feat(insights): read location context from Apollo (#177)

The local location_history table is a one-time Takeout import: it ends
in 2019, still has the ghost-device and coarse cell-fix samples Apollo
has since excluded, and was read loosely. The per-photo line took the
nearest sample within +/-3 h at any distance (17% of photo moments got a
position >2 km away), and get_location_history listed the first 20 rows
of a +/-14-day window sorted ascending (always ~14 days before the date).

With APOLLO_API_BASE_URL set:
- per-photo context comes from /api/location/at (30 min max gap; no
  sample -> no line). A Place stay renders as "at Home (14:02-18:30)" in
  the display zone; an unnamed sample is reverse-geocoded.
- get_location_history returns Apollo's /api/location/day timeline for
  the date (+/-1 day at most), and is offered even with an empty local
  table.

Both fall back to the local table when Apollo is unset or a call fails;
the local tool path now covers the requested local day(s) and samples
evenly instead of listing a window's first rows.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ai/apollo_client.rs

@@ -1,4 +1,5 @@
-//! Thin async HTTP client for Apollo's `/api/places/*` endpoints.
+//! Thin async HTTP client for Apollo's `/api/places/*` and
+//! `/api/location/*` endpoints.
 //!
 //! Apollo (the personal location-history viewer at the sibling repo) owns
 //! user-defined Places: `name + lat/lon + radius_m + description (+ optional
@@ -10,6 +11,14 @@
 //! 2. The agentic `get_personal_place_at` tool — lets the LLM ask "what
 //!    user-defined place contains this lat/lon" during chat continuation.
 //!
+//! Apollo also owns the location track itself — cleaned of ghost devices
+//! and coarse cell fixes, and current (HA siphon, Garmin), unlike the
+//! frozen 2019 Takeout import in our `location_history` table. The
+//! insight path's location context (`/api/location/at`) and the
+//! `get_location_history` tool (`/api/location/day`) read it from Apollo
+//! when configured (ImageApi #177, Apollo #51), falling back to the local
+//! table when Apollo is unset or a call fails.
+//!
 //! Apollo does the haversine. This client is plumbing only — no geometry,
 //! no caching at the moment. If insight throughput ever makes per-photo
 //! HTTP latency a problem, swap to a small `Mutex<HashMap>` TTL cache here.
@@ -46,6 +55,73 @@ struct PlacesResponse {
     places: Vec<ApolloPlace>,
 }
 
+/// A kept location sample from Apollo, `offset_s` = sample ts − asked ts.
+#[allow(dead_code)]
+#[derive(Debug, Clone, Deserialize)]
+pub struct LocationSample {
+    pub ts: i64,
+    pub lat: f64,
+    pub lon: f64,
+    #[serde(default)]
+    pub accuracy: Option<i32>,
+    #[serde(default)]
+    pub activity: Option<String>,
+    pub offset_s: i64,
+}
+
+#[allow(dead_code)]
+#[derive(Debug, Clone, Deserialize)]
+pub struct LocationPlace {
+    pub id: i32,
+    pub name: String,
+    #[serde(default)]
+    pub category: Option<String>,
+    pub radius_m: i32,
+}
+
+/// The Place stay (run of samples inside one Place) covering an instant.
+#[allow(dead_code)]
+#[derive(Debug, Clone, Deserialize)]
+pub struct LocationStay {
+    pub place_id: i32,
+    #[serde(default)]
+    pub name: Option<String>,
+    pub t0: i64,
+    pub t1: i64,
+}
+
+/// `/api/location/at`: where the owner was at an instant. `sample` is
+/// `None` when no kept sample lies within `max_gap` — Apollo says "no
+/// data" rather than handing back a position from hours away.
+#[allow(dead_code)]
+#[derive(Debug, Clone, Deserialize)]
+pub struct LocationAt {
+    pub ts: i64,
+    #[serde(default)]
+    pub sample: Option<LocationSample>,
+    #[serde(default)]
+    pub nearest_offset_s: Option<i64>,
+    #[serde(default)]
+    pub bracketed: bool,
+    #[serde(default)]
+    pub place: Option<LocationPlace>,
+    #[serde(default)]
+    pub stay: Option<LocationStay>,
+}
+
+/// `/api/location/day`: the owner's timeline for one local day. `text` is
+/// Apollo's compact rendering (one "HH:MM–HH:MM at Home" line per stay /
+/// dwell / travel / gap), meant to go into a tool result as-is; the
+/// structured `items` aren't needed here.
+#[allow(dead_code)]
+#[derive(Debug, Clone, Deserialize)]
+pub struct LocationDay {
+    pub tz: String,
+    pub points: i64,
+    pub km: f64,
+    pub text: String,
+}
+
 #[derive(Clone)]
 pub struct ApolloClient {
     client: Client,
@@ -90,6 +166,52 @@ impl ApolloClient {
         }
     }
 
