fstab 0.4.0

use log::{debug, trace};

use std::fs::File;
use std::io::{Error, ErrorKind, Read, Write};
use std::path::{Path, PathBuf};
use std::str::FromStr;

#[test]
fn test_parser() {
    use std::io::Cursor;
    let expected_results = vec![
        FsEntry {
            fs_spec: "/dev/mapper/xubuntu--vg--ssd-root".to_string(),
            mountpoint: PathBuf::from("/"),
            vfs_type: "ext4".to_string(),
            mount_options: vec!["noatime".to_string(), "errors=remount-ro".to_string()],
            dump: false,
            fsck_order: 1,
        },
        FsEntry {
            fs_spec: "UUID=378f3c86-b21a-4172-832d-e2b3d4bc7511".to_string(),
            mountpoint: PathBuf::from("/boot"),
            vfs_type: "ext2".to_string(),
            mount_options: vec!["defaults".to_string()],
            dump: false,
            fsck_order: 2,
        },
        FsEntry {
            fs_spec: "/dev/mapper/xubuntu--vg--ssd-swap_1".to_string(),
            mountpoint: PathBuf::from("none"),
            vfs_type: "swap".to_string(),
            mount_options: vec!["sw".to_string()],
            dump: false,
            fsck_order: 0,
        },
        FsEntry {
            fs_spec: "UUID=be8a49b9-91a3-48df-b91b-20a0b409ba0f".to_string(),
            mountpoint: PathBuf::from("/mnt/raid"),
            vfs_type: "ext4".to_string(),
            mount_options: vec!["errors=remount-ro".to_string(), "user".to_string()],
            dump: false,
            fsck_order: 1,
        },
    ];
    let input = r#"
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
/dev/mapper/xubuntu--vg--ssd-root /               ext4    noatime,errors=remount-ro 0       1
# /boot was on /dev/sda1 during installation
UUID=378f3c86-b21a-4172-832d-e2b3d4bc7511 /boot           ext2    defaults        0       2
/dev/mapper/xubuntu--vg--ssd-swap_1 none            swap    sw              0       0
UUID=be8a49b9-91a3-48df-b91b-20a0b409ba0f /mnt/raid ext4 errors=remount-ro,user 0 1
# tmpfs /tmp tmpfs rw,nosuid,nodev
"#;
    let bytes = input.as_bytes();
    let mut buff = Cursor::new(bytes);
    let fstab = FsTab::new(&Path::new("/fake"));
    let results = fstab.parse_entries(&mut buff).unwrap();
    println!("Result: {:?}", results);
    assert_eq!(results, expected_results);

    //Modify an entry and then update it and see what the results are

    //let bytes_written = super::add_entry(expected_results[1].clone(), Path::new("/tmp/fstab"))
    //    .unwrap();
    //println!("Wrote: {}", bytes_written);
}

/// For help with what these fields mean consult: `man fstab` on linux.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct FsEntry {
    /// The device identifier
    pub fs_spec: String,
    /// The mount point
    pub mountpoint: PathBuf,
    /// Which filesystem type it is
    pub vfs_type: String,
    /// Mount options to use
    pub mount_options: Vec<String>,
    /// This field is used by dump(8) to determine which filesystems need to be dumped
    pub dump: bool,
    /// This field is used by fsck(8) to determine the order in which filesystem checks
    /// are done at boot time.
    pub fsck_order: u16,
}

#[derive(Debug)]
pub struct FsTab {
    location: PathBuf,
}

impl Default for FsTab {
    fn default() -> Self {
        FsTab { location: PathBuf::from("/etc/fstab") }
    }
}

impl FsTab {
    pub fn new(fstab: &Path) -> Self {
        FsTab { location: fstab.to_path_buf() }
    }

