#ifdef LLVM_AVAILABLE

#include <unordered_map>
#include <map>
#include <unordered_set>
#include <set>
#include <array>
#include <deque>

#include "types.h"
#include "StrFmt.h"
#include "File.h"
#include "Log.h"
#include "VirtualMemory.h"

#ifdef _MSC_VER
#pragma warning(push, 0)
#endif
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/ExecutionEngine/ExecutionEngine.h"
#include "llvm/ExecutionEngine/RTDyldMemoryManager.h"
#include "llvm/ExecutionEngine/JITEventListener.h"
#include "llvm/ExecutionEngine/ObjectCache.h"
#ifdef _MSC_VER
#pragma warning(pop)
#endif

#ifdef _WIN32
#include <Windows.h>
#endif

#include "JIT.h"

// Global LLVM context (thread-unsafe)
llvm::LLVMContext g_llvm_ctx;

// Size of virtual memory area reserved: 512 MB
static const u64 s_memory_size = 0x20000000;

// Try to reserve a portion of virtual memory in the first 2 GB address space beforehand, if possible.
static void* const s_memory = []() -> void*
{
	for (u64 addr = 0x10000000; addr <= 0x80000000 - s_memory_size; addr += 0x1000000)
	{
		if (auto ptr = utils::memory_reserve(s_memory_size, (void*)addr))
		{
			return ptr;
		}
	}

	return utils::memory_reserve(s_memory_size);
}();

static void* s_next;

// Code section
static u8* s_code_addr;

#ifdef _WIN32
static std::deque<std::vector<RUNTIME_FUNCTION>> s_unwater;
static std::vector<std::vector<RUNTIME_FUNCTION>> s_unwind; // .pdata
#endif

// Helper class
struct MemoryManager final : llvm::RTDyldMemoryManager
{
	std::unordered_map<std::string, std::uintptr_t>& m_link;

	std::array<u8, 16>* m_tramps;

	MemoryManager(std::unordered_map<std::string, std::uintptr_t>& table)
		: m_link(table)
		, m_tramps(nullptr)
	{
		s_next = s_memory;
	}

	[[noreturn]] static void null()
	{
		fmt::throw_exception("Null function" HERE);
	}

	llvm::JITSymbol findSymbol(const std::string& name) override
	{
		auto& addr = m_link[name];

		// Find function address
		if (!addr)
		{
			addr = RTDyldMemoryManager::getSymbolAddress(name);

			if (addr)
			{
				LOG_WARNING(GENERAL, "LLVM: Symbol requested: %s -> 0x%016llx", name, addr);
			}
			else
			{
				LOG_ERROR(GENERAL, "LLVM: Linkage failed: %s", name);
				addr = (u64)null;
			}
		}

		// Verify address for small code model
		if ((u64)s_memory > 0x80000000 - s_memory_size ? (u64)addr - (u64)s_memory >= s_memory_size : addr >= 0x80000000)
		{
			// Allocate memory for trampolines
			if (!m_tramps)
			{
				m_tramps = reinterpret_cast<decltype(m_tramps)>(s_next);
				utils::memory_commit(s_next, 4096, utils::protection::wx);
				s_next = (u8*)((u64)s_next + 4096);
			}

			// Create a trampoline
			auto& data = *m_tramps++;
			data[0x0] = 0xff; // JMP [rip+2]
			data[0x1] = 0x25;
			data[0x2] = 0x02;
			data[0x3] = 0x00;
			data[0x4] = 0x00;
			data[0x5] = 0x00;
			data[0x6] = 0x48; // MOV rax, imm64 (not executed)
			data[0x7] = 0xb8;
			std::memcpy(data.data() + 8, &addr, 8);
			addr = (u64)&data;

			// Reset pointer (memory page exhausted)
			if (((u64)m_tramps % 4096) == 0)
			{
				m_tramps = nullptr;
			}
		}

		return {addr, llvm::JITSymbolFlags::Exported};
	}

	virtual u8* allocateCodeSection(std::uintptr_t size, uint align, uint sec_id, llvm::StringRef sec_name) override
	{
		// Simple allocation
		const u64 next = ::align((u64)s_next + size, 4096);

		if (next > (u64)s_memory + s_memory_size)
		{
			LOG_FATAL(GENERAL, "LLVM: Out of memory (size=0x%llx, aligned 0x%x)", size, align);
			return nullptr;
		}

		utils::memory_commit(s_next, size, utils::protection::wx);
		s_code_addr = (u8*)s_next;

