use std::ffi::CString;
use std::io::{Error, ErrorKind};
use std::str::FromStr;

use chrono::Datelike;
use log::LevelFilter;
use simple_logger::SimpleLogger;

use crate::errors::EmgauwaError;
use crate::settings::Permissions;
use crate::types::Weekday;


pub fn init_logging(level: &str) -> Result<(), EmgauwaError> {
	let log_level: LevelFilter = LevelFilter::from_str(level)
		.map_err(|_| EmgauwaError::Other(format!("Invalid log level: {}", level)))?;
	log::trace!("Log level set to {:?}", log_level);

	SimpleLogger::new()
		.with_level(log_level)
		.init()
		.map_err(|err| EmgauwaError::Other(format!("Failed to initialize logger: {}", err)))?;

	Ok(())
}

// https://blog.lxsang.me/post/id/28.0
pub fn drop_privileges(permissions: &Permissions) -> Result<(), Error> {
	log::info!(
		"Dropping privileges to {}:{}",
		permissions.user,
		permissions.group
	);

	// the group id need to be set first, because, when the user privileges drop,
	// we are unable to drop the group privileges
	if !permissions.group.is_empty() {
		drop_privileges_group(&permissions.group)?;
	}
	if !permissions.user.is_empty() {
		drop_privileges_user(&permissions.user)?;
	}
	Ok(())
}

fn drop_privileges_group(group: &str) -> Result<(), Error> {
	// get the gid from username
	if let Ok(cstr) = CString::new(group.as_bytes()) {
		let p = unsafe { libc::getgrnam(cstr.as_ptr()) };
		if p.is_null() {
			return Err(Error::new(
				ErrorKind::Other,
				format!("Unable to find group: {}", group),
			));
		}
		if unsafe { libc::setgid((*p).gr_gid) } != 0 {
			return Err(Error::new(
				ErrorKind::Other,
				format!("Unable set gid for group: {}", group),
			));
		}
	} else {
		return Err(Error::new(
			ErrorKind::Other,
			format!("Cannot create CString from groupname: {}", group),
		));
	}
	Ok(())
}

fn drop_privileges_user(user: &str) -> Result<(), Error> {
	// get the uid from username
	if let Ok(cstr) = CString::new(user.as_bytes()) {
		let p = unsafe { libc::getpwnam(cstr.as_ptr()) };
		if p.is_null() {
			return Err(Error::new(
				ErrorKind::Other,
				format!("Unable to find user: {}", user),
			));
		}
		if unsafe { libc::setuid((*p).pw_uid) } != 0 {
			return Err(Error::new(
				ErrorKind::Other,
				format!("Unable set uid for user: {}", user),
			));
		}
	} else {
		return Err(Error::new(
			ErrorKind::Other,
			format!("Cannot create CString from username: {}", user),
		));
	}
	Ok(())
}

pub fn get_weekday() -> Weekday {
	(chrono::offset::Local::now()
		.date_naive()
		.weekday()
		.number_from_monday()
		- 1) as Weekday
}