// 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/>.

use clock;
use db::{self, dir, writer};
use failure::Error;
use fnv::FnvHashMap;
use futures::{Future, Stream};
use std::error::Error as StdError;
use std::sync::Arc;
use std::sync::atomic::{AtomicBool, Ordering};
use std::thread;
use stream;
use streamer;
use tokio;
use tokio_signal::unix::{Signal, SIGINT, SIGTERM};
use web;

// These are used in a hack to get the name of the current time zone (e.g. America/Los_Angeles).
// They seem to be correct for Linux and macOS at least.
const LOCALTIME_PATH: &'static str = "/etc/localtime";
const TIMEZONE_PATH: &'static str = "/etc/timezone";
const ZONEINFO_PATHS: [&'static str; 2] = [
    "/usr/share/zoneinfo/",       // Linux, macOS < High Sierra
    "/var/db/timezone/zoneinfo/"  // macOS High Sierra
];

const USAGE: &'static str = r#"
Usage: moonfire-nvr run [options]

Options:
    -h, --help             Show this message.
    --db-dir=DIR           Set the directory holding the SQLite3 index database.
                           This is typically on a flash device.
                           [default: /var/lib/moonfire-nvr/db]
    --ui-dir=DIR           Set the directory with the user interface files
                           (.html, .js, etc).
                           [default: /usr/local/lib/moonfire-nvr/ui]
    --http-addr=ADDR       Set the bind address for the unencrypted HTTP server.
                           [default: 0.0.0.0:8080]
    --read-only            Forces read-only mode / disables recording.
    --allow-origin=ORIGIN  If present, adds a Access-Control-Allow-Origin:
                           header to HTTP responses. This may be useful for
                           Javascript development.
"#;

#[derive(Debug, Deserialize)]
struct Args {
    flag_db_dir: String,
    flag_http_addr: String,
    flag_ui_dir: String,
    flag_read_only: bool,
    flag_allow_origin: Option<String>,
}

fn setup_shutdown() -> impl Future<Item = (), Error = ()> + Send {
    let int = Signal::new(SIGINT).flatten_stream().into_future();
    let term = Signal::new(SIGTERM).flatten_stream().into_future();
    int.select(term)
       .map(|_| ())
       .map_err(|_| ())
}

fn trim_zoneinfo(p: &str) -> &str {
    for zp in &ZONEINFO_PATHS {
        if p.starts_with(zp) {
            return &p[zp.len()..];
        }
    }
    return p;
}

/// Attempt to resolve the timezone of the server.
/// The Javascript running in the browser needs this to match the server's timezone calculations.
fn resolve_zone() -> Result<String, Error> {
    // If the environmental variable `TZ` exists, is valid UTF-8, and doesn't just reference
    // `/etc/localtime/`, use that.
    if let Ok(tz) = ::std::env::var("TZ") {
        let mut p: &str = &tz;

        // Strip of an initial `:` if present. Having `TZ` set in this way is a trick to avoid
        // repeated `tzset` calls:
        // https://blog.packagecloud.io/eng/2017/02/21/set-environment-variable-save-thousands-of-system-calls/
        if p.starts_with(':') {
            p = &p[1..];
        }

        p = trim_zoneinfo(p);

        if !p.starts_with('/') {
            return Ok(p.to_owned());
        }
        if p != LOCALTIME_PATH {
            bail!("Unable to resolve env TZ={} to a timezone.", &tz);
        }
    }

    // If `LOCALTIME_PATH` is a symlink, use that. On some systems, it's instead a copy of the
    // desired timezone, which unfortunately doesn't contain its own name.
    match ::std::fs::read_link(LOCALTIME_PATH) {
        Ok(localtime_dest) => {
            let localtime_dest = match localtime_dest.to_str() {
                Some(d) => d,
                None => bail!("{} symlink destination is invalid UTF-8", LOCALTIME_PATH),
            };
            let p = trim_zoneinfo(localtime_dest);
            if p.starts_with('/') {
                bail!("Unable to resolve {} symlink destination {} to a timezone.",
                      LOCALTIME_PATH, &localtime_dest);
            }
            return Ok(p.to_owned());
        },
        Err(e) => {
            use ::std::io::ErrorKind;
            if e.kind() != ErrorKind::NotFound && e.kind() != ErrorKind::InvalidInput {
                bail!("Unable to read {} symlink: {}", LOCALTIME_PATH, e);
            }
        },
    };

