moonfire-nvr/db/db.rs

// This file is part of Moonfire NVR, a security camera digital video recorder.
// Copyright (C) 2016 Scott Lamb <slamb@slamb.org>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// In addition, as a special exception, the copyright holders give
// permission to link the code of portions of this program with the
// OpenSSL library under certain conditions as described in each
// individual source file, and distribute linked combinations including
// the two.
//
// You must obey the GNU General Public License in all respects for all
// of the code used other than OpenSSL. If you modify file(s) with this
// exception, you may extend this exception to your version of the
// file(s), but you are not obligated to do so. If you do not wish to do
// so, delete this exception statement from your version. If you delete
// this exception statement from all source files in the program, then
// also delete it here.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

//! Database access logic for the Moonfire NVR SQLite schema.
//!
//! The SQLite schema includes everything except the actual video samples (see the `dir` module
//! for management of those). See `schema.sql` for a more detailed description.
//!
//! The `Database` struct caches data in RAM, making the assumption that only one process is
//! accessing the database at a time. Performance and efficiency notes:
//!
//!   * several query operations here feature row callbacks. The callback is invoked with
//!     the database lock. Thus, the callback shouldn't perform long-running operations.
//!
//!   * startup may be slow, as it scans the entire index for the recording table. This seems
//!     acceptable.
//!
//!   * the operations used for web file serving should return results with acceptable latency.
//!
//!   * however, the database lock may be held for longer than is acceptable for
//!     the critical path of recording frames. The caller should preallocate sample file uuids
//!     and such to avoid database operations in these paths.
//!
//!   * adding and removing recordings done during normal operations use a batch interface.
//!     A list of mutations is built up in-memory and occasionally flushed to reduce SSD write
//!     cycles.

use dir;
use failure::Error;
use fnv::{self, FnvHashMap, FnvHashSet};
use lru_cache::LruCache;
use openssl::hash;
use parking_lot::{Mutex,MutexGuard};
use raw;
use recording::{self, TIME_UNITS_PER_SEC};
use rusqlite;
use schema;
use std::collections::{BTreeMap, VecDeque};
use std::collections::btree_map;
use std::cell::RefCell;
use std::cmp;
use std::io::Write;
use std::ops::Range;
use std::mem;
use std::str;
use std::string::String;
use std::sync::Arc;
use std::vec::Vec;
use time;
use uuid::Uuid;

/// Expected schema version. See `guide/schema.md` for more information.
pub const EXPECTED_VERSION: i32 = 3;

const GET_RECORDING_PLAYBACK_SQL: &'static str = r#"
    select
      video_index
    from
      recording_playback
    where
      composite_id = :composite_id
"#;

const INSERT_VIDEO_SAMPLE_ENTRY_SQL: &'static str = r#"
    insert into video_sample_entry (sha1,  width,  height,  rfc6381_codec, data)
                            values (:sha1, :width, :height, :rfc6381_codec, :data)
"#;

const UPDATE_NEXT_RECORDING_ID_SQL: &'static str =
    "update stream set next_recording_id = :next_recording_id where id = :stream_id";

const LIST_RECORDINGS_BY_ID_SQL: &'static str = r#"
    select
        recording.composite_id,
        recording.run_offset,
        recording.flags,
        recording.start_time_90k,
        recording.duration_90k,
        recording.sample_file_bytes,
        recording.video_samples,
        recording.video_sync_samples,
        recording.video_sample_entry_id
    from
        recording
    where
        :start <= composite_id and
        composite_id < :end
    order by
        recording.composite_id
"#;

pub struct FromSqlUuid(pub Uuid);

impl rusqlite::types::FromSql for FromSqlUuid {
    fn column_result(value: rusqlite::types::ValueRef) -> rusqlite::types::FromSqlResult<Self> {
        let uuid = Uuid::from_bytes(value.as_blob()?)
            .map_err(|e| rusqlite::types::FromSqlError::Other(Box::new(e)))?;
        Ok(FromSqlUuid(uuid))
    }
}

struct VideoIndex(Box<[u8]>);

impl rusqlite::types::FromSql for VideoIndex {
    fn column_result(value: rusqlite::types::ValueRef) -> rusqlite::types::FromSqlResult<Self> {
        let blob = value.as_blob()?;
        let len = blob.len();
        let mut v = Vec::with_capacity(len);
        unsafe { v.set_len(len) };
        v.copy_from_slice(blob);
        Ok(VideoIndex(v.into_boxed_slice()))
    }
}

/// A concrete box derived from a ISO/IEC 14496-12 section 8.5.2 VisualSampleEntry box. Describes
/// the codec, width, height, etc.
#[derive(Debug)]
pub struct VideoSampleEntry {
    pub data: Vec<u8>,
    pub rfc6381_codec: String,
    pub id: i32,
    pub width: u16,
    pub height: u16,
    pub sha1: [u8; 20],
}

/// A row used in `list_recordings_by_time` and `list_recordings_by_id`.
#[derive(Debug)]
pub struct ListRecordingsRow {
    pub start: recording::Time,
    pub video_sample_entry: Arc<VideoSampleEntry>,

    pub id: CompositeId,

    /// This is a recording::Duration, but a single recording's duration fits into an i32.
    pub duration_90k: i32,
    pub video_samples: i32,
    pub video_sync_samples: i32,
    pub sample_file_bytes: i32,
    pub run_offset: i32,
    pub flags: i32,
}

/// A row used in `list_aggregated_recordings`.
#[derive(Clone, Debug)]
pub struct ListAggregatedRecordingsRow {
    pub time: Range<recording::Time>,
    pub ids: Range<i32>,
    pub video_samples: i64,
    pub video_sync_samples: i64,
    pub sample_file_bytes: i64,
    pub video_sample_entry: Arc<VideoSampleEntry>,
    pub stream_id: i32,
    pub flags: i32,
    pub run_start_id: i32,
}

/// Select fields from the `recordings_playback` table. Retrieve with `with_recording_playback`.
#[derive(Debug)]
pub struct RecordingPlayback<'a> {
    pub video_index: &'a [u8],
}

/// Bitmask in the `flags` field in the `recordings` table; see `schema.sql`.
pub enum RecordingFlags {
    TrailingZero = 1,
}

/// A recording to pass to `insert_recording`.
#[derive(Clone, Debug)]
pub(crate) struct RecordingToInsert {
    pub run_offset: i32,
    pub flags: i32,
    pub sample_file_bytes: i32,
    pub time: Range<recording::Time>,
    pub local_time_delta: recording::Duration,
    pub video_samples: i32,
    pub video_sync_samples: i32,
    pub video_sample_entry_id: i32,
    pub video_index: Vec<u8>,
    pub sample_file_sha1: [u8; 20],
}

/// A row used in `raw::list_oldest_recordings` and `db::delete_oldest_recordings`.
#[derive(Copy, Clone, Debug)]
pub(crate) struct ListOldestRecordingsRow {
    pub id: CompositeId,
    pub start: recording::Time,
    pub duration: i32,
    pub sample_file_bytes: i32,
}

/// A calendar day in `YYYY-mm-dd` format.
#[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
pub struct StreamDayKey([u8; 10]);

impl StreamDayKey {
    fn new(tm: time::Tm) -> Result<Self, Error> {
        let mut s = StreamDayKey([0u8; 10]);
        write!(&mut s.0[..], "{}", tm.strftime("%Y-%m-%d")?)?;
        Ok(s)
    }

    pub fn bounds(&self) -> Range<recording::Time> {
        let mut my_tm = time::strptime(self.as_ref(), "%Y-%m-%d").expect("days must be parseable");
        my_tm.tm_utcoff = 1;  // to the time crate, values != 0 mean local time.
        my_tm.tm_isdst = -1;
        let start = recording::Time(my_tm.to_timespec().sec * recording::TIME_UNITS_PER_SEC);
        my_tm.tm_hour = 0;
        my_tm.tm_min = 0;
        my_tm.tm_sec = 0;
        my_tm.tm_mday += 1;
        let end = recording::Time(my_tm.to_timespec().sec * recording::TIME_UNITS_PER_SEC);
        start .. end
    }
}

impl AsRef<str> for StreamDayKey {
    fn as_ref(&self) -> &str { str::from_utf8(&self.0[..]).expect("days are always UTF-8") }
}

/// In-memory state about a particular camera on a particular day.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub struct StreamDayValue {
    /// The number of recordings that overlap with this day. Note that `adjust_day` automatically
    /// prunes days with 0 recordings.
    pub recordings: i64,

    /// The total duration recorded on this day. This can be 0; because frames' durations are taken
    /// from the time of the next frame, a recording that ends unexpectedly after a single frame
    /// will have 0 duration of that frame and thus the whole recording.
    pub duration: recording::Duration,
}

#[derive(Debug)]
pub struct SampleFileDir {
    pub id: i32,
    pub path: String,
    pub uuid: Uuid,
    dir: Option<Arc<dir::SampleFileDir>>,
    last_complete_open: Option<Open>,
    to_gc: Vec<CompositeId>,
    pub(crate) garbage: FnvHashSet<CompositeId>,
}

impl SampleFileDir {
    /// Returns a cloned copy of the directory, or Err if closed.
    ///
    /// Use `LockedDatabase::open_sample_file_dirs` prior to calling this method.
    pub fn get(&self) -> Result<Arc<dir::SampleFileDir>, Error> {
        Ok(self.dir
               .as_ref()
               .ok_or_else(|| format_err!("sample file dir {} is closed", self.id))?
               .clone())
    }
}

