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/*

Copyright (C) 2018 Anders Blomdell <anders.blomdell@control.lth.se>

This file is part of hashtoc.

Hashtoc is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, version 3.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program. If not, see <https://www.gnu.org/licenses/>.

*/

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use std::io::{self, Write};
use std::path::Path;
use std::ffi::CString;
use std::os::unix::ffi::OsStrExt;
use std::fs::{read_dir, symlink_metadata, Metadata};
use std::os::unix::fs::MetadataExt;
use libc::{AT_FDCWD, R_OK, X_OK, AT_SYMLINK_NOFOLLOW};
use libc;

macro_rules! reportln {
    () => (writeln!(io::stderr()).unwrap_or(()));
    ($($arg:tt)*) => (writeln!(io::stderr(), $($arg)*).unwrap_or(()));
}

fn need_access_check() -> bool
{
    let uid : libc::uid_t;
    let euid : libc::uid_t;
    let gid : libc::gid_t;
    let egid : libc::gid_t;
    unsafe {
        uid = libc::getuid();
        euid = libc::geteuid();
        gid = libc::getgid();
        egid = libc::getegid();
    }
    return uid != euid || gid != egid;
}

fn check_path(path: &Path, mode: libc::c_int) -> bool
{
    
    let ospath = path.as_os_str();
    if ospath.is_empty() {
        return true;
    } else {
        let cstring = CString::new(ospath.as_bytes()).unwrap();
        let result : libc::c_int;
        unsafe {
            result = libc::faccessat(AT_FDCWD, cstring.as_ptr(),
                                     mode, AT_SYMLINK_NOFOLLOW);
        }
        return result == 0;
    }
}

fn check_full_path(path: &Path, mode: libc::c_int) -> bool
{
    let mut result = check_path(path, mode);
    let mut parent = path;
    loop {
        match parent.parent() {
            Some(p) => {
                result &= check_path(p, R_OK|X_OK);
                parent = p;
            },
            _ => break
        }
    }
    return result;
}

fn inner_visit(path: &Path,
               metadata: &Metadata,
               checkpath: bool,
               cb: &Fn(&Path, &Metadata)) -> io::Result<()>
{
    if checkpath {
        if metadata.file_type().is_dir() {
            check_full_path(&path, R_OK|X_OK);
        } else {
            check_full_path(&path, R_OK);
        }
    }
    let access = if ! checkpath {
        true
    } else {
        if metadata.file_type().is_dir() {
            check_path(&path, R_OK|X_OK)
        } else {
            check_path(&path, R_OK)
        }
    };
    if ! access {
        reportln!("Could not access {:?}", path);
        return Ok(());
    } else {
        cb(&path, &metadata);
        if ! metadata.file_type().is_symlink() && metadata.is_dir() {
            match read_dir(path) {
                Ok(readdir) => {
                    let mut paths: Vec<_> =
                        readdir.map(|r| r.unwrap()).collect();   
                    paths.sort_by_key(|entry| entry.file_name());
                    for entry in paths {
                        let p = entry.path();
                        match symlink_metadata(&p) {
                            Ok(m) => {
                                if metadata.dev() != m.dev() {
                                    reportln!("Warning: Skipping mountpoint {:?}", p);
                                    continue;
                                }
                                inner_visit(&p, &m, checkpath, cb).unwrap();
                            },
                            Err(e) => {
                                reportln!("Error: {:?} [{}]", p, e)
                            }
                        }
                    }
                },
                Err(e) => {
                    reportln!("Error: {:?} {}", path, e);
                }
            }            
        }
    }
    Ok(())
}

pub fn visit(path: &Path, cb: &Fn(&Path, &Metadata)) -> io::Result<()>
{
    let checkpath = need_access_check();
    let metadata = symlink_metadata(path);
    let access = match metadata {
        Ok(ref m) => {
            if ! checkpath {
                true
            } else {
                if m.file_type().is_dir() {
                    check_full_path(&path, R_OK|X_OK)
                } else {
                    check_full_path(&path, R_OK)
                }
            }
        },
        _ => false
    };
    if ! access {
        reportln!("Could not access {:?}", path);
        return Ok(());
    } else {
        let metadata = metadata.unwrap();
        try!(inner_visit(&path, &metadata, checkpath, cb));
    }
    Ok(())
}