#include "../std_include.hpp"
#include "module_mapping.hpp"
#include <address_utils.hpp>

#include <utils/buffer_accessor.hpp>

namespace
{
	uint64_t get_first_section_offset(const IMAGE_NT_HEADERS& nt_headers, const uint64_t nt_headers_offset)
	{
		const auto first_section_absolute = reinterpret_cast<uint64_t>(IMAGE_FIRST_SECTION(&nt_headers));
		const auto absolute_base = reinterpret_cast<uint64_t>(&nt_headers);
		return nt_headers_offset + (first_section_absolute - absolute_base);
	}

	std::vector<uint8_t> read_mapped_memory(emulator& emu, const mapped_module& binary)
	{
		std::vector<uint8_t> memory{};
		memory.resize(binary.size_of_image);
		emu.read_memory(binary.image_base, memory.data(), memory.size());

		return memory;
	}

	void collect_exports(mapped_module& binary, const utils::safe_buffer_accessor<const uint8_t> buffer,
	                     const IMAGE_OPTIONAL_HEADER& optional_header)
	{
		auto& export_directory_entry = optional_header.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT];
		if (export_directory_entry.VirtualAddress == 0 || export_directory_entry.Size == 0)
		{
			return;
		}

		const auto export_directory = buffer.as<IMAGE_EXPORT_DIRECTORY>(export_directory_entry.
			VirtualAddress).get();

		//const auto function_count = export_directory->NumberOfFunctions;
		const auto names_count = export_directory.NumberOfNames;

		const auto names = buffer.as<DWORD>(export_directory.AddressOfNames);
		const auto ordinals = buffer.as<WORD>(export_directory.AddressOfNameOrdinals);
		const auto functions = buffer.as<DWORD>(export_directory.AddressOfFunctions);

		for (DWORD i = 0; i < names_count; i++)
		{
			exported_symbol symbol{};
			symbol.ordinal = ordinals.get(i);
			symbol.name = buffer.as_string(names.get(i));
			symbol.rva = functions.get(symbol.ordinal);
			symbol.address = binary.image_base + symbol.rva;

			binary.exports.push_back(std::move(symbol));
		}

		for (const auto& symbol : binary.exports)
		{
			binary.address_names.try_emplace(symbol.address, symbol.name);
		}
	}

	template <typename T>
		requires(std::is_integral_v<T>)
	void apply_relocation(const utils::safe_buffer_accessor<uint8_t> buffer, const uint64_t offset,
	                      const uint64_t delta)
	{
		const auto obj = buffer.as<T>(offset);
		const auto value = obj.get();
		const auto new_value = value + static_cast<T>(delta);
		obj.set(new_value);
	}

	void apply_relocations(const mapped_module& binary, const utils::safe_buffer_accessor<uint8_t> buffer,
	                       const IMAGE_OPTIONAL_HEADER& optional_header)
	{
		const auto delta = binary.image_base - optional_header.ImageBase;
		if (delta == 0)
		{
			return;
		}

		const auto directory = &optional_header.DataDirectory[IMAGE_DIRECTORY_ENTRY_BASERELOC];
		if (directory->Size == 0)
		{
			return;
		}

		auto relocation_offset = directory->VirtualAddress;
		const auto relocation_end = relocation_offset + directory->Size;

		while (relocation_offset < relocation_end)
		{
			const auto relocation = buffer.as<IMAGE_BASE_RELOCATION>(relocation_offset).get();

			if (relocation.VirtualAddress <= 0 || relocation.SizeOfBlock <= sizeof(IMAGE_BASE_RELOCATION))
			{
				break;
			}

			const auto data_size = relocation.SizeOfBlock - sizeof(IMAGE_BASE_RELOCATION);
			const auto entry_count = data_size / sizeof(uint16_t);

			const auto entries = buffer.as<uint16_t>(relocation_offset + sizeof(IMAGE_BASE_RELOCATION));

			relocation_offset += relocation.SizeOfBlock;

			for (size_t i = 0; i < entry_count; ++i)
			{
				const auto entry = entries.get(i);

				const int type = entry >> 12;
				const int offset = entry & 0xfff;
				const auto total_offset = relocation.VirtualAddress + offset;

				switch (type)
				{
				case IMAGE_REL_BASED_ABSOLUTE:
					break;

				case IMAGE_REL_BASED_HIGHLOW:
					apply_relocation<DWORD>(buffer, total_offset, delta);
					break;

				case IMAGE_REL_BASED_DIR64:
					apply_relocation<ULONGLONG>(buffer, total_offset, delta);
					break;