    /// Takes the location to the fstab and parses it.  On linux variants
    /// this is usually /etc/fstab.  On SVR4 systems store block devices and
    /// mount point information in /etc/vfstab file. AIX stores block device
    /// and mount points information in /etc/filesystems file.
    pub fn get_entries(&self) -> Result<Vec<FsEntry>, Error> {
        let mut file = File::open(&self.location)?;
        let entries = self.parse_entries(&mut file)?;
        Ok(entries)
    }

    fn parse_entries<T: Read>(&self, file: &mut T) -> Result<Vec<FsEntry>, Error> {
        let mut entries: Vec<FsEntry> = Vec::new();
        let mut contents = String::new();
        file.read_to_string(&mut contents)?;

        for line in contents.lines() {
            if line.starts_with("#") {
                trace!("Skipping commented line: {}", line);
                continue;
            }
            let parts: Vec<&str> = line.split_whitespace().collect();
            if parts.len() != 6 {
                debug!("Unknown fstab entry: {}", line);
                continue;
            }
            let fsck_order = u16::from_str(parts[5]).map_err(|e| {
                Error::new(ErrorKind::InvalidInput, e)
            })?;
            entries.push(FsEntry {
                fs_spec: parts[0].to_string(),
                mountpoint: PathBuf::from(parts[1]),
                vfs_type: parts[2].to_string(),
                mount_options: parts[3].split(",").map(|s| s.to_string()).collect(),
                dump: if parts[4] == "0" { false } else { true },
                fsck_order: fsck_order,
            })
        }
        Ok(entries)
    }

    fn save_fstab(&self, entries: &Vec<FsEntry>) -> Result<usize, Error> {
        let mut file = File::create(&self.location)?;
        let mut bytes_written: usize = 0;
        for entry in entries {
            bytes_written += file.write(&format!(
                "{spec} {mount} {vfs} {options} {dump} {fsck}\n",
                spec = entry.fs_spec,
                mount = entry.mountpoint.display(),
                vfs = entry.vfs_type,
                options = entry.mount_options.join(","),
                dump = if entry.dump { "1" } else { "0" },
                fsck = entry.fsck_order
            ).as_bytes())?;
        }
        file.flush()?;
        debug!("Wrote {} bytes to fstab", bytes_written);
        Ok(bytes_written)
    }

    /// Add a new entry to the fstab.  If the fstab previously did not contain this entry
    /// then true is returned.  Otherwise it will return false indicating it has been updated
    pub fn add_entry(&self, entry: FsEntry) -> Result<bool, Error> {
        let mut entries = self.get_entries()?;

        let position = entries.iter().position(|e| e == &entry);
        if let Some(pos) = position {
            debug!("Removing {} from fstab entries", pos);
            entries.remove(pos);
        }
        entries.push(entry);
        self.save_fstab(&mut entries)?;

        match position {
            Some(_) => Ok(false),
            None => Ok(true),
        }
    }

    /// Bulk add a new entries to the fstab.
    pub fn add_entries(&self, entries: Vec<FsEntry>) -> Result<(), Error> {
        let mut existing_entries = self.get_entries()?;
        for new_entry in entries {
            match existing_entries.contains(&new_entry) {
                false => existing_entries.push(new_entry),
                true => {
                    // The old entries contain this so lets update it
                    let position = existing_entries
                        .iter()
                        .position(|e| e == &new_entry)
                        .unwrap();
                    existing_entries.remove(position);
                    existing_entries.push(new_entry);
                }
            }
        }
        self.save_fstab(&mut existing_entries)?;
        Ok(())
    }

    /// Remove the fstab entry that corresponds to the spec given.  IE: first fields match
    /// Returns true if the value was present in the fstab.
    pub fn remove_entry(&self, spec: &str) -> Result<bool, Error> {
        let mut entries = self.get_entries()?;
        let position = entries.iter().position(|e| e.fs_spec == spec);

        match position {
            Some(pos) => {
                debug!("Removing {} from fstab entries", pos);
                entries.remove(pos);
                self.save_fstab(&mut entries)?;
                Ok(true)
            }
            None => Ok(false),
        }
    }
}