		LOG_NOTICE(GENERAL, "LLVM: Code section %u '%s' allocated -> %p (size=0x%llx, aligned 0x%x)", sec_id, sec_name.data(), s_next, size, align);
		return (u8*)std::exchange(s_next, (void*)next);
	}

	virtual u8* allocateDataSection(std::uintptr_t size, uint align, uint sec_id, llvm::StringRef sec_name, bool is_ro) override
	{
		// Simple allocation
		const u64 next = ::align((u64)s_next + size, 4096);

		if (next > (u64)s_memory + s_memory_size)
		{
			LOG_FATAL(GENERAL, "LLVM: Out of memory (size=0x%llx, aligned 0x%x)", size, align);
			return nullptr;
		}

		if (!is_ro)
		{
			LOG_ERROR(GENERAL, "LLVM: Writeable data section not supported!");
		}

		utils::memory_commit(s_next, size);

		LOG_NOTICE(GENERAL, "LLVM: Data section %u '%s' allocated -> %p (size=0x%llx, aligned 0x%x, %s)", sec_id, sec_name.data(), s_next, size, align, is_ro ? "ro" : "rw");
		return (u8*)std::exchange(s_next, (void*)next);
	}

	virtual bool finalizeMemory(std::string* = nullptr) override
	{
		// TODO: make only read-only sections read-only
//#ifdef _WIN32
//		DWORD op;
//		VirtualProtect(s_memory, (u64)m_next - (u64)s_memory, PAGE_READONLY, &op);
//		VirtualProtect(s_code_addr, s_code_size, PAGE_EXECUTE_READ, &op);
//#else
//		::mprotect(s_memory, (u64)m_next - (u64)s_memory, PROT_READ);
//		::mprotect(s_code_addr, s_code_size, PROT_READ | PROT_EXEC);
//#endif
		return false;
	}

	virtual void registerEHFrames(u8* addr, u64 load_addr, std::size_t size) override
	{
#ifdef _WIN32
		// Use s_memory as a BASE, compute the difference
		const u64 unwind_diff = (u64)addr - (u64)s_memory;

		// Fix RUNTIME_FUNCTION records (.pdata section)
		auto pdata = std::move(s_unwater.front());
		s_unwater.pop_front();

		for (auto& rf : pdata)
		{
			rf.UnwindData += static_cast<DWORD>(unwind_diff);
		}

		// Register .xdata UNWIND_INFO structs
		if (!RtlAddFunctionTable(pdata.data(), (DWORD)pdata.size(), (u64)s_memory))
		{
			LOG_ERROR(GENERAL, "RtlAddFunctionTable() failed! Error %u", GetLastError());
		}
		else
		{
			s_unwind.emplace_back(std::move(pdata));
		}
#endif

		return RTDyldMemoryManager::registerEHFrames(addr, load_addr, size);
	}

	virtual void deregisterEHFrames(u8* addr, u64 load_addr, std::size_t size) override
	{
		LOG_ERROR(GENERAL, "deregisterEHFrames() called"); // Not expected

		return RTDyldMemoryManager::deregisterEHFrames(addr, load_addr, size);
	}

	~MemoryManager()
	{
#ifdef _WIN32
		for (auto&& unwind : s_unwind)
		{
			if (!RtlDeleteFunctionTable(unwind.data()))
			{
				LOG_FATAL(GENERAL, "RtlDeleteFunctionTable() failed! Error %u", GetLastError());
			}
		}

		s_unwind.clear();
#else
		// TODO: unregister EH frames if necessary
#endif

		utils::memory_decommit(s_memory, s_memory_size);
	}
};

// Helper class
struct EventListener final : llvm::JITEventListener
{
	virtual void NotifyObjectEmitted(const llvm::object::ObjectFile& obj, const llvm::RuntimeDyld::LoadedObjectInfo& inf) override
	{
#ifdef _WIN32
		for (auto it = obj.section_begin(), end = obj.section_end(); it != end; ++it)
		{
			llvm::StringRef name;
			it->getName(name);

			if (name == ".pdata")
			{
				llvm::StringRef data;
				it->getContents(data);

				std::vector<RUNTIME_FUNCTION> rfs(data.size() / sizeof(RUNTIME_FUNCTION));

				auto offsets = reinterpret_cast<DWORD*>(rfs.data());

