#include <BAN/Endianness.h>
#include <BAN/ScopeGuard.h>
#include <BAN/StringView.h>
#include <BAN/UTF8.h>
#include <kernel/BootInfo.h>
#include <kernel/FS/DevFS/FileSystem.h>
#include <kernel/FS/VirtualFileSystem.h>
#include <kernel/Lock/LockGuard.h>
#include <kernel/PCI.h>
#include <kernel/Storage/StorageDevice.h>
#include <kernel/Thread.h>

namespace Kernel
{

	struct GPTHeader
	{
		char						signature[8];
		BAN::LittleEndian<uint32_t> revision;
		BAN::LittleEndian<uint32_t> size;
		BAN::LittleEndian<uint32_t> crc32;
		BAN::LittleEndian<uint32_t> reserved;
		BAN::LittleEndian<uint64_t> my_lba;
		BAN::LittleEndian<uint64_t> alternate_lba;
		BAN::LittleEndian<uint64_t> first_usable_lba;
		BAN::LittleEndian<uint64_t> last_usable_lba;
		BAN::GUID					disk_guid;
		BAN::LittleEndian<uint64_t> partition_entry_lba;
		BAN::LittleEndian<uint32_t> partition_entry_count;
		BAN::LittleEndian<uint32_t> partition_entry_size;
		BAN::LittleEndian<uint32_t> partition_entry_array_crc32;
	};

	struct PartitionEntry
	{
		BAN::GUID partition_type_guid;
		BAN::GUID unique_partition_guid;
		BAN::LittleEndian<uint64_t> starting_lba;
		BAN::LittleEndian<uint64_t> ending_lba;
		BAN::LittleEndian<uint64_t> attributes;
		BAN::LittleEndian<uint16_t> partition_name[36];
	};

	static uint32_t crc32_table[256] =
	{
		0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA,
		0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3,
		0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988,
		0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91,
		0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
		0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
		0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC,
		0x14015C4F, 0x63066CD9, 0xFA0F3D63, 0x8D080DF5,
		0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172,
		0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
		0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940,
		0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
		0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116,
		0x21B4F4B5, 0x56B3C423, 0xCFBA9599, 0xB8BDA50F,
		0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
		0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D,
		0x76DC4190, 0x01DB7106, 0x98D220BC, 0xEFD5102A,
		0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433,
		0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818,
		0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
		0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E,
		0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457,
		0x65B0D9C6, 0x12B7E950, 0x8BBEB8EA, 0xFCB9887C,
		0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
		0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
		0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB,
		0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0,
		0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9,
		0x5005713C, 0x270241AA, 0xBE0B1010, 0xC90C2086,
		0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
		0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4,
		0x59B33D17, 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD,
		0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A,
		0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683,
		0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
		0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1,
		0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE,
		0xF762575D, 0x806567CB, 0x196C3671, 0x6E6B06E7,
		0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC,
		0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
		0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252,
		0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
		0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60,
		0xDF60EFC3, 0xA867DF55, 0x316E8EEF, 0x4669BE79,
		0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
		0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F,
		0xC5BA3BBE, 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04,
		0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
		0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A,
		0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
		0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38,
		0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21,
		0x86D3D2D4, 0xF1D4E242, 0x68DDB3F8, 0x1FDA836E,
		0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
		0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
		0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45,
		0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2,
		0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB,
		0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, 0x37D83BF0,
		0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
		0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6,
		0xBAD03605, 0xCDD70693, 0x54DE5729, 0x23D967BF,
		0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94,
		0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D,
	};

	static uint32_t crc32_checksum(const uint8_t* data, size_t count)
	{
		uint32_t crc32 = 0xFFFFFFFF;
		for (size_t i = 0; i < count; i++)
		{
			uint8_t index = (crc32 ^ data[i]) & 0xFF;
			crc32 = (crc32 >> 8) ^ crc32_table[index];
		}
		return crc32 ^ 0xFFFFFFFF;
	}

