use super::{Cmd, Feedback};
use crate::{args, pw};
use clap::{Arg, ArgAction, ArgGroup, ArgMatches, Command, ValueHint};
use std::{
    error::Error,
    fs::File,
    io,
    os::{fd::AsRawFd, unix::prelude::MetadataExt},
    path::PathBuf,
};
use walkdir::{DirEntry, WalkDir};

mod chgrp;
pub use chgrp::Chgrp;

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

impl Cmd for Chown {
    fn cli(&self) -> clap::Command {
        Command::new("chown")
            .about("change file owner and group")
            .author("Nathan Fisher")
            .version(env!("CARGO_PKG_VERSION"))
            .arg(
                Arg::new("user")
                    .value_name("OWNER[:GROUP]")
                    .value_hint(ValueHint::Username)
                    .num_args(1)
                    .required(true),
            )
            .args(args())
            .group(
                ArgGroup::new("links")
                    .args(["cli-traverse", "full-traverse", "no-traverse"])
                    .requires("recursive")
                    .multiple(false),
            )
    }

    fn run(&self, matches: &clap::ArgMatches) -> Result<(), Box<dyn std::error::Error>> {
        let recurse = Recurse::from_matches(matches);
        let feedback = Feedback::from_matches(matches);
        let (user, group) = if let Some(who) = matches.get_one::<String>("user") {
            if let Some((u, g)) = who.split_once(':') {
                let uid = pw::get_uid_for_name(u)
                    .ok_or(io::Error::new(io::ErrorKind::Other, "cannot get uid"))?;
                let gid = pw::get_gid_for_groupname(g)
                    .ok_or(io::Error::new(io::ErrorKind::Other, "cannot get gid"))?;
                (User { name: u, uid }, Some(Group { name: g, gid }))
            } else {
                let uid = pw::get_uid_for_name(who)
                    .ok_or(io::Error::new(io::ErrorKind::Other, "cannot get uid"))?;
                (User { name: who, uid }, None)
            }
        } else {
            return Err(Box::new(io::Error::new(
                io::ErrorKind::Other,
                "no user specified",
            )));
        };
        if let Some(files) = matches.get_many::<String>("file") {
            for f in files {
                let action = Action {
                    path: PathBuf::from(f),
                    user: user.clone(),
                    group: group.clone(),
                    feedback,
                };
                if let Some(r) = recurse {
                    if action.path.is_dir() {
                        action.recurse(recurse)?;
                    } else if action.path.is_symlink() {
                        if r.traversal != Traversal::NoLinks {
                            action.recurse(recurse)?;
                        }
                    }
                }
                action.apply()?;
            }
        }
        Ok(())
    }

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

fn args() -> [Arg; 8] {
    [
        args::changes(),
        args::verbose(),
        args::recursive(),
        Arg::new("cli-traverse")
            .help("if a command line argument is a symbolic link to a directory, traverse it")
            .short('H')
            .action(ArgAction::SetTrue),
        Arg::new("full-traverse")
            .help("traverse every symbolic link encountered in a directory")
            .short('L')
            .action(ArgAction::SetTrue),
        Arg::new("no-traverse")
            .help("do not traverse any symbolic links (default)")
            .short('P')
            .action(ArgAction::SetTrue),
        Arg::new("same-filesystem")
            .help("do not cross filesystem boundaries (requires recursive)")
            .short('s')
            .requires("recursive")
            .long("same-filesystem")
            .action(ArgAction::SetTrue),
        Arg::new("file")
            .value_name("FILE")
            .value_hint(ValueHint::AnyPath)
            .num_args(1..)
            .required(true),
    ]
}

#[derive(Clone, Copy, Debug, PartialEq)]
enum Traversal {
    CliLinks,
    FullLinks,
    NoLinks,
}

impl Traversal {
    fn from_matches(matches: &ArgMatches) -> Self {
        if matches.get_flag("full-traverse") {
            Traversal::FullLinks
        } else if matches.get_flag("cli-traverse") {
            Self::CliLinks
        } else {
            Self::NoLinks
        }
    }
}

#[derive(Clone, Copy, Debug)]
struct Recurse {
    traversal: Traversal,
    same_filesystem: bool,
}

impl Recurse {
    fn from_matches(matches: &ArgMatches) -> Option<Self> {
        if matches.get_flag("recursive") {
            Some(Self {
                traversal: Traversal::from_matches(matches),
                same_filesystem: matches.get_flag("same-filesystem"),
            })
        } else {
            None
        }
    }
}

#[derive(Clone, Debug)]
struct User<'a> {
    name: &'a str,
    uid: u32,
}

#[derive(Clone, Debug)]
struct Group<'a> {
    name: &'a str,
    gid: u32,
}

#[derive(Debug)]
struct Action<'a> {
    path: PathBuf,
    user: User<'a>,
    group: Option<Group<'a>>,
    feedback: Option<Feedback>,
}

impl Action<'_> {
    fn apply(&self) -> Result<(), Box<dyn Error>> {
        let fd = File::open(&self.path)?;
        let meta = fd.metadata()?;
        let uid = meta.uid();
        let gid = meta.gid();
        unsafe {
            if libc::fchown(
                fd.as_raw_fd(),
                self.user.uid,
                self.group.as_ref().map(|x| x.gid).unwrap_or(gid),
            ) != 0
            {
                return Err(io::Error::last_os_error().into());
            }
        }
        drop(fd);
        if let Some(feedback) = self.feedback {
            match feedback {
                Feedback::Full => {
                    if self.user.uid != uid || self.group.as_ref().map(|x| x.gid) != Some(gid) {
                        self.display_changes(uid, gid)?;
                    } else {
                        self.display_retained();
                    }
                }
                Feedback::Changes => {
                    if self.user.uid != uid || self.group.as_ref().map(|x| x.gid) != Some(gid) {
                        self.display_changes(uid, gid)?;
                    }
                }
            }
        }
        Ok(())
    }

    fn display_changes(&self, uid: u32, gid: u32) -> Result<(), std::str::Utf8Error> {
        let username = pw::get_username_for_uid(uid)?;
        let groupname = pw::get_groupname_for_gid(gid)?;
        if let Some(g) = &self.group {
            println!(
                "{} changed from {username}:{groupname} to {}:{}",
                &self.path.display(),
                &self.user.name,
                &g.name
            );
        } else {
            println!(
                "{} changed from {username} to {}",
                &self.path.display(),
                &self.user.name
            );
        }
        Ok(())
    }

    fn display_retained(&self) {
        if let Some(g) = &self.group {
            println!(
                "{} retained as {}:{}",
                &self.path.display(),
                &self.user.name,
                &g.name
            );
        } else {
            println!("{} retained as {}", &self.path.display(), &self.user.name);
        }
    }

    fn into_child(&self, entry: DirEntry) -> Result<Self, Box<dyn Error>> {
        let path = entry.path().to_path_buf();
        Ok(Self {
            path,
            user: self.user.clone(),
            group: self.group.clone(),
            feedback: self.feedback,
        })
    }

    fn recurse(&self, recurse: Option<Recurse>) -> Result<(), Box<dyn Error>> {
        let walker = WalkDir::new(&self.path)
            .max_open(1)
            .same_file_system(recurse.map_or(false, |x| x.same_filesystem))
            .follow_links(recurse.map_or(false, |x| match x.traversal {
                Traversal::FullLinks => true,
                _ => false,
            }));
        for entry in walker {
            let entry = entry?;
            let action = self.into_child(entry)?;
            action.apply()?;
        }
        Ok(())
    }
}