// This file is part of Moonfire NVR, a security camera network video recorder.
// Copyright (C) 2016 The Moonfire NVR Authors
//
// 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 db::dir;
use failure::{Error, Fail};
use nix::fcntl::FlockArg;
use rusqlite;
use std::path::Path;

pub mod check;
pub mod config;
pub mod login;
pub mod init;
pub mod run;
pub mod sql;
pub mod ts;
pub mod upgrade;

#[derive(Copy, Clone, PartialEq, Eq)]
enum OpenMode {
    ReadOnly,
    ReadWrite,
    Create
}

/// Locks the directory without opening the database.
/// The returned `dir::Fd` holds the lock and should be kept open as long as the `Connection` is.
fn open_dir(db_dir: &Path, mode: OpenMode) -> Result<dir::Fd, Error> {
    let dir = dir::Fd::open(db_dir, mode == OpenMode::Create)
        .map_err(|e| e.context(if e == nix::Error::Sys(nix::errno::Errno::ENOENT) {
                                   format!("db dir {} not found; try running moonfire-nvr init",
                                           db_dir.display())
                               } else {
                                   format!("unable to open db dir {}: {}", db_dir.display(), &e)
                               }))?;
    let ro = mode == OpenMode::ReadOnly;
    dir.lock(if ro { FlockArg::LockSharedNonblock } else { FlockArg::LockExclusiveNonblock })
       .map_err(|e| e.context(format!("db dir {} already in use; can't get {} lock",
                                      db_dir.display(), if ro { "shared" } else { "exclusive" })))?;
    Ok(dir)
}

/// Locks and opens the database.
/// The returned `dir::Fd` holds the lock and should be kept open as long as the `Connection` is.
fn open_conn(db_dir: &Path, mode: OpenMode) -> Result<(dir::Fd, rusqlite::Connection), Error> {
    let dir = open_dir(db_dir, mode)?;
    let conn = rusqlite::Connection::open_with_flags(
        db_dir.join("db"),
        match mode {
            OpenMode::ReadOnly => rusqlite::OpenFlags::SQLITE_OPEN_READ_ONLY,
            OpenMode::ReadWrite => rusqlite::OpenFlags::SQLITE_OPEN_READ_WRITE,
            OpenMode::Create => {
                rusqlite::OpenFlags::SQLITE_OPEN_READ_WRITE | rusqlite::OpenFlags::SQLITE_OPEN_CREATE
            },
        } |
        // rusqlite::Connection is not Sync, so there's no reason to tell SQLite3 to use the
        // serialized threading mode.
        rusqlite::OpenFlags::SQLITE_OPEN_NO_MUTEX)?;
    Ok((dir, conn))
}
