#include <pslang/jit/host_executable.hpp>
#include <pslang/jit/linker.hpp>
#include <pslang/jit/foreign.hpp>

#include <system_error>

#if defined(__linux__) || defined(__APPLE__)
#include <sys/mman.h>
#include <unistd.h>
#endif

#include <stdexcept>

namespace pslang::jit
{

	namespace
	{

		std::size_t native_page_size()
		{
#if defined(__linux__) || defined(__APPLE__)
			return getpagesize();
#else
			throw std::runtime_error("Native page size is not supported for this platform");
#endif
		}

	}

	host_executable_program make_host_executable(std::vector<compiled_module> const & modules)
	{
#if defined(__linux__) || defined(__APPLE__)
		auto const page_size = native_page_size();
		auto const abi = host_abi();

		for (auto const & module : modules)
			if (module.abi != abi)
				throw std::runtime_error("Internal error: wrong compiled module ABI for host-executable binary");

		auto link_info = prepare_link(modules, {.section_alignment = page_size});

		auto storage = (std::uint8_t *)mmap(nullptr, link_info.total_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
		if (storage == MAP_FAILED)
			throw std::system_error(errno, std::generic_category());

		host_executable_program result;
		result.mapping.reset(storage, [total_size = link_info.total_size](void * ptr){ munmap(ptr, total_size); });

		link(modules, link_info, storage);

		for (auto const & relocation : link_info.relocation_offset)
			*(void **)(storage + relocation.second) = load_foreign(relocation.first);

		if (mprotect(storage + link_info.code.begin, link_info.code.size, PROT_READ | PROT_EXEC) != 0)
			throw std::system_error(errno, std::generic_category());

		if (mprotect(storage + link_info.relocations.begin, link_info.relocations.size, PROT_READ) != 0)
			throw std::system_error(errno, std::generic_category());

		result.functions = std::move(link_info.functions);
		result.globals = std::move(link_info.globals);
		result.entry_points = std::move(link_info.entry_points);

		return result;
#else
		throw std::runtime_error("Host-executable modules are not supported for this platform");
#endif
	}

}