/* SPDX-License-Identifier: BSL-1.0 OR BSD-3-Clause */

#ifndef MPT_BASE_DEBUGGING_HPP
#define MPT_BASE_DEBUGGING_HPP



#include "mpt/base/detect.hpp"
#include "mpt/base/integer.hpp"
#include "mpt/base/namespace.hpp"
#include "mpt/base/macros.hpp"

#if MPT_CXX_AT_LEAST(26)
#include <debugging>
#endif // C++26

#if MPT_CXX_BEFORE(26)
#if MPT_OS_LINUX
#include <cerrno>
#include <cstring>
#endif
#endif // !C++26

#if MPT_CXX_BEFORE(26)
#if MPT_OS_LINUX
#include <fcntl.h>
#include <signal.h>
#include <unistd.h>
#endif
#endif // !C++26

#if MPT_CXX_BEFORE(26)
#if MPT_OS_WINDOWS
#include <windows.h>
#endif
#endif // !C++26

#if MPT_CXX_BEFORE(26)
#if MPT_COMPILER_MSVC
#include <intrin.h>
#endif
#endif // !C++26



namespace mpt {
inline namespace MPT_INLINE_NS {



#if MPT_CXX_AT_LEAST(26)

using std::breakpoint;
using std::breakpoint_if_debugging;
using std::is_debugger_present;

#else // !C++26

#if MPT_OS_WINDOWS

inline bool is_debugger_present() noexcept {
	return (IsDebuggerPresent() != FALSE);
}

MPT_ATTR_ALWAYSINLINE MPT_INLINE_FORCE void breakpoint() noexcept {
#if MPT_COMPILER_MSVC
	__debugbreak();
#elif MPT_COMPILER_CLANG
	__builtin_debugtrap();
#elif MPT_COMPILER_GCC && (MPT_ARCH_X86 || MPT_ARCH_AMD64)
	__asm__ __volatile__("int 3");
#else
	DebugBreak();
#endif
}

#elif MPT_OS_LINUX

namespace detail {
namespace debugging {

inline bool parse_proc_status_line(char * buf, std::size_t size) noexcept {
	if (std::strncmp(buf, "TracerPid:\t", 11) != 0) {
		return false;
	}
	unsigned long long pid = 0;
	std::size_t pos = 11;
	while (pos < size) {
		unsigned char byte = static_cast<unsigned char>(buf[pos]);
		if (!(static_cast<unsigned char>('0') <= byte && byte <= static_cast<unsigned char>('9'))) {
			return false;
		}
		uint8 digit = static_cast<uint8>(byte - static_cast<unsigned char>('0'));
		pid = (pid * 10) + digit;
		pos++;
	}
	return (pid != 0);
}

inline bool parse_proc_status() noexcept {
	int olderrno = errno;
	bool detected_debugger = false;
	int error = 0;
	int fd = -1;
	bool open_done = false;
	while (!open_done) {
		int res = open("/proc/self/status", O_RDONLY);
		if (res >= 0) {
			fd = res;
			open_done = true;
		} else if (errno != EINTR) {
			error = errno;
			open_done = true;
		}
	}
	if (error != 0) {
		errno = olderrno;
		return false;
	}
	if (fd < 0) {
		errno = olderrno;
		return false;
	}
	bool eof = false;
	uint8 iobuf[1024];
	std::size_t iobuf_size = 0;
	char linebuf[128];
	std::size_t linebuf_size = 0;
	while (!eof) {
		ssize_t bytes_read = read(fd, iobuf, 1024);
		if (bytes_read == -1) {
			if (errno == EINTR) {
				continue;
			}
		} else if (bytes_read == 0) {
			eof = true;
		}
		iobuf_size = static_cast<std::size_t>(bytes_read);
		for (std::size_t i = 0; i < iobuf_size; ++i) {
			if (static_cast<unsigned char>(iobuf[i]) == static_cast<unsigned char>('\n')) {
				if (parse_proc_status_line(linebuf, linebuf_size)) {
					detected_debugger = true;
				}
				linebuf_size = 0;
			} else {
				if (linebuf_size < 128) {
					linebuf[linebuf_size] = static_cast<char>(static_cast<unsigned char>(iobuf[i]));
					linebuf_size++;
				}
			}
		}
		if (linebuf_size > 0) {
			if (parse_proc_status_line(linebuf, linebuf_size)) {
				detected_debugger = true;
			}
			linebuf_size = 0;
		}
	}
	bool close_done = false;
	while (!close_done) {
		int res = close(fd);
		if (res == 0) {
			fd = -1;
			close_done = true;
		} else if (errno != EINTR) {
			error = errno;
			close_done = true;
		}
	}
	if (error != 0) {
		errno = olderrno;
		return false;
	}
	errno = olderrno;
	return detected_debugger;
}

} // namespace debugging
} // namespace detail

MPT_ATTR_NOINLINE MPT_DECL_NOINLINE inline bool is_debugger_present() noexcept {
	return mpt::detail::debugging::parse_proc_status();
}

MPT_ATTR_ALWAYSINLINE MPT_INLINE_FORCE void breakpoint() noexcept {
#if MPT_COMPILER_CLANG
	__builtin_debugtrap();
#elif MPT_COMPILER_GCC && (MPT_ARCH_X86 || MPT_ARCH_AMD64)
	__asm__ __volatile__("int 3");
#else
	kill(getpid(), SIGTRAP);
#endif
}

#else

inline bool is_debugger_present() noexcept {
	return false;
}

MPT_ATTR_ALWAYSINLINE MPT_INLINE_FORCE void breakpoint() noexcept {
#if MPT_COMPILER_MSVC
	__debugbreak();
#elif MPT_COMPILER_CLANG
	__builtin_debugtrap();
#elif MPT_COMPILER_GCC && (MPT_ARCH_X86 || MPT_ARCH_AMD64)
	__asm__ __volatile__("int 3");
#endif
}

#endif

MPT_ATTR_ALWAYSINLINE MPT_INLINE_FORCE void breakpoint_if_debugging() noexcept {
	if (mpt::is_debugger_present()) {
		mpt::breakpoint();
	}
}

#endif // C++26



} // namespace MPT_INLINE_NS
} // namespace mpt



#endif // MPT_BASE_DEBUGGING_HPP