/// In-memory state about a camera.
#[derive(Debug)]
pub struct Camera {
    pub id: i32,
    pub uuid: Uuid,
    pub short_name: String,
    pub description: String,
    pub host: String,
    pub username: String,
    pub password: String,
    pub streams: [Option<i32>; 2],
}

#[derive(Copy, Clone, Debug)]
pub enum StreamType { MAIN, SUB }

impl StreamType {
    pub fn from_index(i: usize) -> Option<Self> {
        match i {
            0 => Some(StreamType::MAIN),
            1 => Some(StreamType::SUB),
            _ => None,
        }
    }

    pub fn index(self) -> usize {
        match self {
            StreamType::MAIN => 0,
            StreamType::SUB => 1,
        }
    }

    pub fn as_str(self) -> &'static str {
        match self {
            StreamType::MAIN => "main",
            StreamType::SUB => "sub",
        }
    }

    pub fn parse(type_: &str) -> Option<Self> {
        match type_ {
            "main" => Some(StreamType::MAIN),
            "sub" => Some(StreamType::SUB),
            _ => None,
        }
    }
}

impl ::std::fmt::Display for StreamType {
    fn fmt(&self, f: &mut ::std::fmt::Formatter) -> Result<(), ::std::fmt::Error> {
        f.write_str(self.as_str())
    }
}

pub const ALL_STREAM_TYPES: [StreamType; 2] = [StreamType::MAIN, StreamType::SUB];

#[derive(Clone, Debug)]
pub struct Stream {
    pub id: i32,
    pub camera_id: i32,
    pub sample_file_dir_id: Option<i32>,
    pub type_: StreamType,
    pub rtsp_path: String,
    pub retain_bytes: i64,
    pub flush_if_sec: i64,

    /// `flush_if_sec` converted to a duration for convenience.
    pub flush_if: recording::Duration,

    /// The time range of recorded data associated with this stream (minimum start time and maximum
    /// end time). `None` iff there are no recordings for this camera.
    pub range: Option<Range<recording::Time>>,
    pub sample_file_bytes: i64,

    /// On flush, delete the following recordings. Note they must be the oldest recordings.
    to_delete: Vec<ListOldestRecordingsRow>,

    /// The total bytes to delete.
    pub bytes_to_delete: i64,

    /// The total duration of recorded data. This may not be `range.end - range.start` due to
    /// gaps and overlap.
    pub duration: recording::Duration,

    /// Mapping of calendar day (in the server's time zone) to a summary of recordings on that day.
    pub days: BTreeMap<StreamDayKey, StreamDayValue>,
    pub record: bool,

    /// The `next_recording_id` currently committed to the database.
    pub(crate) next_recording_id: i32,

    /// The recordings which have been added via `LockedDatabase::add_recording` but have yet to
    /// committed to the database.
    ///
    /// `uncommitted[i]` uses sample filename `CompositeId::new(id, next_recording_id + 1)`;
    /// `next_recording_id` should be advanced when one is committed to maintain this invariant.
    ///
    /// TODO: alter the serving path to show these just as if they were already committed.
    uncommitted: VecDeque<Arc<Mutex<UncommittedRecording>>>,
}

impl Stream {
    /// Returns the duration of synced but uncommitted recordings for the given stream.
    /// Note recordings must be flushed in order, so a recording is considered unsynced if any
    /// before it are unsynced.
    pub(crate) fn unflushed(&self) -> recording::Duration {
        let mut dur = recording::Duration(0);
        for u in &self.uncommitted {
            let l = u.lock();
            if !l.synced {
                break;
            }
            if let Some(ref r) = l.recording {
                dur += r.time.end - r.time.start;
            }
        }
        dur
    }
}

#[derive(Debug)]
pub(crate) struct UncommittedRecording {
    /// If this recording has been synced to disk and thus is ready to commit to the database.
    /// `recording` should not be modified after this is set to true.
    pub(crate) synced: bool,

    /// The recording to add. Absent iff the recording has been abandoned.
    /// TODO: modify `SampleIndexEncoder` to update this record as it goes.
    pub(crate) recording: Option<RecordingToInsert>,
}

#[derive(Debug, Default)]
pub struct StreamChange {
    pub sample_file_dir_id: Option<i32>,
    pub rtsp_path: String,
    pub record: bool,
    pub flush_if_sec: i64,
}

/// Information about a camera, used by `add_camera` and `update_camera`.
#[derive(Debug)]
pub struct CameraChange {
    pub short_name: String,
    pub description: String,
    pub host: String,
    pub username: String,
    pub password: String,

    /// `StreamType t` is represented by `streams[t.index()]`. A default StreamChange will
    /// correspond to no stream in the database, provided there are no existing recordings for that
    /// stream.
    pub streams: [StreamChange; 2],
}

/// Adds non-zero `delta` to the day represented by `day` in the map `m`.
/// Inserts a map entry if absent; removes the entry if it has 0 entries on exit.
fn adjust_day(day: StreamDayKey, delta: StreamDayValue,
              m: &mut BTreeMap<StreamDayKey, StreamDayValue>) {
    use ::std::collections::btree_map::Entry;
    match m.entry(day) {
        Entry::Vacant(e) => { e.insert(delta); },
        Entry::Occupied(mut e) => {
            let remove = {
                let v = e.get_mut();
                v.recordings += delta.recordings;
                v.duration += delta.duration;
                v.recordings == 0
            };
            if remove {
                e.remove_entry();
            }
        },
    }
}

/// Adjusts the day map `m` to reflect the range of the given recording.
/// Note that the specified range may span two days. It will never span more because the maximum
/// length of a recording entry is less than a day (even a 23-hour "spring forward" day).
///
/// This function swallows/logs date formatting errors because they shouldn't happen and there's
/// not much that can be done about them. (The database operation has already gone through.)
fn adjust_days(r: Range<recording::Time>, sign: i64,
               m: &mut BTreeMap<StreamDayKey, StreamDayValue>) {
    // Find first day key.
    let mut my_tm = time::at(time::Timespec{sec: r.start.unix_seconds(), nsec: 0});
    let day = match StreamDayKey::new(my_tm) {
        Ok(d) => d,
        Err(ref e) => {
            error!("Unable to fill first day key from {:?}: {}; will ignore.", my_tm, e);
            return;
        }
    };

    // Determine the start of the next day.
    // Use mytm to hold a non-normalized representation of the boundary.
    my_tm.tm_isdst = -1;
    my_tm.tm_hour = 0;
    my_tm.tm_min = 0;
    my_tm.tm_sec = 0;
    my_tm.tm_mday += 1;
    let boundary = my_tm.to_timespec();
    let boundary_90k = boundary.sec * TIME_UNITS_PER_SEC;

    // Adjust the first day.
    let first_day_delta = StreamDayValue{
        recordings: sign,
        duration: recording::Duration(sign * (cmp::min(r.end.0, boundary_90k) - r.start.0)),
    };
    adjust_day(day, first_day_delta, m);

    if r.end.0 <= boundary_90k {
        return;
    }

    // Fill day with the second day. This requires a normalized representation so recalculate.
    // (The C mktime(3) already normalized for us once, but .to_timespec() discarded that result.)
    let my_tm = time::at(boundary);
    let day = match StreamDayKey::new(my_tm) {
        Ok(d) => d,
        Err(ref e) => {
            error!("Unable to fill second day key from {:?}: {}; will ignore.", my_tm, e);
            return;
        }
    };
    let second_day_delta = StreamDayValue{
        recordings: sign,
        duration: recording::Duration(sign * (r.end.0 - boundary_90k)),
    };
    adjust_day(day, second_day_delta, m);
}

impl Stream {
    /// Adds a single recording with the given properties to the in-memory state.
    fn add_recording(&mut self, r: Range<recording::Time>, sample_file_bytes: i32) {
        self.range = Some(match self.range {
            Some(ref e) => cmp::min(e.start, r.start) .. cmp::max(e.end, r.end),
            None => r.start .. r.end,
        });
        self.duration += r.end - r.start;
        self.sample_file_bytes += sample_file_bytes as i64;
        adjust_days(r, 1, &mut self.days);
    }
}

/// Initializes the recordings associated with the given camera.
fn init_recordings(conn: &mut rusqlite::Connection, stream_id: i32, camera: &Camera,
                   stream: &mut Stream)
    -> Result<(), Error> {
    info!("Loading recordings for camera {} stream {:?}", camera.short_name, stream.type_);
    let mut stmt = conn.prepare(r#"
        select
          recording.start_time_90k,
          recording.duration_90k,
          recording.sample_file_bytes
        from
          recording
        where
          stream_id = :stream_id
    "#)?;
    let mut rows = stmt.query_named(&[(":stream_id", &stream_id)])?;
    let mut i = 0;
    while let Some(row) = rows.next() {
        let row = row?;
        let start = recording::Time(row.get_checked(0)?);
        let duration = recording::Duration(row.get_checked(1)?);
        let bytes = row.get_checked(2)?;
        stream.add_recording(start .. start + duration, bytes);
        i += 1;
    }
    info!("Loaded {} recordings for camera {} stream {:?}", i, camera.short_name, stream.type_);
    Ok(())
}

pub struct LockedDatabase {
    conn: rusqlite::Connection,
    uuid: Uuid,

    /// If the database is open in read-write mode, the information about the current Open row.
    open: Option<Open>,
    sample_file_dirs_by_id: BTreeMap<i32, SampleFileDir>,
    cameras_by_id: BTreeMap<i32, Camera>,
    streams_by_id: BTreeMap<i32, Stream>,
    cameras_by_uuid: BTreeMap<Uuid, i32>,  // values are ids.
    video_sample_entries: BTreeMap<i32, Arc<VideoSampleEntry>>,
    list_recordings_by_time_sql: String,
    video_index_cache: RefCell<LruCache<i64, Box<[u8]>, fnv::FnvBuildHasher>>,
    on_flush: Vec<Box<Fn() + Send>>,
}

