heldar-kernel 0.1.6

//! Evidence clip export: concatenates the segments overlapping a time range and trims to
//! the requested window with `-c copy` (no re-encode). Keyframe-aligned (Stage 0 precision).

use std::process::Stdio;
use std::time::Duration;

use chrono::{DateTime, Utc};
use serde::Serialize;
use tokio::process::Command;
use uuid::Uuid;

use crate::error::{AppError, AppResult};
use crate::models::Segment;
use crate::state::AppState;

const MAX_CLIP_SECONDS: f64 = 3600.0;

#[derive(Debug, Serialize)]
pub struct ClipResult {
    pub id: String,
    pub camera_id: String,
    pub filename: String,
    pub url: String,
    pub from: DateTime<Utc>,
    pub to: DateTime<Utc>,
    pub requested_seconds: f64,
    /// Seconds of the requested window for which footage actually exists. Equals `requested_seconds`
    /// for a fully-covered clip; less when the window spans recording gaps.
    pub covered_seconds: f64,
    /// Recording gaps WITHIN the requested window. The concat output bridges these (the footage does
    /// not exist), so they are reported here rather than silently presented as continuous video.
    pub gaps: Vec<ClipGap>,
    pub size_bytes: u64,
    pub segment_count: usize,
}

/// A span within a requested clip window for which no recorded footage exists.
#[derive(Debug, Serialize)]
pub struct ClipGap {
    pub from: DateTime<Utc>,
    pub to: DateTime<Utc>,
}

/// Tolerance for sub-second seams between adjacent segments — below this, abutting segments are
/// treated as continuous (not a gap).
const GAP_TOLERANCE_MS: i64 = 1000;

/// Compute covered seconds + the recording gaps within `[from, to]` from the (start-ordered)
/// overlapping segments. A gap is a span longer than [`GAP_TOLERANCE_MS`] with no footage.
fn coverage_and_gaps(
    segments: &[Segment],
    from: DateTime<Utc>,
    to: DateTime<Utc>,
) -> (f64, Vec<ClipGap>) {
    let mut gaps = Vec::new();
    let mut cursor = from;
    for s in segments {
        let cs = s.start_time.max(from);
        let ce = s.end_time.min(to);
        if ce <= cs {
            continue;
        }
        if (cs - cursor).num_milliseconds() > GAP_TOLERANCE_MS {
            gaps.push(ClipGap {
                from: cursor,
                to: cs,
            });
        }
        if ce > cursor {
            cursor = ce;
        }
    }
    if (to - cursor).num_milliseconds() > GAP_TOLERANCE_MS {
        gaps.push(ClipGap { from: cursor, to });
    }
    let requested = (to - from).num_milliseconds() as f64 / 1000.0;
    let gap_secs: f64 = gaps
        .iter()
        .map(|g| (g.to - g.from).num_milliseconds() as f64 / 1000.0)
        .sum();
    ((requested - gap_secs).max(0.0), gaps)
}

pub async fn export_clip(
    state: &AppState,
    camera_id: &str,
    from: DateTime<Utc>,
    to: DateTime<Utc>,
) -> AppResult<ClipResult> {
    if to <= from {
        return Err(AppError::BadRequest("`to` must be after `from`".into()));
    }
    let requested = (to - from).num_milliseconds() as f64 / 1000.0;
    if requested > MAX_CLIP_SECONDS {
        return Err(AppError::BadRequest(format!(
            "clip too long ({requested:.0}s); max {MAX_CLIP_SECONDS:.0}s"
        )));
    }

    let camera_exists: Option<(String,)> = sqlx::query_as("SELECT id FROM cameras WHERE id = ?")
        .bind(camera_id)
        .fetch_optional(&state.pool)
        .await?;
    if camera_exists.is_none() {
        return Err(AppError::NotFound(format!("camera {camera_id} not found")));
    }

    let segments: Vec<Segment> = sqlx::query_as::<_, Segment>(
        "SELECT * FROM segments
         WHERE camera_id = ? AND start_time < ? AND end_time > ?
         ORDER BY start_time ASC",
    )
    .bind(camera_id)
    .bind(to)
    .bind(from)
    .fetch_all(&state.pool)
    .await?;
    if segments.is_empty() {
        return Err(AppError::NotFound(
            "no recorded footage in the requested range".into(),
        ));
    }

    tokio::fs::create_dir_all(&state.cfg.clips_dir)
        .await
        .map_err(|e| AppError::Other(e.into()))?;

    let id = format!("clip_{}", Uuid::new_v4().simple());
    let filename = format!("{id}.mp4");
    let out_path = state.cfg.clips_dir.join(&filename);
    let list_path = state.cfg.clips_dir.join(format!("{id}.txt"));