+    /// Where the owner was at `ts` (real UTC seconds). `None` when the
+    /// integration is disabled or the call fails — callers fall back to
+    /// the local table; `Some` with `sample: None` means Apollo answered
+    /// "no data within `max_gap`", which callers should respect.
+    pub async fn location_at(&self, ts: i64, max_gap: i64) -> Option<LocationAt> {
+        let base = self.base_url.as_deref()?;
+        let url = format!("{}/api/location/at", base.trim_end_matches('/'));
+        let result: Result<LocationAt> = async {
+            Ok(self
+                .client
+                .get(&url)
+                .query(&[("ts", ts), ("max_gap", max_gap)])
+                .send()
+                .await?
+                .error_for_status()?
+                .json()
+                .await?)
+        }
+        .await;
+        result
+            .map_err(|err| log::warn!("apollo_client: location_at({ts}) failed: {err}"))
+            .ok()
+    }
+
+    /// The owner's timeline for `date` (YYYY-MM-DD) as a local day in
+    /// `tz` (IANA). `None` when disabled or the call fails.
+    pub async fn location_day(&self, date: &str, tz: &str) -> Option<LocationDay> {
+        let base = self.base_url.as_deref()?;
+        let url = format!("{}/api/location/day", base.trim_end_matches('/'));
+        let result: Result<LocationDay> = async {
+            Ok(self
+                .client
+                .get(&url)
+                .query(&[("date", date), ("tz", tz)])
+                .send()
+                .await?
+                .error_for_status()?
+                .json()
+                .await?)
+        }
+        .await;
+        result
+            .map_err(|err| log::warn!("apollo_client: location_day({date}, {tz}) failed: {err}"))
+            .ok()
+    }
+
     async fn fetch_places_containing(
         &self,
         base: &str,
@@ -108,3 +230,50 @@ impl ApolloClient {
         Ok(body.places)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn location_at_parses_hit_and_miss() {
+        let hit: LocationAt = serde_json::from_str(
+            r#"{"ts": 100, "max_gap": 1800,
+                "sample": {"ts": 120, "lat": 41.46, "lon": -81.93, "accuracy": 19, "activity": "STILL", "offset_s": 20},
+                "nearest_offset_s": 20, "bracketed": true,
+                "place": {"id": 7, "name": "Work", "category": null, "radius_m": 250},
+                "stay": {"place_id": 7, "name": "Work", "t0": 50, "t1": 900}}"#,
+        )
+        .unwrap();
+        assert_eq!(hit.sample.unwrap().offset_s, 20);
+        assert_eq!(hit.place.unwrap().name, "Work");
+        assert_eq!(hit.stay.unwrap().t1, 900);
+
+        let miss: LocationAt = serde_json::from_str(
+            r#"{"ts": 100, "max_gap": 1800, "sample": null, "nearest_offset_s": -7200,
+                "bracketed": false, "place": null, "stay": null}"#,
+        )
+        .unwrap();
+        assert!(miss.sample.is_none());
+        assert_eq!(miss.nearest_offset_s, Some(-7200));
+    }
+
+    #[test]
+    fn location_day_ignores_items() {
+        let day: LocationDay = serde_json::from_str(
+            r#"{"start": 0, "end": 86400, "tz": "America/New_York",
+                "items": [{"kind": "gap", "t0": 0, "t1": 1}], "points": 3, "km": 1.5,
+                "text": "00:00–23:59 at Home"}"#,
+        )
+        .unwrap();
+        assert_eq!(day.text, "00:00–23:59 at Home");
+        assert_eq!(day.points, 3);
+    }
+
+    #[tokio::test]
+    async fn disabled_client_returns_none() {
+        let c = ApolloClient::new(None);
+        assert!(c.location_at(0, 1800).await.is_none());
+        assert!(c.location_day("2016-01-01", "UTC").await.is_none());
+    }
+}

src/ai/insight_generator.rs

@@ -11,7 +11,7 @@ use std::sync::{Arc, Mutex};
 use tracing::Instrument;
 use tracing_opentelemetry::OpenTelemetrySpanExt;
 
