use std::{
	fmt::Debug,
	fs::File,
	io::Read,
	path::Path,
};

use serde::de::DeserializeOwned;

use crate::errors::LoadTomlError;

pub const CONFIG_PERMISSIONS_MODE: u32 = 33152;

fn load_inner <
	T: DeserializeOwned
> (
	mut f: File
) -> Result <T, LoadTomlError> {
	let mut buffer = vec! [0_u8; 4096];
	let bytes_read = f.read (&mut buffer)?;
	buffer.truncate (bytes_read);
	
	let config_s = String::from_utf8 (buffer)?;
	Ok (toml::from_str (&config_s)?)
}

/// For files that contain public-viewable information

fn load_public <
	T: DeserializeOwned,
	P: AsRef <Path> + Debug
> (
	config_file_path: P
) -> Result <T, LoadTomlError> {
	let f = File::open (&config_file_path)?;
	load_inner (f)
}

/// For files that may contain secrets and should have permissions or other
/// safeties checked

#[cfg (unix)]
pub fn load <
	T: DeserializeOwned,
	P: AsRef <Path> + Debug
> (
	config_file_path: P
) -> Result <T, LoadTomlError> {
	use std::os::unix::fs::PermissionsExt;
	
	let f = File::open (&config_file_path)?;
	
	let mode = f.metadata ()?.permissions ().mode ();
	if mode != CONFIG_PERMISSIONS_MODE {
		return Err (LoadTomlError::ConfigBadPermissions);
	}
	
	load_inner (f)
}

// The permission check doesn't work on Windows

#[cfg (not (unix))]
pub fn load <
	T: DeserializeOwned,
	P: AsRef <Path> + Debug
> (
	config_file_path: P
) -> Result <T, LoadTomlError> {
	load_public (config_file_path)
}