	static bool is_valid_gpt_header(const GPTHeader& header, uint32_t sector_size)
	{
		if (memcmp(header.signature, "EFI PART", 8) != 0)
			return false;
		if (header.revision != 0x00010000)
			return false;
		if (header.size < 92 || header.size > sector_size)
			return false;
		if (header.my_lba != 1)
			return false;
		return true;
	}

	static bool is_valid_gpt_crc32(const GPTHeader& header, BAN::Vector<uint8_t> lba1, const BAN::Vector<uint8_t>& entry_array)
	{
		memset(lba1.data() + 16, 0, 4);
		if (header.crc32 != crc32_checksum(lba1.data(), header.size))
			return false;
		if (header.partition_entry_array_crc32 != crc32_checksum(entry_array.data(), header.partition_entry_count * header.partition_entry_size))
			return false;
		return true;
	}

	BAN::ErrorOr<void> StorageDevice::initialize_partitions(BAN::StringView name_prefix)
	{
		if (total_size() < sizeof(GPTHeader))
			return BAN::Error::from_error_code(ErrorCode::Storage_GPTHeader);

		BAN::Vector<uint8_t> lba1;
		TRY(lba1.resize(sector_size()));

		TRY(read_sectors(1, 1, BAN::ByteSpan { lba1.span() }));

		const GPTHeader& header = *(const GPTHeader*)lba1.data();
		if (!is_valid_gpt_header(header, sector_size()))
			return BAN::Error::from_error_code(ErrorCode::Storage_GPTHeader);

		uint32_t size = header.partition_entry_count * header.partition_entry_size;
		if (uint32_t remainder = size % sector_size())
			size += sector_size() - remainder;

		if (total_size() < header.partition_entry_lba * sector_size() + size)
			return BAN::Error::from_error_code(ErrorCode::Storage_GPTHeader);

		BAN::Vector<uint8_t> entry_array;
		TRY(entry_array.resize(size));
		TRY(read_sectors(header.partition_entry_lba, size / sector_size(), BAN::ByteSpan { entry_array.span() }));

		if (!is_valid_gpt_crc32(header, lba1, entry_array))
			return BAN::Error::from_error_code(ErrorCode::Storage_GPTHeader);

		for (uint32_t i = 0; i < header.partition_entry_count; i++)
		{
			const PartitionEntry& entry = *(const PartitionEntry*)(entry_array.data() + header.partition_entry_size * i);

			BAN::GUID zero {};
			if (memcmp(&entry.partition_type_guid, &zero, sizeof(BAN::GUID)) == 0)
				continue;

			char utf8_name[36 * 4 + 1];
			BAN::UTF8::from_codepoints(entry.partition_name, 36, utf8_name);

			auto partition = TRY(Partition::create(
				this,
				entry.partition_type_guid,
				entry.unique_partition_guid,
				entry.starting_lba,
				entry.ending_lba,
				entry.attributes,
				utf8_name,
				i + 1,
				name_prefix
			));
			TRY(m_partitions.push_back(BAN::move(partition)));
		}

		for (auto partition : m_partitions)
			DevFileSystem::get().add_device(partition);

		return {};
	}

	StorageDevice::~StorageDevice()
	{
		for (auto& partition : m_partitions)
			if (partition)
				DevFileSystem::get().remove_device(partition);
	}

	void StorageDevice::add_disk_cache()
	{
		LockGuard _(m_mutex);
		ASSERT(!m_disk_cache.has_value());
		m_disk_cache.emplace(sector_size(), *this);
	}

	BAN::ErrorOr<void> StorageDevice::sync_disk_cache()
	{
		LockGuard _(m_mutex);
		if (m_disk_cache.has_value())
			TRY(m_disk_cache->sync());
		return {};
	}

	BAN::ErrorOr<void> StorageDevice::read_sectors(uint64_t lba, size_t sector_count, BAN::ByteSpan buffer)
	{
		ASSERT(buffer.size() >= sector_count * sector_size());