				// Initialize .pdata section using relocation info
				for (auto ri = it->relocation_begin(), end = it->relocation_end(); ri != end; ++ri)
				{
					if (ri->getType() == 3 /*R_X86_64_GOT32*/)
					{
						const u64 value = *reinterpret_cast<const DWORD*>(data.data() + ri->getOffset());
						offsets[ri->getOffset() / sizeof(DWORD)] = static_cast<DWORD>(value + ri->getSymbol()->getAddress().get());
					}
				}

				// Use s_memory as a BASE, compute the difference
				const u64 code_diff = (u64)s_code_addr - (u64)s_memory;

				// Fix RUNTIME_FUNCTION records (.pdata section)
				for (auto& rf : rfs)
				{
					rf.BeginAddress += static_cast<DWORD>(code_diff);
					rf.EndAddress   += static_cast<DWORD>(code_diff);
				}

				s_unwater.emplace_back(std::move(rfs));
			}
		}
#endif
	}
};

static EventListener s_listener;

// Helper class
class ObjectCache final : public llvm::ObjectCache
{
	const std::string& m_path;

public:
	ObjectCache(const std::string& path)
		: m_path(path)
	{
	}

	~ObjectCache() override = default;

	void notifyObjectCompiled(const llvm::Module* module, llvm::MemoryBufferRef obj) override
	{
		std::string name = m_path;
		name.append(module->getName());
		fs::file(name, fs::rewrite).write(obj.getBufferStart(), obj.getBufferSize());
		LOG_SUCCESS(GENERAL, "LLVM: Created module: %s", module->getName().data());
	}

	std::unique_ptr<llvm::MemoryBuffer> getObject(const llvm::Module* module) override
	{
		std::string name = m_path;
		name.append(module->getName());

		if (fs::file cached{name, fs::read})
		{
			auto buf = llvm::MemoryBuffer::getNewUninitMemBuffer(cached.size());
			cached.read(const_cast<char*>(buf->getBufferStart()), buf->getBufferSize());
			LOG_SUCCESS(GENERAL, "LLVM: Loaded module: %s", module->getName().data());
			return buf;
		}
		else
		{
			return nullptr;
		}
	}
};

jit_compiler::jit_compiler(std::unordered_map<std::string, std::uintptr_t> init_linkage_info, std::string _cpu)
	: m_link(std::move(init_linkage_info))
	, m_cpu(std::move(_cpu))
{
	// Initialization
	llvm::InitializeNativeTarget();
	llvm::InitializeNativeTargetAsmPrinter();
	LLVMLinkInMCJIT();

	if (m_cpu.empty())
	{
		m_cpu = llvm::sys::getHostCPUName();
	}

	std::string result;

	m_engine.reset(llvm::EngineBuilder(std::make_unique<llvm::Module>("", g_llvm_ctx))
		.setErrorStr(&result)
		.setMCJITMemoryManager(std::make_unique<MemoryManager>(m_link))
		.setOptLevel(llvm::CodeGenOpt::Aggressive)
		.setCodeModel(llvm::CodeModel::Small)
		.setMCPU(m_cpu)
		.create());

	if (!m_engine)
	{
		fmt::throw_exception("LLVM: Failed to create ExecutionEngine: %s", result);
	}

	m_engine->RegisterJITEventListener(&s_listener);

	LOG_SUCCESS(GENERAL, "LLVM: JIT initialized (%s)", m_cpu);
}

void jit_compiler::add(std::unique_ptr<llvm::Module> module, const std::string& path)
{
	ObjectCache cache{path};
	m_engine->setObjectCache(&cache);

	const auto ptr = module.get();
	m_engine->addModule(std::move(module));
	m_engine->generateCodeForModule(ptr);
	m_engine->setObjectCache(nullptr);

	for (auto& func : ptr->functions())
	{
		// Delete IR to lower memory consumption
		func.deleteBody();
	}
}

void jit_compiler::fin(const std::string& path)
{
	m_engine->finalizeObject();
}

void jit_compiler::add(std::unordered_map<std::string, std::string> data)
{
	std::size_t size = 0;

	for (auto&& pair : data)
	{
		size += ::align(pair.second.size(), 16);
	}

	utils::memory_commit(s_next, size, utils::protection::wx);
	std::memset(s_next, 0xc3, ::align(size, 4096));

	for (auto&& pair : data)
	{
		std::memcpy(s_next, pair.second.data(), pair.second.size());
		m_link.emplace(pair.first, (u64)s_next);
		s_next = (void*)::align((u64)s_next + pair.second.size(), 16);
	}

	s_next = (void*)::align((u64)s_next, 4096);
}

jit_compiler::~jit_compiler()
{
}

#endif