity sink
                Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx_ex)), // 6 exposure sink
            ],
            signatures: vec![
                Sma::builder().schema().clone(),
                Sma::builder().schema().clone(),
                Sub::builder().schema().clone(),
                Exposure::builder().schema().clone(),
                SimBroker::builder(0.0001).schema().clone(),
                f64_recorder_sig(),
                f64_recorder_sig(),
            ],
            sources: vec![SourceSpec {
                kind: ScalarKind::F64,
                targets: vec![
                    Target { node: 0, slot: 0 },
                    Target { node: 1, slot: 0 },
                    Target { node: 4, slot: 1 }, // price into the broker
                ],
            }],
            edges: vec![
                Edge { from: 0, to: 2, slot: 0, from_field: 0 },
                Edge { from: 1, to: 2, slot: 1, from_field: 0 },
                Edge { from: 2, to: 3, slot: 0, from_field: 0 },
                Edge { from: 3, to: 4, slot: 0, from_field: 0 },
                Edge { from: 4, to: 5, slot: 0, from_field: 0 }, // equity -> sink 5
                Edge { from: 3, to: 6, slot: 0, from_field: 0 }, // exposure -> sink 6
            ],
        })
        .expect("valid signal-quality DAG");
        (h, rx_eq, rx_ex)
    }

    fn run_once() -> RunReport {
        let (mut h, rx_eq, rx_ex) = build_two_sink_harness();
        h.run(vec![Box::new(VecSource::new(f64_stream(&[
            (1, 1.0000),
            (2, 1.0010),
            (3, 1.0025),
            (4, 1.0020),
            (5, 1.0040),
        ])))]);
        let eq_rows: Vec<(Timestamp, Vec<Scalar>)> = rx_eq.try_iter().collect();
        let ex_rows: Vec<(Timestamp, Vec<Scalar>)> = rx_ex.try_iter().collect();
        let equity = f64_field(&eq_rows, 0);
        let exposure = f64_field(&ex_rows, 0);
        let metrics = summarize(&equity, &exposure);
        RunReport {
            manifest: RunManifest {
                commit: "test-commit".to_string(),
                params: vec![
                    ("sma_fast".to_string(), Scalar::i64(2)),
                    ("sma_slow".to_string(), Scalar::i64(4)),
                    ("exposure_scale".to_string(), Scalar::f64(0.5)),
                ],
                window: (Timestamp(1), Timestamp(5)),
                seed: 0,
                broker: "sim-optimal(pip_size=0.0001)".to_string(),
            },
            metrics,
        }
    }

    #[test]
    fn report_is_deterministic_end_to_end() {
        let r1 = run_once();
        let r2 = run_once();
        // a run actually emitted metrics over a non-empty pip curve
        assert!(r1.metrics.total_pips.is_finite());
        // same manifest -> same metrics (C1/C12): two runs are bit-identical
        assert_eq!(r1.metrics, r2.metrics);
        assert_eq!(r1.to_json(), r2.to_json());
    }

    fn samples(values: &[f64]) -> Vec<(Timestamp, f64)> {
        values
            .iter()
            .enumerate()
            .map(|(i, &v)| (Timestamp(i as i64 + 1), v))
            .collect()
    }

    #[test]
    fn summarize_total_pips_is_last_cumulative_value() {
        let equity = samples(&[0.0, 5.0, 4.0, 12.0]);
        let m = summarize(&equity, &[]);
        assert_eq!(m.total_pips, 12.0);
    }

    #[test]
    fn summarize_is_zero_on_empty_streams() {
        let m = summarize(&[], &[]);
        assert_eq!(m.total_pips, 0.0);
        assert_eq!(m.max_drawdown, 0.0);
        assert_eq!(m.exposure_sign_flips, 0);
    }