/// Represents a row of the `open` database table.
#[derive(Copy, Clone, Debug)]
pub(crate) struct Open {
    pub(crate) id: u32,
    pub(crate) uuid: Uuid,
}

/// A modification to be done to a `Stream`, used within `LockedDatabase::flush`.
#[derive(Default)]
struct StreamModification {
    num_recordings_to_commit: i32,
    range: Option<Range<recording::Time>>,
}

#[derive(Copy, Clone, Debug, Eq, Hash, PartialEq)]
pub struct CompositeId(pub i64);

impl CompositeId {
    pub fn new(stream_id: i32, recording_id: i32) -> Self {
        CompositeId((stream_id as i64) << 32 | recording_id as i64)
    }

    pub fn stream(self) -> i32 { (self.0 >> 32) as i32 }
    pub fn recording(self) -> i32 { self.0 as i32 }
}

impl ::std::fmt::Display for CompositeId {
    fn fmt(&self, f: &mut ::std::fmt::Formatter) -> Result<(), ::std::fmt::Error> {
        write!(f, "{}/{}", self.stream(), self.recording())
    }
}

/// Inserts, updates, or removes streams in the `State` object to match a set of `StreamChange`
/// structs.
struct StreamStateChanger {
    sids: [Option<i32>; 2],
    streams: Vec<(i32, Option<Stream>)>,
}

impl StreamStateChanger {
    /// Performs the database updates (guarded by the given transaction) and returns the state
    /// change to be applied on successful commit.
    fn new(tx: &rusqlite::Transaction, camera_id: i32, existing: Option<&Camera>,
           streams_by_id: &BTreeMap<i32, Stream>, change: &mut CameraChange)
           -> Result<Self, Error> {
        let mut sids = [None; 2];
        let mut streams = Vec::with_capacity(2);
        let existing_streams = existing.map(|e| e.streams).unwrap_or_default();
        for (i, ref mut sc) in change.streams.iter_mut().enumerate() {
            let mut have_data = false;
            if let Some(sid) = existing_streams[i] {
                let s = streams_by_id.get(&sid).unwrap();
                if s.range.is_some() {
                    have_data = true;
                    if let (Some(d), false) = (s.sample_file_dir_id,
                                               s.sample_file_dir_id == sc.sample_file_dir_id) {
                        bail!("can't change sample_file_dir_id {:?}->{:?} for non-empty stream {}",
                              d, sc.sample_file_dir_id, sid);
                    }
                }
                if !have_data && sc.rtsp_path.is_empty() && sc.sample_file_dir_id.is_none() &&
                   !sc.record {
                    // Delete stream.
                    let mut stmt = tx.prepare_cached(r#"
                        delete from stream where id = ?
                    "#)?;
                    if stmt.execute(&[&sid])? != 1 {
                        bail!("missing stream {}", sid);
                    }
                    streams.push((sid, None));
                } else {
                    // Update stream.
                    let mut stmt = tx.prepare_cached(r#"
                        update stream set
                            rtsp_path = :rtsp_path,
                            record = :record,
                            sample_file_dir_id = :sample_file_dir_id
                        where
                            id = :id
                    "#)?;
                    let rows = stmt.execute_named(&[
                        (":rtsp_path", &sc.rtsp_path),
                        (":record", &sc.record),
                        (":sample_file_dir_id", &sc.sample_file_dir_id),
                        (":id", &sid),
                    ])?;
                    if rows != 1 {
                        bail!("missing stream {}", sid);
                    }
                    sids[i] = Some(sid);
                    let s = (*s).clone();
                    streams.push((sid, Some(Stream {
                        sample_file_dir_id: sc.sample_file_dir_id,
                        rtsp_path: mem::replace(&mut sc.rtsp_path, String::new()),
                        record: sc.record,
                        flush_if_sec: sc.flush_if_sec,
                        flush_if: recording::Duration(sc.flush_if_sec *
                                                      recording::TIME_UNITS_PER_SEC),
                        ..s
                    })));
                }
            } else {
                if sc.rtsp_path.is_empty() && sc.sample_file_dir_id.is_none() && !sc.record {
                    // Do nothing; there is no record and we want to keep it that way.
                    continue;
                }
                // Insert stream.
                let mut stmt = tx.prepare_cached(r#"
                    insert into stream (camera_id,  sample_file_dir_id,  type,  rtsp_path,  record,
                                        retain_bytes, flush_if_sec,  next_recording_id)
                                values (:camera_id, :sample_file_dir_id, :type, :rtsp_path, :record,
                                        0,            :flush_if_sec, 1)
                "#)?;
                let type_ = StreamType::from_index(i).unwrap();
                stmt.execute_named(&[
                    (":camera_id", &camera_id),
                    (":sample_file_dir_id", &sc.sample_file_dir_id),
                    (":type", &type_.as_str()),
                    (":rtsp_path", &sc.rtsp_path),
                    (":record", &sc.record),
                    (":flush_if_sec", &sc.flush_if_sec),
                ])?;
                let id = tx.last_insert_rowid() as i32;
                sids[i] = Some(id);
                streams.push((id, Some(Stream {
                    id,
                    type_,
                    camera_id,
                    sample_file_dir_id: sc.sample_file_dir_id,
                    rtsp_path: mem::replace(&mut sc.rtsp_path, String::new()),
                    retain_bytes: 0,
                    flush_if_sec: sc.flush_if_sec,
                    flush_if: recording::Duration(sc.flush_if_sec * recording::TIME_UNITS_PER_SEC),
                    range: None,
                    sample_file_bytes: 0,
                    to_delete: Vec::new(),
                    bytes_to_delete: 0,
                    duration: recording::Duration(0),
                    days: BTreeMap::new(),
                    record: sc.record,
                    next_recording_id: 1,
                    uncommitted: VecDeque::new(),
                })));
            }
        }
        Ok(StreamStateChanger {
            sids,
            streams,
        })
    }

    /// Applies the change to the given `streams_by_id`. The caller is expected to set
    /// `Camera::streams` to the return value.
    fn apply(mut self, streams_by_id: &mut BTreeMap<i32, Stream>) -> [Option<i32>; 2] {
        for (id, mut stream) in self.streams.drain(..) {
            use ::std::collections::btree_map::Entry;
            match (streams_by_id.entry(id), stream) {
                (Entry::Vacant(mut e), Some(new)) => { e.insert(new); },
                (Entry::Vacant(_), None) => {},
                (Entry::Occupied(mut e), Some(new)) => { e.insert(new); },
                (Entry::Occupied(mut e), None) => { e.remove(); },
            };
        }
        self.sids
    }
}

/// A retention change as expected by `LockedDatabase::update_retention`.
pub struct RetentionChange {
    pub stream_id: i32,
    pub new_record: bool,
    pub new_limit: i64,
}

impl LockedDatabase {
    /// Returns an immutable view of the cameras by id.
    pub fn cameras_by_id(&self) -> &BTreeMap<i32, Camera> { &self.cameras_by_id }
    pub fn sample_file_dirs_by_id(&self) -> &BTreeMap<i32, SampleFileDir> {
        &self.sample_file_dirs_by_id
    }

    pub(crate) fn add_recording(&mut self, stream_id: i32)
                             -> Result<(CompositeId, Arc<Mutex<UncommittedRecording>>), Error> {
        let stream = match self.streams_by_id.get_mut(&stream_id) {
            None => bail!("no such stream {}", stream_id),
            Some(s) => s,
        };
        let id = CompositeId::new(stream_id,
                                  stream.next_recording_id + (stream.uncommitted.len() as i32));
        let recording = Arc::new(Mutex::new(UncommittedRecording {
            synced: false,
            recording: None,
        }));
        stream.uncommitted.push_back(Arc::clone(&recording));
        Ok((id, recording))
    }

    pub(crate) fn delete_garbage(&mut self, dir_id: i32, ids: &mut Vec<CompositeId>)
                                 -> Result<(), Error> {
        let dir = match self.sample_file_dirs_by_id.get_mut(&dir_id) {
            None => bail!("no such dir {}", dir_id),
            Some(d) => d,
        };
        dir.to_gc.append(ids);
        Ok(())
    }

    /// Tries to flush unwritten changes from the stream directories.
    ///
    ///    * commits any recordings added with `add_recording` that have since been marked as
    ///      synced.
    ///    * moves old recordings to the garbage table as requested by `delete_oldest_recordings`.
    ///    * removes entries from the garbage table as requested by `mark_sample_files_deleted`.
    ///
    /// On success, for each affected sample file directory with a flush watcher set, sends a
    /// `Flush` event.
    pub(crate) fn flush(&mut self, reason: &str) -> Result<(), Error> {
        let o = match self.open.as_ref() {
            None => bail!("database is read-only"),
            Some(o) => o,
        };
        let tx = self.conn.transaction()?;
        let mut mods = FnvHashMap::with_capacity_and_hasher(self.streams_by_id.len(),
                                                            Default::default());
        {
            let mut stmt = tx.prepare_cached(UPDATE_NEXT_RECORDING_ID_SQL)?;
            for (&stream_id, s) in &self.streams_by_id {
                // Process additions.
                let mut i = 0;
                for recording in &s.uncommitted {
                    let l = recording.lock();
                    if !l.synced { break; }
                    if let Some(ref r) = l.recording {
                        raw::insert_recording(
                            &tx, o, CompositeId::new(stream_id, s.next_recording_id + i), &r)?;
                    }
                    i += 1;
                }
                if i > 0 {
                    let m = mods.entry(stream_id).or_insert_with(StreamModification::default);
                    m.num_recordings_to_commit = i;
                    stmt.execute_named(&[
                        (":stream_id", &stream_id),
                        (":next_recording_id", &(s.next_recording_id + i)),
                    ])?;
                }