				default:
					throw std::runtime_error("Unknown relocation type: " + std::to_string(type));
				}
			}
		}
	}

	void map_sections(emulator& emu, const mapped_module& binary,
	                  const utils::safe_buffer_accessor<const uint8_t> buffer,
	                  const IMAGE_NT_HEADERS& nt_headers, const uint64_t nt_headers_offset)
	{
		const auto first_section_offset = get_first_section_offset(nt_headers, nt_headers_offset);
		const auto sections = buffer.as<IMAGE_SECTION_HEADER>(first_section_offset);

		for (size_t i = 0; i < nt_headers.FileHeader.NumberOfSections; ++i)
		{
			const auto section = sections.get(i);
			const auto target_ptr = binary.image_base + section.VirtualAddress;

			if (section.SizeOfRawData > 0)
			{
				const auto size_of_data = std::min(section.SizeOfRawData, section.Misc.VirtualSize);
				const auto* source_ptr = buffer.get_pointer_for_range(section.PointerToRawData, size_of_data);
				emu.write_memory(target_ptr, source_ptr, size_of_data);
			}

			auto permissions = memory_permission::none;

			if (section.Characteristics & IMAGE_SCN_MEM_EXECUTE)
			{
				permissions |= memory_permission::exec;
			}

			if (section.Characteristics & IMAGE_SCN_MEM_READ)
			{
				permissions |= memory_permission::read;
			}

			if (section.Characteristics & IMAGE_SCN_MEM_WRITE)
			{
				permissions |= memory_permission::write;
			}

			const auto size_of_section = page_align_up(std::max(section.SizeOfRawData, section.Misc.VirtualSize));

			emu.protect_memory(target_ptr, size_of_section, permissions, nullptr);
		}
	}

	std::vector<uint8_t> load_file(const std::filesystem::path& file)
	{
		std::ifstream stream(file, std::ios::in | std::ios::binary);
		return {(std::istreambuf_iterator<char>(stream)), std::istreambuf_iterator<char>()};
	}
}


std::optional<mapped_module> map_module_from_data(emulator& emu, const std::span<const uint8_t> data,
                                                  std::filesystem::path file)
{
	mapped_module binary{};
	binary.path = std::move(file);
	binary.name = binary.path.filename().string();

	utils::safe_buffer_accessor buffer{data};

	const auto dos_header = buffer.as<IMAGE_DOS_HEADER>(0).get();
	const auto nt_headers_offset = dos_header.e_lfanew;

	const auto nt_headers = buffer.as<IMAGE_NT_HEADERS>(nt_headers_offset).get();
	auto& optional_header = nt_headers.OptionalHeader;

	binary.image_base = optional_header.ImageBase;
	binary.size_of_image = optional_header.SizeOfImage; // TODO: Sanitize

	if (!emu.allocate_memory(binary.image_base, binary.size_of_image, memory_permission::read))
	{
		binary.image_base = emu.find_free_allocation_base(binary.size_of_image);
		if ((optional_header.DllCharacteristics &
				IMAGE_DLLCHARACTERISTICS_DYNAMIC_BASE) == 0 || //
			!emu.allocate_memory(
				binary.image_base, binary.size_of_image, memory_permission::read))
		{
			return {};
		}
	}

	binary.entry_point = binary.image_base + optional_header.AddressOfEntryPoint;

	printf("Mapping %s at %llX\n", binary.path.generic_string().c_str(), binary.image_base);

	const auto* header_buffer = buffer.get_pointer_for_range(0, optional_header.SizeOfHeaders);
	emu.write_memory(binary.image_base, header_buffer,
	                 optional_header.SizeOfHeaders);

	map_sections(emu, binary, buffer, nt_headers, nt_headers_offset);

	auto mapped_memory = read_mapped_memory(emu, binary);
	utils::safe_buffer_accessor<uint8_t> mapped_buffer{mapped_memory};

	apply_relocations(binary, mapped_buffer, optional_header);
	collect_exports(binary, mapped_buffer, optional_header);

	emu.write_memory(binary.image_base, mapped_memory.data(), mapped_memory.size());

	return binary;
}

std::optional<mapped_module> map_module_from_file(emulator& emu, std::filesystem::path file)
{
	const auto data = load_file(file);
	if (data.empty())
	{
		return {};
	}

	return map_module_from_data(emu, data, std::move(file));
}

bool unmap_module(emulator& emu, const mapped_module& mod)
{
	return emu.release_memory(mod.image_base, mod.size_of_image);
}