    #[test]
    fn summarize_max_drawdown_is_worst_peak_to_trough() {
        // peak 10 then trough 5 (drop 5), recovers to 8; worst drop is 5,
        // not the final drop (10 -> 8 = 2).
        let equity = samples(&[0.0, 10.0, 5.0, 8.0]);
        let m = summarize(&equity, &[]);
        assert_eq!(m.max_drawdown, 5.0);
    }

    #[test]
    fn summarize_max_drawdown_zero_on_monotonic_curve() {
        let equity = samples(&[0.0, 1.0, 2.0, 3.0]);
        let m = summarize(&equity, &[]);
        assert_eq!(m.max_drawdown, 0.0);
    }

    #[test]
    fn summarize_sign_flips_counts_signum_changes() {
        // signum series: + + - 0 -  ->  flips at +->-, -->0, 0->- = 3.
        let exposure = samples(&[0.5, 0.5, -0.5, 0.0, -0.5]);
        let m = summarize(&[], &exposure);
        assert_eq!(m.exposure_sign_flips, 3);
    }

    #[test]
    fn summarize_sign_flips_zero_on_constant_sign() {
        let exposure = samples(&[0.2, 0.5, 1.0, 0.7]);
        let m = summarize(&[], &exposure);
        assert_eq!(m.exposure_sign_flips, 0);
    }

    #[test]
    fn f64_field_projects_the_named_field() {
        let rows = vec![
            (Timestamp(1), vec![Scalar::f64(1.5), Scalar::i64(9)]),
            (Timestamp(2), vec![Scalar::f64(2.5), Scalar::i64(8)]),
        ];
        assert_eq!(
            f64_field(&rows, 0),
            vec![(Timestamp(1), 1.5), (Timestamp(2), 2.5)],
        );
    }

    #[test]
    #[should_panic(expected = "not an f64 scalar")]
    fn f64_field_panics_on_kind_mismatch() {
        let rows = vec![(Timestamp(1), vec![Scalar::i64(7)])];
        let _ = f64_field(&rows, 0);
    }

    #[test]
    fn to_json_renders_the_canonical_form() {
        let report = RunReport {
            manifest: RunManifest {
                commit: "abc123".to_string(),
                params: vec![
                    ("sma_fast".to_string(), Scalar::i64(2)),
                    ("sma_slow".to_string(), Scalar::i64(4)),
                    ("exposure_scale".to_string(), Scalar::f64(1.0)),
                ],
                window: (Timestamp(1), Timestamp(6)),
                seed: 0,
                broker: "sim-optimal(pip_size=1.0)".to_string(),
            },
            metrics: RunMetrics {
                total_pips: 12.0,
                max_drawdown: 1.0,
                exposure_sign_flips: 1,
            },
        };
        assert_eq!(
            report.to_json(),
            r#"{"manifest":{"commit":"abc123","params":[["sma_fast",{"I64":2}],["sma_slow",{"I64":4}],["exposure_scale",{"F64":1.0}]],"window":[1,6],"seed":0,"broker":"sim-optimal(pip_size=1.0)"},"metrics":{"total_pips":12.0,"max_drawdown":1.0,"exposure_sign_flips":1}}"#,
        );
    }

    #[test]
    fn to_json_equals_serde_disk_shape() {
        // the same RunReport value the canonical-form test builds.
        let report = RunReport {
            manifest: RunManifest {
                commit: "abc123".to_string(),
                params: vec![
                    ("sma_fast".to_string(), Scalar::i64(2)),
                    ("sma_slow".to_string(), Scalar::i64(4)),
                    ("exposure_scale".to_string(), Scalar::f64(1.0)),
                ],
                window: (Timestamp(1), Timestamp(6)),
                seed: 0,
                broker: "sim-optimal(pip_size=1.0)".to_string(),
            },
            metrics: RunMetrics { total_pips: 12.0, max_drawdown: 1.0, exposure_sign_flips: 1 },
        };
        // stdout (to_json) and disk (serde_json::to_string) are now the same bytes.
        assert_eq!(report.to_json(), serde_json::to_string(&report).unwrap());
    }

