//! Sync errors
#pragma once

#include <stop_token>
#include <stdexcept>

namespace fx::error {
	/// Thrown when an operation is aborted via a stop signal. 
	///
	/// The state may be inconsistent after the thrown exception.
	struct OperationCancelledError : virtual std::runtime_error {
		OperationCancelledError() noexcept;
		OperationCancelledError(OperationCancelledError const&) noexcept = default;
		OperationCancelledError& operator=(OperationCancelledError const&) noexcept = default;

		virtual ~OperationCancelledError();
	};

	/// Thrown when a task is cancelled via a stop signal.
	///
	/// The state is **not** left in an inconsistent state after the thrown exception.
	struct TaskCancelledError final : OperationCancelledError {
		TaskCancelledError() noexcept;
		TaskCancelledError(TaskCancelledError const&) noexcept = default;
		TaskCancelledError& operator=(TaskCancelledError const&) noexcept = default;

		virtual ~TaskCancelledError();
	};

	// Throw an `OperationCancelledError` (or, optionally, a `TaskCancelledError` if there is a completed task that was cancelled instead of an operation being aborted.)
	[[gnu::noinline, gnu::cold, noreturn]]
	void throw_cancelled(bool clean = false);

	[[gnu::gnu_inline]]
	extern inline
	void throw_if_cancelled(std::stop_token const& st, bool clean = false) {
		if(not st.stop_requested()) return;
		else
			throw_cancelled(clean);
	}

	namespace details [[gnu::visibility("internal")]] {
		// NOTE: This assumes the existence of `extern "C" void ::throw_last_system_error()` which throws the current `errno` as a generic-categoried `std::system_error`. If that does not exist, it is re-implemented below. (XXX: There is no reason for this now? We have an impl to call... Ffs...) //
		static void throw_last_system_error() __attribute__((cold, noreturn, weakref("throw_last_system_error")));
	}

	[[gnu::gnu_inline, gnu::cold, noreturn]]
	extern inline
	void throw_last_system_error()
	{
		if(__builtin_expect(details::throw_last_system_error != nullptr, true))
			details::throw_last_system_error();
		else	(&throw_last_system_error)();
		__builtin_unreachable();
	}
}