                // Process deletions.
                if let Some(l) = s.to_delete.last() {
                    // Add a placeholder for recomputing the range.
                    mods.entry(stream_id).or_insert_with(StreamModification::default);
                    let dir = match s.sample_file_dir_id {
                        None => bail!("stream {} has no directory!", stream_id),
                        Some(d) => d,
                    };
                    let end = CompositeId(l.id.0 + 1);
                    raw::delete_recordings(&tx, dir, CompositeId::new(stream_id, 0) .. end)?;
                }
            }
        }
        for dir in self.sample_file_dirs_by_id.values() {
            raw::mark_sample_files_deleted(&tx, &dir.to_gc)?;
        }
        for (&stream_id, m) in &mut mods {
            m.range = raw::get_range(&tx, stream_id)?;
        }
        tx.commit()?;

        // Process delete_garbage.
        let mut gced = 0;
        for dir in self.sample_file_dirs_by_id.values_mut() {
            gced += dir.to_gc.len();
            for id in dir.to_gc.drain(..) {
                dir.garbage.remove(&id);
            }
        }

        let mut added = 0;
        let mut deleted = 0;
        for (stream_id, m) in mods.drain() {
            let s = self.streams_by_id.get_mut(&stream_id).unwrap();
            let d = self.sample_file_dirs_by_id.get_mut(&s.sample_file_dir_id.unwrap()).unwrap();

            // Process delete_oldest_recordings.
            deleted += s.to_delete.len();
            s.sample_file_bytes -= s.bytes_to_delete;
            s.bytes_to_delete = 0;
            for row in s.to_delete.drain(..) {
                d.garbage.insert(row.id);
                let d = recording::Duration(row.duration as i64);
                s.duration -= d;
                adjust_days(row.start .. row.start + d, -1, &mut s.days);
            }

            // Process add_recordings.
            s.next_recording_id += m.num_recordings_to_commit;
            added += m.num_recordings_to_commit;
            for _ in 0..m.num_recordings_to_commit {
                let u = s.uncommitted.pop_front().unwrap();
                let l = u.lock();
                if let Some(ref r) = l.recording {
                    s.add_recording(r.time.clone(), r.sample_file_bytes);
                }
            }

            // Fix the range.
            s.range = m.range;
        }
        info!("Flush due to {}: added {} recordings, deleted {}, marked {} files GCed.",
              reason, added, deleted, gced);
        for cb in &self.on_flush {
            cb();
        }
        Ok(())
    }

    /// Sets a watcher which will receive an (empty) event on successful flush.
    /// The lock will be held while this is run, so it should not do any I/O.
    pub(crate) fn on_flush(&mut self, run: Box<Fn() + Send>) {
        self.on_flush.push(run);
    }

    // TODO: find a cleaner way to do this. Seems weird for src/cmds/run.rs to clear the on flush
    // handlers given that it didn't add them.
    pub fn clear_on_flush(&mut self) {
        self.on_flush.clear();
    }

    /// Opens the given sample file directories.
    ///
    /// `ids` is implicitly de-duplicated.
    ///
    /// When the database is in read-only mode, this simply opens all the directories after
    /// locking and verifying their metadata matches the database state. In read-write mode, it
    /// performs a single database transaction to update metadata for all dirs, then performs a like
    /// update to the directories' on-disk metadata.
    ///
    /// Note this violates the principle of never accessing disk while holding the database lock.
    /// Currently this only happens at startup (or during configuration), so this isn't a problem
    /// in practice.
    pub fn open_sample_file_dirs(&mut self, ids: &[i32]) -> Result<(), Error> {
        let mut in_progress = FnvHashMap::with_capacity_and_hasher(ids.len(), Default::default());
        let o = self.open.as_ref();
        for &id in ids {
            let e = in_progress.entry(id);
            use ::std::collections::hash_map::Entry;
            let e = match e {
                Entry::Occupied(_) => continue,  // suppress duplicate.
                Entry::Vacant(e) => e,
            };
            let dir = self
                          .sample_file_dirs_by_id
                          .get_mut(&id)
                          .ok_or_else(|| format_err!("no such dir {}", id))?;
            if dir.dir.is_some() { continue }
            let mut meta = schema::DirMeta::default();
            meta.db_uuid.extend_from_slice(&self.uuid.as_bytes()[..]);
            meta.dir_uuid.extend_from_slice(&dir.uuid.as_bytes()[..]);
            if let Some(o) = dir.last_complete_open {
                let open = meta.mut_last_complete_open();
                open.id = o.id;
                open.uuid.extend_from_slice(&o.uuid.as_bytes()[..]);
            }
            if let Some(o) = o {
                let open = meta.mut_in_progress_open();
                open.id = o.id;
                open.uuid.extend_from_slice(&o.uuid.as_bytes()[..]);
            }
            let d = dir::SampleFileDir::open(&dir.path, &meta)?;
            if o.is_none() {  // read-only mode; it's already fully opened.
                dir.dir = Some(d);
            } else {  // read-write mode; there are more steps to do.
                e.insert((meta, d));
            }
        }

        let o = match o {
            None => return Ok(()),  // read-only mode; all done.
            Some(o) => o,
        };

        let tx = self.conn.transaction()?;
        {
            let mut stmt = tx.prepare_cached(r#"
                update sample_file_dir set last_complete_open_id = ? where id = ?
            "#)?;
            for &id in in_progress.keys() {
                if stmt.execute(&[&o.id, &id])? != 1 {
                    bail!("unable to update dir {}", id);
                }
            }
        }
        tx.commit()?;

        for (id, (mut meta, d)) in in_progress.drain() {
            let dir = self.sample_file_dirs_by_id.get_mut(&id).unwrap();
            meta.last_complete_open.clear();
            mem::swap(&mut meta.last_complete_open, &mut meta.in_progress_open);
            d.write_meta(&meta)?;
            dir.dir = Some(d);
        }

        Ok(())
    }

    pub fn streams_by_id(&self) -> &BTreeMap<i32, Stream> { &self.streams_by_id }

    /// Returns an immutable view of the video sample entries.
    pub fn video_sample_entries(&self) -> btree_map::Values<i32, Arc<VideoSampleEntry>> {
        self.video_sample_entries.values()
    }

    /// Gets a given camera by uuid.
    pub fn get_camera(&self, uuid: Uuid) -> Option<&Camera> {
        match self.cameras_by_uuid.get(&uuid) {
            Some(id) => Some(self.cameras_by_id.get(id).expect("uuid->id requires id->cam")),
            None => None,
        }
    }

    /// Lists the specified recordings in ascending order by start time, passing them to a supplied
    /// function. Given that the function is called with the database lock held, it should be quick.
    pub fn list_recordings_by_time(
        &self, stream_id: i32, desired_time: Range<recording::Time>,
        f: &mut FnMut(ListRecordingsRow) -> Result<(), Error>) -> Result<(), Error> {
        let mut stmt = self.conn.prepare_cached(&self.list_recordings_by_time_sql)?;
        let rows = stmt.query_named(&[
            (":stream_id", &stream_id),
            (":start_time_90k", &desired_time.start.0),
            (":end_time_90k", &desired_time.end.0)])?;
        self.list_recordings_inner(rows, f)
    }

    /// Lists the specified recordigs in ascending order by id.
    pub fn list_recordings_by_id(
        &self, stream_id: i32, desired_ids: Range<i32>,
        f: &mut FnMut(ListRecordingsRow) -> Result<(), Error>) -> Result<(), Error> {
        let mut stmt = self.conn.prepare_cached(LIST_RECORDINGS_BY_ID_SQL)?;
        let rows = stmt.query_named(&[
            (":start", &CompositeId::new(stream_id, desired_ids.start).0),
            (":end", &CompositeId::new(stream_id, desired_ids.end).0),
        ])?;
        self.list_recordings_inner(rows, f)
    }

    fn list_recordings_inner(
        &self, mut rows: rusqlite::Rows,
        f: &mut FnMut(ListRecordingsRow) -> Result<(), Error>) -> Result<(), Error> {
        while let Some(row) = rows.next() {
            let row = row?;
            let id = CompositeId(row.get_checked::<_, i64>(0)?);
            let vse_id = row.get_checked(8)?;
            let video_sample_entry = match self.video_sample_entries.get(&vse_id) {
                Some(v) => v,
                None => bail!("recording {} references nonexistent video_sample_entry {}",
                              id, vse_id),
            };
            let out = ListRecordingsRow {
                id,
                run_offset: row.get_checked(1)?,
                flags: row.get_checked(2)?,
                start: recording::Time(row.get_checked(3)?),
                duration_90k: row.get_checked(4)?,
                sample_file_bytes: row.get_checked(5)?,
                video_samples: row.get_checked(6)?,
                video_sync_samples: row.get_checked(7)?,
                video_sample_entry: video_sample_entry.clone(),
            };
            f(out)?;
        }
        Ok(())
    }