-use crate::ai::apollo_client::{ApolloClient, ApolloPlace};
+use crate::ai::apollo_client::{ApolloClient, ApolloPlace, LocationAt};
 use crate::ai::backend::{BackendKind, ResolvedBackend, SamplingOverrides};
 use crate::ai::llamacpp::LlamaCppClient;
 use crate::ai::llm_client::LlmClient;
@@ -114,6 +114,105 @@ fn compose_location_string(
     }
 }
 
+/// How far from a photo's instant Apollo may look for a location sample
+/// for the always-on insight context. Past this Apollo answers "no data"
+/// — the old local lookup took the nearest sample within ±3 h at any
+/// distance, and 17 % of photo moments got a position > 2 km from where
+/// the photo was taken.
+const APOLLO_LOCATION_MAX_GAP_S: i64 = 1800;
+
+/// Apollo activities that say nothing about what the owner was doing.
+const UNINFORMATIVE_ACTIVITIES: &[&str] = &["UNKNOWN", "TILTING", "EXITING_VEHICLE"];
+
+/// Render Apollo's `/api/location/at` answer as the insight prompt's
+/// location-history line, or `None` when it adds nothing:
+///
+/// - no sample within the gap → `None` ("no data" beats a stale position);
+/// - the photo has EXIF GPS within 500 m of the sample and Apollo knows no
+///   stay or activity → `None` (the EXIF location line already says it);
+/// - otherwise "You were at Home (14:02–18:30)", "at Home", or "near
+///   <nominatim or coords>", plus the activity and, when the fix is more
+///   than 5 min from the photo, how far off it is.
+///
+/// Stay times render in the owner's display zone. Free function so it can
+/// be tested without an InsightGenerator; `nominatim` is the caller's
+/// reverse-geocode of the sample (only needed when there's no Place).
+fn render_apollo_location(
+    at: &LocationAt,
+    exif_gps: Option<(f64, f64)>,
+    zone: chrono_tz::Tz,
+    nominatim: Option<String>,
+) -> Option<String> {
+    let sample = at.sample.as_ref()?;
+    let activity = sample
+        .activity
+        .as_deref()
+        .filter(|a| !UNINFORMATIVE_ACTIVITIES.contains(a));
+    if let Some((lat, lon)) = exif_gps {
+        let km = InsightGenerator::haversine_distance(lat, lon, sample.lat, sample.lon);
+        if km < 0.5 && at.stay.is_none() && activity.is_none() {
+            return None;
+        }
+    }
+    let hm = |ts: i64| {
+        DateTime::from_timestamp(ts, 0)
+            .map(|d| d.with_timezone(&zone).format("%H:%M").to_string())
+            .unwrap_or_default()
+    };
+    let place_name = at
+        .stay
+        .as_ref()
+        .and_then(|s| s.name.clone())
+        .or_else(|| at.place.as_ref().map(|p| p.name.clone()));
+    let mut line = match (&at.stay, place_name) {
+        (Some(stay), Some(name)) => {
+            format!("You were at {} ({}–{})", name, hm(stay.t0), hm(stay.t1))
+        }
+        (None, Some(name)) => format!("You were at {}", name),
+        (_, None) => match nominatim {
+            Some(n) => format!("You were near {}", n),
+            None => format!("You were near {:.4}, {:.4}", sample.lat, sample.lon),
+        },
+    };
+    if let Some(a) = activity {
+        line.push_str(&format!(" ({})", a));
+    }
+    if sample.offset_s.abs() > 300 {
+        line.push_str(&format!(
+            " [location fix {} min {} the photo]",
+            sample.offset_s.abs() / 60,
+            if sample.offset_s < 0 {
+                "before"
+            } else {
+                "after"
+            }
+        ));
+    }
+    Some(format!("Location history: {}", line))
+}
+
+/// One day of Apollo's timeline as a tool-result block.
+fn format_apollo_day(date: &str, day: &crate::ai::apollo_client::LocationDay) -> String {
+    format!(
+        "{} ({} location points, {:.1} km):\n{}",
+        date, day.points, day.km, day.text
+    )
+}
+
+/// Up to `limit` items spaced evenly through `items`, first and last
+/// included, in their original order.
+fn spread_evenly<T>(items: &[T], limit: usize) -> Vec<&T> {
+    if items.len() <= limit {
+        return items.iter().collect();
+    }
+    if limit < 2 {
+        return items.iter().take(limit).collect();
+    }
+    (0..limit)
+        .map(|k| &items[k * (items.len() - 1) / (limit - 1)])
+        .collect()
+}
+
 #[derive(Deserialize)]
 struct NominatimResponse {
     display_name: Option<String>,
@@ -352,7 +451,8 @@ impl InsightGenerator {
                 .expect("Unable to lock CalendarEventDao");
             dao.get_event_count().map(|n| n > 0).unwrap_or(false)
         };
-        let location_history_present = {
+        // Apollo serves the tool when configured, local table or not.
+        let location_history_present = self.apollo_enabled() || {
             let mut dao = self
                 .location_dao
                 .lock()
@@ -827,8 +927,10 @@ impl InsightGenerator {
         }
     }
 
