use crate::disk::inode::InodeMode;
use libc::{F_OK, S_ISGID, S_ISUID, S_IXGRP, X_OK};
use std::fs::File;
use std::io::BufRead;

pub(crate) fn get_groups(pid: u32) -> Vec<u32> {
    let file = File::open(format!("/proc/{pid}/task/{pid}/status"))
        .expect(format!("pid {pid} incorrect!").as_str());
    for line in std::io::BufReader::new(file).lines() {
        let line = line.unwrap();
        if line.starts_with("Groups:") {
            return line["Groups: ".len()..]
                .split(' ')
                .filter(|x| !x.trim().is_empty())
                .map(|x| x.parse::<u32>().unwrap())
                .collect();
        }
    }

    Vec::new()
}

pub(crate) fn clear_suid_sgid(mut mode: InodeMode) -> InodeMode {
    mode.0 &= !S_ISUID as u16;
    if mode.0 & S_IXGRP as u16 != 0 {
        mode.0 &= !S_ISGID as u16;
    }
    mode
}

pub(crate) fn check_access(
    incoming_uid: u32,
    incoming_gid: u32,
    uid: u32,
    gid: u32,
    mode: InodeMode,
    mut mask: i32,
) -> bool {
    if mask == F_OK {
        return true;
    }

    let perm = i32::from(mode.0);
    // root
    if incoming_uid == 0 {
        // 读写任何东西都是可以的, 执行只有 IXOTH/IXGRP/IXUSR 之一设置才可以
        mask &= X_OK;
        mask -= mask & (perm >> 6);
        mask -= mask & (perm >> 3);
        mask -= mask & perm;
        return mask == 0;
    }

    if incoming_uid == uid {
        mask -= mask & (perm >> 6);
    } else if incoming_gid == gid {
        mask -= mask & (perm >> 3);
    } else {
        mask -= mask & perm;
    }
    mask == 0
}