    // If `TIMEZONE_PATH` is a file, use its contents as the zone name.
    match ::std::fs::read_to_string(TIMEZONE_PATH) {
        Ok(z) => return Ok(z),
        Err(e) => {
            bail!("Unable to resolve timezone from TZ env, {}, or {}. Last error: {}",
                  LOCALTIME_PATH, TIMEZONE_PATH, e);
        }
    }
}

struct Syncer {
    dir: Arc<dir::SampleFileDir>,
    channel: writer::SyncerChannel<::std::fs::File>,
    join: thread::JoinHandle<()>,
}

pub fn run() -> Result<(), Error> {
    let args: Args = super::parse_args(USAGE)?;
    let clocks = clock::RealClocks {};
    let (_db_dir, conn) = super::open_conn(
        &args.flag_db_dir,
        if args.flag_read_only { super::OpenMode::ReadOnly } else { super::OpenMode::ReadWrite })?;
    let db = Arc::new(db::Database::new(clocks.clone(), conn, !args.flag_read_only).unwrap());
    info!("Database is loaded.");

    {
        let mut l = db.lock();
        let dirs_to_open: Vec<_> =
            l.streams_by_id().values().filter_map(|s| s.sample_file_dir_id).collect();
        l.open_sample_file_dirs(&dirs_to_open)?;
    }
    info!("Directories are opened.");

    let zone = resolve_zone()?;
    info!("Resolved timezone: {}", &zone);
    let s = web::Service::new(db.clone(), Some(&args.flag_ui_dir), args.flag_allow_origin, zone)?;

    // Start a streamer for each stream.
    let shutdown_streamers = Arc::new(AtomicBool::new(false));
    let mut streamers = Vec::new();
    let syncers = if !args.flag_read_only {
        let l = db.lock();
        let mut dirs = FnvHashMap::with_capacity_and_hasher(
            l.sample_file_dirs_by_id().len(), Default::default());
        let streams = l.streams_by_id().len();
        let env = streamer::Environment {
            db: &db,
            opener: &*stream::FFMPEG,
            shutdown: &shutdown_streamers,
        };

        // Get the directories that need syncers.
        for stream in l.streams_by_id().values() {
            if let (Some(id), true) = (stream.sample_file_dir_id, stream.record) {
                dirs.entry(id).or_insert_with(|| {
                    let d = l.sample_file_dirs_by_id().get(&id).unwrap();
                    info!("Starting syncer for path {}", d.path);
                    d.get().unwrap()
                });
            }
        }

        // Then, with the lock dropped, create syncers.
        drop(l);
        let mut syncers = FnvHashMap::with_capacity_and_hasher(dirs.len(), Default::default());
        for (id, dir) in dirs.drain() {
            let (channel, join) = writer::start_syncer(db.clone(), id)?;
            syncers.insert(id, Syncer {
                dir,
                channel,
                join,
            });
        }

        // Then start up streams.
        let l = db.lock();
        for (i, (id, stream)) in l.streams_by_id().iter().enumerate() {
            if !stream.record {
                continue;
            }
            let camera = l.cameras_by_id().get(&stream.camera_id).unwrap();
            let sample_file_dir_id = match stream.sample_file_dir_id {
                Some(s) => s,
                None => {
                    warn!("Can't record stream {} ({}/{}) because it has no sample file dir",
                          id, camera.short_name, stream.type_.as_str());
                    continue;
                },
            };
            let rotate_offset_sec = streamer::ROTATE_INTERVAL_SEC * i as i64 / streams as i64;
            let syncer = syncers.get(&sample_file_dir_id).unwrap();
            let mut streamer = streamer::Streamer::new(&env, syncer.dir.clone(),
                                                       syncer.channel.clone(), *id, camera, stream,
                                                       rotate_offset_sec,
                                                       streamer::ROTATE_INTERVAL_SEC);
            info!("Starting streamer for {}", streamer.short_name());
            let name = format!("s-{}", streamer.short_name());
            streamers.push(thread::Builder::new().name(name).spawn(move|| {
                streamer.run();
            }).expect("can't create thread"));
        }
        drop(l);
        Some(syncers)
    } else { None };

    // Start the web interface.
    let addr = args.flag_http_addr.parse().unwrap();
    let server = ::hyper::server::Server::bind(&addr).tcp_nodelay(true).serve(
        move || Ok::<_, Box<StdError + Send + Sync>>(s.clone()));

    let shutdown = setup_shutdown().shared();

    info!("Ready to serve HTTP requests");
    let reactor = ::std::thread::spawn({
        let shutdown = shutdown.clone();
        || tokio::run(server.with_graceful_shutdown(shutdown.map(|_| ()))
                            .map_err(|e| error!("hyper error: {}", e)))
    });
    shutdown.wait().unwrap();

    info!("Shutting down streamers.");
    shutdown_streamers.store(true, Ordering::SeqCst);
    for streamer in streamers.drain(..) {
        streamer.join().unwrap();
    }

    if let Some(mut ss) = syncers {
        // The syncers shut down when all channels to them have been dropped.
        // The database maintains one; and `ss` holds one. Drop both.
        db.lock().clear_on_flush();
        for (_, s) in ss.drain() {
            drop(s.channel);
            s.join.join().unwrap();
        }
    }

    info!("Waiting for HTTP requests to finish.");
    reactor.join().unwrap();
    info!("Exiting.");
    Ok(())
}