		LockGuard _(m_mutex);

		if (!m_disk_cache.has_value())
			return read_sectors_impl(lba, sector_count, buffer);

		uint64_t sectors_done = 0;
		while (sectors_done < sector_count)
		{
			const uint32_t segment_sector_count = BAN::Math::min<uint32_t>(sector_count - sectors_done, 64);
			uint64_t needed_sector_bitmask = (static_cast<uint64_t>(1) << segment_sector_count) - 1;
			for (uint32_t i = 0; i < segment_sector_count; i++)
				if (m_disk_cache->read_from_cache(lba + sectors_done + i, buffer.slice((sectors_done + i) * sector_size(), sector_size())))
					needed_sector_bitmask &= ~(static_cast<uint64_t>(1) << i);

			for (uint32_t i = 0; i < segment_sector_count && needed_sector_bitmask; i++)
			{
				if (!(needed_sector_bitmask & (static_cast<uint64_t>(1) << i)))
					continue;
				uint32_t len = 1;
				while (needed_sector_bitmask & (static_cast<uint64_t>(1) << (i + len)))
					len++;
				auto segment_buffer = buffer.slice((sectors_done + i) * sector_size(), len * sector_size());
				TRY(read_sectors_impl(lba + sectors_done + i, len, segment_buffer));
				for (uint32_t j = 0; j < len; j++)
					(void)m_disk_cache->write_to_cache(lba + sectors_done + i + j, segment_buffer.slice(j * sector_size(), sector_size()), false);
				needed_sector_bitmask &= ~(((static_cast<uint64_t>(1) << len) - 1) << i);
				i += len;
			}

			sectors_done += segment_sector_count;
		}

		return {};
	}

	BAN::ErrorOr<void> StorageDevice::write_sectors(uint64_t lba, size_t sector_count, BAN::ConstByteSpan buffer)
	{
		ASSERT(buffer.size() >= sector_count * sector_size());

		LockGuard _(m_mutex);

		if (g_disable_disk_write)
		{
			if (!m_disk_cache.has_value())
				return BAN::Error::from_errno(EIO);
			for (size_t i = 0; i < sector_count; i++)
				TRY(m_disk_cache->write_to_cache(lba + i, buffer.slice(i * sector_size(), sector_size()), true));
			return {};
		}

		if (!m_disk_cache.has_value())
			return write_sectors_impl(lba, sector_count, buffer);

		for (uint8_t offset = 0; offset < sector_count; offset++)
		{
			auto sector_buffer = buffer.slice(offset * sector_size(), sector_size());
			if (m_disk_cache->write_to_cache(lba + offset, sector_buffer, true).is_error())
				TRY(write_sectors_impl(lba + offset, 1, sector_buffer));
		}

		return {};
	}

	BAN::ErrorOr<void> StorageDevice::sync_blocks(uint64_t block, size_t block_count)
	{
		if (!m_disk_cache.has_value())
			return {};
		return m_disk_cache->sync(block, block_count);
	}

	BAN::ErrorOr<size_t> StorageDevice::read_impl(off_t offset, BAN::ByteSpan buffer)
	{
		if (offset % sector_size())
			return BAN::Error::from_errno(EINVAL);
		if (buffer.size() % sector_size())
			return BAN::Error::from_errno(EINVAL);
		TRY(read_sectors(offset / sector_size(), buffer.size() / sector_size(), buffer));
		return buffer.size();
	}

	BAN::ErrorOr<size_t> StorageDevice::write_impl(off_t offset, BAN::ConstByteSpan buffer)
	{
		if (offset % sector_size())
			return BAN::Error::from_errno(EINVAL);
		if (buffer.size() % sector_size())
			return BAN::Error::from_errno(EINVAL);
		TRY(write_sectors(offset / sector_size(), buffer.size() / sector_size(), buffer));
		return buffer.size();
	}

}
