// This file is part of Moonfire NVR, a security camera network video recorder.
// Copyright (C) 2016 The Moonfire NVR Authors; see AUTHORS and LICENSE.txt.
// SPDX-License-Identifier: GPL-v3.0-or-later WITH GPL-3.0-linking-exception.

use base::{err, Error};
use db::dir;
use nix::fcntl::FlockArg;
use std::path::Path;
use tracing::info;

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

#[derive(Copy, Clone, Debug, 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| {
        if mode == OpenMode::Create {
            err!(e, msg("unable to create db dir {}", db_dir.display()))
        } else if e == nix::Error::ENOENT {
            err!(
                NotFound,
                msg(
                    "db dir {} not found; try running moonfire-nvr init",
                    db_dir.display(),
                ),
            )
        } else {
            err!(e, msg("unable to open db dir {}", db_dir.display()))
        }
    })?;
    let ro = mode == OpenMode::ReadOnly;
    dir.lock(if ro {
        FlockArg::LockSharedNonblock
    } else {
        FlockArg::LockExclusiveNonblock
    })
    .map_err(|e| {
        err!(
            e,
            msg(
                "unable to get {} lock on db dir {} ",
                if ro { "shared" } else { "exclusive" },
                db_dir.display(),
            ),
        )
    })?;
    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 db_path = db_dir.join("db");
    info!(
        "Opening {} in {:?} mode with SQLite version {}",
        db_path.display(),
        mode,
        rusqlite::version()
    );
    let conn = rusqlite::Connection::open_with_flags_and_vfs(
        db_path,
        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,
        // In read/write mode, Moonfire holds a directory lock for its entire operation, as
        // described above. There's then no point in SQLite releasing its lock after each
        // transaction and reacquiring it, or in using shared memory for the wal-index.
        // See the following page: <https://www.sqlite.org/vfs.html>
        match mode {
            OpenMode::ReadOnly => "unix",
            _ => "unix-excl",
        },
    )?;
    Ok((dir, conn))
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn open_dir_error_msg() {
        let tmpdir = tempfile::Builder::new()
            .prefix("moonfire-nvr-test")
            .tempdir()
            .unwrap();
        let mut nonexistent_dir = tmpdir.path().to_path_buf();
        nonexistent_dir.push("nonexistent");
        let nonexistent_open = open_dir(&nonexistent_dir, OpenMode::ReadOnly).unwrap_err();
        assert!(
            nonexistent_open
                .to_string()
                .contains("try running moonfire-nvr init"),
            "unexpected error {}",
            &nonexistent_open
        );
    }

    #[test]
    fn create_dir_error_msg() {
        let tmpdir = tempfile::Builder::new()
            .prefix("moonfire-nvr-test")
            .tempdir()
            .unwrap();
        let mut nonexistent_dir = tmpdir.path().to_path_buf();
        nonexistent_dir.push("nonexistent");
        nonexistent_dir.push("db");
        let nonexistent_create = open_dir(&nonexistent_dir, OpenMode::Create).unwrap_err();
        assert!(
            nonexistent_create.to_string().contains("unable to create"),
            "unexpected error {}",
            &nonexistent_create
        );
    }
}