    // Read-lock the source segments so the retention sweeper can't delete them out from under ffmpeg
    // mid-export (TOCTOU). The RAII guard releases on EVERY outcome — normal return, `?` error,
    // timeout, AND cancellation/panic (where a manual unlock would be skipped, leaking the lock).
    let seg_ids: Vec<String> = segments.iter().map(|s| s.id.clone()).collect();
    let _read_lock = crate::repo::SegReadLock::acquire(&state.pool, seg_ids).await;

    let size_outcome: AppResult<u64> = async {
        let mut list = String::new();
        for s in &segments {
            let escaped = s.path.replace('\'', "'\\''");
            list.push_str(&format!("file '{escaped}'\n"));
        }
        tokio::fs::write(&list_path, list)
            .await
            .map_err(|e| AppError::Other(e.into()))?;

        let first_start = segments[0].start_time;
        let ss = ((from - first_start).num_milliseconds() as f64 / 1000.0).max(0.0);

        let mut cmd = Command::new(&state.cfg.ffmpeg_bin);
        cmd.kill_on_drop(true)
            .args([
                "-hide_banner",
                "-loglevel",
                "error",
                "-f",
                "concat",
                "-safe",
                "0",
            ])
            .arg("-i")
            .arg(&list_path)
            .args(["-ss", &format!("{ss:.3}")])
            .args(["-t", &format!("{requested:.3}")])
            .args([
                "-c",
                "copy",
                "-avoid_negative_ts",
                "make_zero",
                "-movflags",
                "+faststart",
            ])
            .arg(&out_path)
            .stdin(Stdio::null())
            .stdout(Stdio::null())
            .stderr(Stdio::piped());

        // Remux of even an hour of footage is fast; bound it so a hung/cancelled job can't wedge the
        // request or orphan ffmpeg (kill_on_drop kills the child when the timed-out future is dropped).
        let result = tokio::time::timeout(Duration::from_secs(180), cmd.output()).await;
        // Always remove the temp concat list, on every outcome.
        let _ = tokio::fs::remove_file(&list_path).await;

        let out = match result {
            Err(_) => {
                let _ = tokio::fs::remove_file(&out_path).await;
                return Err(AppError::Other(anyhow::anyhow!("clip export timed out")));
            }
            Ok(Err(e)) => {
                let _ = tokio::fs::remove_file(&out_path).await;
                return Err(AppError::Other(e.into()));
            }
            Ok(Ok(out)) => out,
        };

        if !out.status.success() {
            let _ = tokio::fs::remove_file(&out_path).await;
            return Err(AppError::Other(anyhow::anyhow!(
                "ffmpeg clip export failed: {}",
                String::from_utf8_lossy(&out.stderr).trim()
            )));
        }

        Ok(tokio::fs::metadata(&out_path)
            .await
            .map(|m| m.len())
            .unwrap_or(0))
    }
    .await;

    // `_read_lock` releases on drop (here or on any early return above). Surface any export error.
    let size_bytes = size_outcome?;

    // Report coverage honestly: the concat bridges any recording gaps in the window (that footage
    // does not exist), so disclose them rather than presenting bridged video as continuous.
    let (covered_seconds, gaps) = coverage_and_gaps(&segments, from, to);

    Ok(ClipResult {
        id,
        camera_id: camera_id.to_string(),
        url: format!("/media/clips/{filename}"),
        filename,
        from,
        to,
        requested_seconds: requested,
        covered_seconds,
        gaps,
        size_bytes,
        segment_count: segments.len(),
    })
}

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

    fn seg(start: DateTime<Utc>, end: DateTime<Utc>) -> Segment {
        Segment {
            id: "s".into(),
            camera_id: "c".into(),
            path: "/x.mp4".into(),
            start_time: start,
            end_time: end,
            duration_s: (end - start).num_milliseconds() as f64 / 1000.0,
            codec: None,
            width: None,
            height: None,
            size_bytes: 0,
            container: "mp4".into(),
            locked: false,
            evidence_locked: false,
            incident_id: None,
            created_at: start,
        }
    }

    #[test]
    fn coverage_and_gaps_detects_interior_and_trailing_gaps() {
        let t0 = "2026-06-18T00:00:00Z".parse::<DateTime<Utc>>().unwrap();
        let m = |secs: i64| t0 + chrono::Duration::seconds(secs);
        // Window [0,100]; footage [0,30] and [60,90]. Gaps: interior [30,60] + trailing [90,100].
        let segs = vec![seg(m(0), m(30)), seg(m(60), m(90))];
        let (covered, gaps) = coverage_and_gaps(&segs, m(0), m(100));
        assert_eq!(gaps.len(), 2, "{gaps:?}");
        assert_eq!((gaps[0].from, gaps[0].to), (m(30), m(60)));
        assert_eq!((gaps[1].from, gaps[1].to), (m(90), m(100)));
        assert!((covered - 60.0).abs() < 0.01, "covered={covered}");
    }