    /// Calls `list_recordings_by_time` and aggregates consecutive recordings.
    /// Rows are given to the callback in arbitrary order. Callers which care about ordering
    /// should do their own sorting.
    pub fn list_aggregated_recordings(
        &self, stream_id: i32, desired_time: Range<recording::Time>,
        forced_split: recording::Duration,
        f: &mut FnMut(&ListAggregatedRecordingsRow) -> Result<(), Error>)
        -> Result<(), Error> {
        // Iterate, maintaining a map from a recording_id to the aggregated row for the latest
        // batch of recordings from the run starting at that id. Runs can be split into multiple
        // batches for a few reasons:
        //
        // * forced split (when exceeding a duration limit)
        // * a missing id (one that was deleted out of order)
        // * video_sample_entry mismatch (if the parameters changed during a RTSP session)
        //
        // This iteration works because in a run, the start_time+duration of recording id r
        // is equal to the start_time of recording id r+1. Thus ascending times guarantees
        // ascending ids within a run. (Different runs, however, can be arbitrarily interleaved if
        // their timestamps overlap. Tracking all active runs prevents that interleaving from
        // causing problems.)
        let mut aggs: BTreeMap<i32, ListAggregatedRecordingsRow> = BTreeMap::new();
        self.list_recordings_by_time(stream_id, desired_time, &mut |row| {
            let recording_id = row.id.recording();
            let run_start_id = recording_id - row.run_offset;
            let needs_flush = if let Some(a) = aggs.get(&run_start_id) {
                let new_dur = a.time.end - a.time.start +
                              recording::Duration(row.duration_90k as i64);
                a.ids.end != recording_id || row.video_sample_entry.id != a.video_sample_entry.id ||
                   new_dur >= forced_split
            } else {
                false
            };
            if needs_flush {
                let a = aggs.remove(&run_start_id).expect("needs_flush when agg is None");
                f(&a)?;
            }
            let need_insert = if let Some(ref mut a) = aggs.get_mut(&run_start_id) {
                if a.time.end != row.start {
                    bail!("stream {} recording {} ends at {}; {} starts at {}; expected same",
                          stream_id, a.ids.end - 1, a.time.end, row.id, row.start);
                }
                a.time.end.0 += row.duration_90k as i64;
                a.ids.end = recording_id + 1;
                a.video_samples += row.video_samples as i64;
                a.video_sync_samples += row.video_sync_samples as i64;
                a.sample_file_bytes += row.sample_file_bytes as i64;
                false
            } else {
                true
            };
            if need_insert {
                aggs.insert(run_start_id, ListAggregatedRecordingsRow{
                        time: row.start ..  recording::Time(row.start.0 + row.duration_90k as i64),
                        ids: recording_id .. recording_id+1,
                        video_samples: row.video_samples as i64,
                        video_sync_samples: row.video_sync_samples as i64,
                        sample_file_bytes: row.sample_file_bytes as i64,
                        video_sample_entry: row.video_sample_entry,
                        stream_id,
                        run_start_id,
                        flags: row.flags,
                });
            };
            Ok(())
        })?;
        for a in aggs.values() {
            f(a)?;
        }
        Ok(())
    }

    /// Calls `f` with a single `recording_playback` row.
    /// Note the lock is held for the duration of `f`.
    /// This uses a LRU cache to reduce the number of retrievals from the database.
    pub fn with_recording_playback<F, R>(&self, id: CompositeId, f: F) -> Result<R, Error>
    where F: FnOnce(&RecordingPlayback) -> Result<R, Error> {
        let mut cache = self.video_index_cache.borrow_mut();
        if let Some(video_index) = cache.get_mut(&id.0) {
            trace!("cache hit for recording {}", id);
            return f(&RecordingPlayback { video_index });
        }
        trace!("cache miss for recording {}", id);
        let mut stmt = self.conn.prepare_cached(GET_RECORDING_PLAYBACK_SQL)?;
        let mut rows = stmt.query_named(&[(":composite_id", &id.0)])?;
        if let Some(row) = rows.next() {
            let row = row?;
            let video_index: VideoIndex = row.get_checked(0)?;
            let result = f(&RecordingPlayback { video_index: &video_index.0[..] });
            cache.insert(id.0, video_index.0);
            return result;
        }
        Err(format_err!("no such recording {}", id))
    }

    /// Deletes the oldest recordings that aren't already queued for deletion.
    /// `f` should return true for each row that should be deleted.
    pub(crate) fn delete_oldest_recordings(
        &mut self, stream_id: i32, f: &mut FnMut(&ListOldestRecordingsRow) -> bool)
        -> Result<(), Error> {
        let s = match self.streams_by_id.get_mut(&stream_id) {
            None => bail!("no stream {}", stream_id),
            Some(s) => s,
        };
        let end = match s.to_delete.last() {
            None => 0,
            Some(row) => row.id.recording() + 1,
        };
        raw::list_oldest_recordings(&self.conn, CompositeId::new(stream_id, end), &mut |r| {
            if f(&r) {
                s.to_delete.push(r);
                s.bytes_to_delete += r.sample_file_bytes as i64;
                return true;
            }
            false
        })
    }

    /// Initializes the video_sample_entries. To be called during construction.
    fn init_video_sample_entries(&mut self) -> Result<(), Error> {
        info!("Loading video sample entries");
        let mut stmt = self.conn.prepare(r#"
            select
                id,
                sha1,
                width,
                height,
                rfc6381_codec,
                data
            from
                video_sample_entry
        "#)?;
        let mut rows = stmt.query(&[])?;
        while let Some(row) = rows.next() {
            let row = row?;
            let id = row.get_checked(0)?;
            let mut sha1 = [0u8; 20];
            let sha1_vec: Vec<u8> = row.get_checked(1)?;
            if sha1_vec.len() != 20 {
                bail!("video sample entry id {} has sha1 {} of wrong length", id, sha1_vec.len());
            }
            sha1.copy_from_slice(&sha1_vec);
            let data: Vec<u8> = row.get_checked(5)?;

            self.video_sample_entries.insert(id, Arc::new(VideoSampleEntry {
                id: id as i32,
                width: row.get_checked::<_, i32>(2)? as u16,
                height: row.get_checked::<_, i32>(3)? as u16,
                sha1,
                data,
                rfc6381_codec: row.get_checked(4)?,
            }));
        }
        info!("Loaded {} video sample entries",
              self.video_sample_entries.len());
        Ok(())
    }

    /// Initializes the sample file dirs.
    /// To be called during construction.
    fn init_sample_file_dirs(&mut self) -> Result<(), Error> {
        info!("Loading sample file dirs");
        let mut stmt = self.conn.prepare(r#"
            select
              d.id,
              d.path,
              d.uuid,
              d.last_complete_open_id,
              o.uuid
            from
              sample_file_dir d left join open o on (d.last_complete_open_id = o.id);
        "#)?;
        let mut rows = stmt.query(&[])?;
        while let Some(row) = rows.next() {
            let row = row?;
            let id = row.get_checked(0)?;
            let dir_uuid: FromSqlUuid = row.get_checked(2)?;
            let open_id: Option<u32> = row.get_checked(3)?;
            let open_uuid: Option<FromSqlUuid> = row.get_checked(4)?;
            let last_complete_open = match (open_id, open_uuid) {
                (Some(id), Some(uuid)) => Some(Open { id, uuid: uuid.0, }),
                (None, None) => None,
                _ => bail!("open table missing id {}", id),
            };
            self.sample_file_dirs_by_id.insert(id, SampleFileDir {
                id,
                uuid: dir_uuid.0,
                path: row.get_checked(1)?,
                dir: None,
                last_complete_open,
                to_gc: Vec::new(),
                garbage: raw::list_garbage(&self.conn, id)?,
            });
        }
        info!("Loaded {} sample file dirs", self.sample_file_dirs_by_id.len());
        Ok(())
    }

    /// Initializes the cameras, but not their matching recordings.
    /// To be called during construction.
    fn init_cameras(&mut self) -> Result<(), Error> {
        info!("Loading cameras");
        let mut stmt = self.conn.prepare(r#"
            select
              id,
              uuid,
              short_name,
              description,
              host,
              username,
              password
            from
              camera;
        "#)?;
        let mut rows = stmt.query(&[])?;
        while let Some(row) = rows.next() {
            let row = row?;
            let id = row.get_checked(0)?;
            let uuid: FromSqlUuid = row.get_checked(1)?;
            self.cameras_by_id.insert(id, Camera {
                id: id,
                uuid: uuid.0,
                short_name: row.get_checked(2)?,
                description: row.get_checked(3)?,
                host: row.get_checked(4)?,
                username: row.get_checked(5)?,
                password: row.get_checked(6)?,
                streams: Default::default(),
            });
            self.cameras_by_uuid.insert(uuid.0, id);
        }
        info!("Loaded {} cameras", self.cameras_by_id.len());
        Ok(())
    }

    /// Initializes the streams, but not their matching recordings.
    /// To be called during construction.
    fn init_streams(&mut self) -> Result<(), Error> {
        info!("Loading streams");
        let mut stmt = self.conn.prepare(r#"
            select
              id,
              type,
              camera_id,
              sample_file_dir_id,
              rtsp_path,
              retain_bytes,
              flush_if_sec,
              next_recording_id,
              record
            from
              stream;
        "#)?;
        let mut rows = stmt.query(&[])?;
        while let Some(row) = rows.next() {
            let row = row?;
            let id = row.get_checked(0)?;
            let type_: String = row.get_checked(1)?;
            let type_ = StreamType::parse(&type_).ok_or_else(
                || format_err!("no such stream type {}", type_))?;
            let camera_id = row.get_checked(2)?;
            let c = self
                        .cameras_by_id
                        .get_mut(&camera_id)
                        .ok_or_else(|| format_err!("missing camera {} for stream {}",
                                                   camera_id, id))?;
            let flush_if_sec = row.get_checked(6)?;
            self.streams_by_id.insert(id, Stream {
                id,
                type_,
                camera_id,
                sample_file_dir_id: row.get_checked(3)?,
                rtsp_path: row.get_checked(4)?,
                retain_bytes: row.get_checked(5)?,
                flush_if_sec,
                flush_if: recording::Duration(flush_if_sec * recording::TIME_UNITS_PER_SEC),
                range: None,
                sample_file_bytes: 0,
                to_delete: Vec::new(),
                bytes_to_delete: 0,
                duration: recording::Duration(0),
                days: BTreeMap::new(),
                next_recording_id: row.get_checked(7)?,
                record: row.get_checked(8)?,
                uncommitted: VecDeque::new(),
            });
            c.streams[type_.index()] = Some(id);
        }
        info!("Loaded {} streams", self.streams_by_id.len());
        Ok(())
    }

