#[cfg(unix)]
use nix::sys::resource::{Resource, getrlimit};

use crate::{Result, apply, debug, utils::math::usize_from_u64_truncated};

#[cfg(unix)]
/// This is needed for opening lots of file descriptors, which tends to
/// happen more often when using RocksDB and making lots of federation
/// connections at startup. The soft limit is usually 1024, and the hard
/// limit is usually 512000; I've personally seen it hit >2000.
///
/// * <https://www.freedesktop.org/software/systemd/man/systemd.exec.html#id-1.12.2.1.17.6>
/// * <https://github.com/systemd/systemd/commit/0abf94923b4a95a7d89bc526efc84e7ca2b71741>
pub fn maximize_fd_limit() -> Result {
	use nix::sys::resource::setrlimit;

	let (soft_limit, hard_limit) = max_file_descriptors()?;
	if soft_limit < hard_limit {
		let new_limit = hard_limit.try_into()?;
		setrlimit(Resource::RLIMIT_NOFILE, new_limit, new_limit)?;
		assert_eq!((hard_limit, hard_limit), max_file_descriptors()?, "getrlimit != setrlimit");
		debug!(to = hard_limit, from = soft_limit, "Raised RLIMIT_NOFILE");
	}

	Ok(())
}

#[cfg(not(unix))]
pub fn maximize_fd_limit() -> Result { Ok(()) }

#[cfg(unix)]
/// Some distributions ship with very low defaults for thread counts; similar to
/// low default file descriptor limits. But unlike fd's, thread limit is rarely
/// reached, though on large systems (32+ cores) shipping with defaults of
/// ~1024 as have been observed are problematic.
pub fn maximize_thread_limit() -> Result {
	use nix::sys::resource::setrlimit;

	let (soft_limit, hard_limit) = max_threads()?;
	if soft_limit < hard_limit {
		let new_limit = hard_limit.try_into()?;
		setrlimit(Resource::RLIMIT_NPROC, new_limit, new_limit)?;
		assert_eq!((hard_limit, hard_limit), max_threads()?, "getrlimit != setrlimit");
		debug!(to = hard_limit, from = soft_limit, "Raised RLIMIT_NPROC");
	}

	Ok(())
}

#[cfg(not(unix))]
pub fn maximize_thread_limit() -> Result { Ok(()) }

#[cfg(unix)]
pub fn max_file_descriptors() -> Result<(usize, usize)> {
	getrlimit(Resource::RLIMIT_NOFILE)
		.map(apply!(2, usize_from_u64_truncated))
		.map_err(Into::into)
}

#[cfg(not(unix))]
pub fn max_file_descriptors() -> Result<(usize, usize)> { Ok((usize::MAX, usize::MAX)) }

#[cfg(unix)]
pub fn max_stack_size() -> Result<(usize, usize)> {
	getrlimit(Resource::RLIMIT_STACK)
		.map(apply!(2, usize_from_u64_truncated))
		.map_err(Into::into)
}

#[cfg(not(unix))]
pub fn max_stack_size() -> Result<(usize, usize)> { Ok((usize::MAX, usize::MAX)) }

#[cfg(any(linux_android, netbsdlike, target_os = "freebsd",))]
pub fn max_memory_locked() -> Result<(usize, usize)> {
	getrlimit(Resource::RLIMIT_MEMLOCK)
		.map(apply!(2, usize_from_u64_truncated))
		.map_err(Into::into)
}

#[cfg(not(any(linux_android, netbsdlike, target_os = "freebsd",)))]
pub fn max_memory_locked() -> Result<(usize, usize)> { Ok((usize::MIN, usize::MIN)) }

#[cfg(any(
	linux_android,
	netbsdlike,
	target_os = "aix",
	target_os = "freebsd",
))]
pub fn max_threads() -> Result<(usize, usize)> {
	getrlimit(Resource::RLIMIT_NPROC)
		.map(apply!(2, usize_from_u64_truncated))
		.map_err(Into::into)
}

#[cfg(not(any(
	linux_android,
	netbsdlike,
	target_os = "aix",
	target_os = "freebsd",
)))]
pub fn max_threads() -> Result<(usize, usize)> { Ok((usize::MAX, usize::MAX)) }