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// Copyright 2018-2022 System76 <info@system76.com>
// SPDX-License-Identifier: MIT

//! High level abstraction over the `mount` and `umount2` system calls.
//!
//! If the `loop` feature is enabled (default), additionally supports creating loopback devices
//! automatically when mounting an iso or squashfs file.
//!
//! # Example
//!
//! ```rust,no_run
//! extern crate sys_mount;
//!
//! use std::process::exit;
//! use sys_mount::{
//!     Mount,
//!     MountFlags,
//!     SupportedFilesystems,
//!     Unmount,
//!     UnmountFlags
//! };
//!
//! fn main() {
//!     // Fetch a list of supported file systems.
//!     // When mounting, a file system will be selected from this.
//!     let supported = SupportedFilesystems::new().unwrap();
//!
//!     // Attempt to mount the src device to the dest directory.
//!     let mount_result = Mount::new(
//!         "/imaginary/block/device",
//!         "/tmp/location",
//!         &supported,
//!         MountFlags::empty(),
//!         None
//!     );
//!
//!     match mount_result {
//!         Ok(mount) => {
//!             // Make the mount temporary, so that it will be unmounted on drop.
//!             let mount = mount.into_unmount_drop(UnmountFlags::DETACH);
//!             // Do thing with the mounted device.
//!         }
//!         Err(why) => {
//!             eprintln!("failed to mount device: {}", why);
//!             exit(1);
//!         }
//!     }
//! }

extern crate libc;
#[cfg(feature = "loop")]
extern crate loopdev;
#[macro_use]
extern crate bitflags;
#[macro_use]
extern crate thiserror;

mod builder;
mod fstype;
mod mount;
mod supported;
mod umount;

pub use self::{builder::*, fstype::*, mount::*, supported::*, umount::*};

use libc::swapoff as c_swapoff;
use std::{
    ffi::CString,
    io::{self, Error, ErrorKind},
    os::unix::ffi::OsStrExt,
    path::Path,
    ptr,
};

#[derive(Debug, Error)]
pub enum ScopedMountError {
    #[error("cannot get list of supported file systems")]
    Supported(#[source] io::Error),
    #[error("could not mount partition")]
    Mount(#[source] io::Error),
}

/// Mount a partition temporarily for the duration of the scoped block within.
pub fn scoped_mount<T, S: FnOnce() -> T>(
    source: &Path,
    mount_at: &Path,
    scope: S,
) -> Result<T, ScopedMountError> {
    let supported = SupportedFilesystems::new().map_err(ScopedMountError::Supported)?;

    Mount::new(&source, mount_at, &supported, MountFlags::empty(), None)
        .map_err(ScopedMountError::Mount)?;

    let result = scope();

    if let Err(why) = unmount(mount_at, UnmountFlags::empty()) {
        tracing::warn!("{}: failed to unmount: {}", mount_at.display(), why);
    }

    Ok(result)
}

/// Unmounts a swap partition using `libc::swapoff`
pub fn swapoff<P: AsRef<Path>>(dest: P) -> io::Result<()> {
    unsafe {
        let swap = CString::new(dest.as_ref().as_os_str().as_bytes().to_owned());
        let swap_ptr = swap.as_ref().ok().map_or(ptr::null(), |cstr| cstr.as_ptr());

        match c_swapoff(swap_ptr) {
            0 => Ok(()),
            _err => Err(Error::new(
                ErrorKind::Other,
                format!(
                    "failed to swapoff {}: {}",
                    dest.as_ref().display(),
                    Error::last_os_error()
                ),
            )),
        }
    }
}

fn to_cstring(data: &[u8]) -> io::Result<CString> {
    CString::new(data).map_err(|why| {
        io::Error::new(
            io::ErrorKind::InvalidData,
            format!("failed to create `CString`: {}", why),
        )
    })
}