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

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

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

    fn run(&self, matches: Option<&clap::ArgMatches>) -> Result<(), Box<dyn std::error::Error>> {
        let Some(matches) = matches else {
            return Err(Box::new(io::Error::new(io::ErrorKind::Other, "no input")));
        };
        let recurse = Recurse::from_matches(matches);
        let feedback = Feedback::from_matches(matches);
        let group = if let Some(grp) = matches.get_one::<String>("group") {
            let gid = pw::get_gid_for_groupname(grp)
                .ok_or(io::Error::new(io::ErrorKind::Other, "cannot get gid"))?;
            Group { name: grp, gid }
        } 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),
                    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)
    }
}

#[derive(Debug)]
struct Action<'a> {
    path: PathBuf,
    group: 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(), uid, self.group.gid) != 0 {
                return Err(io::Error::last_os_error().into());
            }
        }
        drop(fd);
        if let Some(feedback) = self.feedback {
            match feedback {
                Feedback::Full => {
                    if self.group.gid != gid {
                        self.display_changes(gid)?;
                    } else {
                        self.display_retained();
                    }
                }
                Feedback::Changes => {
                    if self.group.gid != gid {
                        self.display_changes(gid)?;
                    }
                }
            }
        }
        Ok(())
    }

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

    fn display_retained(&self) {
        println!("{} retained as {}", &self.path.display(), &self.group.name);
    }

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