-    /// Gather location context for photo timestamp
-    /// Finds nearest location record (±30 minutes)
+    /// Gather location context for photo timestamp. Asks Apollo
+    /// (`/api/location/at`, cleaned + current track, ±30 min) when it's
+    /// configured; falls back to the nearest local `location_history`
+    /// record within ±3 h when it isn't, or when the call fails.
     #[tracing::instrument(name = "ai.context.location", skip_all)]
     async fn gather_location_context(
         &self,
@@ -837,6 +939,27 @@ impl InsightGenerator {
     ) -> Result<Option<String>> {
         let span = tracing::Span::current();
 
+        if let Some(at) = self
+            .apollo_client
+            .location_at(timestamp, APOLLO_LOCATION_MAX_GAP_S)
+            .await
+        {
+            span.set_attribute("location_source", "apollo");
+            // Reverse-geocode only an unnamed sample on a photo without
+            // EXIF GPS — with EXIF, the location line already has it.
+            let nominatim = match (&at.sample, &at.place, &at.stay, exif_gps) {
+                (Some(s), None, None, None) => self.reverse_geocode(s.lat, s.lon).await,
+                _ => None,
+            };
+            span.set_status(Status::Ok);
+            return Ok(render_apollo_location(
+                &at,
+                exif_gps,
+                self.display_zone(),
+                nominatim,
+            ));
+        }
+
         let nearest = {
             let mut dao = self
                 .location_dao
@@ -2339,53 +2462,85 @@ Return ONLY the summary, nothing else."#,
         }
     }
 
-    /// Tool: get_location_history — fetch location records near a date
+    /// Tool: get_location_history — where the owner was on a date.
+    ///
+    /// With Apollo configured: Apollo's day timeline (`/api/location/day`:
+    /// Place stays, stops, travel with km, gaps) for the date's local day
+    /// in the owner's display zone, or for date±1 at most. Otherwise, or
+    /// if every Apollo call fails: up to `LOCATION_HISTORY_DISPLAY_LIMIT`
+    /// raw local records spaced evenly across the requested local days.
+    /// (The local path used to list the first 20 rows of a ±14-day window
+    /// sorted ascending — always ~14 days before the date asked about.)
     async fn tool_get_location_history(&self, args: &serde_json::Value) -> String {
         let date_str = match args.get("date").and_then(|v| v.as_str()) {
             Some(d) => d,
             None => return "Error: missing required parameter 'date'".to_string(),
         };
-        let days_radius = args
-            .get("days_radius")
-            .and_then(|v| v.as_i64())
-            .unwrap_or(14)
-            .clamp(1, 30);
-
         let date = match NaiveDate::parse_from_str(date_str, "%Y-%m-%d") {
             Ok(d) => d,
             Err(e) => return format!("Error: failed to parse date '{}': {}", date_str, e),
         };
-        let timestamp = date.and_hms_opt(12, 0, 0).unwrap().and_utc().timestamp();
+        let days_radius = args
+            .get("days_radius")
+            .and_then(|v| v.as_i64())
+            .unwrap_or(0);
+        let zone = self.display_zone();
 
         log::info!(
-            "tool_get_location_history: date={}, days_radius={}",
+            "tool_get_location_history: date={}, days_radius={}, apollo={}",
             date,
-            days_radius
+            days_radius,
+            self.apollo_client.is_enabled()
         );
 