    #[test]
    fn runreport_serde_round_trips() {
        let report = RunReport {
            manifest: RunManifest {
                commit: "abc123".to_string(),
                params: vec![
                    ("sma_fast".to_string(), Scalar::i64(2)),
                    ("sma_slow".to_string(), Scalar::i64(4)),
                    ("exposure_scale".to_string(), Scalar::f64(1.0)),
                ],
                window: (Timestamp(1), Timestamp(6)),
                seed: 0,
                broker: "sim-optimal(pip_size=1.0)".to_string(),
            },
            metrics: RunMetrics { total_pips: 12.0, max_drawdown: 1.0, exposure_sign_flips: 1 },
        };
        let json = serde_json::to_string(&report).expect("serialize RunReport");
        // window is a 2-element [from, to] array (Timestamp newtype is transparent)
        assert!(json.contains("\"window\":[1,6]"), "window shape: {json}");
        let back: RunReport = serde_json::from_str(&json).expect("deserialize RunReport");
        assert_eq!(back, report);
    }

    #[test]
    fn join_on_ts_aligns_streams_of_different_cardinality() {
        // spine fires every bar; side A is one row shorter (no ts 10, like cold
        // Delay(1) on the first bar); side B fires on a subset (only ts 20, 40,
        // like a Session filter before the open).
        let spine = vec![
            (Timestamp(10), vec![Scalar::f64(1.0)]),
            (Timestamp(20), vec![Scalar::f64(2.0)]),
            (Timestamp(30), vec![Scalar::f64(3.0)]),
            (Timestamp(40), vec![Scalar::f64(4.0)]),
        ];
        let side_a = vec![
            (Timestamp(20), vec![Scalar::bool(true)]),
            (Timestamp(30), vec![Scalar::bool(false)]),
            (Timestamp(40), vec![Scalar::bool(true)]),
        ];
        let side_b = vec![
            (Timestamp(20), vec![Scalar::i64(0)]),
            (Timestamp(40), vec![Scalar::i64(2)]),
        ];

        let joined = join_on_ts(&spine, &[&side_a, &side_b]);

        // one row per spine entry, in spine order
        assert_eq!(joined.len(), 4);
        assert_eq!(
            joined.iter().map(|j| j.ts).collect::<Vec<_>>(),
            vec![Timestamp(10), Timestamp(20), Timestamp(30), Timestamp(40)]
        );

        // ts 10: spine present, both sides absent (the zip-by-index misalignment case)
        assert_eq!(joined[0].spine, vec![Scalar::f64(1.0)]);
        assert_eq!(joined[0].sides[0], None);
        assert_eq!(joined[0].sides[1], None);

        // ts 20: both sides present and aligned to THIS ts
        assert_eq!(joined[1].sides[0], Some(vec![Scalar::bool(true)]));
        assert_eq!(joined[1].sides[1], Some(vec![Scalar::i64(0)]));

        // ts 30: side A present, side B absent
        assert_eq!(joined[2].sides[0], Some(vec![Scalar::bool(false)]));
        assert_eq!(joined[2].sides[1], None);

        // ts 40: both present
        assert_eq!(joined[3].sides[0], Some(vec![Scalar::bool(true)]));
        assert_eq!(joined[3].sides[1], Some(vec![Scalar::i64(2)]));
    }

    #[test]
    fn join_on_ts_drops_side_rows_absent_from_spine() {
        // a side row whose ts is not in the spine is dropped — the spine defines
        // the row set.
        let spine = vec![(Timestamp(10), vec![Scalar::f64(1.0)])];
        let side = vec![
            (Timestamp(10), vec![Scalar::i64(7)]),
            (Timestamp(99), vec![Scalar::i64(8)]), // ts 99 absent from spine -> dropped
        ];

        let joined = join_on_ts(&spine, &[&side]);

        assert_eq!(joined.len(), 1);
        assert_eq!(joined[0].ts, Timestamp(10));
        assert_eq!(joined[0].sides[0], Some(vec![Scalar::i64(7)]));
    }