    /// Inserts the specified video sample entry if absent.
    /// On success, returns the id of a new or existing row.
    pub fn insert_video_sample_entry(&mut self, width: u16, height: u16, data: Vec<u8>,
                                     rfc6381_codec: String) -> Result<i32, Error> {
        let sha1 = hash::hash(hash::MessageDigest::sha1(), &data)?;
        let mut sha1_bytes = [0u8; 20];
        sha1_bytes.copy_from_slice(&sha1);

        // Check if it already exists.
        // There shouldn't be too many entries, so it's fine to enumerate everything.
        for (&id, v) in &self.video_sample_entries {
            if v.sha1 == sha1_bytes {
                // The width and height should match given that they're also specified within data
                // and thus included in the just-compared hash.
                if v.width != width || v.height != height {
                    bail!("database entry for {:?} is {}x{}, not {}x{}",
                          &sha1[..], v.width, v.height, width, height);
                }
                return Ok(id);
            }
        }

        let mut stmt = self.conn.prepare_cached(INSERT_VIDEO_SAMPLE_ENTRY_SQL)?;
        stmt.execute_named(&[
            (":sha1", &&sha1_bytes[..]),
            (":width", &(width as i64)),
            (":height", &(height as i64)),
            (":rfc6381_codec", &rfc6381_codec),
            (":data", &data),
        ])?;

        let id = self.conn.last_insert_rowid() as i32;
        self.video_sample_entries.insert(id, Arc::new(VideoSampleEntry {
            id,
            width,
            height,
            sha1: sha1_bytes,
            data,
            rfc6381_codec,
        }));

        Ok(id)
    }

    pub fn add_sample_file_dir(&mut self, path: String) -> Result<i32, Error> {
        let mut meta = schema::DirMeta::default();
        let uuid = Uuid::new_v4();
        let uuid_bytes = &uuid.as_bytes()[..];
        let o = self
                    .open
                    .as_ref()
                    .ok_or_else(|| format_err!("database is read-only"))?;

        // Populate meta.
        {
            meta.db_uuid.extend_from_slice(&self.uuid.as_bytes()[..]);
            meta.dir_uuid.extend_from_slice(uuid_bytes);
            let open = meta.mut_in_progress_open();
            open.id = o.id;
            open.uuid.extend_from_slice(&o.uuid.as_bytes()[..]);
        }

        let dir = dir::SampleFileDir::create(&path, &meta)?;
        // TODO: ensure the dir is empty?
        let uuid = Uuid::new_v4();
        self.conn.execute(r#"
            insert into sample_file_dir (path, uuid, last_complete_open_id)
                                 values (?,    ?,    ?)
        "#, &[&path, &uuid_bytes, &o.id])?;
        let id = self.conn.last_insert_rowid() as i32;
        use ::std::collections::btree_map::Entry;
        let e = self.sample_file_dirs_by_id.entry(id);
        let d = match e {
            Entry::Vacant(e) => e.insert(SampleFileDir {
                id,
                path,
                uuid,
                dir: Some(dir),
                last_complete_open: None,
                to_gc: Vec::new(),
                garbage: FnvHashSet::default(),
            }),
            Entry::Occupied(_) => Err(format_err!("duplicate sample file dir id {}", id))?,
        };
        d.last_complete_open = Some(*o);
        mem::swap(&mut meta.last_complete_open, &mut meta.in_progress_open);
        d.dir.as_ref().unwrap().write_meta(&meta)?;
        Ok(id)
    }

    pub fn delete_sample_file_dir(&mut self, dir_id: i32) -> Result<(), Error> {
        for (&id, s) in self.streams_by_id.iter() {
            if s.sample_file_dir_id == Some(dir_id) {
                bail!("can't delete dir referenced by stream {}", id);
            }
        }
        // TODO: remove/update metadata stored in the directory? at present this will have to
        // be manually deleted before the dir can be reused.
        if self.conn.execute("delete from sample_file_dir where id = ?", &[&dir_id])? != 1 {
            bail!("no such dir {} to remove", dir_id);
        }
        self.sample_file_dirs_by_id.remove(&dir_id).expect("sample file dir should exist!");
        Ok(())
    }

    /// Adds a camera.
    pub fn add_camera(&mut self, mut camera: CameraChange) -> Result<i32, Error> {
        let uuid = Uuid::new_v4();
        let uuid_bytes = &uuid.as_bytes()[..];
        let tx = self.conn.transaction()?;
        let streams;
        let camera_id;
        {
            let mut stmt = tx.prepare_cached(r#"
                insert into camera (uuid,  short_name,  description,  host,  username,  password)
                            values (:uuid, :short_name, :description, :host, :username, :password)
            "#)?;
            stmt.execute_named(&[
                (":uuid", &uuid_bytes),
                (":short_name", &camera.short_name),
                (":description", &camera.description),
                (":host", &camera.host),
                (":username", &camera.username),
                (":password", &camera.password),
            ])?;
            camera_id = tx.last_insert_rowid() as i32;
            streams = StreamStateChanger::new(&tx, camera_id, None, &self.streams_by_id,
                                         &mut camera)?;
        }
        tx.commit()?;
        let streams = streams.apply(&mut self.streams_by_id);
        self.cameras_by_id.insert(camera_id, Camera {
            id: camera_id,
            uuid,
            short_name: camera.short_name,
            description: camera.description,
            host: camera.host,
            username: camera.username,
            password: camera.password,
            streams,
        });
        self.cameras_by_uuid.insert(uuid, camera_id);
        Ok(camera_id)
    }

    /// Updates a camera.
    pub fn update_camera(&mut self, camera_id: i32, mut camera: CameraChange) -> Result<(), Error> {
        // TODO: sample_file_dir_id. disallow change when data is stored; change otherwise.
        let tx = self.conn.transaction()?;
        let streams;
        let c = self
                    .cameras_by_id
                    .get_mut(&camera_id)
                    .ok_or_else(|| format_err!("no such camera {}", camera_id))?;
        {
            streams = StreamStateChanger::new(&tx, camera_id, Some(c), &self.streams_by_id,
                                         &mut camera)?;
            let mut stmt = tx.prepare_cached(r#"
                update camera set
                    short_name = :short_name,
                    description = :description,
                    host = :host,
                    username = :username,
                    password = :password
                where
                    id = :id
            "#)?;
            let rows = stmt.execute_named(&[
                (":id", &camera_id),
                (":short_name", &camera.short_name),
                (":description", &camera.description),
                (":host", &camera.host),
                (":username", &camera.username),
                (":password", &camera.password),
            ])?;
            if rows != 1 {
                bail!("Camera {} missing from database", camera_id);
            }
        }
        tx.commit()?;
        c.short_name = camera.short_name;
        c.description = camera.description;
        c.host = camera.host;
        c.username = camera.username;
        c.password = camera.password;
        c.streams = streams.apply(&mut self.streams_by_id);
        Ok(())
    }

    /// Deletes a camera and its streams. The camera must have no recordings.
    pub fn delete_camera(&mut self, id: i32) -> Result<(), Error> {
        let uuid = self.cameras_by_id.get(&id)
                       .map(|c| c.uuid)
                       .ok_or_else(|| format_err!("No such camera {} to remove", id))?;
        let mut streams_to_delete = Vec::new();
        let tx = self.conn.transaction()?;
        {
            let mut stream_stmt = tx.prepare_cached(r"delete from stream where id = :id")?;
            for (stream_id, stream) in &self.streams_by_id {
                if stream.camera_id != id { continue };
                if stream.range.is_some() {
                    bail!("Can't remove camera {}; has recordings.", id);
                }
                let rows = stream_stmt.execute_named(&[(":id", stream_id)])?;
                if rows != 1 {
                    bail!("Stream {} missing from database", id);
                }
                streams_to_delete.push(*stream_id);
            }
            let mut cam_stmt = tx.prepare_cached(r"delete from camera where id = :id")?;
            let rows = cam_stmt.execute_named(&[(":id", &id)])?;
            if rows != 1 {
                bail!("Camera {} missing from database", id);
            }
        }
        tx.commit()?;
        for id in streams_to_delete {
            self.streams_by_id.remove(&id);
        }
        self.cameras_by_id.remove(&id);
        self.cameras_by_uuid.remove(&uuid);
        return Ok(())
    }

    pub fn update_retention(&mut self, changes: &[RetentionChange]) -> Result<(), Error> {
        let tx = self.conn.transaction()?;
        {
            let mut stmt = tx.prepare_cached(r#"
                update stream
                set
                  record = :record,
                  retain_bytes = :retain
                where
                  id = :id
            "#)?;
            for c in changes {
                if c.new_limit < 0 {
                    bail!("can't set limit for stream {} to {}; must be >= 0",
                          c.stream_id, c.new_limit);
                }
                let rows = stmt.execute_named(&[
                    (":record", &c.new_record),
                    (":retain", &c.new_limit),
                    (":id", &c.stream_id),
                ])?;
                if rows != 1 {
                    bail!("no such stream {}", c.stream_id);
                }
            }
        }
        tx.commit()?;
        for c in changes {
            let s = self.streams_by_id.get_mut(&c.stream_id).expect("stream in db but not state");
            s.record = c.new_record;
            s.retain_bytes = c.new_limit;
        }
        Ok(())
    }
}