    #[test]
    fn coverage_and_gaps_tolerates_subsecond_seam() {
        let t0 = "2026-06-18T00:00:00Z".parse::<DateTime<Utc>>().unwrap();
        let m = |secs: i64| t0 + chrono::Duration::seconds(secs);
        // A 0.5s seam (< tolerance) between abutting segments is NOT reported as a gap.
        let segs = vec![
            seg(m(0), m(50)),
            seg(t0 + chrono::Duration::milliseconds(50_500), m(100)),
        ];
        let (covered, gaps) = coverage_and_gaps(&segs, m(0), m(100));
        assert!(
            gaps.is_empty(),
            "sub-second seam must not be a gap: {gaps:?}"
        );
        assert!(covered > 99.0, "covered={covered}");
    }

    async fn test_state() -> AppState {
        let pool = sqlx::sqlite::SqlitePoolOptions::new()
            .max_connections(1)
            .connect("sqlite::memory:")
            .await
            .unwrap();
        crate::db::run_migrations(&pool).await.unwrap();
        let cfg = std::sync::Arc::new(crate::config::Config::from_env());
        AppState {
            recorder: crate::services::recorder::RecorderManager::new(pool.clone(), cfg.clone()),
            sampler: crate::services::sampler::SamplerManager::new(pool.clone(), cfg.clone()),
            mirror: None,
            consumers: std::sync::Arc::new(Vec::new()),
            modules: std::sync::Arc::new(Vec::new()),
            catalog: std::sync::Arc::new(crate::services::registry::CatalogService::new(&cfg)),
            http: reqwest::Client::new(),
            started_at: Utc::now(),
            pool,
            cfg,
        }
    }

    async fn insert_camera(pool: &sqlx::SqlitePool, id: &str) {
        let now = Utc::now();
        sqlx::query("INSERT INTO cameras (id, name, created_at, updated_at) VALUES (?, ?, ?, ?)")
            .bind(id)
            .bind(format!("Camera {id}"))
            .bind(now)
            .bind(now)
            .execute(pool)
            .await
            .unwrap();
    }

    #[tokio::test]
    async fn rejects_to_before_from() {
        let state = test_state().await;
        let from = Utc::now();
        let to = from - chrono::Duration::seconds(5);
        match export_clip(&state, "anycam", from, to).await {
            Err(AppError::BadRequest(msg)) => assert_eq!(msg, "`to` must be after `from`"),
            other => panic!("expected BadRequest, got {other:?}"),
        }
    }

    #[tokio::test]
    async fn rejects_to_equal_from() {
        // `to <= from` covers the equality boundary.
        let state = test_state().await;
        let from = Utc::now();
        match export_clip(&state, "anycam", from, from).await {
            Err(AppError::BadRequest(msg)) => assert_eq!(msg, "`to` must be after `from`"),
            other => panic!("expected BadRequest, got {other:?}"),
        }
    }

    #[tokio::test]
    async fn rejects_clip_exceeding_max_length() {
        // 3601s exceeds the 3600s cap; rejected before any DB lookup, so no camera is needed.
        let state = test_state().await;
        let from = Utc::now();
        let to = from + chrono::Duration::seconds(3601);
        match export_clip(&state, "anycam", from, to).await {
            Err(AppError::BadRequest(msg)) => {
                assert!(msg.contains("clip too long"), "msg was: {msg}");
                assert!(msg.contains("3601s"), "msg was: {msg}");
                assert!(msg.contains("3600s"), "msg was: {msg}");
            }
            other => panic!("expected BadRequest, got {other:?}"),
        }
    }

    #[tokio::test]
    async fn max_length_boundary_passes_length_check() {
        // Exactly MAX_CLIP_SECONDS (3600s) is allowed (the guard uses a strict `>`), so validation
        // falls through to the camera lookup instead of returning the length error.
        let state = test_state().await;
        let from = Utc::now();
        let to = from + chrono::Duration::seconds(3600);
        match export_clip(&state, "cam_boundary", from, to).await {
            Err(AppError::NotFound(msg)) => assert_eq!(msg, "camera cam_boundary not found"),
            other => {
                panic!(
                    "expected NotFound (length check should pass at the boundary), got {other:?}"
                )
            }
        }
    }

    #[tokio::test]
    async fn unknown_camera_is_not_found() {
        let state = test_state().await;
        let from = Utc::now();
        let to = from + chrono::Duration::seconds(60);
        match export_clip(&state, "ghost", from, to).await {
            Err(AppError::NotFound(msg)) => assert_eq!(msg, "camera ghost not found"),
            other => panic!("expected NotFound, got {other:?}"),
        }
    }

    #[tokio::test]
    async fn existing_camera_without_segments_is_not_found() {
        let state = test_state().await;
        insert_camera(&state.pool, "cam_empty").await;
        let from = Utc::now();
        let to = from + chrono::Duration::seconds(60);
        match export_clip(&state, "cam_empty", from, to).await {
            Err(AppError::NotFound(msg)) => {
                assert_eq!(msg, "no recorded footage in the requested range")
            }
            other => panic!("expected NotFound, got {other:?}"),
        }
    }
}