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

use serde::de::DeserializeOwned;

pub const CONFIG_PERMISSIONS_MODE: u32 = 33152;

fn load_inner <
	T: DeserializeOwned
> (
	mut f: File
) -> T {
	let mut buffer = vec! [0u8; 4096];
	let bytes_read = f.read (&mut buffer).unwrap_or_else (|_| panic! ("Can't read config"));
	buffer.truncate (bytes_read);
	
	let config_s = String::from_utf8 (buffer).unwrap_or_else (|_| panic! ("Can't parse config as UTF-8"));
	toml::from_str (&config_s).unwrap_or_else (|e| panic! ("Can't parse config as TOML: {}", e))
}

/// For files that contain public-viewable information

pub fn load_public <
	T: DeserializeOwned,
	P: AsRef <Path> + Debug
> (
	config_file_path: P
) -> T {
	let mut f = File::open (&config_file_path).unwrap_or_else (|_| panic! ("Can't open {:?}", config_file_path));
	load_inner (f)
}

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

pub fn load <
	T: DeserializeOwned,
	P: AsRef <Path> + Debug
> (
	config_file_path: P
) -> T {
	use std::os::unix::fs::PermissionsExt;
	
	let mut f = File::open (&config_file_path).unwrap_or_else (|_| panic! ("Can't open {:?}", config_file_path));
	
	let mode = f.metadata ().unwrap ().permissions ().mode ();
	assert_eq! (mode, CONFIG_PERMISSIONS_MODE, "Config file has bad permissions mode, it should be octal 0600");
	
	load_inner (f)
}