/// Gets the schema version from the given database connection.
/// A fully initialized database will return `Ok(Some(version))` where `version` is an integer that
/// can be compared to `EXPECTED_VERSION`. An empty database will return `Ok(None)`. A partially
/// initialized database (in particular, one without a version row) will return some error.
pub fn get_schema_version(conn: &rusqlite::Connection) -> Result<Option<i32>, Error> {
    let ver_tables: i32 = conn.query_row_and_then(
        "select count(*) from sqlite_master where name = 'version'",
        &[], |row| row.get_checked(0))?;
    if ver_tables == 0 {
        return Ok(None);
    }
    Ok(Some(conn.query_row_and_then("select max(id) from version", &[], |row| row.get_checked(0))?))
}

/// The recording database. Abstracts away SQLite queries. Also maintains in-memory state
/// (loaded on startup, and updated on successful commit) to avoid expensive scans over the
/// recording table on common queries.
pub struct Database(
    /// This is wrapped in an `Option` to allow the `Drop` implementation and `close` to coexist.
    Option<Mutex<LockedDatabase>>
);

impl Drop for Database {
    fn drop(&mut self) {
        if let Some(m) = self.0.take() {
            if let Err(e) = m.into_inner().flush("drop") {
                error!("Final database flush failed: {}", e);
            }
        }
    }
}

impl Database {
    /// Creates the database from a caller-supplied SQLite connection.
    pub fn new(conn: rusqlite::Connection, read_write: bool) -> Result<Database, Error> {
        conn.execute("pragma foreign_keys = on", &[])?;
        {
            let ver = get_schema_version(&conn)?.ok_or_else(|| format_err!(
                    "no such table: version. \
                    \
                    If you are starting from an \
                    empty database, see README.md to complete the \
                    installation. If you are starting from a database \
                    that predates schema versioning, see guide/schema.md."))?;
            if ver < EXPECTED_VERSION {
                bail!("Database schema version {} is too old (expected {}); \
                       see upgrade instructions in guide/upgrade.md.",
                      ver, EXPECTED_VERSION);
            } else if ver > EXPECTED_VERSION {
                bail!("Database schema version {} is too new (expected {}); \
                       must use a newer binary to match.", ver,
                      EXPECTED_VERSION);

            }
        }

        // Note: the meta check comes after the version check to improve the error message when
        // trying to open a version 0 or version 1 database (which lacked the meta table).
        let uuid = conn.query_row("select uuid from meta", &[], |row| -> Result<Uuid, Error> {
            let uuid: FromSqlUuid = row.get_checked(0)?;
            Ok(uuid.0)
        })??;
        let list_recordings_by_time_sql = format!(r#"
            select
                recording.composite_id,
                recording.run_offset,
                recording.flags,
                recording.start_time_90k,
                recording.duration_90k,
                recording.sample_file_bytes,
                recording.video_samples,
                recording.video_sync_samples,
                recording.video_sample_entry_id
            from
                recording
            where
                stream_id = :stream_id and
                recording.start_time_90k > :start_time_90k - {} and
                recording.start_time_90k < :end_time_90k and
                recording.start_time_90k + recording.duration_90k > :start_time_90k
            order by
                recording.start_time_90k
        "#, recording::MAX_RECORDING_DURATION);
        let open = if read_write {
            let mut stmt = conn.prepare(" insert into open (uuid) values (?)")?;
            let uuid = Uuid::new_v4();
            let uuid_bytes = &uuid.as_bytes()[..];
            stmt.execute(&[&uuid_bytes])?;
            Some(Open {
                id: conn.last_insert_rowid() as u32,
                uuid,
            })
        } else { None };
        let db = Database(Some(Mutex::new(LockedDatabase {
            conn: conn,
            uuid,
            open,
            sample_file_dirs_by_id: BTreeMap::new(),
            cameras_by_id: BTreeMap::new(),
            cameras_by_uuid: BTreeMap::new(),
            streams_by_id: BTreeMap::new(),
            video_sample_entries: BTreeMap::new(),
            video_index_cache: RefCell::new(LruCache::with_hasher(1024, Default::default())),
            list_recordings_by_time_sql,
            on_flush: Vec::new(),
        })));
        {
            let l = &mut *db.lock();
            l.init_video_sample_entries()?;
            l.init_sample_file_dirs()?;
            l.init_cameras()?;
            l.init_streams()?;
            for (&stream_id, ref mut stream) in &mut l.streams_by_id {
                // TODO: we could use one thread per stream if we had multiple db conns.
                let camera = l.cameras_by_id.get(&stream.camera_id).unwrap();
                init_recordings(&mut l.conn, stream_id, camera, stream)?;
            }
        }
        Ok(db)
    }

    /// Initializes a database.
    /// Note this doesn't set journal options, so that it can be used on in-memory databases for
    /// test code.
    pub fn init(conn: &mut rusqlite::Connection) -> Result<(), Error> {
        let tx = conn.transaction()?;
        tx.execute_batch(include_str!("schema.sql"))?;
        {
            let uuid = ::uuid::Uuid::new_v4();
            let uuid_bytes = &uuid.as_bytes()[..];
            tx.execute("insert into meta (uuid) values (?)", &[&uuid_bytes])?;
        }
        tx.commit()?;
        Ok(())
    }

    /// Locks the database; the returned reference is the only way to perform (read or write)
    /// operations.
    pub fn lock(&self) -> MutexGuard<LockedDatabase> { self.0.as_ref().unwrap().lock() }

    /// For testing: closes the database (without flushing) and returns the connection.
    /// This allows verification that a newly opened database is in an acceptable state.
    #[cfg(test)]
    fn close(mut self) -> rusqlite::Connection {
        self.0.take().unwrap().into_inner().conn
    }
}

#[cfg(test)]
mod tests {
    extern crate tempdir;

    use recording::{self, TIME_UNITS_PER_SEC};
    use rusqlite::Connection;
    use std::collections::BTreeMap;
    use testutil;
    use super::*;
    use super::adjust_days;  // non-public.
    use uuid::Uuid;

    fn setup_conn() -> Connection {
        let mut conn = Connection::open_in_memory().unwrap();
        Database::init(&mut conn).unwrap();
        conn
    }

    fn assert_no_recordings(db: &Database, uuid: Uuid) {
        let mut rows = 0;
        let mut camera_id = -1;
        {
            let db = db.lock();
            for row in db.cameras_by_id().values() {
                rows += 1;
                camera_id = row.id;
                assert_eq!(uuid, row.uuid);
                assert_eq!("test-camera", row.host);
                assert_eq!("foo", row.username);
                assert_eq!("bar", row.password);
                //assert_eq!("/main", row.main_rtsp_path);
                //assert_eq!("/sub", row.sub_rtsp_path);
                //assert_eq!(42, row.retain_bytes);
                //assert_eq!(None, row.range);
                //assert_eq!(recording::Duration(0), row.duration);
                //assert_eq!(0, row.sample_file_bytes);
            }
        }
        assert_eq!(1, rows);

        let stream_id = camera_id;  // TODO
        rows = 0;
        {
            let db = db.lock();
            let all_time = recording::Time(i64::min_value()) .. recording::Time(i64::max_value());
            db.list_recordings_by_time(stream_id, all_time, &mut |_row| {
                rows += 1;
                Ok(())
            }).unwrap();
        }
        assert_eq!(0, rows);
    }

    fn assert_single_recording(db: &Database, stream_id: i32, r: &RecordingToInsert) {
        {
            let db = db.lock();
            let stream = db.streams_by_id().get(&stream_id).unwrap();
            assert_eq!(Some(r.time.clone()), stream.range);
            assert_eq!(r.sample_file_bytes as i64, stream.sample_file_bytes);
            assert_eq!(r.time.end - r.time.start, stream.duration);
            db.cameras_by_id().get(&stream.camera_id).unwrap();
        }

        // TODO(slamb): test that the days logic works correctly.

        let mut rows = 0;
        let mut recording_id = None;
        {
            let db = db.lock();
            let all_time = recording::Time(i64::min_value()) .. recording::Time(i64::max_value());
            db.list_recordings_by_time(stream_id, all_time, &mut |row| {
                rows += 1;
                recording_id = Some(row.id);
                assert_eq!(r.time,
                           row.start .. row.start + recording::Duration(row.duration_90k as i64));
                assert_eq!(r.video_samples, row.video_samples);
                assert_eq!(r.video_sync_samples, row.video_sync_samples);
                assert_eq!(r.sample_file_bytes, row.sample_file_bytes);
                assert_eq!(row.video_sample_entry.rfc6381_codec, "avc1.4d0029");
                Ok(())
            }).unwrap();
        }
        assert_eq!(1, rows);

        rows = 0;
        raw::list_oldest_recordings(&db.lock().conn, CompositeId::new(stream_id, 0), &mut |row| {
            rows += 1;
            assert_eq!(recording_id, Some(row.id));
            assert_eq!(r.time.start, row.start);
            assert_eq!(r.time.end - r.time.start, recording::Duration(row.duration as i64));
            assert_eq!(r.sample_file_bytes, row.sample_file_bytes);
            true
        }).unwrap();
        assert_eq!(1, rows);

