use std::io;
use clap::{Arg, ArgAction, ArgMatches, Command, ValueHint};
use mount::MntEntries;
use shitbox::{args, Cmd};

#[derive(Debug, Default)]
pub struct Umount;

impl Cmd for Umount {
    fn cli(&self) -> Command {
        Command::new("umount")
            .about("unmount filesystems")
            .author("Nathan Fisher")
            .version(env!("CARGO_PKG_VERSION"))
            .args([
                Arg::new("all")
                    .help(
                        "All of the filesystems described in /proc/self/mountinfo \
                        are unmounted, except the proc, devfs, devpts, sysfs, rpc_pipefs \
                        and nfsd filesystems.",
                    )
                    .short('a')
                    .long("all")
                    .action(ArgAction::SetTrue),
                Arg::new("force")
                    .help("Force an unmount (in case of an unreachable NFS system).")
                    .short('f')
                    .long("force")
                    .action(ArgAction::SetTrue),
                Arg::new("types")
                    .help(
                        "Indicate that the actions should only be taken on filesystems \
                        of the specified type.",
                    )
                    .long_help(
                        "Indicate that the actions should only be taken on filesystems \
                        of the specified type. More than one type may be specified in a \
                        comma-separated list. The list of filesystem types can be prefixed \
                        with no to indicate that no action should be taken for all of the \
                        mentioned types.",
                    )
                    .short('t')
                    .long("types")
                    .value_delimiter(',')
                    .value_name("type")
                    .requires("all")
                    .num_args(1..),
                args::verbose(),
                Arg::new("spec")
                    .value_name("directory|device")
                    .value_hint(ValueHint::AnyPath)
                    .num_args(0..)
                    .required_unless_present("all"),
            ])
    }

    fn run(&self, matches: &ArgMatches) -> Result<(), Box<dyn std::error::Error>> {
        let flags = if matches.get_flag("force") {
            libc::MNT_FORCE
        } else {
            0
        };
        if matches.get_flag("all") {
            let mut mntpts: Vec<mount::MntEntry> = MntEntries::new("/proc/mounts")?
                .filter(|x| {
                    x.fstype != "proc"
                        && x.fstype != "sysfs"
                        && x.fstype != "devfs"
                        && x.fstype != "devpts"
                        && x.fstype != "rpc_pipefs"
                        && x.fstype != "nfsd"
                        && x.fstype != "swap"
                })
                .collect();
            if let Some(types) = matches.get_many::<String>("types") {
                for t in types {
                    if t.starts_with("no") {
                        let t = t.strip_prefix("no").unwrap();
                        mntpts.retain(|x| x.fstype != t);
                    } else {
                       mntpts.retain(|x| &x.fstype == t);
                    }
                }
            }
            if let Some(spec) = matches.get_many::<String>("spec") {
                for s in spec {
                    for p in &mntpts {
                        if &p.dir == s {
                            mount::umount(s, flags as u32)?;
                            if matches.get_flag("verbose") {
                                println!("umount: {s} unmounted");
                            }
                        }
                    }
                }
            } else {
                for p in &mntpts {
                    mount::umount(&p.dir, flags as u32)?;
                    if matches.get_flag("verbose") {
                        println!("umount: {} unmounted", &p.dir);
                    }
                }
            }
        } else {
            if let Some(spec) = matches.get_many::<String>("spec") {
                for s in spec {
                    let mntpt = get_mntpt(s)?;
                    mount::umount(&mntpt, flags as u32)?;
                    if matches.get_flag("verbose") {
                        println!("umount: {mntpt} unmounted");
                    }
                }
            }
        }
        Ok(())
    }

    fn path(&self) -> Option<shitbox::Path> {
        Some(shitbox::Path::Bin)
    }
}

fn get_mntpt(spec: &str) -> io::Result<String> {
    let entries = MntEntries::new("/proc/mounts")?;
    for e in entries {
        if e.fsname == spec {
            return Ok(e.dir.clone());
        } else if e.dir == spec {
            return Ok(spec.to_string());
        }
    }
    Err(io::Error::new(io::ErrorKind::Other, "no such mount"))
}