// This file is part of Moonfire NVR, a security camera digital video recorder.
// Copyright (C) 2018 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/>.

/// Upgrades a version 2 schema to a version 3 schema.
/// Note that a version 2 schema is never actually used; so we know the upgrade from version 1 was
/// completed, and possibly an upgrade from 2 to 3 is half-finished.

use db::{self, FromSqlUuid};
use dir;
use failure::Error;
use libc;
use schema;
use std::io::{self, Write};
use std::mem;
use std::sync::Arc;
use rusqlite;
use uuid::Uuid;

/// Opens the sample file dir.
///
/// Makes a couple simplifying assumptions valid for version 2:
/// *   there's only one dir.
/// *   it has a last completed open.
fn open_sample_file_dir(tx: &rusqlite::Transaction) -> Result<Arc<dir::SampleFileDir>, Error> {
    let (p, s_uuid, o_id, o_uuid, db_uuid): (String, FromSqlUuid, i32, FromSqlUuid, FromSqlUuid) =
        tx.query_row(r#"
        select
          s.path, s.uuid, s.last_complete_open_id, o.uuid, m.uuid
        from
          sample_file_dir s
          join open o on (s.last_complete_open_id = o.id)
          cross join meta m
    "#, &[], |row| {
      (row.get_checked(0).unwrap(),
       row.get_checked(1).unwrap(),
       row.get_checked(2).unwrap(),
       row.get_checked(3).unwrap(),
       row.get_checked(4).unwrap())
    })?;
    let mut meta = schema::DirMeta::default();
    meta.db_uuid.extend_from_slice(&db_uuid.0.as_bytes()[..]);
    meta.dir_uuid.extend_from_slice(&s_uuid.0.as_bytes()[..]);
    {
        let open = meta.mut_last_complete_open();
        open.id = o_id as u32;
        open.uuid.extend_from_slice(&o_uuid.0.as_bytes()[..]);
    }
    dir::SampleFileDir::open(&p, &meta)
}

pub fn run(_args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error> {
    let d = open_sample_file_dir(&tx)?;
    let mut stmt = tx.prepare(r#"
        select
          composite_id,
          sample_file_uuid
        from
          recording_playback
    "#)?;
    let mut rows = stmt.query(&[])?;
    while let Some(row) = rows.next() {
        let row = row?;
        let id = db::CompositeId(row.get_checked(0)?);
        let sample_file_uuid: FromSqlUuid = row.get_checked(1)?;
        let from_path = get_uuid_pathname(sample_file_uuid.0);
        let to_path = get_id_pathname(id);
        let r = unsafe { dir::renameat(&d.fd, from_path.as_ptr(), &d.fd, to_path.as_ptr()) };
        if let Err(e) = r {
            if e.kind() == io::ErrorKind::NotFound {
                continue;  // assume it was already moved.
            }
            Err(e)?;
        }
    }

    // These create statements match the schema.sql when version 3 was the latest.
    tx.execute_batch(r#"
        alter table recording_playback rename to old_recording_playback;
        create table recording_playback (
          composite_id integer primary key references recording (composite_id),
          video_index blob not null check (length(video_index) > 0)
        );
        insert into recording_playback
        select
          composite_id,
          video_index
        from
          old_recording_playback;
        drop table old_recording_playback;
    "#)?;
    Ok(())
}

/// Gets a pathname for a sample file suitable for passing to open or unlink.
fn get_uuid_pathname(uuid: Uuid) -> [libc::c_char; 37] {
    let mut buf = [0u8; 37];
    write!(&mut buf[..36], "{}", uuid.hyphenated()).expect("can't format uuid to pathname buf");

    // libc::c_char seems to be i8 on some platforms (Linux/arm) and u8 on others (Linux/amd64).
    unsafe { mem::transmute::<[u8; 37], [libc::c_char; 37]>(buf) }
}

fn get_id_pathname(id: db::CompositeId) -> [libc::c_char; 17] {
    let mut buf = [0u8; 17];
    write!(&mut buf[..16], "{:016x}", id.0).expect("can't format id to pathname buf");
    unsafe { mem::transmute::<[u8; 17], [libc::c_char; 17]>(buf) }
}