file_statx

use rustler::{NifStruct, NifTaggedEnum};
use std::{
    fs::{self, Metadata},
    os::unix::fs::{MetadataExt, PermissionsExt},
    time::SystemTime,
};

#[derive(Debug, NifTaggedEnum)]
enum FileType {
    Regular,
    Directory,
    Symlink,
}

#[derive(Debug, NifTaggedEnum)]
enum StatError {
    Enoent,
    Eacces,
    Other(String),
}

#[derive(Debug, NifStruct)]
#[module = "FileStatx"]
struct FileStatx {
    r#type: FileType,
    atime: Option<u128>,
    ctime: Option<u128>,
    mtime: Option<u128>,
    size: u64,
    mode: u32,
}

#[rustler::nif]
fn stat(path: String) -> Result<FileStatx, StatError> {
    let metadata = fs::metadata(path).map_err(|err| get_stat_error(&err.kind()))?;
    Ok(FileStatx {
        r#type: get_file_type(&metadata),
        ctime: metadata.created().ok().and_then(to_unix),
        mtime: metadata.modified().ok().and_then(to_unix),
        atime: metadata.accessed().ok().and_then(to_unix),
        size: metadata.size(),
        mode: metadata.permissions().mode(),
    })
}

fn to_unix(t: SystemTime) -> Option<u128> {
    let d = t.duration_since(SystemTime::UNIX_EPOCH).ok()?;
    Some(d.as_nanos())
}

fn get_file_type(m: &Metadata) -> FileType {
    if m.is_dir() {
        FileType::Directory
    } else if m.is_file() {
        FileType::Regular
    } else {
        FileType::Symlink
    }
}

fn get_stat_error(err: &std::io::ErrorKind) -> StatError {
    match err {
        std::io::ErrorKind::NotFound => StatError::Enoent,
        std::io::ErrorKind::PermissionDenied => StatError::Eacces,
        _ => StatError::Other(err.to_string()),
    }
}

rustler::init!("Elixir.FileStatx");