        // TODO: list_aggregated_recordings.
        // TODO: with_recording_playback.
    }

    #[test]
    fn test_adjust_days() {
        testutil::init();
        let mut m = BTreeMap::new();

        // Create a day.
        let test_time = recording::Time(130647162600000i64);  // 2015-12-31 23:59:00 (Pacific).
        let one_min = recording::Duration(60 * TIME_UNITS_PER_SEC);
        let two_min = recording::Duration(2 * 60 * TIME_UNITS_PER_SEC);
        let three_min = recording::Duration(3 * 60 * TIME_UNITS_PER_SEC);
        let four_min = recording::Duration(4 * 60 * TIME_UNITS_PER_SEC);
        let test_day1 = &StreamDayKey(*b"2015-12-31");
        let test_day2 = &StreamDayKey(*b"2016-01-01");
        adjust_days(test_time .. test_time + one_min, 1, &mut m);
        assert_eq!(1, m.len());
        assert_eq!(Some(&StreamDayValue{recordings: 1, duration: one_min}), m.get(test_day1));

        // Add to a day.
        adjust_days(test_time .. test_time + one_min, 1, &mut m);
        assert_eq!(1, m.len());
        assert_eq!(Some(&StreamDayValue{recordings: 2, duration: two_min}), m.get(test_day1));

        // Subtract from a day.
        adjust_days(test_time .. test_time + one_min, -1, &mut m);
        assert_eq!(1, m.len());
        assert_eq!(Some(&StreamDayValue{recordings: 1, duration: one_min}), m.get(test_day1));

        // Remove a day.
        adjust_days(test_time .. test_time + one_min, -1, &mut m);
        assert_eq!(0, m.len());

        // Create two days.
        adjust_days(test_time .. test_time + three_min, 1, &mut m);
        assert_eq!(2, m.len());
        assert_eq!(Some(&StreamDayValue{recordings: 1, duration: one_min}), m.get(test_day1));
        assert_eq!(Some(&StreamDayValue{recordings: 1, duration: two_min}), m.get(test_day2));

        // Add to two days.
        adjust_days(test_time .. test_time + three_min, 1, &mut m);
        assert_eq!(2, m.len());
        assert_eq!(Some(&StreamDayValue{recordings: 2, duration: two_min}), m.get(test_day1));
        assert_eq!(Some(&StreamDayValue{recordings: 2, duration: four_min}), m.get(test_day2));

        // Subtract from two days.
        adjust_days(test_time .. test_time + three_min, -1, &mut m);
        assert_eq!(2, m.len());
        assert_eq!(Some(&StreamDayValue{recordings: 1, duration: one_min}), m.get(test_day1));
        assert_eq!(Some(&StreamDayValue{recordings: 1, duration: two_min}), m.get(test_day2));

        // Remove two days.
        adjust_days(test_time .. test_time + three_min, -1, &mut m);
        assert_eq!(0, m.len());
    }

    #[test]
    fn test_day_bounds() {
        testutil::init();
        assert_eq!(StreamDayKey(*b"2017-10-10").bounds(),  // normal day (24 hrs)
                   recording::Time(135685692000000) .. recording::Time(135693468000000));
        assert_eq!(StreamDayKey(*b"2017-03-12").bounds(),  // spring forward (23 hrs)
                   recording::Time(134037504000000) .. recording::Time(134044956000000));
        assert_eq!(StreamDayKey(*b"2017-11-05").bounds(),  // fall back (25 hrs)
                   recording::Time(135887868000000) .. recording::Time(135895968000000));
    }

    #[test]
    fn test_no_meta_or_version() {
        testutil::init();
        let e = Database::new(Connection::open_in_memory().unwrap(), false).err().unwrap();
        assert!(e.to_string().starts_with("no such table"), "{}", e);
    }

    #[test]
    fn test_version_too_old() {
        testutil::init();
        let c = setup_conn();
        c.execute_batch("delete from version; insert into version values (2, 0, '');").unwrap();
        let e = Database::new(c, false).err().unwrap();
        assert!(e.to_string().starts_with(
                "Database schema version 2 is too old (expected 3)"), "got: {:?}", e);
    }

    #[test]
    fn test_version_too_new() {
        testutil::init();
        let c = setup_conn();
        c.execute_batch("delete from version; insert into version values (4, 0, '');").unwrap();
        let e = Database::new(c, false).err().unwrap();
        assert!(e.to_string().starts_with(
                "Database schema version 4 is too new (expected 3)"), "got: {:?}", e);
    }

    /// Basic test of running some queries on a fresh database.
    #[test]
    fn test_fresh_db() {
        testutil::init();
        let conn = setup_conn();
        let db = Database::new(conn, true).unwrap();
        let db = db.lock();
        assert_eq!(0, db.cameras_by_id().values().count());
    }

    /// Basic test of the full lifecycle of recording. Does not exercise error cases.
    #[test]
    fn test_full_lifecycle() {
        testutil::init();
        let conn = setup_conn();
        let db = Database::new(conn, true).unwrap();
        let tmpdir = tempdir::TempDir::new("moonfire-nvr-test").unwrap();
        let path = tmpdir.path().to_str().unwrap().to_owned();
        let sample_file_dir_id = { db.lock() }.add_sample_file_dir(path).unwrap();
        let camera_id = { db.lock() }.add_camera(CameraChange {
            short_name: "testcam".to_owned(),
            description: "".to_owned(),
            host: "test-camera".to_owned(),
            username: "foo".to_owned(),
            password: "bar".to_owned(),
            streams: [
                StreamChange {
                    sample_file_dir_id: Some(sample_file_dir_id),
                    rtsp_path: "/main".to_owned(),
                    record: true,
                    flush_if_sec: 0,
                },
                StreamChange {
                    sample_file_dir_id: Some(sample_file_dir_id),
                    rtsp_path: "/sub".to_owned(),
                    record: true,
                    flush_if_sec: 0,
                },
            ],
        }).unwrap();
        {
            let mut l = db.lock();
            let stream_id = l.cameras_by_id().get(&camera_id).unwrap().streams[0].unwrap();
            l.update_retention(&[super::RetentionChange {
                stream_id,
                new_record: true,
                new_limit: 42,
            }]).unwrap();
        }
        let camera_uuid = { db.lock().cameras_by_id().get(&camera_id).unwrap().uuid };
        assert_no_recordings(&db, camera_uuid);

        // Closing and reopening the database should present the same contents.
        let conn = db.close();
        let db = Database::new(conn, true).unwrap();
        assert_no_recordings(&db, camera_uuid);

        // TODO: assert_eq!(db.lock().list_garbage(sample_file_dir_id).unwrap(), &[]);

        let vse_id = db.lock().insert_video_sample_entry(
            1920, 1080, include_bytes!("testdata/avc1").to_vec(),
            "avc1.4d0029".to_owned()).unwrap();
        assert!(vse_id > 0, "vse_id = {}", vse_id);

        // Inserting a recording should succeed and advance the next recording id.
        let start = recording::Time(1430006400 * TIME_UNITS_PER_SEC);
        let stream_id = camera_id;  // TODO
        let recording = RecordingToInsert {
            sample_file_bytes: 42,
            run_offset: 0,
            flags: 0,
            time: start .. start + recording::Duration(TIME_UNITS_PER_SEC),
            local_time_delta: recording::Duration(0),
            video_samples: 1,
            video_sync_samples: 1,
            video_sample_entry_id: vse_id,
            video_index: [0u8; 100].to_vec(),
            sample_file_sha1: [0u8; 20],
        };
        let id = {
            let mut db = db.lock();
            let (id, u) = db.add_recording(stream_id).unwrap();
            u.lock().recording = Some(recording.clone());
            u.lock().synced = true;
            db.flush("add test").unwrap();
            id
        };
        assert_eq!(db.lock().streams_by_id().get(&stream_id).unwrap().next_recording_id, 2);

        // Queries should return the correct result (with caches update on insert).
        assert_single_recording(&db, stream_id, &recording);

        // Queries on a fresh database should return the correct result (with caches populated from
        // existing database contents rather than built on insert).
        let conn = db.close();
        let db = Database::new(conn, true).unwrap();
        assert_single_recording(&db, stream_id, &recording);

        // Deleting a recording should succeed, update the min/max times, and mark it as garbage.
        {
            let mut db = db.lock();
            let mut n = 0;
            db.delete_oldest_recordings(stream_id, &mut |_| { n += 1; true }).unwrap();
            assert_eq!(n, 1);
            {
                let s = db.streams_by_id().get(&stream_id).unwrap();
                assert_eq!(s.sample_file_bytes, 42);
                assert_eq!(s.bytes_to_delete, 42);
            }
            n = 0;

            // A second run
            db.delete_oldest_recordings(stream_id, &mut |_| { n += 1; true }).unwrap();
            assert_eq!(n, 0);
            assert_eq!(db.streams_by_id().get(&stream_id).unwrap().bytes_to_delete, 42);
            db.flush("delete test").unwrap();
            let s = db.streams_by_id().get(&stream_id).unwrap();
            assert_eq!(s.sample_file_bytes, 0);
            assert_eq!(s.bytes_to_delete, 0);
        }
        assert_no_recordings(&db, camera_uuid);
        let g: Vec<_> = db.lock()
                          .sample_file_dirs_by_id()
                          .get(&sample_file_dir_id)
                          .unwrap()
                          .garbage
                          .iter()
                          .map(|&id| id)
                          .collect();
        assert_eq!(&g, &[id]);
    }
}