-        let start_ts = timestamp - (days_radius * 86400);
-        let end_ts = timestamp + (days_radius * 86400);
+        if self.apollo_client.is_enabled() {
+            let r = days_radius.clamp(0, 1);
+            let mut days = Vec::new();
+            for d in -r..=r {
+                let day = date + chrono::Duration::days(d);
+                let day_str = day.format("%Y-%m-%d").to_string();
+                if let Some(t) = self.apollo_client.location_day(&day_str, zone.name()).await {
+                    days.push(format_apollo_day(&day_str, &t));
+                }
+            }
+            if !days.is_empty() {
+                return format!(
+                    "Location timeline ({}):\n\n{}",
+                    zone.name(),
+                    days.join("\n\n")
+                );
+            }
+            // Every call failed — fall through to the local table.
+        }
+
+        let r = days_radius.clamp(0, 30);
+        let midnight = |d: NaiveDate| {
+            zone.from_local_datetime(&d.and_hms_opt(0, 0, 0).unwrap())
+                .earliest()
+                .map(|t| t.timestamp())
+        };
+        let (Some(start_ts), Some(end_ts)) = (
+            midnight(date - chrono::Duration::days(r)),
+            midnight(date + chrono::Duration::days(r + 1)),
+        ) else {
+            return format!("Error: could not resolve local midnight for {}", date);
+        };
 
         let locations = {
             let mut dao = self
                 .location_dao
                 .lock()
                 .expect("Unable to lock LocationHistoryDao");
-            dao.find_locations_in_range(start_ts, end_ts).ok()
+            dao.find_locations_in_range(start_ts, end_ts - 1).ok()
         };
 
         match locations {
             Some(locs) if !locs.is_empty() => {
-                let formatted: Vec<String> = locs
-                    .iter()
-                    .take(LOCATION_HISTORY_DISPLAY_LIMIT)
+                let formatted: Vec<String> = spread_evenly(&locs, LOCATION_HISTORY_DISPLAY_LIMIT)
+                    .into_iter()
                     .map(|loc| {
                         let dt = DateTime::from_timestamp(loc.timestamp, 0)
-                            .map(|dt| {
-                                dt.with_timezone(&Local)
-                                    .format("%Y-%m-%d %H:%M")
-                                    .to_string()
-                            })
+                            .map(|dt| dt.with_timezone(&zone).format("%Y-%m-%d %H:%M").to_string())
                             .unwrap_or_else(|| "unknown".to_string());
                         let activity = loc
                             .activity
@@ -2403,14 +2558,18 @@ Return ONLY the summary, nothing else."#,
                         )
                     })
                     .collect();
-                format!(
-                    "{}\n{}",
-                    Self::found_header(locs.len(), formatted.len(), "location records"),
-                    formatted.join("\n")
-                )
+                let header = if formatted.len() < locs.len() {
+                    format!(
+                        "Found {} location records (showing {}, evenly spaced across the window):",
+                        locs.len(),
+                        formatted.len()
+                    )
+                } else {
+                    Self::found_header(locs.len(), formatted.len(), "location records")
+                };
+                format!("{}\n{}", header, formatted.join("\n"))
             }
-            Some(_) => "No location history found.".to_string(),
-            None => "No location history found.".to_string(),
+            _ => "No location history found.".to_string(),
         }
     }
 
@@ -3406,15 +3565,16 @@ Return ONLY the summary, nothing else."#,
         if opts.location_history_present {
             tools.push(Tool::function(
                 "get_location_history",
-                "Fetch raw location records (lat/lon/timestamp/activity) near a date. The default 14-day radius is \
-                 wide because location density varies; tighten to ±1 day for a single-trip query. For a coordinate's \
-                 named place, use `reverse_geocode` (or `get_personal_place_at` when Apollo is enabled).",
+                "Where the user was on a date: a timeline of named places (Home, Work, …) with arrival/departure \
+                 times, stops, travel with distances, and gaps with no data — or, without Apollo, raw location \
+                 records spread across the day. Times are local. For a coordinate's named place, use \
+                 `get_personal_place_at` (Apollo) or `reverse_geocode`.",
                 serde_json::json!({
                     "type": "object",
                     "required": ["date"],
                     "properties": {
-                        "date":        { "type": "string", "description": "Center date, YYYY-MM-DD." },
-                        "days_radius": { "type": "integer", "description": "Days before and after to include (default 14)." }
+                        "date":        { "type": "string", "description": "The day, YYYY-MM-DD (local)." },
+                        "days_radius": { "type": "integer", "description": "Also include this many days before and after (default 0; at most 1 with Apollo)." }
                     }
                 }),
             ));
@@ -4948,6 +5108,85 @@ mod tests {
         );
     }
 
