#pragma once

#include "handle.h"
#include "visibility.h"
#include <optional>
#include <string>
#include <sys/types.h>
#include <utility>
#include <vector>

namespace AdHoc::System {
	/// Spawn a process and attach to its IO handles.
	class DLL_PUBLIC ProcessPipes {
	public:
		/**
		 * Spawn a new process, providing (optional) access to its stdin, stdout and
		 * stderr file handles.
		 * @param args path and arguments to spawn (passed to execv)
		 * @param in Attach to stdin?
		 * @param out Attach to stdout?
		 * @param err Attach to stderr?
		 */
		ProcessPipes(const std::vector<std::string> & args, bool in, bool out, bool err);

		/// Close input pipe to process
		int closeIn();

		/** FD handle to child's stdin. */
		[[nodiscard]] int fdIn() const noexcept;
		/** FD handle to child's stdout. */
		[[nodiscard]] int fdOut() const noexcept;
		/** FD handle to child's stderr. */
		[[nodiscard]] int fdError() const noexcept;
		/** Process id of child. */
		[[nodiscard]] pid_t pid() const noexcept;

	private:
		using PipePair = std::pair<int, int>;
		using InitPipe = std::optional<PipePair>;

		ProcessPipes(const std::vector<std::string> & args, InitPipe &&, InitPipe &&, InitPipe &&);

		static InitPipe pipeSetup(bool setup, bool swap);
		static void closeChild(const InitPipe & child) noexcept;
		static void dupChild(int, const InitPipe & child) noexcept;
		static void closeAllOpenFiles() noexcept;

		using FHandle = ::AdHoc::Handle<int, int (*)(int)>;
		using OFHandle = std::optional<FHandle>;
		const pid_t child;
		OFHandle in;
		const OFHandle out, error;
	};
}