// 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/>.

/// Upgrades the database schema.
///
/// See `guide/schema.md` for more information.

use db;
use failure::Error;
use rusqlite::{self, types::ToSql};

mod v0_to_v1;
mod v1_to_v2;
mod v2_to_v3;

const UPGRADE_NOTES: &'static str =
    concat!("upgraded using moonfire-db ", env!("CARGO_PKG_VERSION"));

#[derive(Debug)]
pub struct Args<'a> {
    pub flag_sample_file_dir: Option<&'a str>,
    pub flag_preset_journal: &'a str,
    pub flag_no_vacuum: bool,
}

fn set_journal_mode(conn: &rusqlite::Connection, requested: &str) -> Result<(), Error> {
    assert!(!requested.contains(';'));  // quick check for accidental sql injection.
    let actual = conn.query_row(&format!("pragma journal_mode = {}", requested), &[] as &[&ToSql],
                                |row| row.get_checked::<_, String>(0))??;
    info!("...database now in journal_mode {} (requested {}).", actual, requested);
    Ok(())
}

pub fn run(args: &Args, conn: &mut rusqlite::Connection) -> Result<(), Error> {
    let upgraders = [
        v0_to_v1::run,
        v1_to_v2::run,
        v2_to_v3::run,
    ];

    {
        assert_eq!(upgraders.len(), db::EXPECTED_VERSION as usize);
        let old_ver =
            conn.query_row("select max(id) from version", &[] as &[&ToSql],
                           |row| row.get_checked(0))??;
        if old_ver > db::EXPECTED_VERSION {
            bail!("Database is at version {}, later than expected {}",
                  old_ver, db::EXPECTED_VERSION);
        } else if old_ver < 0 {
            bail!("Database is at negative version {}!", old_ver);
        }
        info!("Upgrading database from version {} to version {}...", old_ver, db::EXPECTED_VERSION);
        set_journal_mode(&conn, args.flag_preset_journal).unwrap();
        for ver in old_ver .. db::EXPECTED_VERSION {
            info!("...from version {} to version {}", ver, ver + 1);
            let tx = conn.transaction()?;
            upgraders[ver as usize](&args, &tx)?;
            tx.execute(r#"
                insert into version (id, unix_time, notes)
                             values (?, cast(strftime('%s', 'now') as int32), ?)
            "#, &[&(ver + 1) as &ToSql, &UPGRADE_NOTES])?;
            tx.commit()?;
        }
    }

    // Enforce foreign keys. This is on by default with --features=bundled (as rusqlite
    // compiles the SQLite3 amalgamation with -DSQLITE_DEFAULT_FOREIGN_KEYS=1). Ensure it's
    // always on. Note that our foreign keys are immediate rather than deferred, so we have to
    // be careful about the order of operations during the upgrade.
    conn.execute("pragma foreign_keys = on", &[] as &[&ToSql])?;

    // WAL is the preferred journal mode for normal operation; it reduces the number of syncs
    // without compromising safety.
    set_journal_mode(&conn, "wal").unwrap();
    if !args.flag_no_vacuum {
        info!("...vacuuming database after upgrade.");
        conn.execute_batch(r#"
            pragma page_size = 16384;
            vacuum;
        "#).unwrap();
    }
    info!("...done.");
    Ok(())
}