+    fn apollo_at(json: &str) -> LocationAt {
+        serde_json::from_str(json).unwrap()
+    }
+
+    const NY: chrono_tz::Tz = chrono_tz::Tz::America__New_York;
+
+    #[test]
+    fn apollo_location_no_sample_says_nothing() {
+        let at = apollo_at(r#"{"ts": 0, "sample": null, "nearest_offset_s": 7200}"#);
+        assert_eq!(
+            render_apollo_location(&at, None, NY, Some("Medina, OH".into())),
+            None
+        );
+    }
+
+    #[test]
+    fn apollo_location_renders_stay_in_display_zone() {
+        // 2017-01-17 08:07 / 16:19 EST
+        let at = apollo_at(
+            r#"{"ts": 1484669220,
+                "sample": {"ts": 1484669240, "lat": 41.469, "lon": -81.934, "activity": "TILTING", "offset_s": 20},
+                "place": {"id": 7, "name": "Hyland Software", "radius_m": 250},
+                "stay": {"place_id": 7, "name": "Hyland Software", "t0": 1484658450, "t1": 1484687985}}"#,
+        );
+        assert_eq!(
+            render_apollo_location(&at, None, NY, None).as_deref(),
+            Some("Location history: You were at Hyland Software (08:07–16:19)")
+        );
+    }
+
+    #[test]
+    fn apollo_location_unnamed_uses_nominatim_activity_and_offset() {
+        let at = apollo_at(
+            r#"{"ts": 1000,
+                "sample": {"ts": 100, "lat": 41.1, "lon": -81.8, "activity": "IN_VEHICLE", "offset_s": -900}}"#,
+        );
+        assert_eq!(
+            render_apollo_location(&at, None, NY, Some("Medina, OH".into())).as_deref(),
+            Some(
+                "Location history: You were near Medina, OH (IN_VEHICLE) [location fix 15 min before the photo]"
+            )
+        );
+        assert_eq!(
+            render_apollo_location(&at, None, NY, None).as_deref(),
+            Some(
+                "Location history: You were near 41.1000, -81.8000 (IN_VEHICLE) [location fix 15 min before the photo]"
+            )
+        );
+    }
+
+    #[test]
+    fn apollo_location_skips_what_exif_already_says() {
+        let plain = apollo_at(
+            r#"{"ts": 0, "sample": {"ts": 0, "lat": 41.1, "lon": -81.8, "activity": "UNKNOWN", "offset_s": 0},
+                "place": {"id": 1, "name": "Park", "radius_m": 300}}"#,
+        );
+        // EXIF 100 m away, no stay, no informative activity → nothing new.
+        assert_eq!(
+            render_apollo_location(&plain, Some((41.1009, -81.8)), NY, None),
+            None
+        );
+        // Without EXIF the same answer is worth a line.
+        assert_eq!(
+            render_apollo_location(&plain, None, NY, None).as_deref(),
+            Some("Location history: You were at Park")
+        );
+    }
+
+    #[test]
+    fn spread_evenly_keeps_ends_and_order() {
+        let v: Vec<i32> = (0..100).collect();
+        let picked: Vec<i32> = spread_evenly(&v, 20).into_iter().copied().collect();
+        assert_eq!(picked.len(), 20);
+        assert_eq!((picked[0], picked[19]), (0, 99));
+        assert!(picked.windows(2).all(|w| w[0] < w[1]));
+        assert_eq!(spread_evenly(&v[..5], 20).len(), 5);
+        assert_eq!(spread_evenly(&v, 1), vec![&0]);
+    }
+
     #[test]
     fn found_header_labels_truncation_honestly() {
         // Truncated: total exceeds what's listed below the header.