// Take a look at the license at the top of the repository in the LICENSE file.

use crate::{
    common::{Gid, Uid},
    User,
};

use libc::{getgrgid, getgrouplist};
use std::fs::File;
use std::io::Read;

pub fn get_users_list() -> Vec<User> {
    let mut s = String::new();
    let mut ngroups = 100;
    let mut groups = vec![0; ngroups as usize];

    let _ = File::open("/etc/passwd").and_then(|mut f| f.read_to_string(&mut s));
    s.lines()
        .filter_map(|line| {
            let mut parts = line.split(':');
            if let Some(username) = parts.next() {
                let mut parts = parts.skip(1);
                // Skip the user if the uid cannot be parsed correctly
                if let Some(uid) = parts.next().and_then(parse_id) {
                    if let Some(group_id) = parts.next().and_then(parse_id) {
                        if let Some(command) = parts.last() {
                            if command.is_empty()
                                || command.ends_with("/false")
                                || command.ends_with("/nologin")
                            {
                                // We don't want "fake" users so in case the user command is "bad", we
                                // ignore this user.
                                return None;
                            }
                            let mut c_user = username.as_bytes().to_vec();
                            c_user.push(0);
                            loop {
                                let mut current = ngroups;

                                unsafe {
                                    if getgrouplist(
                                        c_user.as_ptr() as *const _,
                                        group_id,
                                        groups.as_mut_ptr(),
                                        &mut current,
                                    ) == -1
                                    {
                                        if current > ngroups {
                                            groups.resize(current as _, 0);
                                            ngroups = current;
                                            continue;
                                        }
                                        // It really failed, let's move on...
                                        return None;
                                    }
                                    // Let's get all the group names!
                                    return Some(User {
                                        uid: Uid(uid),
                                        gid: Gid(group_id),
                                        name: username.to_owned(),
                                        groups: groups[..current as usize]
                                            .iter()
                                            .filter_map(|id| {
                                                let g = getgrgid(*id as _);
                                                if g.is_null() {
                                                    return None;
                                                }
                                                let mut group_name = Vec::new();
                                                let c_group_name = (*g).gr_name;
                                                let mut x = 0;
                                                loop {
                                                    let c = *c_group_name.offset(x);
                                                    if c == 0 {
                                                        break;
                                                    }
                                                    group_name.push(c as u8);
                                                    x += 1;
                                                }
                                                String::from_utf8(group_name).ok()
                                            })
                                            .collect(),
                                    });
                                }
                            }
                        }
                    }
                }
            }
            None
        })
        .collect()
}

#[inline]
fn parse_id(id: &str) -> Option<u32> {
    id.parse::<u32>().ok()
}