    #[test]
    fn columnar_trace_round_trips_f64_rows() {
        let rows = vec![
            (Timestamp(2), vec![Scalar::f64(10.0)]),
            (Timestamp(3), vec![Scalar::f64(20.0)]),
            (Timestamp(4), vec![Scalar::f64(30.0)]),
        ];
        let ct = ColumnarTrace::from_rows("equity", &[ScalarKind::F64], &rows);
        assert_eq!(ct.tap, "equity");
        assert_eq!(ct.kinds, vec!["F64".to_string()]);
        assert_eq!(ct.ts, vec![2, 3, 4]);
        assert_eq!(ct.columns, vec![vec![10.0, 20.0, 30.0]]);
        // to_rows is the inverse for f64 taps
        assert_eq!(ct.to_rows(), rows);
    }

    #[test]
    fn columnar_trace_empty_rows_yields_empty_columns_sized_to_kinds() {
        let ct = ColumnarTrace::from_rows("exposure", &[ScalarKind::F64], &[]);
        assert_eq!(ct.ts, Vec::<i64>::new());
        assert_eq!(ct.columns, vec![Vec::<f64>::new()]);
        assert!(ct.to_rows().is_empty());
    }

    #[test]
    fn columnar_trace_coerces_non_f64_kinds_to_f64() {
        let rows = vec![
            (Timestamp(1), vec![Scalar::i64(7), Scalar::bool(true)]),
            (Timestamp(2), vec![Scalar::i64(9), Scalar::bool(false)]),
        ];
        let ct = ColumnarTrace::from_rows("mix", &[ScalarKind::I64, ScalarKind::Bool], &rows);
        assert_eq!(ct.kinds, vec!["I64".to_string(), "Bool".to_string()]);
        assert_eq!(ct.columns, vec![vec![7.0, 9.0], vec![1.0, 0.0]]);
    }

    /// The fourth coercion arm: a Timestamp-kind column tags as "Timestamp" and
    /// its epoch-ns survives the f64 projection (`scalar_to_f64` reads `as_ts().0`),
    /// closing the kind for which `from_rows` would otherwise be untested.
    #[test]
    fn columnar_trace_coerces_timestamp_kind_to_epoch_f64() {
        let rows = vec![
            (Timestamp(1), vec![Scalar::ts(Timestamp(1_700_000_000_000_000_000))]),
            (Timestamp(2), vec![Scalar::ts(Timestamp(1_700_000_000_000_000_060))]),
        ];
        let ct = ColumnarTrace::from_rows("clock", &[ScalarKind::Timestamp], &rows);
        assert_eq!(ct.kinds, vec!["Timestamp".to_string()]);
        assert_eq!(
            ct.columns,
            vec![vec![1_700_000_000_000_000_000.0, 1_700_000_000_000_000_060.0]],
        );
    }

    /// A row wider than the declared kinds is a wiring bug (a sink's column count
    /// is fixed at bootstrap), surfaced as a named panic like `f64_field` — not a
    /// bare index-out-of-bounds.
    #[test]
    #[should_panic(expected = "row width 2 disagrees with kinds.len() 1")]
    fn from_rows_panics_on_row_wider_than_kinds() {
        let rows = vec![(Timestamp(1), vec![Scalar::f64(1.0), Scalar::f64(2.0)])];
        let _ = ColumnarTrace::from_rows("wide", &[ScalarKind::F64], &rows);
    }

    /// Symmetric to the wide case: a row narrower than the declared kinds is the
    /// same wiring-bug class and carries the same named panic.
    #[test]
    #[should_panic(expected = "row width 1 disagrees with kinds.len() 2")]
    fn from_rows_panics_on_row_narrower_than_kinds() {
        let rows = vec![(Timestamp(1), vec![Scalar::f64(1.0)])];
        let _ = ColumnarTrace::from_rows("narrow", &[ScalarKind::F64, ScalarKind::F64], &rows);
    }
}